ref: 310af750eb5726b4143a43208f2bc03677c6f5db
dir: /libcelt/entcode.h/
/* Copyright (c) 2001-2011 Timothy B. Terriberry
Copyright (c) 2008-2009 Xiph.Org Foundation */
/*
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
- Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "celt_types.h"
#if !defined(_entcode_H)
# define _entcode_H (1)
# include <limits.h>
# include <stddef.h>
# include "ecintrin.h"
/*OPT: ec_window must be at least 32 bits, but if you have fast arithmetic on a
larger type, you can speed up the decoder by using it here.*/
typedef celt_uint32 ec_window;
typedef struct ec_ctx ec_ctx;
typedef struct ec_ctx ec_enc;
typedef struct ec_ctx ec_dec;
# define EC_WINDOW_SIZE ((int)sizeof(ec_window)*CHAR_BIT)
/*The number of bits to use for the range-coded part of unsigned integers.*/
# define EC_UINT_BITS (8)
/*The resolution of fractional-precision bit usage measurements, i.e.,
3 => 1/8th bits.*/
# define BITRES 3
/*The entropy encoder/decoder context.
We use the same structure for both, so that common functions like ec_tell()
can be used on either one.*/
struct ec_ctx{
/*Buffered input/output.*/
unsigned char *buf;
/*The size of the buffer.*/
celt_uint32 storage;
/*The offset at which the last byte containing raw bits was read/written.*/
celt_uint32 end_offs;
/*Bits that will be read from/written at the end.*/
ec_window end_window;
/*Number of valid bits in end_window.*/
int nend_bits;
/*The total number of whole bits read/written.
This does not include partial bits currently in the range coder.*/
int nbits_total;
/*The offset at which the next range coder byte will be read/written.*/
celt_uint32 offs;
/*The number of values in the current range.*/
celt_uint32 rng;
/*In the decoder: the difference between the top of the current range and
the input value, minus one.
In the encoder: the low end of the current range.*/
celt_uint32 val;
/*In the decoder: the saved normalization factor from ec_decode().
In the encoder: the number of oustanding carry propagating symbols.*/
celt_uint32 ext;
/*A buffered input/output symbol, awaiting carry propagation.*/
int rem;
/*Nonzero if an error occurred.*/
int error;
};
/*Shared functions.*/
static inline void ec_reset(ec_ctx *_this){
_this->offs=_this->end_offs=0;
}
static inline celt_uint32 ec_range_bytes(ec_ctx *_this){
return _this->offs;
}
static inline unsigned char *ec_get_buffer(ec_ctx *_this){
return _this->buf;
}
static inline int ec_get_error(ec_ctx *_this){
return _this->error;
}
/*Returns the number of bits "used" by the encoded or decoded symbols so far.
This same number can be computed in either the encoder or the decoder, and is
suitable for making coding decisions.
Return: The number of bits.
This will always be slightly larger than the exact value (e.g., all
rounding error is in the positive direction).*/
static inline int ec_tell(ec_ctx *_this){
return _this->nbits_total-EC_ILOG(_this->rng);
}
/*Returns the number of bits "used" by the encoded or decoded symbols so far.
This same number can be computed in either the encoder or the decoder, and is
suitable for making coding decisions.
Return: The number of bits scaled by 2**BITRES.
This will always be slightly larger than the exact value (e.g., all
rounding error is in the positive direction).*/
celt_uint32 ec_tell_frac(ec_ctx *_this);
#endif