libvpx: Add VP9 decoder.

source/libvpx/vp9/encoder/vp9_treewriter.h

+/*
+ *  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_ENCODER_VP9_TREEWRITER_H_
+#define VP9_ENCODER_VP9_TREEWRITER_H_
+
+/* Trees map alphabets into huffman-like codes suitable for an arithmetic
+   bit coder.  Timothy S Murphy  11 October 2004 */
+
+#include "vp9/common/vp9_treecoder.h"
+
+#include "vp9/encoder/vp9_boolhuff.h"       /* for now */
+
+typedef BOOL_CODER vp9_writer;
+
+#define vp9_write encode_bool
+#define vp9_write_literal vp9_encode_value
+#define vp9_write_bit(W, V) vp9_write(W, V, vp9_prob_half)
+
+/* Approximate length of an encoded bool in 256ths of a bit at given prob */
+
+#define vp9_cost_zero(x) (vp9_prob_cost[x])
+#define vp9_cost_one(x) vp9_cost_zero(vp9_complement(x))
+
+#define vp9_cost_bit(x, b) vp9_cost_zero((b) ? vp9_complement(x) : (x))
+
+/* VP8BC version is scaled by 2^20 rather than 2^8; see bool_coder.h */
+
+
+/* Both of these return bits, not scaled bits. */
+
+static __inline unsigned int cost_branch(const unsigned int ct[2],
+                                         vp9_prob p) {
+  /* Imitate existing calculation */
+  return ((ct[0] * vp9_cost_zero(p))
+          + (ct[1] * vp9_cost_one(p))) >> 8;
+}
+
+static __inline unsigned int cost_branch256(const unsigned int ct[2],
+                                            vp9_prob p) {
+  /* Imitate existing calculation */
+  return ((ct[0] * vp9_cost_zero(p))
+          + (ct[1] * vp9_cost_one(p)));
+}
+
+/* Small functions to write explicit values and tokens, as well as
+   estimate their lengths. */
+
+static __inline void treed_write(vp9_writer *const w,
+                                 vp9_tree t,
+                                 const vp9_prob *const p,
+                                 int v,
+                                 /* number of bits in v, assumed nonzero */
+                                 int n) {
+  vp9_tree_index i = 0;
+
+  do {
+    const int b = (v >> --n) & 1;
+    vp9_write(w, b, p[i >> 1]);
+    i = t[i + b];
+  } while (n);
+}
+
+static __inline void write_token(vp9_writer *const w,
+                                 vp9_tree t,
+                                 const vp9_prob *const p,
+                                 vp9_token *const x) {
+  treed_write(w, t, p, x->value, x->Len);
+}
+
+static __inline int treed_cost(vp9_tree t,
+                               const vp9_prob *const p,
+                               int v,
+                               /* number of bits in v, assumed nonzero */
+                               int n) {
+  int c = 0;
+  vp9_tree_index i = 0;
+
+  do {
+    const int b = (v >> --n) & 1;
+    c += vp9_cost_bit(p[i >> 1], b);
+    i = t[i + b];
+  } while (n);
+
+  return c;
+}
+
+static __inline int cost_token(vp9_tree t,
+                               const vp9_prob *const p,
+                               vp9_token *const x) {
+  return treed_cost(t, p, x->value, x->Len);
+}
+
+/* Fill array of costs for all possible token values. */
+
+void vp9_cost_tokens(int *Costs, const vp9_prob *, vp9_tree);
+
+void vp9_cost_tokens_skip(int *c, const vp9_prob *p, vp9_tree t);
+
+#endif