bitwindow.cc

来自「pixil 最新的嵌入linux 應用程序集,別的地方很難下載」· CC 代码 · 共 65 行

/* MPEG/WAVE Sound library
   (C) 1997 by Jung woo-jae 

   Portions Copyright (c) 2003 Century Software, Inc.   All Rights Reserved.     
*/

// Bitwindow.cc
// It's bit reservior for MPEG layer 3

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "mpegsound.h"

#ifndef WORDS_BIGENDIAN
#define _KEY 0
#else
#define _KEY 3
#endif

int
Mpegbitwindow::getbits(int bits)
{
    union
    {
	char store[4];
	int current;
    }
    u;
    int bi;

    if (!bits)
	return 0;

    u.current = 0;
    bi = (bitindex & 7);
    //  u.store[_KEY]=buffer[(bitindex>>3)&(WINDOWSIZE-1)]<<bi;
    u.store[_KEY] = buffer[bitindex >> 3] << bi;
    bi = 8 - bi;
    bitindex += bi;

    while (bits) {
	if (!bi) {
	    //      u.store[_KEY]=buffer[(bitindex>>3)&(WINDOWSIZE-1)];
	    u.store[_KEY] = buffer[bitindex >> 3];
	    bitindex += 8;
	    bi = 8;
	}

	if (bits >= bi) {
	    u.current <<= bi;
	    bits -= bi;
	    bi = 0;
	} else {
	    u.current <<= bits;
	    bi -= bits;
	    bits = 0;
	}
    }
    bitindex -= bi;

    return (u.current >> 8);
}