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/bitreader_buffer.c

@@ -0,0 +1,47 @@
+/*
+ * 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 "./aom_config.h"
+#include "./bitreader_buffer.h"
+
+size_t aom_rb_bytes_read(struct aom_read_bit_buffer *rb) {
+  return (rb->bit_offset + 7) >> 3;
+}
+
+int aom_rb_read_bit(struct aom_read_bit_buffer *rb) {
+  const uint32_t off = rb->bit_offset;
+  const uint32_t p = off >> 3;
+  const int q = 7 - (int)(off & 0x7);
+  if (rb->bit_buffer + p < rb->bit_buffer_end) {
+    const int bit = (rb->bit_buffer[p] >> q) & 1;
+    rb->bit_offset = off + 1;
+    return bit;
+  } else {
+    rb->error_handler(rb->error_handler_data);
+    return 0;
+  }
+}
+
+int aom_rb_read_literal(struct aom_read_bit_buffer *rb, int bits) {
+  int value = 0, bit;
+  for (bit = bits - 1; bit >= 0; bit--) value |= aom_rb_read_bit(rb) << bit;
+  return value;
+}
+
+int aom_rb_read_signed_literal(struct aom_read_bit_buffer *rb, int bits) {
+  const int value = aom_rb_read_literal(rb, bits);
+  return aom_rb_read_bit(rb) ? -value : value;
+}
+
+int aom_rb_read_inv_signed_literal(struct aom_read_bit_buffer *rb, int bits) {
+  const int nbits = sizeof(unsigned) * 8 - bits - 1;
+  const unsigned value = (unsigned)aom_rb_read_literal(rb, bits + 1) << nbits;
+  return ((int)value) >> nbits;
+}