1/* Copyright (c) 2001-2011 Timothy B. Terriberry
2   Copyright (c) 2008-2009 Xiph.Org Foundation */
3/*
4   Redistribution and use in source and binary forms, with or without
5   modification, are permitted provided that the following conditions
6   are met:
7
8   - Redistributions of source code must retain the above copyright
9   notice, this list of conditions and the following disclaimer.
10
11   - Redistributions in binary form must reproduce the above copyright
12   notice, this list of conditions and the following disclaimer in the
13   documentation and/or other materials provided with the distribution.
14
15   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
18   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
19   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
22   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
23   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
24   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
25   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26*/
27
28#include "opus_types.h"
29#include "opus_defines.h"
30
31#if !defined(_entcode_H)
32# define _entcode_H (1)
33# include <limits.h>
34# include <stddef.h>
35# include "ecintrin.h"
36
37/*OPT: ec_window must be at least 32 bits, but if you have fast arithmetic on a
38   larger type, you can speed up the decoder by using it here.*/
39typedef opus_uint32           ec_window;
40typedef struct ec_ctx         ec_ctx;
41typedef struct ec_ctx         ec_enc;
42typedef struct ec_ctx         ec_dec;
43
44# define EC_WINDOW_SIZE ((int)sizeof(ec_window)*CHAR_BIT)
45
46/*The number of bits to use for the range-coded part of unsigned integers.*/
47# define EC_UINT_BITS   (8)
48
49/*The resolution of fractional-precision bit usage measurements, i.e.,
50   3 => 1/8th bits.*/
51# define BITRES 3
52
53/*The entropy encoder/decoder context.
54  We use the same structure for both, so that common functions like ec_tell()
55   can be used on either one.*/
56struct ec_ctx{
57   /*Buffered input/output.*/
58   unsigned char *buf;
59   /*The size of the buffer.*/
60   opus_uint32    storage;
61   /*The offset at which the last byte containing raw bits was read/written.*/
62   opus_uint32    end_offs;
63   /*Bits that will be read from/written at the end.*/
64   ec_window      end_window;
65   /*Number of valid bits in end_window.*/
66   int            nend_bits;
67   /*The total number of whole bits read/written.
68     This does not include partial bits currently in the range coder.*/
69   int            nbits_total;
70   /*The offset at which the next range coder byte will be read/written.*/
71   opus_uint32    offs;
72   /*The number of values in the current range.*/
73   opus_uint32    rng;
74   /*In the decoder: the difference between the top of the current range and
75      the input value, minus one.
76     In the encoder: the low end of the current range.*/
77   opus_uint32    val;
78   /*In the decoder: the saved normalization factor from ec_decode().
79     In the encoder: the number of oustanding carry propagating symbols.*/
80   opus_uint32    ext;
81   /*A buffered input/output symbol, awaiting carry propagation.*/
82   int            rem;
83   /*Nonzero if an error occurred.*/
84   int            error;
85};
86
87static OPUS_INLINE opus_uint32 ec_range_bytes(ec_ctx *_this){
88  return _this->offs;
89}
90
91static OPUS_INLINE unsigned char *ec_get_buffer(ec_ctx *_this){
92  return _this->buf;
93}
94
95static OPUS_INLINE int ec_get_error(ec_ctx *_this){
96  return _this->error;
97}
98
99/*Returns the number of bits "used" by the encoded or decoded symbols so far.
100  This same number can be computed in either the encoder or the decoder, and is
101   suitable for making coding decisions.
102  Return: The number of bits.
103          This will always be slightly larger than the exact value (e.g., all
104           rounding error is in the positive direction).*/
105static OPUS_INLINE int ec_tell(ec_ctx *_this){
106  return _this->nbits_total-EC_ILOG(_this->rng);
107}
108
109/*Returns the number of bits "used" by the encoded or decoded symbols so far.
110  This same number can be computed in either the encoder or the decoder, and is
111   suitable for making coding decisions.
112  Return: The number of bits scaled by 2**BITRES.
113          This will always be slightly larger than the exact value (e.g., all
114           rounding error is in the positive direction).*/
115opus_uint32 ec_tell_frac(ec_ctx *_this);
116
117#endif
118