Bytecode uint varlen encoding: support arbitrary values.

2 files changed, 25 insertions, 15 deletions

diff --git a/py/emitbc.c b/py/emitbc.c
index 269fcdeb7e..4fe7ae8cd0 100644
--- a/py/emitbc.c
+++ b/py/emitbc.c
@@ -108,19 +108,19 @@ STATIC void emit_write_byte_code_byte_byte(emit_t* emit, byte b1, uint b2) {
 }
 
 STATIC void emit_write_byte_code_uint(emit_t* emit, uint num) {
-    if (num <= 127) { // fits in 0x7f
-        // fit argument in single byte
-        byte* c = emit_get_cur_to_write_byte_code(emit, 1);
-        c[0] = num;
-    } else if (num <= 16383) { // fits in 0x3fff
-        // fit argument in two bytes
-        byte* c = emit_get_cur_to_write_byte_code(emit, 2);
-        c[0] = (num >> 8) | 0x80;
-        c[1] = num;
-    } else {
-        // larger numbers not implemented/supported
-        assert(0);
-    }
+    // We store each 7 bits in a separate byte, and that's how many bytes needed
+    byte buf[(BYTES_PER_WORD * 8 + 7) / 7];
+    byte *p = buf + sizeof(buf);
+    // We encode in little-ending order, but store in big-endian, to help decoding
+    do {
+        *--p = num & 0x7f;
+        num >>= 7;
+    } while (num != 0);
+    byte* c = emit_get_cur_to_write_byte_code(emit, buf + sizeof(buf) - p);
+    while (p != buf + sizeof(buf) - 1) {
+        *c++ = *p++ | 0x80;
+    }
+    *c = *p;
 }
 
 // integers (for small ints) are stored as 24 bits, in excess
diff --git a/py/vm.c b/py/vm.c
index 573167b57d..0fdf5d4e31 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -38,10 +38,20 @@ typedef enum {
     UNWIND_JUMP,
 } mp_unwind_reason_t;
 
-#define DECODE_UINT do { unum = *ip++; if (unum > 127) { unum = ((unum & 0x3f) << 8) | (*ip++); } } while (0)
+#define DECODE_UINT { \
+    unum = 0; \
+    do { \
+        unum = (unum << 7) + (*ip & 0x7f); \
+    } while ((*ip++ & 0x80) != 0); \
+}
 #define DECODE_ULABEL do { unum = (ip[0] | (ip[1] << 8)); ip += 2; } while (0)
 #define DECODE_SLABEL do { unum = (ip[0] | (ip[1] << 8)) - 0x8000; ip += 2; } while (0)
-#define DECODE_QSTR do { qst = *ip++; if (qst > 127) { qst = ((qst & 0x3f) << 8) | (*ip++); } } while (0)
+#define DECODE_QSTR { \
+    qst = 0; \
+    do { \
+        qst = (qst << 7) + (*ip & 0x7f); \
+    } while ((*ip++ & 0x80) != 0); \
+}
 #define PUSH(val) *++sp = (val)
 #define POP() (*sp--)
 #define TOP() (*sp)