Move bit reader files to vpx_dsp

Change-Id: Ib1cb1fbe92a39ff5312cee069559be6d3ea458d0

1 files changed, 140 insertions, 0 deletions

diff --git a/vpx_dsp/vp9_reader.h b/vpx_dsp/vp9_reader.h
new file mode 100644
index 000000000..f022fb1cc
--- /dev/null
+++ b/vpx_dsp/vp9_reader.h
@@ -0,0 +1,140 @@
+/*
+ *  Copyright (c) 2010 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.
+ */
+
+#ifndef VP9_DECODER_VP9_READER_H_
+#define VP9_DECODER_VP9_READER_H_
+
+#include <stddef.h>
+#include <limits.h>
+
+#include "./vpx_config.h"
+#include "vpx_ports/mem.h"
+#include "vpx/vp8dx.h"
+#include "vpx/vpx_integer.h"
+#include "vpx_dsp/vp9_prob.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef size_t BD_VALUE;
+
+#define BD_VALUE_SIZE ((int)sizeof(BD_VALUE) * CHAR_BIT)
+
+// This is meant to be a large, positive constant that can still be efficiently
+// loaded as an immediate (on platforms like ARM, for example).
+// Even relatively modest values like 100 would work fine.
+#define LOTS_OF_BITS 0x40000000
+
+typedef struct {
+  // Be careful when reordering this struct, it may impact the cache negatively.
+  BD_VALUE value;
+  unsigned int range;
+  int count;
+  const uint8_t *buffer_end;
+  const uint8_t *buffer;
+  vpx_decrypt_cb decrypt_cb;
+  void *decrypt_state;
+  uint8_t clear_buffer[sizeof(BD_VALUE) + 1];
+} vp9_reader;
+
+int vp9_reader_init(vp9_reader *r,
+                    const uint8_t *buffer,
+                    size_t size,
+                    vpx_decrypt_cb decrypt_cb,
+                    void *decrypt_state);
+
+void vp9_reader_fill(vp9_reader *r);
+
+const uint8_t *vp9_reader_find_end(vp9_reader *r);
+
+static INLINE int vp9_reader_has_error(vp9_reader *r) {
+  // Check if we have reached the end of the buffer.
+  //
+  // Variable 'count' stores the number of bits in the 'value' buffer, minus
+  // 8. The top byte is part of the algorithm, and the remainder is buffered
+  // to be shifted into it. So if count == 8, the top 16 bits of 'value' are
+  // occupied, 8 for the algorithm and 8 in the buffer.
+  //
+  // When reading a byte from the user's buffer, count is filled with 8 and
+  // one byte is filled into the value buffer. When we reach the end of the
+  // data, count is additionally filled with LOTS_OF_BITS. So when
+  // count == LOTS_OF_BITS - 1, the user's data has been exhausted.
+  //
+  // 1 if we have tried to decode bits after the end of stream was encountered.
+  // 0 No error.
+  return r->count > BD_VALUE_SIZE && r->count < LOTS_OF_BITS;
+}
+
+static INLINE int vp9_read(vp9_reader *r, int prob) {
+  unsigned int bit = 0;
+  BD_VALUE value;
+  BD_VALUE bigsplit;
+  int count;
+  unsigned int range;
+  unsigned int split = (r->range * prob + (256 - prob)) >> CHAR_BIT;
+
+  if (r->count < 0)
+    vp9_reader_fill(r);
+
+  value = r->value;
+  count = r->count;
+
+  bigsplit = (BD_VALUE)split << (BD_VALUE_SIZE - CHAR_BIT);
+
+  range = split;
+
+  if (value >= bigsplit) {
+    range = r->range - split;
+    value = value - bigsplit;
+    bit = 1;
+  }
+
+  {
+    register unsigned int shift = vp9_norm[range];
+    range <<= shift;
+    value <<= shift;
+    count -= shift;
+  }
+  r->value = value;
+  r->count = count;
+  r->range = range;
+
+  return bit;
+}
+
+static INLINE int vp9_read_bit(vp9_reader *r) {
+  return vp9_read(r, 128);  // vp9_prob_half
+}
+
+static INLINE int vp9_read_literal(vp9_reader *r, int bits) {
+  int literal = 0, bit;
+
+  for (bit = bits - 1; bit >= 0; bit--)
+    literal |= vp9_read_bit(r) << bit;
+
+  return literal;
+}
+
+static INLINE int vp9_read_tree(vp9_reader *r, const vp9_tree_index *tree,
+                                const vp9_prob *probs) {
+  vp9_tree_index i = 0;
+
+  while ((i = tree[i + vp9_read(r, probs[i >> 1])]) > 0)
+    continue;
+
+  return -i;
+}
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // VP9_DECODER_VP9_READER_H_