lib/littlefs: Add littlefs v1.7.2 source.

4 files changed, 3301 insertions, 0 deletions

diff --git a/lib/littlefs/lfs1.c b/lib/littlefs/lfs1.c
new file mode 100644
index 0000000000..6a3fd67001
--- /dev/null
+++ b/lib/littlefs/lfs1.c
@@ -0,0 +1,2583 @@
+/*
+ * The little filesystem
+ *
+ * Copyright (c) 2017, Arm Limited. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include "lfs1.h"
+#include "lfs1_util.h"
+
+#include <inttypes.h>
+
+
+/// Caching block device operations ///
+static int lfs1_cache_read(lfs1_t *lfs1, lfs1_cache_t *rcache,
+        const lfs1_cache_t *pcache, lfs1_block_t block,
+        lfs1_off_t off, void *buffer, lfs1_size_t size) {
+    uint8_t *data = buffer;
+    LFS1_ASSERT(block < lfs1->cfg->block_count);
+
+    while (size > 0) {
+        if (pcache && block == pcache->block && off >= pcache->off &&
+                off < pcache->off + lfs1->cfg->prog_size) {
+            // is already in pcache?
+            lfs1_size_t diff = lfs1_min(size,
+                    lfs1->cfg->prog_size - (off-pcache->off));
+            memcpy(data, &pcache->buffer[off-pcache->off], diff);
+
+            data += diff;
+            off += diff;
+            size -= diff;
+            continue;
+        }
+
+        if (block == rcache->block && off >= rcache->off &&
+                off < rcache->off + lfs1->cfg->read_size) {
+            // is already in rcache?
+            lfs1_size_t diff = lfs1_min(size,
+                    lfs1->cfg->read_size - (off-rcache->off));
+            memcpy(data, &rcache->buffer[off-rcache->off], diff);
+
+            data += diff;
+            off += diff;
+            size -= diff;
+            continue;
+        }
+
+        if (off % lfs1->cfg->read_size == 0 && size >= lfs1->cfg->read_size) {
+            // bypass cache?
+            lfs1_size_t diff = size - (size % lfs1->cfg->read_size);
+            int err = lfs1->cfg->read(lfs1->cfg, block, off, data, diff);
+            if (err) {
+                return err;
+            }
+
+            data += diff;
+            off += diff;
+            size -= diff;
+            continue;
+        }
+
+        // load to cache, first condition can no longer fail
+        rcache->block = block;
+        rcache->off = off - (off % lfs1->cfg->read_size);
+        int err = lfs1->cfg->read(lfs1->cfg, rcache->block,
+                rcache->off, rcache->buffer, lfs1->cfg->read_size);
+        if (err) {
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+static int lfs1_cache_cmp(lfs1_t *lfs1, lfs1_cache_t *rcache,
+        const lfs1_cache_t *pcache, lfs1_block_t block,
+        lfs1_off_t off, const void *buffer, lfs1_size_t size) {
+    const uint8_t *data = buffer;
+
+    for (lfs1_off_t i = 0; i < size; i++) {
+        uint8_t c;
+        int err = lfs1_cache_read(lfs1, rcache, pcache,
+                block, off+i, &c, 1);
+        if (err) {
+            return err;
+        }
+
+        if (c != data[i]) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static int lfs1_cache_crc(lfs1_t *lfs1, lfs1_cache_t *rcache,
+        const lfs1_cache_t *pcache, lfs1_block_t block,
+        lfs1_off_t off, lfs1_size_t size, uint32_t *crc) {
+    for (lfs1_off_t i = 0; i < size; i++) {
+        uint8_t c;
+        int err = lfs1_cache_read(lfs1, rcache, pcache,
+                block, off+i, &c, 1);
+        if (err) {
+            return err;
+        }
+
+        lfs1_crc(crc, &c, 1);
+    }
+
+    return 0;
+}
+
+static inline void lfs1_cache_drop(lfs1_t *lfs1, lfs1_cache_t *rcache) {
+    // do not zero, cheaper if cache is readonly or only going to be
+    // written with identical data (during relocates)
+    (void)lfs1;
+    rcache->block = 0xffffffff;
+}
+
+static inline void lfs1_cache_zero(lfs1_t *lfs1, lfs1_cache_t *pcache) {
+    // zero to avoid information leak
+    memset(pcache->buffer, 0xff, lfs1->cfg->prog_size);
+    pcache->block = 0xffffffff;
+}
+
+static int lfs1_cache_flush(lfs1_t *lfs1,
+        lfs1_cache_t *pcache, lfs1_cache_t *rcache) {
+    if (pcache->block != 0xffffffff) {
+        int err = lfs1->cfg->prog(lfs1->cfg, pcache->block,
+                pcache->off, pcache->buffer, lfs1->cfg->prog_size);
+        if (err) {
+            return err;
+        }
+
+        if (rcache) {
+            int res = lfs1_cache_cmp(lfs1, rcache, NULL, pcache->block,
+                    pcache->off, pcache->buffer, lfs1->cfg->prog_size);
+            if (res < 0) {
+                return res;
+            }
+
+            if (!res) {
+                return LFS1_ERR_CORRUPT;
+            }
+        }
+
+        lfs1_cache_zero(lfs1, pcache);
+    }
+
+    return 0;
+}
+
+static int lfs1_cache_prog(lfs1_t *lfs1, lfs1_cache_t *pcache,
+        lfs1_cache_t *rcache, lfs1_block_t block,
+        lfs1_off_t off, const void *buffer, lfs1_size_t size) {
+    const uint8_t *data = buffer;
+    LFS1_ASSERT(block < lfs1->cfg->block_count);
+
+    while (size > 0) {
+        if (block == pcache->block && off >= pcache->off &&
+                off < pcache->off + lfs1->cfg->prog_size) {
+            // is already in pcache?
+            lfs1_size_t diff = lfs1_min(size,
+                    lfs1->cfg->prog_size - (off-pcache->off));
+            memcpy(&pcache->buffer[off-pcache->off], data, diff);
+
+            data += diff;
+            off += diff;
+            size -= diff;
+
+            if (off % lfs1->cfg->prog_size == 0) {
+                // eagerly flush out pcache if we fill up
+                int err = lfs1_cache_flush(lfs1, pcache, rcache);
+                if (err) {
+                    return err;
+                }
+            }
+
+            continue;
+        }
+
+        // pcache must have been flushed, either by programming and
+        // entire block or manually flushing the pcache
+        LFS1_ASSERT(pcache->block == 0xffffffff);
+
+        if (off % lfs1->cfg->prog_size == 0 &&
+                size >= lfs1->cfg->prog_size) {
+            // bypass pcache?
+            lfs1_size_t diff = size - (size % lfs1->cfg->prog_size);
+            int err = lfs1->cfg->prog(lfs1->cfg, block, off, data, diff);
+            if (err) {
+                return err;
+            }
+
+            if (rcache) {
+                int res = lfs1_cache_cmp(lfs1, rcache, NULL,
+                        block, off, data, diff);
+                if (res < 0) {
+                    return res;
+                }
+
+                if (!res) {
+                    return LFS1_ERR_CORRUPT;
+                }
+            }
+
+            data += diff;
+            off += diff;
+            size -= diff;
+            continue;
+        }
+
+        // prepare pcache, first condition can no longer fail
+        pcache->block = block;
+        pcache->off = off - (off % lfs1->cfg->prog_size);
+    }
+
+    return 0;
+}
+
+
+/// General lfs1 block device operations ///
+static int lfs1_bd_read(lfs1_t *lfs1, lfs1_block_t block,
+        lfs1_off_t off, void *buffer, lfs1_size_t size) {
+    // if we ever do more than writes to alternating pairs,
+    // this may need to consider pcache
+    return lfs1_cache_read(lfs1, &lfs1->rcache, NULL,
+            block, off, buffer, size);
+}
+
+static int lfs1_bd_prog(lfs1_t *lfs1, lfs1_block_t block,
+        lfs1_off_t off, const void *buffer, lfs1_size_t size) {
+    return lfs1_cache_prog(lfs1, &lfs1->pcache, NULL,
+            block, off, buffer, size);
+}
+
+static int lfs1_bd_cmp(lfs1_t *lfs1, lfs1_block_t block,
+        lfs1_off_t off, const void *buffer, lfs1_size_t size) {
+    return lfs1_cache_cmp(lfs1, &lfs1->rcache, NULL, block, off, buffer, size);
+}
+
+static int lfs1_bd_crc(lfs1_t *lfs1, lfs1_block_t block,
+        lfs1_off_t off, lfs1_size_t size, uint32_t *crc) {
+    return lfs1_cache_crc(lfs1, &lfs1->rcache, NULL, block, off, size, crc);
+}
+
+static int lfs1_bd_erase(lfs1_t *lfs1, lfs1_block_t block) {
+    return lfs1->cfg->erase(lfs1->cfg, block);
+}
+
+static int lfs1_bd_sync(lfs1_t *lfs1) {
+    lfs1_cache_drop(lfs1, &lfs1->rcache);
+
+    int err = lfs1_cache_flush(lfs1, &lfs1->pcache, NULL);
+    if (err) {
+        return err;
+    }
+
+    return lfs1->cfg->sync(lfs1->cfg);
+}
+
+
+/// Internal operations predeclared here ///
+int lfs1_traverse(lfs1_t *lfs1, int (*cb)(void*, lfs1_block_t), void *data);
+static int lfs1_pred(lfs1_t *lfs1, const lfs1_block_t dir[2], lfs1_dir_t *pdir);
+static int lfs1_parent(lfs1_t *lfs1, const lfs1_block_t dir[2],
+        lfs1_dir_t *parent, lfs1_entry_t *entry);
+static int lfs1_moved(lfs1_t *lfs1, const void *e);
+static int lfs1_relocate(lfs1_t *lfs1,
+        const lfs1_block_t oldpair[2], const lfs1_block_t newpair[2]);
+int lfs1_deorphan(lfs1_t *lfs1);
+
+
+/// Block allocator ///
+static int lfs1_alloc_lookahead(void *p, lfs1_block_t block) {
+    lfs1_t *lfs1 = p;
+
+    lfs1_block_t off = ((block - lfs1->free.off)
+            + lfs1->cfg->block_count) % lfs1->cfg->block_count;
+
+    if (off < lfs1->free.size) {
+        lfs1->free.buffer[off / 32] |= 1U << (off % 32);
+    }
+
+    return 0;
+}
+
+static int lfs1_alloc(lfs1_t *lfs1, lfs1_block_t *block) {
+    while (true) {
+        while (lfs1->free.i != lfs1->free.size) {
+            lfs1_block_t off = lfs1->free.i;
+            lfs1->free.i += 1;
+            lfs1->free.ack -= 1;
+
+            if (!(lfs1->free.buffer[off / 32] & (1U << (off % 32)))) {
+                // found a free block
+                *block = (lfs1->free.off + off) % lfs1->cfg->block_count;
+
+                // eagerly find next off so an alloc ack can
+                // discredit old lookahead blocks
+                while (lfs1->free.i != lfs1->free.size &&
+                        (lfs1->free.buffer[lfs1->free.i / 32]
+                            & (1U << (lfs1->free.i % 32)))) {
+                    lfs1->free.i += 1;
+                    lfs1->free.ack -= 1;
+                }
+
+                return 0;
+            }
+        }
+
+        // check if we have looked at all blocks since last ack
+        if (lfs1->free.ack == 0) {
+            LFS1_WARN("No more free space %" PRIu32,
+                    lfs1->free.i + lfs1->free.off);
+            return LFS1_ERR_NOSPC;
+        }
+
+        lfs1->free.off = (lfs1->free.off + lfs1->free.size)
+                % lfs1->cfg->block_count;
+        lfs1->free.size = lfs1_min(lfs1->cfg->lookahead, lfs1->free.ack);
+        lfs1->free.i = 0;
+
+        // find mask of free blocks from tree
+        memset(lfs1->free.buffer, 0, lfs1->cfg->lookahead/8);
+        int err = lfs1_traverse(lfs1, lfs1_alloc_lookahead, lfs1);
+        if (err) {
+            return err;
+        }
+    }
+}
+
+static void lfs1_alloc_ack(lfs1_t *lfs1) {
+    lfs1->free.ack = lfs1->cfg->block_count;
+}
+
+
+/// Endian swapping functions ///
+static void lfs1_dir_fromle32(struct lfs1_disk_dir *d) {
+    d->rev     = lfs1_fromle32(d->rev);
+    d->size    = lfs1_fromle32(d->size);
+    d->tail[0] = lfs1_fromle32(d->tail[0]);
+    d->tail[1] = lfs1_fromle32(d->tail[1]);
+}
+
+static void lfs1_dir_tole32(struct lfs1_disk_dir *d) {
+    d->rev     = lfs1_tole32(d->rev);
+    d->size    = lfs1_tole32(d->size);
+    d->tail[0] = lfs1_tole32(d->tail[0]);
+    d->tail[1] = lfs1_tole32(d->tail[1]);
+}
+
+static void lfs1_entry_fromle32(struct lfs1_disk_entry *d) {
+    d->u.dir[0] = lfs1_fromle32(d->u.dir[0]);
+    d->u.dir[1] = lfs1_fromle32(d->u.dir[1]);
+}
+
+static void lfs1_entry_tole32(struct lfs1_disk_entry *d) {
+    d->u.dir[0] = lfs1_tole32(d->u.dir[0]);
+    d->u.dir[1] = lfs1_tole32(d->u.dir[1]);
+}
+
+static void lfs1_superblock_fromle32(struct lfs1_disk_superblock *d) {
+    d->root[0]     = lfs1_fromle32(d->root[0]);
+    d->root[1]     = lfs1_fromle32(d->root[1]);
+    d->block_size  = lfs1_fromle32(d->block_size);
+    d->block_count = lfs1_fromle32(d->block_count);
+    d->version     = lfs1_fromle32(d->version);
+}
+
+static void lfs1_superblock_tole32(struct lfs1_disk_superblock *d) {
+    d->root[0]     = lfs1_tole32(d->root[0]);
+    d->root[1]     = lfs1_tole32(d->root[1]);
+    d->block_size  = lfs1_tole32(d->block_size);
+    d->block_count = lfs1_tole32(d->block_count);
+    d->version     = lfs1_tole32(d->version);
+}
+
+
+/// Metadata pair and directory operations ///
+static inline void lfs1_pairswap(lfs1_block_t pair[2]) {
+    lfs1_block_t t = pair[0];
+    pair[0] = pair[1];
+    pair[1] = t;
+}
+
+static inline bool lfs1_pairisnull(const lfs1_block_t pair[2]) {
+    return pair[0] == 0xffffffff || pair[1] == 0xffffffff;
+}
+
+static inline int lfs1_paircmp(
+        const lfs1_block_t paira[2],
+        const lfs1_block_t pairb[2]) {
+    return !(paira[0] == pairb[0] || paira[1] == pairb[1] ||
+             paira[0] == pairb[1] || paira[1] == pairb[0]);
+}
+
+static inline bool lfs1_pairsync(
+        const lfs1_block_t paira[2],
+        const lfs1_block_t pairb[2]) {
+    return (paira[0] == pairb[0] && paira[1] == pairb[1]) ||
+           (paira[0] == pairb[1] && paira[1] == pairb[0]);
+}
+
+static inline lfs1_size_t lfs1_entry_size(const lfs1_entry_t *entry) {
+    return 4 + entry->d.elen + entry->d.alen + entry->d.nlen;
+}
+
+static int lfs1_dir_alloc(lfs1_t *lfs1, lfs1_dir_t *dir) {
+    // allocate pair of dir blocks
+    for (int i = 0; i < 2; i++) {
+        int err = lfs1_alloc(lfs1, &dir->pair[i]);
+        if (err) {
+            return err;
+        }
+    }
+
+    // rather than clobbering one of the blocks we just pretend
+    // the revision may be valid
+    int err = lfs1_bd_read(lfs1, dir->pair[0], 0, &dir->d.rev, 4);
+    if (err && err != LFS1_ERR_CORRUPT) {
+        return err;
+    }
+
+    if (err != LFS1_ERR_CORRUPT) {
+        dir->d.rev = lfs1_fromle32(dir->d.rev);
+    }
+
+    // set defaults
+    dir->d.rev += 1;
+    dir->d.size = sizeof(dir->d)+4;
+    dir->d.tail[0] = 0xffffffff;
+    dir->d.tail[1] = 0xffffffff;
+    dir->off = sizeof(dir->d);
+
+    // don't write out yet, let caller take care of that
+    return 0;
+}
+
+static int lfs1_dir_fetch(lfs1_t *lfs1,
+        lfs1_dir_t *dir, const lfs1_block_t pair[2]) {
+    // copy out pair, otherwise may be aliasing dir
+    const lfs1_block_t tpair[2] = {pair[0], pair[1]};
+    bool valid = false;
+
+    // check both blocks for the most recent revision
+    for (int i = 0; i < 2; i++) {
+        struct lfs1_disk_dir test;
+        int err = lfs1_bd_read(lfs1, tpair[i], 0, &test, sizeof(test));
+        lfs1_dir_fromle32(&test);
+        if (err) {
+            if (err == LFS1_ERR_CORRUPT) {
+                continue;
+            }
+            return err;
+        }
+
+        if (valid && lfs1_scmp(test.rev, dir->d.rev) < 0) {
+            continue;
+        }
+
+        if ((0x7fffffff & test.size) < sizeof(test)+4 ||
+            (0x7fffffff & test.size) > lfs1->cfg->block_size) {
+            continue;
+        }
+
+        uint32_t crc = 0xffffffff;
+        lfs1_dir_tole32(&test);
+        lfs1_crc(&crc, &test, sizeof(test));
+        lfs1_dir_fromle32(&test);
+        err = lfs1_bd_crc(lfs1, tpair[i], sizeof(test),
+                (0x7fffffff & test.size) - sizeof(test), &crc);
+        if (err) {
+            if (err == LFS1_ERR_CORRUPT) {
+                continue;
+            }
+            return err;
+        }
+
+        if (crc != 0) {
+            continue;
+        }
+
+        valid = true;
+
+        // setup dir in case it's valid
+        dir->pair[0] = tpair[(i+0) % 2];
+        dir->pair[1] = tpair[(i+1) % 2];
+        dir->off = sizeof(dir->d);
+        dir->d = test;
+    }
+
+    if (!valid) {
+        LFS1_ERROR("Corrupted dir pair at %" PRIu32 " %" PRIu32 ,
+                tpair[0], tpair[1]);
+        return LFS1_ERR_CORRUPT;
+    }
+
+    return 0;
+}
+
+struct lfs1_region {
+    lfs1_off_t oldoff;
+    lfs1_size_t oldlen;
+    const void *newdata;
+    lfs1_size_t newlen;
+};
+
+static int lfs1_dir_commit(lfs1_t *lfs1, lfs1_dir_t *dir,
+        const struct lfs1_region *regions, int count) {
+    // increment revision count
+    dir->d.rev += 1;
+
+    // keep pairs in order such that pair[0] is most recent
+    lfs1_pairswap(dir->pair);
+    for (int i = 0; i < count; i++) {
+        dir->d.size += regions[i].newlen - regions[i].oldlen;
+    }
+
+    const lfs1_block_t oldpair[2] = {dir->pair[0], dir->pair[1]};
+    bool relocated = false;
+
+    while (true) {
+        if (true) {
+            int err = lfs1_bd_erase(lfs1, dir->pair[0]);
+            if (err) {
+                if (err == LFS1_ERR_CORRUPT) {
+                    goto relocate;
+                }
+                return err;
+            }
+
+            uint32_t crc = 0xffffffff;
+            lfs1_dir_tole32(&dir->d);
+            lfs1_crc(&crc, &dir->d, sizeof(dir->d));
+            err = lfs1_bd_prog(lfs1, dir->pair[0], 0, &dir->d, sizeof(dir->d));
+            lfs1_dir_fromle32(&dir->d);
+            if (err) {
+                if (err == LFS1_ERR_CORRUPT) {
+                    goto relocate;
+                }
+                return err;
+            }
+
+            int i = 0;
+            lfs1_off_t oldoff = sizeof(dir->d);
+            lfs1_off_t newoff = sizeof(dir->d);
+            while (newoff < (0x7fffffff & dir->d.size)-4) {
+                if (i < count && regions[i].oldoff == oldoff) {
+                    lfs1_crc(&crc, regions[i].newdata, regions[i].newlen);
+                    err = lfs1_bd_prog(lfs1, dir->pair[0],
+                            newoff, regions[i].newdata, regions[i].newlen);
+                    if (err) {
+                        if (err == LFS1_ERR_CORRUPT) {
+                            goto relocate;
+                        }
+                        return err;
+                    }
+
+                    oldoff += regions[i].oldlen;
+                    newoff += regions[i].newlen;
+                    i += 1;
+                } else {
+                    uint8_t data;
+                    err = lfs1_bd_read(lfs1, oldpair[1], oldoff, &data, 1);
+                    if (err) {
+                        return err;
+                    }
+
+                    lfs1_crc(&crc, &data, 1);
+                    err = lfs1_bd_prog(lfs1, dir->pair[0], newoff, &data, 1);
+                    if (err) {
+                        if (err == LFS1_ERR_CORRUPT) {
+                            goto relocate;
+                        }
+                        return err;
+                    }
+
+                    oldoff += 1;
+                    newoff += 1;
+                }
+            }
+
+            crc = lfs1_tole32(crc);
+            err = lfs1_bd_prog(lfs1, dir->pair[0], newoff, &crc, 4);
+            crc = lfs1_fromle32(crc);
+            if (err) {
+                if (err == LFS1_ERR_CORRUPT) {
+                    goto relocate;
+                }
+                return err;
+            }
+
+            err = lfs1_bd_sync(lfs1);
+            if (err) {
+                if (err == LFS1_ERR_CORRUPT) {
+                    goto relocate;
+                }
+                return err;
+            }
+
+            // successful commit, check checksum to make sure
+            uint32_t ncrc = 0xffffffff;
+            err = lfs1_bd_crc(lfs1, dir->pair[0], 0,
+                    (0x7fffffff & dir->d.size)-4, &ncrc);
+            if (err) {
+                return err;
+            }
+
+            if (ncrc != crc) {
+                goto relocate;
+            }
+        }
+
+        break;
+relocate:
+        //commit was corrupted
+        LFS1_DEBUG("Bad block at %" PRIu32, dir->pair[0]);
+
+        // drop caches and prepare to relocate block
+        relocated = true;
+        lfs1_cache_drop(lfs1, &lfs1->pcache);
+
+        // can't relocate superblock, filesystem is now frozen
+        if (lfs1_paircmp(oldpair, (const lfs1_block_t[2]){0, 1}) == 0) {
+            LFS1_WARN("Superblock %" PRIu32 " has become unwritable",
+                    oldpair[0]);
+            return LFS1_ERR_CORRUPT;
+        }
+
+        // relocate half of pair
+        int err = lfs1_alloc(lfs1, &dir->pair[0]);
+        if (err) {
+            return err;
+        }
+    }
+
+    if (relocated) {
+        // update references if we relocated
+        LFS1_DEBUG("Relocating %" PRIu32 " %" PRIu32 " to %" PRIu32 " %" PRIu32,
+                oldpair[0], oldpair[1], dir->pair[0], dir->pair[1]);
+        int err = lfs1_relocate(lfs1, oldpair, dir->pair);
+        if (err) {
+            return err;
+        }
+    }
+
+    // shift over any directories that are affected
+    for (lfs1_dir_t *d = lfs1->dirs; d; d = d->next) {
+        if (lfs1_paircmp(d->pair, dir->pair) == 0) {
+            d->pair[0] = dir->pair[0];
+            d->pair[1] = dir->pair[1];
+        }
+    }
+
+    return 0;
+}
+
+static int lfs1_dir_update(lfs1_t *lfs1, lfs1_dir_t *dir,
+        lfs1_entry_t *entry, const void *data) {
+    lfs1_entry_tole32(&entry->d);
+    int err = lfs1_dir_commit(lfs1, dir, (struct lfs1_region[]){
+            {entry->off, sizeof(entry->d), &entry->d, sizeof(entry->d)},
+            {entry->off+sizeof(entry->d), entry->d.nlen, data, entry->d.nlen}
+        }, data ? 2 : 1);
+    lfs1_entry_fromle32(&entry->d);
+    return err;
+}
+
+static int lfs1_dir_append(lfs1_t *lfs1, lfs1_dir_t *dir,
+        lfs1_entry_t *entry, const void *data) {
+    // check if we fit, if top bit is set we do not and move on
+    while (true) {
+        if (dir->d.size + lfs1_entry_size(entry) <= lfs1->cfg->block_size) {
+            entry->off = dir->d.size - 4;
+
+            lfs1_entry_tole32(&entry->d);
+            int err = lfs1_dir_commit(lfs1, dir, (struct lfs1_region[]){
+                    {entry->off, 0, &entry->d, sizeof(entry->d)},
+                    {entry->off, 0, data, entry->d.nlen}
+                }, 2);
+            lfs1_entry_fromle32(&entry->d);
+            return err;
+        }
+
+        // we need to allocate a new dir block
+        if (!(0x80000000 & dir->d.size)) {
+            lfs1_dir_t olddir = *dir;
+            int err = lfs1_dir_alloc(lfs1, dir);
+            if (err) {
+                return err;
+            }
+
+            dir->d.tail[0] = olddir.d.tail[0];
+            dir->d.tail[1] = olddir.d.tail[1];
+            entry->off = dir->d.size - 4;
+            lfs1_entry_tole32(&entry->d);
+            err = lfs1_dir_commit(lfs1, dir, (struct lfs1_region[]){
+                    {entry->off, 0, &entry->d, sizeof(entry->d)},
+                    {entry->off, 0, data, entry->d.nlen}
+                }, 2);
+            lfs1_entry_fromle32(&entry->d);
+            if (err) {
+                return err;
+            }
+
+            olddir.d.size |= 0x80000000;
+            olddir.d.tail[0] = dir->pair[0];
+            olddir.d.tail[1] = dir->pair[1];
+            return lfs1_dir_commit(lfs1, &olddir, NULL, 0);
+        }
+
+        int err = lfs1_dir_fetch(lfs1, dir, dir->d.tail);
+        if (err) {
+            return err;
+        }
+    }
+}
+
+static int lfs1_dir_remove(lfs1_t *lfs1, lfs1_dir_t *dir, lfs1_entry_t *entry) {
+    // check if we should just drop the directory block
+    if ((dir->d.size & 0x7fffffff) == sizeof(dir->d)+4
+            + lfs1_entry_size(entry)) {
+        lfs1_dir_t pdir;
+        int res = lfs1_pred(lfs1, dir->pair, &pdir);
+        if (res < 0) {
+            return res;
+        }
+
+        if (pdir.d.size & 0x80000000) {
+            pdir.d.size &= dir->d.size | 0x7fffffff;
+            pdir.d.tail[0] = dir->d.tail[0];
+            pdir.d.tail[1] = dir->d.tail[1];
+            return lfs1_dir_commit(lfs1, &pdir, NULL, 0);
+        }
+    }
+
+    // shift out the entry
+    int err = lfs1_dir_commit(lfs1, dir, (struct lfs1_region[]){
+            {entry->off, lfs1_entry_size(entry), NULL, 0},
+        }, 1);
+    if (err) {
+        return err;
+    }
+
+    // shift over any files/directories that are affected
+    for (lfs1_file_t *f = lfs1->files; f; f = f->next) {
+        if (lfs1_paircmp(f->pair, dir->pair) == 0) {
+            if (f->poff == entry->off) {
+                f->pair[0] = 0xffffffff;
+                f->pair[1] = 0xffffffff;
+            } else if (f->poff > entry->off) {
+                f->poff -= lfs1_entry_size(entry);
+            }
+        }
+    }
+
+    for (lfs1_dir_t *d = lfs1->dirs; d; d = d->next) {
+        if (lfs1_paircmp(d->pair, dir->pair) == 0) {
+            if (d->off > entry->off) {
+                d->off -= lfs1_entry_size(entry);
+                d->pos -= lfs1_entry_size(entry);
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int lfs1_dir_next(lfs1_t *lfs1, lfs1_dir_t *dir, lfs1_entry_t *entry) {
+    while (dir->off + sizeof(entry->d) > (0x7fffffff & dir->d.size)-4) {
+        if (!(0x80000000 & dir->d.size)) {
+            entry->off = dir->off;
+            return LFS1_ERR_NOENT;
+        }
+
+        int err = lfs1_dir_fetch(lfs1, dir, dir->d.tail);
+        if (err) {
+            return err;
+        }
+
+        dir->off = sizeof(dir->d);
+        dir->pos += sizeof(dir->d) + 4;
+    }
+
+    int err = lfs1_bd_read(lfs1, dir->pair[0], dir->off,
+            &entry->d, sizeof(entry->d));
+    lfs1_entry_fromle32(&entry->d);
+    if (err) {
+        return err;
+    }
+
+    entry->off = dir->off;
+    dir->off += lfs1_entry_size(entry);
+    dir->pos += lfs1_entry_size(entry);
+    return 0;
+}
+
+static int lfs1_dir_find(lfs1_t *lfs1, lfs1_dir_t *dir,
+        lfs1_entry_t *entry, const char **path) {
+    const char *pathname = *path;
+    size_t pathlen;
+    entry->d.type = LFS1_TYPE_DIR;
+    entry->d.elen = sizeof(entry->d) - 4;
+    entry->d.alen = 0;
+    entry->d.nlen = 0;
+    entry->d.u.dir[0] = lfs1->root[0];
+    entry->d.u.dir[1] = lfs1->root[1];
+
+    while (true) {
+nextname:
+        // skip slashes
+        pathname += strspn(pathname, "/");
+        pathlen = strcspn(pathname, "/");
+
+        // skip '.' and root '..'
+        if ((pathlen == 1 && memcmp(pathname, ".", 1) == 0) ||
+            (pathlen == 2 && memcmp(pathname, "..", 2) == 0)) {
+            pathname += pathlen;
+            goto nextname;
+        }
+
+        // skip if matched by '..' in name
+        const char *suffix = pathname + pathlen;
+        size_t sufflen;
+        int depth = 1;
+        while (true) {
+            suffix += strspn(suffix, "/");
+            sufflen = strcspn(suffix, "/");
+            if (sufflen == 0) {
+                break;
+            }
+
+            if (sufflen == 2 && memcmp(suffix, "..", 2) == 0) {
+                depth -= 1;
+                if (depth == 0) {
+                    pathname = suffix + sufflen;
+                    goto nextname;
+                }
+            } else {
+                depth += 1;
+            }
+
+            suffix += sufflen;
+        }
+
+        // found path
+        if (pathname[0] == '\0') {
+            return 0;
+        }
+
+        // update what we've found
+        *path = pathname;
+
+        // continue on if we hit a directory
+        if (entry->d.type != LFS1_TYPE_DIR) {
+            return LFS1_ERR_NOTDIR;
+        }
+
+        int err = lfs1_dir_fetch(lfs1, dir, entry->d.u.dir);
+        if (err) {
+            return err;
+        }
+
+        // find entry matching name
+        while (true) {
+            err = lfs1_dir_next(lfs1, dir, entry);
+            if (err) {
+                return err;
+            }
+
+            if (((0x7f & entry->d.type) != LFS1_TYPE_REG &&
+                 (0x7f & entry->d.type) != LFS1_TYPE_DIR) ||
+                entry->d.nlen != pathlen) {
+                continue;
+            }
+
+            int res = lfs1_bd_cmp(lfs1, dir->pair[0],
+                    entry->off + 4+entry->d.elen+entry->d.alen,
+                    pathname, pathlen);
+            if (res < 0) {
+                return res;
+            }
+
+            // found match
+            if (res) {
+                break;
+            }
+        }
+
+        // check that entry has not been moved
+        if (!lfs1->moving && entry->d.type & 0x80) {
+            int moved = lfs1_moved(lfs1, &entry->d.u);
+            if (moved < 0 || moved) {
+                return (moved < 0) ? moved : LFS1_ERR_NOENT;
+            }
+
+            entry->d.type &= ~0x80;
+        }
+
+        // to next name
+        pathname += pathlen;
+    }
+}
+
+
+/// Top level directory operations ///
+int lfs1_mkdir(lfs1_t *lfs1, const char *path) {
+    // deorphan if we haven't yet, needed at most once after poweron
+    if (!lfs1->deorphaned) {
+        int err = lfs1_deorphan(lfs1);
+        if (err) {
+            return err;
+        }
+    }
+
+    // fetch parent directory
+    lfs1_dir_t cwd;
+    lfs1_entry_t entry;
+    int err = lfs1_dir_find(lfs1, &cwd, &entry, &path);
+    if (err != LFS1_ERR_NOENT || strchr(path, '/') != NULL) {
+        return err ? err : LFS1_ERR_EXIST;
+    }
+
+    // build up new directory
+    lfs1_alloc_ack(lfs1);
+
+    lfs1_dir_t dir;
+    err = lfs1_dir_alloc(lfs1, &dir);
+    if (err) {
+        return err;
+    }
+    dir.d.tail[0] = cwd.d.tail[0];
+    dir.d.tail[1] = cwd.d.tail[1];
+
+    err = lfs1_dir_commit(lfs1, &dir, NULL, 0);
+    if (err) {
+        return err;
+    }
+
+    entry.d.type = LFS1_TYPE_DIR;
+    entry.d.elen = sizeof(entry.d) - 4;
+    entry.d.alen = 0;
+    entry.d.nlen = strlen(path);
+    entry.d.u.dir[0] = dir.pair[0];
+    entry.d.u.dir[1] = dir.pair[1];
+
+    cwd.d.tail[0] = dir.pair[0];
+    cwd.d.tail[1] = dir.pair[1];
+
+    err = lfs1_dir_append(lfs1, &cwd, &entry, path);
+    if (err) {
+        return err;
+    }
+
+    lfs1_alloc_ack(lfs1);
+    return 0;
+}
+
+int lfs1_dir_open(lfs1_t *lfs1, lfs1_dir_t *dir, const char *path) {
+    dir->pair[0] = lfs1->root[0];
+    dir->pair[1] = lfs1->root[1];
+
+    lfs1_entry_t entry;
+    int err = lfs1_dir_find(lfs1, dir, &entry, &path);
+    if (err) {
+        return err;
+    } else if (entry.d.type != LFS1_TYPE_DIR) {
+        return LFS1_ERR_NOTDIR;
+    }
+
+    err = lfs1_dir_fetch(lfs1, dir, entry.d.u.dir);
+    if (err) {
+        return err;
+    }
+
+    // setup head dir
+    // special offset for '.' and '..'
+    dir->head[0] = dir->pair[0];
+    dir->head[1] = dir->pair[1];
+    dir->pos = sizeof(dir->d) - 2;
+    dir->off = sizeof(dir->d);
+
+    // add to list of directories
+    dir->next = lfs1->dirs;
+    lfs1->dirs = dir;
+
+    return 0;
+}
+
+int lfs1_dir_close(lfs1_t *lfs1, lfs1_dir_t *dir) {
+    // remove from list of directories
+    for (lfs1_dir_t **p = &lfs1->dirs; *p; p = &(*p)->next) {
+        if (*p == dir) {
+            *p = dir->next;
+            break;
+        }
+    }
+
+    return 0;
+}
+
+int lfs1_dir_read(lfs1_t *lfs1, lfs1_dir_t *dir, struct lfs1_info *info) {
+    memset(info, 0, sizeof(*info));
+
+    // special offset for '.' and '..'
+    if (dir->pos == sizeof(dir->d) - 2) {
+        info->type = LFS1_TYPE_DIR;
+        strcpy(info->name, ".");
+        dir->pos += 1;
+        return 1;
+    } else if (dir->pos == sizeof(dir->d) - 1) {
+        info->type = LFS1_TYPE_DIR;
+        strcpy(info->name, "..");
+        dir->pos += 1;
+        return 1;
+    }
+
+    lfs1_entry_t entry;
+    while (true) {
+        int err = lfs1_dir_next(lfs1, dir, &entry);
+        if (err) {
+            return (err == LFS1_ERR_NOENT) ? 0 : err;
+        }
+
+        if ((0x7f & entry.d.type) != LFS1_TYPE_REG &&
+            (0x7f & entry.d.type) != LFS1_TYPE_DIR) {
+            continue;
+        }
+
+        // check that entry has not been moved
+        if (entry.d.type & 0x80) {
+            int moved = lfs1_moved(lfs1, &entry.d.u);
+            if (moved < 0) {
+                return moved;
+            }
+
+            if (moved) {
+                continue;
+            }
+
+            entry.d.type &= ~0x80;
+        }
+
+        break;
+    }
+
+    info->type = entry.d.type;
+    if (info->type == LFS1_TYPE_REG) {
+        info->size = entry.d.u.file.size;
+    }
+
+    int err = lfs1_bd_read(lfs1, dir->pair[0],
+            entry.off + 4+entry.d.elen+entry.d.alen,
+            info->name, entry.d.nlen);
+    if (err) {
+        return err;
+    }
+
+    return 1;
+}
+
+int lfs1_dir_seek(lfs1_t *lfs1, lfs1_dir_t *dir, lfs1_off_t off) {
+    // simply walk from head dir
+    int err = lfs1_dir_rewind(lfs1, dir);
+    if (err) {
+        return err;
+    }
+    dir->pos = off;
+
+    while (off > (0x7fffffff & dir->d.size)) {
+        off -= 0x7fffffff & dir->d.size;
+        if (!(0x80000000 & dir->d.size)) {
+            return LFS1_ERR_INVAL;
+        }
+
+        err = lfs1_dir_fetch(lfs1, dir, dir->d.tail);
+        if (err) {
+            return err;
+        }
+    }
+
+    dir->off = off;
+    return 0;
+}
+
+lfs1_soff_t lfs1_dir_tell(lfs1_t *lfs1, lfs1_dir_t *dir) {
+    (void)lfs1;
+    return dir->pos;
+}
+
+int lfs1_dir_rewind(lfs1_t *lfs1, lfs1_dir_t *dir) {
+    // reload the head dir
+    int err = lfs1_dir_fetch(lfs1, dir, dir->head);
+    if (err) {
+        return err;
+    }
+
+    dir->pair[0] = dir->head[0];
+    dir->pair[1] = dir->head[1];
+    dir->pos = sizeof(dir->d) - 2;
+    dir->off = sizeof(dir->d);
+    return 0;
+}
+
+
+/// File index list operations ///
+static int lfs1_ctz_index(lfs1_t *lfs1, lfs1_off_t *off) {
+    lfs1_off_t size = *off;
+    lfs1_off_t b = lfs1->cfg->block_size - 2*4;
+    lfs1_off_t i = size / b;
+    if (i == 0) {
+        return 0;
+    }
+
+    i = (size - 4*(lfs1_popc(i-1)+2)) / b;
+    *off = size - b*i - 4*lfs1_popc(i);
+    return i;
+}
+
+static int lfs1_ctz_find(lfs1_t *lfs1,
+        lfs1_cache_t *rcache, const lfs1_cache_t *pcache,
+        lfs1_block_t head, lfs1_size_t size,
+        lfs1_size_t pos, lfs1_block_t *block, lfs1_off_t *off) {
+    if (size == 0) {
+        *block = 0xffffffff;
+        *off = 0;
+        return 0;
+    }
+
+    lfs1_off_t current = lfs1_ctz_index(lfs1, &(lfs1_off_t){size-1});
+    lfs1_off_t target = lfs1_ctz_index(lfs1, &pos);
+
+    while (current > target) {
+        lfs1_size_t skip = lfs1_min(
+                lfs1_npw2(current-target+1) - 1,
+                lfs1_ctz(current));
+
+        int err = lfs1_cache_read(lfs1, rcache, pcache, head, 4*skip, &head, 4);
+        head = lfs1_fromle32(head);
+        if (err) {
+            return err;
+        }
+
+        LFS1_ASSERT(head >= 2 && head <= lfs1->cfg->block_count);
+        current -= 1 << skip;
+    }
+
+    *block = head;
+    *off = pos;
+    return 0;
+}
+
+static int lfs1_ctz_extend(lfs1_t *lfs1,
+        lfs1_cache_t *rcache, lfs1_cache_t *pcache,
+        lfs1_block_t head, lfs1_size_t size,
+        lfs1_block_t *block, lfs1_off_t *off) {
+    while (true) {
+        // go ahead and grab a block
+        lfs1_block_t nblock;
+        int err = lfs1_alloc(lfs1, &nblock);
+        if (err) {
+            return err;
+        }
+        LFS1_ASSERT(nblock >= 2 && nblock <= lfs1->cfg->block_count);
+
+        if (true) {
+            err = lfs1_bd_erase(lfs1, nblock);
+            if (err) {
+                if (err == LFS1_ERR_CORRUPT) {
+                    goto relocate;
+                }
+                return err;
+            }
+
+            if (size == 0) {
+                *block = nblock;
+                *off = 0;
+                return 0;
+            }
+
+            size -= 1;
+            lfs1_off_t index = lfs1_ctz_index(lfs1, &size);
+            size += 1;
+
+            // just copy out the last block if it is incomplete
+            if (size != lfs1->cfg->block_size) {
+                for (lfs1_off_t i = 0; i < size; i++) {
+                    uint8_t data;
+                    err = lfs1_cache_read(lfs1, rcache, NULL,
+                            head, i, &data, 1);
+                    if (err) {
+                        return err;
+                    }
+
+                    err = lfs1_cache_prog(lfs1, pcache, rcache,
+                            nblock, i, &data, 1);
+                    if (err) {
+                        if (err == LFS1_ERR_CORRUPT) {
+                            goto relocate;
+                        }
+                        return err;
+                    }
+                }
+
+                *block = nblock;
+                *off = size;
+                return 0;
+            }
+
+            // append block
+            index += 1;
+            lfs1_size_t skips = lfs1_ctz(index) + 1;
+
+            for (lfs1_off_t i = 0; i < skips; i++) {
+                head = lfs1_tole32(head);
+                err = lfs1_cache_prog(lfs1, pcache, rcache,
+                        nblock, 4*i, &head, 4);
+                head = lfs1_fromle32(head);
+                if (err) {
+                    if (err == LFS1_ERR_CORRUPT) {
+                        goto relocate;
+                    }
+                    return err;
+                }
+
+                if (i != skips-1) {
+                    err = lfs1_cache_read(lfs1, rcache, NULL,
+                            head, 4*i, &head, 4);
+                    head = lfs1_fromle32(head);
+                    if (err) {
+                        return err;
+                    }
+                }
+
+                LFS1_ASSERT(head >= 2 && head <= lfs1->cfg->block_count);
+            }
+
+            *block = nblock;
+            *off = 4*skips;
+            return 0;
+        }
+
+relocate:
+        LFS1_DEBUG("Bad block at %" PRIu32, nblock);
+
+        // just clear cache and try a new block
+        lfs1_cache_drop(lfs1, &lfs1->pcache);
+    }
+}
+
+static int lfs1_ctz_traverse(lfs1_t *lfs1,
+        lfs1_cache_t *rcache, const lfs1_cache_t *pcache,
+        lfs1_block_t head, lfs1_size_t size,
+        int (*cb)(void*, lfs1_block_t), void *data) {
+    if (size == 0) {
+        return 0;
+    }
+
+    lfs1_off_t index = lfs1_ctz_index(lfs1, &(lfs1_off_t){size-1});
+
+    while (true) {
+        int err = cb(data, head);
+        if (err) {
+            return err;
+        }
+
+        if (index == 0) {
+            return 0;
+        }
+
+        lfs1_block_t heads[2];
+        int count = 2 - (index & 1);
+        err = lfs1_cache_read(lfs1, rcache, pcache, head, 0, &heads, count*4);
+        heads[0] = lfs1_fromle32(heads[0]);
+        heads[1] = lfs1_fromle32(heads[1]);
+        if (err) {
+            return err;
+        }
+
+        for (int i = 0; i < count-1; i++) {
+            err = cb(data, heads[i]);
+            if (err) {
+                return err;
+            }
+        }
+
+        head = heads[count-1];
+        index -= count;
+    }
+}
+
+
+/// Top level file operations ///
+int lfs1_file_opencfg(lfs1_t *lfs1, lfs1_file_t *file,
+        const char *path, int flags,
+        const struct lfs1_file_config *cfg) {
+    // deorphan if we haven't yet, needed at most once after poweron
+    if ((flags & 3) != LFS1_O_RDONLY && !lfs1->deorphaned) {
+        int err = lfs1_deorphan(lfs1);
+        if (err) {
+            return err;
+        }
+    }
+
+    // allocate entry for file if it doesn't exist
+    lfs1_dir_t cwd;
+    lfs1_entry_t entry;
+    int err = lfs1_dir_find(lfs1, &cwd, &entry, &path);
+    if (err && (err != LFS1_ERR_NOENT || strchr(path, '/') != NULL)) {
+        return err;
+    }
+
+    if (err == LFS1_ERR_NOENT) {
+        if (!(flags & LFS1_O_CREAT)) {
+            return LFS1_ERR_NOENT;
+        }
+
+        // create entry to remember name
+        entry.d.type = LFS1_TYPE_REG;
+        entry.d.elen = sizeof(entry.d) - 4;
+        entry.d.alen = 0;
+        entry.d.nlen = strlen(path);
+        entry.d.u.file.head = 0xffffffff;
+        entry.d.u.file.size = 0;
+        err = lfs1_dir_append(lfs1, &cwd, &entry, path);
+        if (err) {
+            return err;
+        }
+    } else if (entry.d.type == LFS1_TYPE_DIR) {
+        return LFS1_ERR_ISDIR;
+    } else if (flags & LFS1_O_EXCL) {
+        return LFS1_ERR_EXIST;
+    }
+
+    // setup file struct
+    file->cfg = cfg;
+    file->pair[0] = cwd.pair[0];
+    file->pair[1] = cwd.pair[1];
+    file->poff = entry.off;
+    file->head = entry.d.u.file.head;
+    file->size = entry.d.u.file.size;
+    file->flags = flags;
+    file->pos = 0;
+
+    if (flags & LFS1_O_TRUNC) {
+        if (file->size != 0) {
+            file->flags |= LFS1_F_DIRTY;
+        }
+        file->head = 0xffffffff;
+        file->size = 0;
+    }
+
+    // allocate buffer if needed
+    file->cache.block = 0xffffffff;
+    if (file->cfg && file->cfg->buffer) {
+        file->cache.buffer = file->cfg->buffer;
+    } else if (lfs1->cfg->file_buffer) {
+        if (lfs1->files) {
+            // already in use
+            return LFS1_ERR_NOMEM;
+        }
+        file->cache.buffer = lfs1->cfg->file_buffer;
+    } else if ((file->flags & 3) == LFS1_O_RDONLY) {
+        file->cache.buffer = lfs1_malloc(lfs1->cfg->read_size);
+        if (!file->cache.buffer) {
+            return LFS1_ERR_NOMEM;
+        }
+    } else {
+        file->cache.buffer = lfs1_malloc(lfs1->cfg->prog_size);
+        if (!file->cache.buffer) {
+            return LFS1_ERR_NOMEM;
+        }
+    }
+
+    // zero to avoid information leak
+    lfs1_cache_drop(lfs1, &file->cache);
+    if ((file->flags & 3) != LFS1_O_RDONLY) {
+        lfs1_cache_zero(lfs1, &file->cache);
+    }
+
+    // add to list of files
+    file->next = lfs1->files;
+    lfs1->files = file;
+
+    return 0;
+}
+
+int lfs1_file_open(lfs1_t *lfs1, lfs1_file_t *file,
+        const char *path, int flags) {
+    return lfs1_file_opencfg(lfs1, file, path, flags, NULL);
+}
+
+int lfs1_file_close(lfs1_t *lfs1, lfs1_file_t *file) {
+    int err = lfs1_file_sync(lfs1, file);
+
+    // remove from list of files
+    for (lfs1_file_t **p = &lfs1->files; *p; p = &(*p)->next) {
+        if (*p == file) {
+            *p = file->next;
+            break;
+        }
+    }
+
+    // clean up memory
+    if (!(file->cfg && file->cfg->buffer) && !lfs1->cfg->file_buffer) {
+        lfs1_free(file->cache.buffer);
+    }
+
+    return err;
+}
+
+static int lfs1_file_relocate(lfs1_t *lfs1, lfs1_file_t *file) {
+relocate:
+    LFS1_DEBUG("Bad block at %" PRIu32, file->block);
+
+    // just relocate what exists into new block
+    lfs1_block_t nblock;
+    int err = lfs1_alloc(lfs1, &nblock);
+    if (err) {
+        return err;
+    }
+
+    err = lfs1_bd_erase(lfs1, nblock);
+    if (err) {
+        if (err == LFS1_ERR_CORRUPT) {
+            goto relocate;
+        }
+        return err;
+    }
+
+    // either read from dirty cache or disk
+    for (lfs1_off_t i = 0; i < file->off; i++) {
+        uint8_t data;
+        err = lfs1_cache_read(lfs1, &lfs1->rcache, &file->cache,
+                file->block, i, &data, 1);
+        if (err) {
+            return err;
+        }
+
+        err = lfs1_cache_prog(lfs1, &lfs1->pcache, &lfs1->rcache,
+                nblock, i, &data, 1);
+        if (err) {
+            if (err == LFS1_ERR_CORRUPT) {
+                goto relocate;
+            }
+            return err;
+        }
+    }
+
+    // copy over new state of file
+    memcpy(file->cache.buffer, lfs1->pcache.buffer, lfs1->cfg->prog_size);
+    file->cache.block = lfs1->pcache.block;
+    file->cache.off = lfs1->pcache.off;
+    lfs1_cache_zero(lfs1, &lfs1->pcache);
+
+    file->block = nblock;
+    return 0;
+}
+
+static int lfs1_file_flush(lfs1_t *lfs1, lfs1_file_t *file) {
+    if (file->flags & LFS1_F_READING) {
+        // just drop read cache
+        lfs1_cache_drop(lfs1, &file->cache);
+        file->flags &= ~LFS1_F_READING;
+    }
+
+    if (file->flags & LFS1_F_WRITING) {
+        lfs1_off_t pos = file->pos;
+
+        // copy over anything after current branch
+        lfs1_file_t orig = {
+            .head = file->head,
+            .size = file->size,
+            .flags = LFS1_O_RDONLY,
+            .pos = file->pos,
+            .cache = lfs1->rcache,
+        };
+        lfs1_cache_drop(lfs1, &lfs1->rcache);
+
+        while (file->pos < file->size) {
+            // copy over a byte at a time, leave it up to caching
+            // to make this efficient
+            uint8_t data;
+            lfs1_ssize_t res = lfs1_file_read(lfs1, &orig, &data, 1);
+            if (res < 0) {
+                return res;
+            }
+
+            res = lfs1_file_write(lfs1, file, &data, 1);
+            if (res < 0) {
+                return res;
+            }
+
+            // keep our reference to the rcache in sync
+            if (lfs1->rcache.block != 0xffffffff) {
+                lfs1_cache_drop(lfs1, &orig.cache);
+                lfs1_cache_drop(lfs1, &lfs1->rcache);
+            }
+        }
+
+        // write out what we have
+        while (true) {
+            int err = lfs1_cache_flush(lfs1, &file->cache, &lfs1->rcache);
+            if (err) {
+                if (err == LFS1_ERR_CORRUPT) {
+                    goto relocate;
+                }
+                return err;
+            }
+
+            break;
+relocate:
+            err = lfs1_file_relocate(lfs1, file);
+            if (err) {
+                return err;
+            }
+        }
+
+        // actual file updates
+        file->head = file->block;
+        file->size = file->pos;
+        file->flags &= ~LFS1_F_WRITING;
+        file->flags |= LFS1_F_DIRTY;
+
+        file->pos = pos;
+    }
+
+    return 0;
+}
+
+int lfs1_file_sync(lfs1_t *lfs1, lfs1_file_t *file) {
+    int err = lfs1_file_flush(lfs1, file);
+    if (err) {
+        return err;
+    }
+
+    if ((file->flags & LFS1_F_DIRTY) &&
+            !(file->flags & LFS1_F_ERRED) &&
+            !lfs1_pairisnull(file->pair)) {
+        // update dir entry
+        lfs1_dir_t cwd;
+        err = lfs1_dir_fetch(lfs1, &cwd, file->pair);
+        if (err) {
+            return err;
+        }
+
+        lfs1_entry_t entry = {.off = file->poff};
+        err = lfs1_bd_read(lfs1, cwd.pair[0], entry.off,
+                &entry.d, sizeof(entry.d));
+        lfs1_entry_fromle32(&entry.d);
+        if (err) {
+            return err;
+        }
+
+        LFS1_ASSERT(entry.d.type == LFS1_TYPE_REG);
+        entry.d.u.file.head = file->head;
+        entry.d.u.file.size = file->size;
+
+        err = lfs1_dir_update(lfs1, &cwd, &entry, NULL);
+        if (err) {
+            return err;
+        }
+
+        file->flags &= ~LFS1_F_DIRTY;
+    }
+
+    return 0;
+}
+
+lfs1_ssize_t lfs1_file_read(lfs1_t *lfs1, lfs1_file_t *file,
+        void *buffer, lfs1_size_t size) {
+    uint8_t *data = buffer;
+    lfs1_size_t nsize = size;
+
+    if ((file->flags & 3) == LFS1_O_WRONLY) {
+        return LFS1_ERR_BADF;
+    }
+
+    if (file->flags & LFS1_F_WRITING) {
+        // flush out any writes
+        int err = lfs1_file_flush(lfs1, file);
+        if (err) {
+            return err;
+        }
+    }
+
+    if (file->pos >= file->size) {
+        // eof if past end
+        return 0;
+    }
+
+    size = lfs1_min(size, file->size - file->pos);
+    nsize = size;
+
+    while (nsize > 0) {
+        // check if we need a new block
+        if (!(file->flags & LFS1_F_READING) ||
+                file->off == lfs1->cfg->block_size) {
+            int err = lfs1_ctz_find(lfs1, &file->cache, NULL,
+                    file->head, file->size,
+                    file->pos, &file->block, &file->off);
+            if (err) {
+                return err;
+            }
+
+            file->flags |= LFS1_F_READING;
+        }
+
+        // read as much as we can in current block
+        lfs1_size_t diff = lfs1_min(nsize, lfs1->cfg->block_size - file->off);
+        int err = lfs1_cache_read(lfs1, &file->cache, NULL,
+                file->block, file->off, data, diff);
+        if (err) {
+            return err;
+        }
+
+        file->pos += diff;
+        file->off += diff;
+        data += diff;
+        nsize -= diff;
+    }
+
+    return size;
+}
+
+lfs1_ssize_t lfs1_file_write(lfs1_t *lfs1, lfs1_file_t *file,
+        const void *buffer, lfs1_size_t size) {
+    const uint8_t *data = buffer;
+    lfs1_size_t nsize = size;
+
+    if ((file->flags & 3) == LFS1_O_RDONLY) {
+        return LFS1_ERR_BADF;
+    }
+
+    if (file->flags & LFS1_F_READING) {
+        // drop any reads
+        int err = lfs1_file_flush(lfs1, file);
+        if (err) {
+            return err;
+        }
+    }
+
+    if ((file->flags & LFS1_O_APPEND) && file->pos < file->size) {
+        file->pos = file->size;
+    }
+
+    if (file->pos + size > LFS1_FILE_MAX) {
+        // larger than file limit?
+        return LFS1_ERR_FBIG;
+    }
+
+    if (!(file->flags & LFS1_F_WRITING) && file->pos > file->size) {
+        // fill with zeros
+        lfs1_off_t pos = file->pos;
+        file->pos = file->size;
+
+        while (file->pos < pos) {
+            lfs1_ssize_t res = lfs1_file_write(lfs1, file, &(uint8_t){0}, 1);
+            if (res < 0) {
+                return res;
+            }
+        }
+    }
+
+    while (nsize > 0) {
+        // check if we need a new block
+        if (!(file->flags & LFS1_F_WRITING) ||
+                file->off == lfs1->cfg->block_size) {
+            if (!(file->flags & LFS1_F_WRITING) && file->pos > 0) {
+                // find out which block we're extending from
+                int err = lfs1_ctz_find(lfs1, &file->cache, NULL,
+                        file->head, file->size,
+                        file->pos-1, &file->block, &file->off);
+                if (err) {
+                    file->flags |= LFS1_F_ERRED;
+                    return err;
+                }
+
+                // mark cache as dirty since we may have read data into it
+                lfs1_cache_zero(lfs1, &file->cache);
+            }
+
+            // extend file with new blocks
+            lfs1_alloc_ack(lfs1);
+            int err = lfs1_ctz_extend(lfs1, &lfs1->rcache, &file->cache,
+                    file->block, file->pos,
+                    &file->block, &file->off);
+            if (err) {
+                file->flags |= LFS1_F_ERRED;
+                return err;
+            }
+
+            file->flags |= LFS1_F_WRITING;
+        }
+
+        // program as much as we can in current block
+        lfs1_size_t diff = lfs1_min(nsize, lfs1->cfg->block_size - file->off);
+        while (true) {
+            int err = lfs1_cache_prog(lfs1, &file->cache, &lfs1->rcache,
+                    file->block, file->off, data, diff);
+            if (err) {
+                if (err == LFS1_ERR_CORRUPT) {
+                    goto relocate;
+                }
+                file->flags |= LFS1_F_ERRED;
+                return err;
+            }
+
+            break;
+relocate:
+            err = lfs1_file_relocate(lfs1, file);
+            if (err) {
+                file->flags |= LFS1_F_ERRED;
+                return err;
+            }
+        }
+
+        file->pos += diff;
+        file->off += diff;
+        data += diff;
+        nsize -= diff;
+
+        lfs1_alloc_ack(lfs1);
+    }
+
+    file->flags &= ~LFS1_F_ERRED;
+    return size;
+}
+
+lfs1_soff_t lfs1_file_seek(lfs1_t *lfs1, lfs1_file_t *file,
+        lfs1_soff_t off, int whence) {
+    // write out everything beforehand, may be noop if rdonly
+    int err = lfs1_file_flush(lfs1, file);
+    if (err) {
+        return err;
+    }
+
+    // find new pos
+    lfs1_soff_t npos = file->pos;
+    if (whence == LFS1_SEEK_SET) {
+        npos = off;
+    } else if (whence == LFS1_SEEK_CUR) {
+        npos = file->pos + off;
+    } else if (whence == LFS1_SEEK_END) {
+        npos = file->size + off;
+    }
+
+    if (npos < 0 || npos > LFS1_FILE_MAX) {
+        // file position out of range
+        return LFS1_ERR_INVAL;
+    }
+
+    // update pos
+    file->pos = npos;
+    return npos;
+}
+
+int lfs1_file_truncate(lfs1_t *lfs1, lfs1_file_t *file, lfs1_off_t size) {
+    if ((file->flags & 3) == LFS1_O_RDONLY) {
+        return LFS1_ERR_BADF;
+    }
+
+    lfs1_off_t oldsize = lfs1_file_size(lfs1, file);
+    if (size < oldsize) {
+        // need to flush since directly changing metadata
+        int err = lfs1_file_flush(lfs1, file);
+        if (err) {
+            return err;
+        }
+
+        // lookup new head in ctz skip list
+        err = lfs1_ctz_find(lfs1, &file->cache, NULL,
+                file->head, file->size,
+                size, &file->head, &(lfs1_off_t){0});
+        if (err) {
+            return err;
+        }
+
+        file->size = size;
+        file->flags |= LFS1_F_DIRTY;
+    } else if (size > oldsize) {
+        lfs1_off_t pos = file->pos;
+
+        // flush+seek if not already at end
+        if (file->pos != oldsize) {
+            int err = lfs1_file_seek(lfs1, file, 0, LFS1_SEEK_END);
+            if (err < 0) {
+                return err;
+            }
+        }
+
+        // fill with zeros
+        while (file->pos < size) {
+            lfs1_ssize_t res = lfs1_file_write(lfs1, file, &(uint8_t){0}, 1);
+            if (res < 0) {
+                return res;
+            }
+        }
+
+        // restore pos
+        int err = lfs1_file_seek(lfs1, file, pos, LFS1_SEEK_SET);
+        if (err < 0) {
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+lfs1_soff_t lfs1_file_tell(lfs1_t *lfs1, lfs1_file_t *file) {
+    (void)lfs1;
+    return file->pos;
+}
+
+int lfs1_file_rewind(lfs1_t *lfs1, lfs1_file_t *file) {
+    lfs1_soff_t res = lfs1_file_seek(lfs1, file, 0, LFS1_SEEK_SET);
+    if (res < 0) {
+        return res;
+    }
+
+    return 0;
+}
+
+lfs1_soff_t lfs1_file_size(lfs1_t *lfs1, lfs1_file_t *file) {
+    (void)lfs1;
+    if (file->flags & LFS1_F_WRITING) {
+        return lfs1_max(file->pos, file->size);
+    } else {
+        return file->size;
+    }
+}
+
+
+/// General fs operations ///
+int lfs1_stat(lfs1_t *lfs1, const char *path, struct lfs1_info *info) {
+    lfs1_dir_t cwd;
+    lfs1_entry_t entry;
+    int err = lfs1_dir_find(lfs1, &cwd, &entry, &path);
+    if (err) {
+        return err;
+    }
+
+    memset(info, 0, sizeof(*info));
+    info->type = entry.d.type;
+    if (info->type == LFS1_TYPE_REG) {
+        info->size = entry.d.u.file.size;
+    }
+
+    if (lfs1_paircmp(entry.d.u.dir, lfs1->root) == 0) {
+        strcpy(info->name, "/");
+    } else {
+        err = lfs1_bd_read(lfs1, cwd.pair[0],
+                entry.off + 4+entry.d.elen+entry.d.alen,
+                info->name, entry.d.nlen);
+        if (err) {
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+int lfs1_remove(lfs1_t *lfs1, const char *path) {
+    // deorphan if we haven't yet, needed at most once after poweron
+    if (!lfs1->deorphaned) {
+        int err = lfs1_deorphan(lfs1);
+        if (err) {
+            return err;
+        }
+    }
+
+    lfs1_dir_t cwd;
+    lfs1_entry_t entry;
+    int err = lfs1_dir_find(lfs1, &cwd, &entry, &path);
+    if (err) {
+        return err;
+    }
+
+    lfs1_dir_t dir;
+    if (entry.d.type == LFS1_TYPE_DIR) {
+        // must be empty before removal, checking size
+        // without masking top bit checks for any case where
+        // dir is not empty
+        err = lfs1_dir_fetch(lfs1, &dir, entry.d.u.dir);
+        if (err) {
+            return err;
+        } else if (dir.d.size != sizeof(dir.d)+4) {
+            return LFS1_ERR_NOTEMPTY;
+        }
+    }
+
+    // remove the entry
+    err = lfs1_dir_remove(lfs1, &cwd, &entry);
+    if (err) {
+        return err;
+    }
+
+    // if we were a directory, find pred, replace tail
+    if (entry.d.type == LFS1_TYPE_DIR) {
+        int res = lfs1_pred(lfs1, dir.pair, &cwd);
+        if (res < 0) {
+            return res;
+        }
+
+        LFS1_ASSERT(res); // must have pred
+        cwd.d.tail[0] = dir.d.tail[0];
+        cwd.d.tail[1] = dir.d.tail[1];
+
+        err = lfs1_dir_commit(lfs1, &cwd, NULL, 0);
+        if (err) {
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+int lfs1_rename(lfs1_t *lfs1, const char *oldpath, const char *newpath) {
+    // deorphan if we haven't yet, needed at most once after poweron
+    if (!lfs1->deorphaned) {
+        int err = lfs1_deorphan(lfs1);
+        if (err) {
+            return err;
+        }
+    }
+
+    // find old entry
+    lfs1_dir_t oldcwd;
+    lfs1_entry_t oldentry;
+    int err = lfs1_dir_find(lfs1, &oldcwd, &oldentry, &(const char *){oldpath});
+    if (err) {
+        return err;
+    }
+
+    // mark as moving
+    oldentry.d.type |= 0x80;
+    err = lfs1_dir_update(lfs1, &oldcwd, &oldentry, NULL);
+    if (err) {
+        return err;
+    }
+
+    // allocate new entry
+    lfs1_dir_t newcwd;
+    lfs1_entry_t preventry;
+    err = lfs1_dir_find(lfs1, &newcwd, &preventry, &newpath);
+    if (err && (err != LFS1_ERR_NOENT || strchr(newpath, '/') != NULL)) {
+        return err;
+    }
+
+    // must have same type
+    bool prevexists = (err != LFS1_ERR_NOENT);
+    if (prevexists && preventry.d.type != (0x7f & oldentry.d.type)) {
+        return LFS1_ERR_ISDIR;
+    }
+
+    lfs1_dir_t dir;
+    if (prevexists && preventry.d.type == LFS1_TYPE_DIR) {
+        // must be empty before removal, checking size
+        // without masking top bit checks for any case where
+        // dir is not empty
+        err = lfs1_dir_fetch(lfs1, &dir, preventry.d.u.dir);
+        if (err) {
+            return err;
+        } else if (dir.d.size != sizeof(dir.d)+4) {
+            return LFS1_ERR_NOTEMPTY;
+        }
+    }
+
+    // move to new location
+    lfs1_entry_t newentry = preventry;
+    newentry.d = oldentry.d;
+    newentry.d.type &= ~0x80;
+    newentry.d.nlen = strlen(newpath);
+
+    if (prevexists) {
+        err = lfs1_dir_update(lfs1, &newcwd, &newentry, newpath);
+        if (err) {
+            return err;
+        }
+    } else {
+        err = lfs1_dir_append(lfs1, &newcwd, &newentry, newpath);
+        if (err) {
+            return err;
+        }
+    }
+
+    // fetch old pair again in case dir block changed
+    lfs1->moving = true;
+    err = lfs1_dir_find(lfs1, &oldcwd, &oldentry, &oldpath);
+    if (err) {
+        return err;
+    }
+    lfs1->moving = false;
+
+    // remove old entry
+    err = lfs1_dir_remove(lfs1, &oldcwd, &oldentry);
+    if (err) {
+        return err;
+    }
+
+    // if we were a directory, find pred, replace tail
+    if (prevexists && preventry.d.type == LFS1_TYPE_DIR) {
+        int res = lfs1_pred(lfs1, dir.pair, &newcwd);
+        if (res < 0) {
+            return res;
+        }
+
+        LFS1_ASSERT(res); // must have pred
+        newcwd.d.tail[0] = dir.d.tail[0];
+        newcwd.d.tail[1] = dir.d.tail[1];
+
+        err = lfs1_dir_commit(lfs1, &newcwd, NULL, 0);
+        if (err) {
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+
+/// Filesystem operations ///
+static void lfs1_deinit(lfs1_t *lfs1) {
+    // free allocated memory
+    if (!lfs1->cfg->read_buffer) {
+        lfs1_free(lfs1->rcache.buffer);
+    }
+
+    if (!lfs1->cfg->prog_buffer) {
+        lfs1_free(lfs1->pcache.buffer);
+    }
+
+    if (!lfs1->cfg->lookahead_buffer) {
+        lfs1_free(lfs1->free.buffer);
+    }
+}
+
+static int lfs1_init(lfs1_t *lfs1, const struct lfs1_config *cfg) {
+    lfs1->cfg = cfg;
+
+    // setup read cache
+    if (lfs1->cfg->read_buffer) {
+        lfs1->rcache.buffer = lfs1->cfg->read_buffer;
+    } else {
+        lfs1->rcache.buffer = lfs1_malloc(lfs1->cfg->read_size);
+        if (!lfs1->rcache.buffer) {
+            goto cleanup;
+        }
+    }
+
+    // setup program cache
+    if (lfs1->cfg->prog_buffer) {
+        lfs1->pcache.buffer = lfs1->cfg->prog_buffer;
+    } else {
+        lfs1->pcache.buffer = lfs1_malloc(lfs1->cfg->prog_size);
+        if (!lfs1->pcache.buffer) {
+            goto cleanup;
+        }
+    }
+
+    // zero to avoid information leaks
+    lfs1_cache_zero(lfs1, &lfs1->pcache);
+    lfs1_cache_drop(lfs1, &lfs1->rcache);
+
+    // setup lookahead, round down to nearest 32-bits
+    LFS1_ASSERT(lfs1->cfg->lookahead % 32 == 0);
+    LFS1_ASSERT(lfs1->cfg->lookahead > 0);
+    if (lfs1->cfg->lookahead_buffer) {
+        lfs1->free.buffer = lfs1->cfg->lookahead_buffer;
+    } else {
+        lfs1->free.buffer = lfs1_malloc(lfs1->cfg->lookahead/8);
+        if (!lfs1->free.buffer) {
+            goto cleanup;
+        }
+    }
+
+    // check that program and read sizes are multiples of the block size
+    LFS1_ASSERT(lfs1->cfg->prog_size % lfs1->cfg->read_size == 0);
+    LFS1_ASSERT(lfs1->cfg->block_size % lfs1->cfg->prog_size == 0);
+
+    // check that the block size is large enough to fit ctz pointers
+    LFS1_ASSERT(4*lfs1_npw2(0xffffffff / (lfs1->cfg->block_size-2*4))
+            <= lfs1->cfg->block_size);
+
+    // setup default state
+    lfs1->root[0] = 0xffffffff;
+    lfs1->root[1] = 0xffffffff;
+    lfs1->files = NULL;
+    lfs1->dirs = NULL;
+    lfs1->deorphaned = false;
+    lfs1->moving = false;
+
+    return 0;
+
+cleanup:
+    lfs1_deinit(lfs1);
+    return LFS1_ERR_NOMEM;
+}
+
+int lfs1_format(lfs1_t *lfs1, const struct lfs1_config *cfg) {
+    int err = 0;
+    if (true) {
+        err = lfs1_init(lfs1, cfg);
+        if (err) {
+            return err;
+        }
+
+        // create free lookahead
+        memset(lfs1->free.buffer, 0, lfs1->cfg->lookahead/8);
+        lfs1->free.off = 0;
+        lfs1->free.size = lfs1_min(lfs1->cfg->lookahead, lfs1->cfg->block_count);
+        lfs1->free.i = 0;
+        lfs1_alloc_ack(lfs1);
+
+        // create superblock dir
+        lfs1_dir_t superdir;
+        err = lfs1_dir_alloc(lfs1, &superdir);
+        if (err) {
+            goto cleanup;
+        }
+
+        // write root directory
+        lfs1_dir_t root;
+        err = lfs1_dir_alloc(lfs1, &root);
+        if (err) {
+            goto cleanup;
+        }
+
+        err = lfs1_dir_commit(lfs1, &root, NULL, 0);
+        if (err) {
+            goto cleanup;
+        }
+
+        lfs1->root[0] = root.pair[0];
+        lfs1->root[1] = root.pair[1];
+
+        // write superblocks
+        lfs1_superblock_t superblock = {
+            .off = sizeof(superdir.d),
+            .d.type = LFS1_TYPE_SUPERBLOCK,
+            .d.elen = sizeof(superblock.d) - sizeof(superblock.d.magic) - 4,
+            .d.nlen = sizeof(superblock.d.magic),
+            .d.version = LFS1_DISK_VERSION,
+            .d.magic = {"littlefs"},
+            .d.block_size  = lfs1->cfg->block_size,
+            .d.block_count = lfs1->cfg->block_count,
+            .d.root = {lfs1->root[0], lfs1->root[1]},
+        };
+        superdir.d.tail[0] = root.pair[0];
+        superdir.d.tail[1] = root.pair[1];
+        superdir.d.size = sizeof(superdir.d) + sizeof(superblock.d) + 4;
+
+        // write both pairs to be safe
+        lfs1_superblock_tole32(&superblock.d);
+        bool valid = false;
+        for (int i = 0; i < 2; i++) {
+            err = lfs1_dir_commit(lfs1, &superdir, (struct lfs1_region[]){
+                    {sizeof(superdir.d), sizeof(superblock.d),
+                     &superblock.d, sizeof(superblock.d)}
+                }, 1);
+            if (err && err != LFS1_ERR_CORRUPT) {
+                goto cleanup;
+            }
+
+            valid = valid || !err;
+        }
+
+        if (!valid) {
+            err = LFS1_ERR_CORRUPT;
+            goto cleanup;
+        }
+
+        // sanity check that fetch works
+        err = lfs1_dir_fetch(lfs1, &superdir, (const lfs1_block_t[2]){0, 1});
+        if (err) {
+            goto cleanup;
+        }
+
+        lfs1_alloc_ack(lfs1);
+    }
+
+cleanup:
+    lfs1_deinit(lfs1);
+    return err;
+}
+
+int lfs1_mount(lfs1_t *lfs1, const struct lfs1_config *cfg) {
+    int err = 0;
+    if (true) {
+        err = lfs1_init(lfs1, cfg);
+        if (err) {
+            return err;
+        }
+
+        // setup free lookahead
+        lfs1->free.off = 0;
+        lfs1->free.size = 0;
+        lfs1->free.i = 0;
+        lfs1_alloc_ack(lfs1);
+
+        // load superblock
+        lfs1_dir_t dir;
+        lfs1_superblock_t superblock;
+        err = lfs1_dir_fetch(lfs1, &dir, (const lfs1_block_t[2]){0, 1});
+        if (err && err != LFS1_ERR_CORRUPT) {
+            goto cleanup;
+        }
+
+        if (!err) {
+            err = lfs1_bd_read(lfs1, dir.pair[0], sizeof(dir.d),
+                    &superblock.d, sizeof(superblock.d));
+            lfs1_superblock_fromle32(&superblock.d);
+            if (err) {
+                goto cleanup;
+            }
+
+            lfs1->root[0] = superblock.d.root[0];
+            lfs1->root[1] = superblock.d.root[1];
+        }
+
+        if (err || memcmp(superblock.d.magic, "littlefs", 8) != 0) {
+            LFS1_ERROR("Invalid superblock at %d %d", 0, 1);
+            err = LFS1_ERR_CORRUPT;
+            goto cleanup;
+        }
+
+        uint16_t major_version = (0xffff & (superblock.d.version >> 16));
+        uint16_t minor_version = (0xffff & (superblock.d.version >>  0));
+        if ((major_version != LFS1_DISK_VERSION_MAJOR ||
+             minor_version > LFS1_DISK_VERSION_MINOR)) {
+            LFS1_ERROR("Invalid version %d.%d", major_version, minor_version);
+            err = LFS1_ERR_INVAL;
+            goto cleanup;
+        }
+
+        return 0;
+    }
+
+cleanup:
+
+    lfs1_deinit(lfs1);
+    return err;
+}
+
+int lfs1_unmount(lfs1_t *lfs1) {
+    lfs1_deinit(lfs1);
+    return 0;
+}
+
+
+/// Littlefs specific operations ///
+int lfs1_traverse(lfs1_t *lfs1, int (*cb)(void*, lfs1_block_t), void *data) {
+    if (lfs1_pairisnull(lfs1->root)) {
+        return 0;
+    }
+
+    // iterate over metadata pairs
+    lfs1_dir_t dir;
+    lfs1_entry_t entry;
+    lfs1_block_t cwd[2] = {0, 1};
+
+    while (true) {
+        for (int i = 0; i < 2; i++) {
+            int err = cb(data, cwd[i]);
+            if (err) {
+                return err;
+            }
+        }
+
+        int err = lfs1_dir_fetch(lfs1, &dir, cwd);
+        if (err) {
+            return err;
+        }
+
+        // iterate over contents
+        while (dir.off + sizeof(entry.d) <= (0x7fffffff & dir.d.size)-4) {
+            err = lfs1_bd_read(lfs1, dir.pair[0], dir.off,
+                    &entry.d, sizeof(entry.d));
+            lfs1_entry_fromle32(&entry.d);
+            if (err) {
+                return err;
+            }
+
+            dir.off += lfs1_entry_size(&entry);
+            if ((0x70 & entry.d.type) == (0x70 & LFS1_TYPE_REG)) {
+                err = lfs1_ctz_traverse(lfs1, &lfs1->rcache, NULL,
+                        entry.d.u.file.head, entry.d.u.file.size, cb, data);
+                if (err) {
+                    return err;
+                }
+            }
+        }
+
+        cwd[0] = dir.d.tail[0];
+        cwd[1] = dir.d.tail[1];
+
+        if (lfs1_pairisnull(cwd)) {
+            break;
+        }
+    }
+
+    // iterate over any open files
+    for (lfs1_file_t *f = lfs1->files; f; f = f->next) {
+        if (f->flags & LFS1_F_DIRTY) {
+            int err = lfs1_ctz_traverse(lfs1, &lfs1->rcache, &f->cache,
+                    f->head, f->size, cb, data);
+            if (err) {
+                return err;
+            }
+        }
+
+        if (f->flags & LFS1_F_WRITING) {
+            int err = lfs1_ctz_traverse(lfs1, &lfs1->rcache, &f->cache,
+                    f->block, f->pos, cb, data);
+            if (err) {
+                return err;
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int lfs1_pred(lfs1_t *lfs1, const lfs1_block_t dir[2], lfs1_dir_t *pdir) {
+    if (lfs1_pairisnull(lfs1->root)) {
+        return 0;
+    }
+
+    // iterate over all directory directory entries
+    int err = lfs1_dir_fetch(lfs1, pdir, (const lfs1_block_t[2]){0, 1});
+    if (err) {
+        return err;
+    }
+
+    while (!lfs1_pairisnull(pdir->d.tail)) {
+        if (lfs1_paircmp(pdir->d.tail, dir) == 0) {
+            return true;
+        }
+
+        err = lfs1_dir_fetch(lfs1, pdir, pdir->d.tail);
+        if (err) {
+            return err;
+        }
+    }
+
+    return false;
+}
+
+static int lfs1_parent(lfs1_t *lfs1, const lfs1_block_t dir[2],
+        lfs1_dir_t *parent, lfs1_entry_t *entry) {
+    if (lfs1_pairisnull(lfs1->root)) {
+        return 0;
+    }
+
+    parent->d.tail[0] = 0;
+    parent->d.tail[1] = 1;
+
+    // iterate over all directory directory entries
+    while (!lfs1_pairisnull(parent->d.tail)) {
+        int err = lfs1_dir_fetch(lfs1, parent, parent->d.tail);
+        if (err) {
+            return err;
+        }
+
+        while (true) {
+            err = lfs1_dir_next(lfs1, parent, entry);
+            if (err && err != LFS1_ERR_NOENT) {
+                return err;
+            }
+
+            if (err == LFS1_ERR_NOENT) {
+                break;
+            }
+
+            if (((0x70 & entry->d.type) == (0x70 & LFS1_TYPE_DIR)) &&
+                 lfs1_paircmp(entry->d.u.dir, dir) == 0) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+static int lfs1_moved(lfs1_t *lfs1, const void *e) {
+    if (lfs1_pairisnull(lfs1->root)) {
+        return 0;
+    }
+
+    // skip superblock
+    lfs1_dir_t cwd;
+    int err = lfs1_dir_fetch(lfs1, &cwd, (const lfs1_block_t[2]){0, 1});
+    if (err) {
+        return err;
+    }
+
+    // iterate over all directory directory entries
+    lfs1_entry_t entry;
+    while (!lfs1_pairisnull(cwd.d.tail)) {
+        err = lfs1_dir_fetch(lfs1, &cwd, cwd.d.tail);
+        if (err) {
+            return err;
+        }
+
+        while (true) {
+            err = lfs1_dir_next(lfs1, &cwd, &entry);
+            if (err && err != LFS1_ERR_NOENT) {
+                return err;
+            }
+
+            if (err == LFS1_ERR_NOENT) {
+                break;
+            }
+
+            if (!(0x80 & entry.d.type) &&
+                 memcmp(&entry.d.u, e, sizeof(entry.d.u)) == 0) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+static int lfs1_relocate(lfs1_t *lfs1,
+        const lfs1_block_t oldpair[2], const lfs1_block_t newpair[2]) {
+    // find parent
+    lfs1_dir_t parent;
+    lfs1_entry_t entry;
+    int res = lfs1_parent(lfs1, oldpair, &parent, &entry);
+    if (res < 0) {
+        return res;
+    }
+
+    if (res) {
+        // update disk, this creates a desync
+        entry.d.u.dir[0] = newpair[0];
+        entry.d.u.dir[1] = newpair[1];
+
+        int err = lfs1_dir_update(lfs1, &parent, &entry, NULL);
+        if (err) {
+            return err;
+        }
+
+        // update internal root
+        if (lfs1_paircmp(oldpair, lfs1->root) == 0) {
+            LFS1_DEBUG("Relocating root %" PRIu32 " %" PRIu32,
+                    newpair[0], newpair[1]);
+            lfs1->root[0] = newpair[0];
+            lfs1->root[1] = newpair[1];
+        }
+
+        // clean up bad block, which should now be a desync
+        return lfs1_deorphan(lfs1);
+    }
+
+    // find pred
+    res = lfs1_pred(lfs1, oldpair, &parent);
+    if (res < 0) {
+        return res;
+    }
+
+    if (res) {
+        // just replace bad pair, no desync can occur
+        parent.d.tail[0] = newpair[0];
+        parent.d.tail[1] = newpair[1];
+
+        return lfs1_dir_commit(lfs1, &parent, NULL, 0);
+    }
+
+    // couldn't find dir, must be new
+    return 0;
+}
+
+int lfs1_deorphan(lfs1_t *lfs1) {
+    lfs1->deorphaned = true;
+
+    if (lfs1_pairisnull(lfs1->root)) {
+        return 0;
+    }
+
+    lfs1_dir_t pdir = {.d.size = 0x80000000};
+    lfs1_dir_t cwd = {.d.tail[0] = 0, .d.tail[1] = 1};
+
+    // iterate over all directory directory entries
+    for (lfs1_size_t i = 0; i < lfs1->cfg->block_count; i++) {
+        if (lfs1_pairisnull(cwd.d.tail)) {
+            return 0;
+        }
+
+        int err = lfs1_dir_fetch(lfs1, &cwd, cwd.d.tail);
+        if (err) {
+            return err;
+        }
+
+        // check head blocks for orphans
+        if (!(0x80000000 & pdir.d.size)) {
+            // check if we have a parent
+            lfs1_dir_t parent;
+            lfs1_entry_t entry;
+            int res = lfs1_parent(lfs1, pdir.d.tail, &parent, &entry);
+            if (res < 0) {
+                return res;
+            }
+
+            if (!res) {
+                // we are an orphan
+                LFS1_DEBUG("Found orphan %" PRIu32 " %" PRIu32,
+                        pdir.d.tail[0], pdir.d.tail[1]);
+
+                pdir.d.tail[0] = cwd.d.tail[0];
+                pdir.d.tail[1] = cwd.d.tail[1];
+
+                err = lfs1_dir_commit(lfs1, &pdir, NULL, 0);
+                if (err) {
+                    return err;
+                }
+
+                return 0;
+            }
+
+            if (!lfs1_pairsync(entry.d.u.dir, pdir.d.tail)) {
+                // we have desynced
+                LFS1_DEBUG("Found desync %" PRIu32 " %" PRIu32,
+                        entry.d.u.dir[0], entry.d.u.dir[1]);
+
+                pdir.d.tail[0] = entry.d.u.dir[0];
+                pdir.d.tail[1] = entry.d.u.dir[1];
+
+                err = lfs1_dir_commit(lfs1, &pdir, NULL, 0);
+                if (err) {
+                    return err;
+                }
+
+                return 0;
+            }
+        }
+
+        // check entries for moves
+        lfs1_entry_t entry;
+        while (true) {
+            err = lfs1_dir_next(lfs1, &cwd, &entry);
+            if (err && err != LFS1_ERR_NOENT) {
+                return err;
+            }
+
+            if (err == LFS1_ERR_NOENT) {
+                break;
+            }
+
+            // found moved entry
+            if (entry.d.type & 0x80) {
+                int moved = lfs1_moved(lfs1, &entry.d.u);
+                if (moved < 0) {
+                    return moved;
+                }
+
+                if (moved) {
+                    LFS1_DEBUG("Found move %" PRIu32 " %" PRIu32,
+                            entry.d.u.dir[0], entry.d.u.dir[1]);
+                    err = lfs1_dir_remove(lfs1, &cwd, &entry);
+                    if (err) {
+                        return err;
+                    }
+                } else {
+                    LFS1_DEBUG("Found partial move %" PRIu32 " %" PRIu32,
+                            entry.d.u.dir[0], entry.d.u.dir[1]);
+                    entry.d.type &= ~0x80;
+                    err = lfs1_dir_update(lfs1, &cwd, &entry, NULL);
+                    if (err) {
+                        return err;
+                    }
+                }
+            }
+        }
+
+        memcpy(&pdir, &cwd, sizeof(pdir));
+    }
+
+    // If we reached here, we have more directory pairs than blocks in the
+    // filesystem... So something must be horribly wrong
+    return LFS1_ERR_CORRUPT;
+}
diff --git a/lib/littlefs/lfs1.h b/lib/littlefs/lfs1.h
new file mode 100644
index 0000000000..355c145d08
--- /dev/null
+++ b/lib/littlefs/lfs1.h
@@ -0,0 +1,501 @@
+/*
+ * The little filesystem
+ *
+ * Copyright (c) 2017, Arm Limited. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#ifndef LFS1_H
+#define LFS1_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+
+/// Version info ///
+
+// Software library version
+// Major (top-nibble), incremented on backwards incompatible changes
+// Minor (bottom-nibble), incremented on feature additions
+#define LFS1_VERSION 0x00010007
+#define LFS1_VERSION_MAJOR (0xffff & (LFS1_VERSION >> 16))
+#define LFS1_VERSION_MINOR (0xffff & (LFS1_VERSION >>  0))
+
+// Version of On-disk data structures
+// Major (top-nibble), incremented on backwards incompatible changes
+// Minor (bottom-nibble), incremented on feature additions
+#define LFS1_DISK_VERSION 0x00010001
+#define LFS1_DISK_VERSION_MAJOR (0xffff & (LFS1_DISK_VERSION >> 16))
+#define LFS1_DISK_VERSION_MINOR (0xffff & (LFS1_DISK_VERSION >>  0))
+
+
+/// Definitions ///
+
+// Type definitions
+typedef uint32_t lfs1_size_t;
+typedef uint32_t lfs1_off_t;
+
+typedef int32_t  lfs1_ssize_t;
+typedef int32_t  lfs1_soff_t;
+
+typedef uint32_t lfs1_block_t;
+
+// Max name size in bytes
+#ifndef LFS1_NAME_MAX
+#define LFS1_NAME_MAX 255
+#endif
+
+// Max file size in bytes
+#ifndef LFS1_FILE_MAX
+#define LFS1_FILE_MAX 2147483647
+#endif
+
+// Possible error codes, these are negative to allow
+// valid positive return values
+enum lfs1_error {
+    LFS1_ERR_OK       = 0,    // No error
+    LFS1_ERR_IO       = -5,   // Error during device operation
+    LFS1_ERR_CORRUPT  = -52,  // Corrupted
+    LFS1_ERR_NOENT    = -2,   // No directory entry
+    LFS1_ERR_EXIST    = -17,  // Entry already exists
+    LFS1_ERR_NOTDIR   = -20,  // Entry is not a dir
+    LFS1_ERR_ISDIR    = -21,  // Entry is a dir
+    LFS1_ERR_NOTEMPTY = -39,  // Dir is not empty
+    LFS1_ERR_BADF     = -9,   // Bad file number
+    LFS1_ERR_FBIG     = -27,  // File too large
+    LFS1_ERR_INVAL    = -22,  // Invalid parameter
+    LFS1_ERR_NOSPC    = -28,  // No space left on device
+    LFS1_ERR_NOMEM    = -12,  // No more memory available
+};
+
+// File types
+enum lfs1_type {
+    LFS1_TYPE_REG        = 0x11,
+    LFS1_TYPE_DIR        = 0x22,
+    LFS1_TYPE_SUPERBLOCK = 0x2e,
+};
+
+// File open flags
+enum lfs1_open_flags {
+    // open flags
+    LFS1_O_RDONLY = 1,        // Open a file as read only
+    LFS1_O_WRONLY = 2,        // Open a file as write only
+    LFS1_O_RDWR   = 3,        // Open a file as read and write
+    LFS1_O_CREAT  = 0x0100,   // Create a file if it does not exist
+    LFS1_O_EXCL   = 0x0200,   // Fail if a file already exists
+    LFS1_O_TRUNC  = 0x0400,   // Truncate the existing file to zero size
+    LFS1_O_APPEND = 0x0800,   // Move to end of file on every write
+
+    // internally used flags
+    LFS1_F_DIRTY   = 0x10000, // File does not match storage
+    LFS1_F_WRITING = 0x20000, // File has been written since last flush
+    LFS1_F_READING = 0x40000, // File has been read since last flush
+    LFS1_F_ERRED   = 0x80000, // An error occured during write
+};
+
+// File seek flags
+enum lfs1_whence_flags {
+    LFS1_SEEK_SET = 0,   // Seek relative to an absolute position
+    LFS1_SEEK_CUR = 1,   // Seek relative to the current file position
+    LFS1_SEEK_END = 2,   // Seek relative to the end of the file
+};
+
+
+// Configuration provided during initialization of the littlefs
+struct lfs1_config {
+    // Opaque user provided context that can be used to pass
+    // information to the block device operations
+    void *context;
+
+    // Read a region in a block. Negative error codes are propogated
+    // to the user.
+    int (*read)(const struct lfs1_config *c, lfs1_block_t block,
+            lfs1_off_t off, void *buffer, lfs1_size_t size);
+
+    // Program a region in a block. The block must have previously
+    // been erased. Negative error codes are propogated to the user.
+    // May return LFS1_ERR_CORRUPT if the block should be considered bad.
+    int (*prog)(const struct lfs1_config *c, lfs1_block_t block,
+            lfs1_off_t off, const void *buffer, lfs1_size_t size);
+
+    // Erase a block. A block must be erased before being programmed.
+    // The state of an erased block is undefined. Negative error codes
+    // are propogated to the user.
+    // May return LFS1_ERR_CORRUPT if the block should be considered bad.
+    int (*erase)(const struct lfs1_config *c, lfs1_block_t block);
+
+    // Sync the state of the underlying block device. Negative error codes
+    // are propogated to the user.
+    int (*sync)(const struct lfs1_config *c);
+
+    // Minimum size of a block read. This determines the size of read buffers.
+    // This may be larger than the physical read size to improve performance
+    // by caching more of the block device.
+    lfs1_size_t read_size;
+
+    // Minimum size of a block program. This determines the size of program
+    // buffers. This may be larger than the physical program size to improve
+    // performance by caching more of the block device.
+    // Must be a multiple of the read size.
+    lfs1_size_t prog_size;
+
+    // Size of an erasable block. This does not impact ram consumption and
+    // may be larger than the physical erase size. However, this should be
+    // kept small as each file currently takes up an entire block.
+    // Must be a multiple of the program size.
+    lfs1_size_t block_size;
+
+    // Number of erasable blocks on the device.
+    lfs1_size_t block_count;
+
+    // Number of blocks to lookahead during block allocation. A larger
+    // lookahead reduces the number of passes required to allocate a block.
+    // The lookahead buffer requires only 1 bit per block so it can be quite
+    // large with little ram impact. Should be a multiple of 32.
+    lfs1_size_t lookahead;
+
+    // Optional, statically allocated read buffer. Must be read sized.
+    void *read_buffer;
+
+    // Optional, statically allocated program buffer. Must be program sized.
+    void *prog_buffer;
+
+    // Optional, statically allocated lookahead buffer. Must be 1 bit per
+    // lookahead block.
+    void *lookahead_buffer;
+
+    // Optional, statically allocated buffer for files. Must be program sized.
+    // If enabled, only one file may be opened at a time.
+    void *file_buffer;
+};
+
+// Optional configuration provided during lfs1_file_opencfg
+struct lfs1_file_config {
+    // Optional, statically allocated buffer for files. Must be program sized.
+    // If NULL, malloc will be used by default.
+    void *buffer;
+};
+
+// File info structure
+struct lfs1_info {
+    // Type of the file, either LFS1_TYPE_REG or LFS1_TYPE_DIR
+    uint8_t type;
+
+    // Size of the file, only valid for REG files
+    lfs1_size_t size;
+
+    // Name of the file stored as a null-terminated string
+    char name[LFS1_NAME_MAX+1];
+};
+
+
+/// littlefs data structures ///
+typedef struct lfs1_entry {
+    lfs1_off_t off;
+
+    struct lfs1_disk_entry {
+        uint8_t type;
+        uint8_t elen;
+        uint8_t alen;
+        uint8_t nlen;
+        union {
+            struct {
+                lfs1_block_t head;
+                lfs1_size_t size;
+            } file;
+            lfs1_block_t dir[2];
+        } u;
+    } d;
+} lfs1_entry_t;
+
+typedef struct lfs1_cache {
+    lfs1_block_t block;
+    lfs1_off_t off;
+    uint8_t *buffer;
+} lfs1_cache_t;
+
+typedef struct lfs1_file {
+    struct lfs1_file *next;
+    lfs1_block_t pair[2];
+    lfs1_off_t poff;
+
+    lfs1_block_t head;
+    lfs1_size_t size;
+
+    const struct lfs1_file_config *cfg;
+    uint32_t flags;
+    lfs1_off_t pos;
+    lfs1_block_t block;
+    lfs1_off_t off;
+    lfs1_cache_t cache;
+} lfs1_file_t;
+
+typedef struct lfs1_dir {
+    struct lfs1_dir *next;
+    lfs1_block_t pair[2];
+    lfs1_off_t off;
+
+    lfs1_block_t head[2];
+    lfs1_off_t pos;
+
+    struct lfs1_disk_dir {
+        uint32_t rev;
+        lfs1_size_t size;
+        lfs1_block_t tail[2];
+    } d;
+} lfs1_dir_t;
+
+typedef struct lfs1_superblock {
+    lfs1_off_t off;
+
+    struct lfs1_disk_superblock {
+        uint8_t type;
+        uint8_t elen;
+        uint8_t alen;
+        uint8_t nlen;
+        lfs1_block_t root[2];
+        uint32_t block_size;
+        uint32_t block_count;
+        uint32_t version;
+        char magic[8];
+    } d;
+} lfs1_superblock_t;
+
+typedef struct lfs1_free {
+    lfs1_block_t off;
+    lfs1_block_t size;
+    lfs1_block_t i;
+    lfs1_block_t ack;
+    uint32_t *buffer;
+} lfs1_free_t;
+
+// The littlefs type
+typedef struct lfs1 {
+    const struct lfs1_config *cfg;
+
+    lfs1_block_t root[2];
+    lfs1_file_t *files;
+    lfs1_dir_t *dirs;
+
+    lfs1_cache_t rcache;
+    lfs1_cache_t pcache;
+
+    lfs1_free_t free;
+    bool deorphaned;
+    bool moving;
+} lfs1_t;
+
+
+/// Filesystem functions ///
+
+// Format a block device with the littlefs
+//
+// Requires a littlefs object and config struct. This clobbers the littlefs
+// object, and does not leave the filesystem mounted. The config struct must
+// be zeroed for defaults and backwards compatibility.
+//
+// Returns a negative error code on failure.
+int lfs1_format(lfs1_t *lfs1, const struct lfs1_config *config);
+
+// Mounts a littlefs
+//
+// Requires a littlefs object and config struct. Multiple filesystems
+// may be mounted simultaneously with multiple littlefs objects. Both
+// lfs1 and config must be allocated while mounted. The config struct must
+// be zeroed for defaults and backwards compatibility.
+//
+// Returns a negative error code on failure.
+int lfs1_mount(lfs1_t *lfs1, const struct lfs1_config *config);
+
+// Unmounts a littlefs
+//
+// Does nothing besides releasing any allocated resources.
+// Returns a negative error code on failure.
+int lfs1_unmount(lfs1_t *lfs1);
+
+/// General operations ///
+
+// Removes a file or directory
+//
+// If removing a directory, the directory must be empty.
+// Returns a negative error code on failure.
+int lfs1_remove(lfs1_t *lfs1, const char *path);
+
+// Rename or move a file or directory
+//
+// If the destination exists, it must match the source in type.
+// If the destination is a directory, the directory must be empty.
+//
+// Returns a negative error code on failure.
+int lfs1_rename(lfs1_t *lfs1, const char *oldpath, const char *newpath);
+
+// Find info about a file or directory
+//
+// Fills out the info structure, based on the specified file or directory.
+// Returns a negative error code on failure.
+int lfs1_stat(lfs1_t *lfs1, const char *path, struct lfs1_info *info);
+
+
+/// File operations ///
+
+// Open a file
+//
+// The mode that the file is opened in is determined by the flags, which
+// are values from the enum lfs1_open_flags that are bitwise-ored together.
+//
+// Returns a negative error code on failure.
+int lfs1_file_open(lfs1_t *lfs1, lfs1_file_t *file,
+        const char *path, int flags);
+
+// Open a file with extra configuration
+//
+// The mode that the file is opened in is determined by the flags, which
+// are values from the enum lfs1_open_flags that are bitwise-ored together.
+//
+// The config struct provides additional config options per file as described
+// above. The config struct must be allocated while the file is open, and the
+// config struct must be zeroed for defaults and backwards compatibility.
+//
+// Returns a negative error code on failure.
+int lfs1_file_opencfg(lfs1_t *lfs1, lfs1_file_t *file,
+        const char *path, int flags,
+        const struct lfs1_file_config *config);
+
+// Close a file
+//
+// Any pending writes are written out to storage as though
+// sync had been called and releases any allocated resources.
+//
+// Returns a negative error code on failure.
+int lfs1_file_close(lfs1_t *lfs1, lfs1_file_t *file);
+
+// Synchronize a file on storage
+//
+// Any pending writes are written out to storage.
+// Returns a negative error code on failure.
+int lfs1_file_sync(lfs1_t *lfs1, lfs1_file_t *file);
+
+// Read data from file
+//
+// Takes a buffer and size indicating where to store the read data.
+// Returns the number of bytes read, or a negative error code on failure.
+lfs1_ssize_t lfs1_file_read(lfs1_t *lfs1, lfs1_file_t *file,
+        void *buffer, lfs1_size_t size);
+
+// Write data to file
+//
+// Takes a buffer and size indicating the data to write. The file will not
+// actually be updated on the storage until either sync or close is called.
+//
+// Returns the number of bytes written, or a negative error code on failure.
+lfs1_ssize_t lfs1_file_write(lfs1_t *lfs1, lfs1_file_t *file,
+        const void *buffer, lfs1_size_t size);
+
+// Change the position of the file
+//
+// The change in position is determined by the offset and whence flag.
+// Returns the old position of the file, or a negative error code on failure.
+lfs1_soff_t lfs1_file_seek(lfs1_t *lfs1, lfs1_file_t *file,
+        lfs1_soff_t off, int whence);
+
+// Truncates the size of the file to the specified size
+//
+// Returns a negative error code on failure.
+int lfs1_file_truncate(lfs1_t *lfs1, lfs1_file_t *file, lfs1_off_t size);
+
+// Return the position of the file
+//
+// Equivalent to lfs1_file_seek(lfs1, file, 0, LFS1_SEEK_CUR)
+// Returns the position of the file, or a negative error code on failure.
+lfs1_soff_t lfs1_file_tell(lfs1_t *lfs1, lfs1_file_t *file);
+
+// Change the position of the file to the beginning of the file
+//
+// Equivalent to lfs1_file_seek(lfs1, file, 0, LFS1_SEEK_CUR)
+// Returns a negative error code on failure.
+int lfs1_file_rewind(lfs1_t *lfs1, lfs1_file_t *file);
+
+// Return the size of the file
+//
+// Similar to lfs1_file_seek(lfs1, file, 0, LFS1_SEEK_END)
+// Returns the size of the file, or a negative error code on failure.
+lfs1_soff_t lfs1_file_size(lfs1_t *lfs1, lfs1_file_t *file);
+
+
+/// Directory operations ///
+
+// Create a directory
+//
+// Returns a negative error code on failure.
+int lfs1_mkdir(lfs1_t *lfs1, const char *path);
+
+// Open a directory
+//
+// Once open a directory can be used with read to iterate over files.
+// Returns a negative error code on failure.
+int lfs1_dir_open(lfs1_t *lfs1, lfs1_dir_t *dir, const char *path);
+
+// Close a directory
+//
+// Releases any allocated resources.
+// Returns a negative error code on failure.
+int lfs1_dir_close(lfs1_t *lfs1, lfs1_dir_t *dir);
+
+// Read an entry in the directory
+//
+// Fills out the info structure, based on the specified file or directory.
+// Returns a negative error code on failure.
+int lfs1_dir_read(lfs1_t *lfs1, lfs1_dir_t *dir, struct lfs1_info *info);
+
+// Change the position of the directory
+//
+// The new off must be a value previous returned from tell and specifies
+// an absolute offset in the directory seek.
+//
+// Returns a negative error code on failure.
+int lfs1_dir_seek(lfs1_t *lfs1, lfs1_dir_t *dir, lfs1_off_t off);
+
+// Return the position of the directory
+//
+// The returned offset is only meant to be consumed by seek and may not make
+// sense, but does indicate the current position in the directory iteration.
+//
+// Returns the position of the directory, or a negative error code on failure.
+lfs1_soff_t lfs1_dir_tell(lfs1_t *lfs1, lfs1_dir_t *dir);
+
+// Change the position of the directory to the beginning of the directory
+//
+// Returns a negative error code on failure.
+int lfs1_dir_rewind(lfs1_t *lfs1, lfs1_dir_t *dir);
+
+
+/// Miscellaneous littlefs specific operations ///
+
+// Traverse through all blocks in use by the filesystem
+//
+// The provided callback will be called with each block address that is
+// currently in use by the filesystem. This can be used to determine which
+// blocks are in use or how much of the storage is available.
+//
+// Returns a negative error code on failure.
+int lfs1_traverse(lfs1_t *lfs1, int (*cb)(void*, lfs1_block_t), void *data);
+
+// Prunes any recoverable errors that may have occured in the filesystem
+//
+// Not needed to be called by user unless an operation is interrupted
+// but the filesystem is still mounted. This is already called on first
+// allocation.
+//
+// Returns a negative error code on failure.
+int lfs1_deorphan(lfs1_t *lfs1);
+
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif
diff --git a/lib/littlefs/lfs1_util.c b/lib/littlefs/lfs1_util.c
new file mode 100644
index 0000000000..3832a5ddb3
--- /dev/null
+++ b/lib/littlefs/lfs1_util.c
@@ -0,0 +1,31 @@
+/*
+ * lfs1 util functions
+ *
+ * Copyright (c) 2017, Arm Limited. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include "lfs1_util.h"
+
+// Only compile if user does not provide custom config
+#ifndef LFS1_CONFIG
+
+
+// Software CRC implementation with small lookup table
+void lfs1_crc(uint32_t *restrict crc, const void *buffer, size_t size) {
+    static const uint32_t rtable[16] = {
+        0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
+        0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
+        0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
+        0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
+    };
+
+    const uint8_t *data = buffer;
+
+    for (size_t i = 0; i < size; i++) {
+        *crc = (*crc >> 4) ^ rtable[(*crc ^ (data[i] >> 0)) & 0xf];
+        *crc = (*crc >> 4) ^ rtable[(*crc ^ (data[i] >> 4)) & 0xf];
+    }
+}
+
+
+#endif
diff --git a/lib/littlefs/lfs1_util.h b/lib/littlefs/lfs1_util.h
new file mode 100644
index 0000000000..b33b6a7adc
--- /dev/null
+++ b/lib/littlefs/lfs1_util.h
@@ -0,0 +1,186 @@
+/*
+ * lfs1 utility functions
+ *
+ * Copyright (c) 2017, Arm Limited. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#ifndef LFS1_UTIL_H
+#define LFS1_UTIL_H
+
+// Users can override lfs1_util.h with their own configuration by defining
+// LFS1_CONFIG as a header file to include (-DLFS1_CONFIG=lfs1_config.h).
+//
+// If LFS1_CONFIG is used, none of the default utils will be emitted and must be
+// provided by the config file. To start I would suggest copying lfs1_util.h and
+// modifying as needed.
+#ifdef LFS1_CONFIG
+#define LFS1_STRINGIZE(x) LFS1_STRINGIZE2(x)
+#define LFS1_STRINGIZE2(x) #x
+#include LFS1_STRINGIZE(LFS1_CONFIG)
+#else
+
+// System includes
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+#ifndef LFS1_NO_MALLOC
+#include <stdlib.h>
+#endif
+#ifndef LFS1_NO_ASSERT
+#include <assert.h>
+#endif
+#if !defined(LFS1_NO_DEBUG) || !defined(LFS1_NO_WARN) || !defined(LFS1_NO_ERROR)
+#include <stdio.h>
+#endif
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+
+// Macros, may be replaced by system specific wrappers. Arguments to these
+// macros must not have side-effects as the macros can be removed for a smaller
+// code footprint
+
+// Logging functions
+#ifndef LFS1_NO_DEBUG
+#define LFS1_DEBUG(fmt, ...) \
+    printf("lfs1 debug:%d: " fmt "\n", __LINE__, __VA_ARGS__)
+#else
+#define LFS1_DEBUG(fmt, ...)
+#endif
+
+#ifndef LFS1_NO_WARN
+#define LFS1_WARN(fmt, ...) \
+    printf("lfs1 warn:%d: " fmt "\n", __LINE__, __VA_ARGS__)
+#else
+#define LFS1_WARN(fmt, ...)
+#endif
+
+#ifndef LFS1_NO_ERROR
+#define LFS1_ERROR(fmt, ...) \
+    printf("lfs1 error:%d: " fmt "\n", __LINE__, __VA_ARGS__)
+#else
+#define LFS1_ERROR(fmt, ...)
+#endif
+
+// Runtime assertions
+#ifndef LFS1_NO_ASSERT
+#define LFS1_ASSERT(test) assert(test)
+#else
+#define LFS1_ASSERT(test)
+#endif
+
+
+// Builtin functions, these may be replaced by more efficient
+// toolchain-specific implementations. LFS1_NO_INTRINSICS falls back to a more
+// expensive basic C implementation for debugging purposes
+
+// Min/max functions for unsigned 32-bit numbers
+static inline uint32_t lfs1_max(uint32_t a, uint32_t b) {
+    return (a > b) ? a : b;
+}
+
+static inline uint32_t lfs1_min(uint32_t a, uint32_t b) {
+    return (a < b) ? a : b;
+}
+
+// Find the next smallest power of 2 less than or equal to a
+static inline uint32_t lfs1_npw2(uint32_t a) {
+#if !defined(LFS1_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
+    return 32 - __builtin_clz(a-1);
+#else
+    uint32_t r = 0;
+    uint32_t s;
+    a -= 1;
+    s = (a > 0xffff) << 4; a >>= s; r |= s;
+    s = (a > 0xff  ) << 3; a >>= s; r |= s;
+    s = (a > 0xf   ) << 2; a >>= s; r |= s;
+    s = (a > 0x3   ) << 1; a >>= s; r |= s;
+    return (r | (a >> 1)) + 1;
+#endif
+}
+
+// Count the number of trailing binary zeros in a
+// lfs1_ctz(0) may be undefined
+static inline uint32_t lfs1_ctz(uint32_t a) {
+#if !defined(LFS1_NO_INTRINSICS) && defined(__GNUC__)
+    return __builtin_ctz(a);
+#else
+    return lfs1_npw2((a & -a) + 1) - 1;
+#endif
+}
+
+// Count the number of binary ones in a
+static inline uint32_t lfs1_popc(uint32_t a) {
+#if !defined(LFS1_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
+    return __builtin_popcount(a);
+#else
+    a = a - ((a >> 1) & 0x55555555);
+    a = (a & 0x33333333) + ((a >> 2) & 0x33333333);
+    return (((a + (a >> 4)) & 0xf0f0f0f) * 0x1010101) >> 24;
+#endif
+}
+
+// Find the sequence comparison of a and b, this is the distance
+// between a and b ignoring overflow
+static inline int lfs1_scmp(uint32_t a, uint32_t b) {
+    return (int)(unsigned)(a - b);
+}
+
+// Convert from 32-bit little-endian to native order
+static inline uint32_t lfs1_fromle32(uint32_t a) {
+#if !defined(LFS1_NO_INTRINSICS) && ( \
+    (defined(  BYTE_ORDER  ) &&   BYTE_ORDER   ==   ORDER_LITTLE_ENDIAN  ) || \
+    (defined(__BYTE_ORDER  ) && __BYTE_ORDER   == __ORDER_LITTLE_ENDIAN  ) || \
+    (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__))
+    return a;
+#elif !defined(LFS1_NO_INTRINSICS) && ( \
+    (defined(  BYTE_ORDER  ) &&   BYTE_ORDER   ==   ORDER_BIG_ENDIAN  ) || \
+    (defined(__BYTE_ORDER  ) && __BYTE_ORDER   == __ORDER_BIG_ENDIAN  ) || \
+    (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__))
+    return __builtin_bswap32(a);
+#else
+    return (((uint8_t*)&a)[0] <<  0) |
+           (((uint8_t*)&a)[1] <<  8) |
+           (((uint8_t*)&a)[2] << 16) |
+           (((uint8_t*)&a)[3] << 24);
+#endif
+}
+
+// Convert to 32-bit little-endian from native order
+static inline uint32_t lfs1_tole32(uint32_t a) {
+    return lfs1_fromle32(a);
+}
+
+// Calculate CRC-32 with polynomial = 0x04c11db7
+void lfs1_crc(uint32_t *crc, const void *buffer, size_t size);
+
+// Allocate memory, only used if buffers are not provided to littlefs
+static inline void *lfs1_malloc(size_t size) {
+#ifndef LFS1_NO_MALLOC
+    return malloc(size);
+#else
+    (void)size;
+    return NULL;
+#endif
+}
+
+// Deallocate memory, only used if buffers are not provided to littlefs
+static inline void lfs1_free(void *p) {
+#ifndef LFS1_NO_MALLOC
+    free(p);
+#else
+    (void)p;
+#endif
+}
+
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif
+#endif