py/bc: Move mp_decode_uint_checked to py/bc.c.

dpgeorge · dpgeorge · commit 7429b8f58adf · 2025-02-26T16:16:59.000+11:00
Signed-off-by: Damien George &lt;damien@micropython.org&gt;
diff --git a/extmod/vfs_rom.c b/extmod/vfs_rom.c
@@ -102,23 +102,6 @@ struct _mp_obj_vfs_rom_t {
     const uint8_t *filesystem_end;
 };
 
-// Returns 0 for success, -1 for failure.
-static int mp_decode_uint_checked(const uint8_t **ptr, const uint8_t *ptr_max, mp_uint_t *value_out) {
-    mp_uint_t unum = 0;
-    byte val;
-    const uint8_t *p = *ptr;
-    do {
-        if (p >= ptr_max) {
-            return -1;
-        }
-        val = *p++;
-        unum = (unum << 7) | (val & 0x7f);
-    } while ((val & 0x80) != 0);
-    *ptr = p;
-    *value_out = unum;
-    return 0;
-}
-
 static record_kind_t extract_record(const uint8_t **fs, const uint8_t **fs_next, const uint8_t *fs_max) {
     mp_uint_t record_kind;
     if (mp_decode_uint_checked(fs, fs_max, &record_kind) != 0) {
diff --git a/py/bc.c b/py/bc.c
@@ -88,6 +88,24 @@ const byte *mp_decode_uint_skip(const byte *ptr) {
     return ptr;
 }
 
+// This function does bounds checking when decoding a value.
+// Returns 0 for success, -1 for failure.
+int mp_decode_uint_checked(const uint8_t **ptr, const uint8_t *ptr_max, mp_uint_t *value_out) {
+    mp_uint_t unum = 0;
+    byte val;
+    const uint8_t *p = *ptr;
+    do {
+        if (p >= ptr_max) {
+            return -1;
+        }
+        val = *p++;
+        unum = (unum << 7) | (val & 0x7f);
+    } while ((val & 0x80) != 0);
+    *ptr = p;
+    *value_out = unum;
+    return 0;
+}
+
 static NORETURN void fun_pos_args_mismatch(mp_obj_fun_bc_t *f, size_t expected, size_t given) {
     #if MICROPY_ERROR_REPORTING <= MICROPY_ERROR_REPORTING_TERSE
     // generic message, used also for other argument issues
diff --git a/py/bc.h b/py/bc.h
@@ -272,6 +272,7 @@ void mp_encode_uint(void *env, mp_encode_uint_allocator_t allocator, mp_uint_t v
 mp_uint_t mp_decode_uint(const byte **ptr);
 mp_uint_t mp_decode_uint_value(const byte *ptr);
 const byte *mp_decode_uint_skip(const byte *ptr);
+int mp_decode_uint_checked(const uint8_t **ptr, const uint8_t *ptr_max, mp_uint_t *value_out);
 
 mp_vm_return_kind_t mp_execute_bytecode(mp_code_state_t *code_state,
 #ifndef __cplusplus
