135 lines
6.1 KiB
C
Executable File
135 lines
6.1 KiB
C
Executable File
/* (C) 2001-2008 Timothy B. Terriberry
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(C) 2008 Jean-Marc Valin */
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/*
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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- Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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- Neither the name of the Xiph.org Foundation nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#if !defined(_entdec_H)
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# define _entdec_H (1)
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# include "entcode.h"
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typedef struct ec_dec ec_dec;
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/*The entropy decoder.*/
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struct ec_dec{
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/*The buffer to decode.*/
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ec_byte_buffer *buf;
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/*The remainder of a buffered input symbol.*/
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int rem;
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/*The number of values in the current range.*/
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ec_uint32 rng;
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/*The difference between the input value and the lowest value in the current
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range.*/
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ec_uint32 dif;
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/*Normalization factor.*/
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ec_uint32 nrm;
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};
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/*Initializes the decoder.
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_buf: The input buffer to use.
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Return: 0 on success, or a negative value on error.*/
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void ec_dec_init(ec_dec *_this,ec_byte_buffer *_buf);
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/*Calculates the cumulative frequency for the next symbol.
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This can then be fed into the probability model to determine what that
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symbol is, and the additional frequency information required to advance to
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the next symbol.
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This function cannot be called more than once without a corresponding call to
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ec_dec_update(), or decoding will not proceed correctly.
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_ft: The total frequency of the symbols in the alphabet the next symbol was
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encoded with.
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Return: A cumulative frequency representing the encoded symbol.
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If the cumulative frequency of all the symbols before the one that
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was encoded was fl, and the cumulative frequency of all the symbols
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up to and including the one encoded is fh, then the returned value
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will fall in the range [fl,fh).*/
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unsigned ec_decode(ec_dec *_this,unsigned _ft);
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unsigned ec_decode_bin(ec_dec *_this,unsigned bits);
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/*Advance the decoder past the next symbol using the frequency information the
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symbol was encoded with.
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Exactly one call to ec_decode() must have been made so that all necessary
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intermediate calculations are performed.
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_fl: The cumulative frequency of all symbols that come before the symbol
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decoded.
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_fh: The cumulative frequency of all symbols up to and including the symbol
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decoded.
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Together with _fl, this defines the range [_fl,_fh) in which the value
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returned above must fall.
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_ft: The total frequency of the symbols in the alphabet the symbol decoded
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was encoded in.
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This must be the same as passed to the preceding call to ec_decode().*/
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void ec_dec_update(ec_dec *_this,unsigned _fl,unsigned _fh,
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unsigned _ft);
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/*Extracts a sequence of raw bits from the stream.
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The bits must have been encoded with ec_enc_bits().
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No call to ec_dec_update() is necessary after this call.
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_ftb: The number of bits to extract.
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This must be at least one, and no more than 32.
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Return: The decoded bits.*/
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ec_uint32 ec_dec_bits(ec_dec *_this,int _ftb);
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/*Extracts a sequence of raw bits from the stream.
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The bits must have been encoded with ec_enc_bits64().
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No call to ec_dec_update() is necessary after this call.
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_ftb: The number of bits to extract.
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This must be at least one, and no more than 64.
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Return: The decoded bits.*/
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ec_uint64 ec_dec_bits64(ec_dec *_this,int _ftb);
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/*Extracts a raw unsigned integer with a non-power-of-2 range from the stream.
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The bits must have been encoded with ec_enc_uint().
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No call to ec_dec_update() is necessary after this call.
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_ft: The number of integers that can be decoded (one more than the max).
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This must be at least one, and no more than 2**32-1.
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Return: The decoded bits.*/
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ec_uint32 ec_dec_uint(ec_dec *_this,ec_uint32 _ft);
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/*Extracts a raw unsigned integer with a non-power-of-2 range from the stream.
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The bits must have been encoded with ec_enc_uint64().
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No call to ec_dec_update() is necessary after this call.
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_ft: The number of integers that can be decoded (one more than the max).
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This must be at least one, and no more than 2**64-1.
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Return: The decoded bits.*/
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ec_uint64 ec_dec_uint64(ec_dec *_this,ec_uint64 _ft);
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/*Returns the number of bits "used" by the decoded symbols so far.
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The actual number of bits may be larger, due to rounding to whole bytes, or
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smaller, due to trailing zeros that were be stripped, so this is not an
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estimate of the true packet size.
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This same number can be computed by the encoder, and is suitable for making
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coding decisions.
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_b: The number of extra bits of precision to include.
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At most 16 will be accurate.
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Return: The number of bits scaled by 2**_b.
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This will always be slightly larger than the exact value (e.g., all
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rounding error is in the positive direction).*/
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long ec_dec_tell(ec_dec *_this,int _b);
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#endif
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