c72824786a
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@13769 a1c6a512-1295-4272-9138-f99709370657
107 lines
3.4 KiB
C
107 lines
3.4 KiB
C
/*
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* Common bit i/o utils
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* Copyright (c) 2000, 2001 Fabrice Bellard.
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* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
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*/
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/**
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* @file common.c
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* common internal api.
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*/
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#include "avcodec.h"
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const uint8_t ff_sqrt_tab[128]={
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0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
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9, 9, 9, 9,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,11,11,11,11,11,11,11
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};
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const uint8_t ff_log2_tab[256]={
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0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
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5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
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};
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/**
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* init GetBitContext.
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* @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
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* because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
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* @param bit_size the size of the buffer in bits
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*/
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void init_get_bits(GetBitContext *s,
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const uint8_t *buffer, int bit_size)
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{
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const int buffer_size= (bit_size+7)>>3;
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s->buffer= buffer;
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s->size_in_bits= bit_size;
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s->buffer_end= buffer + buffer_size;
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s->index=0;
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{
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OPEN_READER(re, s)
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UPDATE_CACHE(re, s)
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UPDATE_CACHE(re, s)
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CLOSE_READER(re, s)
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}
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}
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/**
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* reads 0-32 bits.
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*/
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unsigned int get_bits_long(GetBitContext *s, int n){
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if(n<=17) return get_bits(s, n);
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else{
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int ret= get_bits(s, 16) << (n-16);
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return ret | get_bits(s, n-16);
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}
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}
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/**
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* shows 0-32 bits.
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*/
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unsigned int show_bits_long(GetBitContext *s, int n){
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if(n<=17) return show_bits(s, n);
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else{
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GetBitContext gb= *s;
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int ret= get_bits_long(s, n);
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*s= gb;
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return ret;
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}
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}
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void align_get_bits(GetBitContext *s)
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{
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int n= (-get_bits_count(s)) & 7;
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if(n) skip_bits(s, n);
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}
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int check_marker(GetBitContext *s, const char *msg)
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{
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(void)msg;
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int bit= get_bits1(s);
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return bit;
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}
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