1 files changed, 20 insertions, 1 deletions

diff --git a/media/libvpx/libvpx/vpx_dsp/bitwriter_buffer.c b/media/libvpx/libvpx/vpx_dsp/bitwriter_buffer.c
index 7a7e96f02e..b3a2490f2c 100644
--- a/media/libvpx/libvpx/vpx_dsp/bitwriter_buffer.c
+++ b/media/libvpx/libvpx/vpx_dsp/bitwriter_buffer.c
@@ -8,24 +8,43 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include <assert.h>
 #include <limits.h>
 #include <stdlib.h>
 
 #include "./vpx_config.h"
 #include "./bitwriter_buffer.h"
 
+void vpx_wb_init(struct vpx_write_bit_buffer *wb, uint8_t *bit_buffer,
+                 size_t size) {
+  wb->error = 0;
+  wb->bit_offset = 0;
+  wb->size = size;
+  wb->bit_buffer = bit_buffer;
+}
+
+int vpx_wb_has_error(const struct vpx_write_bit_buffer *wb) {
+  return wb->error;
+}
+
 size_t vpx_wb_bytes_written(const struct vpx_write_bit_buffer *wb) {
+  assert(!wb->error);
   return wb->bit_offset / CHAR_BIT + (wb->bit_offset % CHAR_BIT > 0);
 }
 
 void vpx_wb_write_bit(struct vpx_write_bit_buffer *wb, int bit) {
+  if (wb->error) return;
   const int off = (int)wb->bit_offset;
   const int p = off / CHAR_BIT;
   const int q = CHAR_BIT - 1 - off % CHAR_BIT;
+  if ((size_t)p >= wb->size) {
+    wb->error = 1;
+    return;
+  }
   if (q == CHAR_BIT - 1) {
     wb->bit_buffer[p] = bit << q;
   } else {
-    wb->bit_buffer[p] &= ~(1 << q);
+    assert((wb->bit_buffer[p] & (1 << q)) == 0);
     wb->bit_buffer[p] |= bit << q;
   }
   wb->bit_offset = off + 1;