rockbox/apps/codecs/libwma/common.c

/*
 * Common bit i/o utils
 * Copyright (c) 2000, 2001 Fabrice Bellard.
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
 */

/**
 * @file common.c
 * common internal api.
 */

#include "common.h"

const uint8_t ff_sqrt_tab[128]={
        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,
        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,
        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,
        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
};

const uint8_t ff_log2_tab[256]={
        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,
        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,
        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,
        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,
        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,
        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,
        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,
        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
};

/**
 * init GetBitContext.
 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
 * @param bit_size the size of the buffer in bits
 */
void init_get_bits(GetBitContext *s,
                   const uint8_t *buffer, int bit_size)
{
    const int buffer_size= (bit_size+7)>>3;

    s->buffer= buffer;
    s->size_in_bits= bit_size;
    s->buffer_end= buffer + buffer_size;
    s->index=0;
    {
        OPEN_READER(re, s)
        UPDATE_CACHE(re, s)
        UPDATE_CACHE(re, s)
        CLOSE_READER(re, s)
    }
}

/** 
 * reads 0-32 bits.
 */
unsigned int get_bits_long(GetBitContext *s, int n){
    if(n<=17) return get_bits(s, n);
    else{
        int ret= get_bits(s, 16) << (n-16);
        return ret | get_bits(s, n-16);
    }
}

/** 
 * shows 0-32 bits.
 */
unsigned int show_bits_long(GetBitContext *s, int n){
    if(n<=17) return show_bits(s, n);
    else{
        GetBitContext gb= *s;
        int ret= get_bits_long(s, n);
        *s= gb;
        return ret;
    }
}

void align_get_bits(GetBitContext *s)
{
    int n= (-get_bits_count(s)) & 7;
    if(n) skip_bits(s, n);
}

int check_marker(GetBitContext *s, const char *msg)
{
    (void)msg;
    int bit= get_bits1(s);
    return bit;
}

/* VLC decoding */

//#define DEBUG_VLC

#define GET_DATA(v, table, i, wrap, size) \
{\
    const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
    switch(size) {\
    case 1:\
        v = *(const uint8_t *)ptr;\
        break;\
    case 2:\
        v = *(const uint16_t *)ptr;\
        break;\
    default:\
        v = *(const uint32_t *)ptr;\
        break;\
    }\
}

static int alloc_table(VLC *vlc, int size)
{
    int index;
    index = vlc->table_size;
    vlc->table_size += size;
    if (vlc->table_size > vlc->table_allocated) {
        vlc->table_allocated += (1 << vlc->bits);
        if (!vlc->table)
            return -1;
    }
    return index;
}

static int build_table(VLC *vlc, int table_nb_bits,
                int nb_codes,
                const void *bits, int bits_wrap, int bits_size,
                const void *codes, int codes_wrap, int codes_size,
                uint32_t code_prefix, int n_prefix)
{
    int i, j, k, n, table_size, table_index, nb, n1, index;
    uint32_t code;
    VLC_TYPE (*table)[2];

    table_size = 1 << table_nb_bits;
    table_index = alloc_table(vlc, table_size);
    if (table_index < 0)
        return -1;
    table = &vlc->table[table_index];

    for(i=0;i<table_size;i++)
    {
        table[i][1] = 0; //bits
        table[i][0] = -1; //codes
    }

    /* first pass: map codes and compute auxillary table sizes */
    for(i=0;i<nb_codes;i++)
    {
        GET_DATA(n, bits, i, bits_wrap, bits_size);
        GET_DATA(code, codes, i, codes_wrap, codes_size);
        /* we accept tables with holes */
        if (n <= 0)
            continue;
        /* if code matches the prefix, it is in the table */
        n -= n_prefix;
        if (n > 0 && (code >> n) == code_prefix)
        {
            if (n <= table_nb_bits)
            {
                /* no need to add another table */
                j = (code << (table_nb_bits - n)) & (table_size - 1);
                nb = 1 << (table_nb_bits - n);
                for(k=0;k<nb;k++)
                {
                    if (table[j][1] /*bits*/ != 0)
                    {
                        // PJJ exit(-1);
                    }
                    table[j][1] = n; //bits
                    table[j][0] = i; //code
                    j++;
                }
            }
            else
            {
                n -= table_nb_bits;
                j = (code >> n) & ((1 << table_nb_bits) - 1);
                /* compute table size */
                n1 = -table[j][1]; //bits
                if (n > n1)
                    n1 = n;
                table[j][1] = -n1; //bits
            }
        }
    }

    /* second pass : fill auxillary tables recursively */
    for(i=0;i<table_size;i++)
    {
        n = table[i][1]; //bits
        if (n < 0)
        {
            n = -n;
            if (n > table_nb_bits)
            {
                n = table_nb_bits;
                table[i][1] = -n; //bits
            }
            index = build_table(vlc, n, nb_codes,
                                bits, bits_wrap, bits_size,
                                codes, codes_wrap, codes_size,
                                (code_prefix << table_nb_bits) | i,
                                n_prefix + table_nb_bits);
            if (index < 0)
                return -1;
            /* note: realloc has been done, so reload tables */
            table = &vlc->table[table_index];
            table[i][0] = index; //code
        }
    }
    return table_index;
}

/* Build VLC decoding tables suitable for use with get_vlc().

   'nb_bits' set thee decoding table size (2^nb_bits) entries. The
   bigger it is, the faster is the decoding. But it should not be too
   big to save memory and L1 cache. '9' is a good compromise.

   'nb_codes' : number of vlcs codes

   'bits' : table which gives the size (in bits) of each vlc code.

   'codes' : table which gives the bit pattern of of each vlc code.

   'xxx_wrap' : give the number of bytes between each entry of the
   'bits' or 'codes' tables.

   'xxx_size' : gives the number of bytes of each entry of the 'bits'
   or 'codes' tables.

   'wrap' and 'size' allows to use any memory configuration and types
   (byte/word/long) to store the 'bits' and 'codes' tables.
*/
int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
             const void *bits, int bits_wrap, int bits_size,
             const void *codes, int codes_wrap, int codes_size)
{
    vlc->bits = nb_bits;
    vlc->table_size = 0;

    if (build_table(vlc, nb_bits, nb_codes,
                    bits, bits_wrap, bits_size,
                    codes, codes_wrap, codes_size,
                    0, 0) < 0)
    {

        return -1;
    }
    return 0;
}