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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 
22 typedef 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 
vp8_cost_branch(const unsigned int ct[2],vp8_prob p)45 static __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 
vp8_treed_write(vp8_writer * const w,vp8_tree t,const vp8_prob * const p,int v,int n)56 static __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 }
vp8_write_token(vp8_writer * const w,vp8_tree t,const vp8_prob * const p,vp8_token * const x)75 static __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 
vp8_treed_cost(vp8_tree t,const vp8_prob * const p,int v,int n)86 static __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 }
vp8_cost_token(vp8_tree t,const vp8_prob * const p,vp8_token * const x)106 static __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 
118 void vp8_cost_tokens(
119     int *Costs, const vp8_prob *, vp8_tree
120 );
121 
122 #endif
123