extmod: Add generic VFS sub-system.

This provides mp_vfs_XXX functions (eg mount, open, listdir) which are
agnostic to the underlying filesystem type, and just require an object with
the relevant filesystem-like methods (eg .mount, .open, .listidr) which can
then be mounted.

These mp_vfs_XXX functions would typically be used by a port to implement
the "uos" module, and mp_vfs_open would be the builtin open function.

This feature is controlled by MICROPY_VFS, disabled by default.

1 files changed, 97 insertions, 0 deletions

diff --git a/extmod/vfs_reader.c b/extmod/vfs_reader.c
new file mode 100644
index 0000000000..718bdeeb65
--- /dev/null
+++ b/extmod/vfs_reader.c
@@ -0,0 +1,97 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013-2017 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "py/nlr.h"
+#include "py/stream.h"
+#include "py/reader.h"
+#include "extmod/vfs.h"
+
+#if MICROPY_READER_VFS
+
+typedef struct _mp_reader_vfs_t {
+    mp_obj_t file;
+    uint16_t len;
+    uint16_t pos;
+    byte buf[24];
+} mp_reader_vfs_t;
+
+STATIC mp_uint_t mp_reader_vfs_readbyte(void *data) {
+    mp_reader_vfs_t *reader = (mp_reader_vfs_t*)data;
+    if (reader->pos >= reader->len) {
+        if (reader->len < sizeof(reader->buf)) {
+            return MP_READER_EOF;
+        } else {
+            int errcode;
+            reader->len = mp_stream_rw(reader->file, reader->buf, sizeof(reader->buf),
+                &errcode, MP_STREAM_RW_READ | MP_STREAM_RW_ONCE);
+            if (errcode != 0) {
+                // TODO handle errors properly
+                return MP_READER_EOF;
+            }
+            if (reader->len == 0) {
+                return MP_READER_EOF;
+            }
+            reader->pos = 0;
+        }
+    }
+    return reader->buf[reader->pos++];
+}
+
+STATIC void mp_reader_vfs_close(void *data) {
+    mp_reader_vfs_t *reader = (mp_reader_vfs_t*)data;
+    mp_stream_close(reader->file);
+    m_del_obj(mp_reader_vfs_t, reader);
+}
+
+int mp_reader_new_file(mp_reader_t *reader, const char *filename) {
+    mp_reader_vfs_t *rf = m_new_obj_maybe(mp_reader_vfs_t);
+    if (rf == NULL) {
+        return MP_ENOMEM;
+    }
+    // TODO we really should just let this function raise a uPy exception
+    nlr_buf_t nlr;
+    if (nlr_push(&nlr) == 0) {
+        mp_obj_t arg = mp_obj_new_str(filename, strlen(filename), false);
+        rf->file = mp_vfs_open(1, &arg, (mp_map_t*)&mp_const_empty_map);
+        int errcode;
+        rf->len = mp_stream_rw(rf->file, rf->buf, sizeof(rf->buf), &errcode, MP_STREAM_RW_READ | MP_STREAM_RW_ONCE);
+        if (errcode != 0) {
+            return errcode;
+        }
+    } else {
+        return MP_ENOENT; // assume error was "file not found"
+    }
+    rf->pos = 0;
+    reader->data = rf;
+    reader->readbyte = mp_reader_vfs_readbyte;
+    reader->close = mp_reader_vfs_close;
+    return 0; // success
+}
+
+#endif // MICROPY_READER_VFS