1/*
2 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11
12#ifndef __INC_TREEWRITER_H
13#define __INC_TREEWRITER_H
14
15/* Trees map alphabets into huffman-like codes suitable for an arithmetic
16   bit coder.  Timothy S Murphy  11 October 2004 */
17
18#include "treecoder.h"
19
20#include "boolhuff.h"       /* for now */
21
22typedef BOOL_CODER vp8_writer;
23
24#define vp8_write vp8_encode_bool
25#define vp8_write_literal vp8_encode_value
26#define vp8_write_bit( W, V) vp8_write( W, V, vp8_prob_half)
27
28#define vp8bc_write vp8bc_write_bool
29#define vp8bc_write_literal vp8bc_write_bits
30#define vp8bc_write_bit( W, V) vp8bc_write_bits( W, V, 1)
31
32
33/* Approximate length of an encoded bool in 256ths of a bit at given prob */
34
35#define vp8_cost_zero( x) ( vp8_prob_cost[x])
36#define vp8_cost_one( x)  vp8_cost_zero( vp8_complement(x))
37
38#define vp8_cost_bit( x, b) vp8_cost_zero( (b)?  vp8_complement(x) : (x) )
39
40/* VP8BC version is scaled by 2^20 rather than 2^8; see bool_coder.h */
41
42
43/* Both of these return bits, not scaled bits. */
44
45static __inline unsigned int vp8_cost_branch(const unsigned int ct[2], vp8_prob p)
46{
47    /* Imitate existing calculation */
48
49    return ((ct[0] * vp8_cost_zero(p))
50            + (ct[1] * vp8_cost_one(p))) >> 8;
51}
52
53/* Small functions to write explicit values and tokens, as well as
54   estimate their lengths. */
55
56static __inline void vp8_treed_write
57(
58    vp8_writer *const w,
59    vp8_tree t,
60    const vp8_prob *const p,
61    int v,
62    int n               /* number of bits in v, assumed nonzero */
63)
64{
65    vp8_tree_index i = 0;
66
67    do
68    {
69        const int b = (v >> --n) & 1;
70        vp8_write(w, b, p[i>>1]);
71        i = t[i+b];
72    }
73    while (n);
74}
75static __inline void vp8_write_token
76(
77    vp8_writer *const w,
78    vp8_tree t,
79    const vp8_prob *const p,
80    vp8_token *const x
81)
82{
83    vp8_treed_write(w, t, p, x->value, x->Len);
84}
85
86static __inline int vp8_treed_cost(
87    vp8_tree t,
88    const vp8_prob *const p,
89    int v,
90    int n               /* number of bits in v, assumed nonzero */
91)
92{
93    int c = 0;
94    vp8_tree_index i = 0;
95
96    do
97    {
98        const int b = (v >> --n) & 1;
99        c += vp8_cost_bit(p[i>>1], b);
100        i = t[i+b];
101    }
102    while (n);
103
104    return c;
105}
106static __inline int vp8_cost_token
107(
108    vp8_tree t,
109    const vp8_prob *const p,
110    vp8_token *const x
111)
112{
113    return vp8_treed_cost(t, p, x->value, x->Len);
114}
115
116/* Fill array of costs for all possible token values. */
117
118void vp8_cost_tokens(
119    int *Costs, const vp8_prob *, vp8_tree
120);
121
122#endif
123