Import aom library

This is the reference implementation for the Alliance for Open Media's av1 video code.

The commit used was 4d668d7feb1f8abd809d1bca0418570a7f142a36.

third_party/aom/aom_dsp/bitwriter_buffer.c

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2016, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 2 Clause License and
+ * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+ * was not distributed with this source code in the LICENSE file, you can
+ * obtain it at www.aomedia.org/license/software. If the Alliance for Open
+ * Media Patent License 1.0 was not distributed with this source code in the
+ * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+ */
+
+#include <limits.h>
+#include <stdlib.h>
+
+#include "./aom_config.h"
+#include "./bitwriter_buffer.h"
+
+uint32_t aom_wb_bytes_written(const struct aom_write_bit_buffer *wb) {
+  return wb->bit_offset / CHAR_BIT + (wb->bit_offset % CHAR_BIT > 0);
+}
+
+void aom_wb_write_bit(struct aom_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) {
+    // Zero next char and write bit
+    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 aom_wb_overwrite_bit(struct aom_write_bit_buffer *wb, int bit) {
+  // Do not zero bytes but overwrite exisiting values
+  const int off = (int)wb->bit_offset;
+  const int p = off / CHAR_BIT;
+  const int q = CHAR_BIT - 1 - off % CHAR_BIT;
+  wb->bit_buffer[p] &= ~(1 << q);
+  wb->bit_buffer[p] |= bit << q;
+  wb->bit_offset = off + 1;
+}
+
+void aom_wb_write_literal(struct aom_write_bit_buffer *wb, int data, int bits) {
+  int bit;
+  for (bit = bits - 1; bit >= 0; bit--) aom_wb_write_bit(wb, (data >> bit) & 1);
+}
+
+void aom_wb_overwrite_literal(struct aom_write_bit_buffer *wb, int data,
+                              int bits) {
+  int bit;
+  for (bit = bits - 1; bit >= 0; bit--)
+    aom_wb_overwrite_bit(wb, (data >> bit) & 1);
+}
+
+void aom_wb_write_inv_signed_literal(struct aom_write_bit_buffer *wb, int data,
+                                     int bits) {
+  aom_wb_write_literal(wb, data, bits + 1);
+}