libvpx: Pull from upstream

source/libvpx/vp9/encoder/vp9_write_bit_buffer.c

+/*
+ *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "vp9/encoder/vp9_write_bit_buffer.h"
+
+size_t vp9_rb_bytes_written(struct vp9_write_bit_buffer *wb) {
+  return wb->bit_offset / CHAR_BIT + (wb->bit_offset % CHAR_BIT > 0);
+}
+
+void vp9_wb_write_bit(struct vp9_write_bit_buffer *wb, int bit) {
+  const int off = (int)wb->bit_offset;
+  const int p = off / CHAR_BIT;
+  const int q = CHAR_BIT - 1 - off % CHAR_BIT;
+  if (q == CHAR_BIT -1) {
+    wb->bit_buffer[p] = bit << q;
+  } else {
+    wb->bit_buffer[p] &= ~(1 << q);
+    wb->bit_buffer[p] |= bit << q;
+  }
+  wb->bit_offset = off + 1;
+}
+
+void vp9_wb_write_literal(struct vp9_write_bit_buffer *wb, int data, int bits) {
+  int bit;
+  for (bit = bits - 1; bit >= 0; bit--)
+    vp9_wb_write_bit(wb, (data >> bit) & 1);
+}