/*
 *  XmNap  A Motif napster client
 *  
 *  Copyright (C) 2000 Mats Peterson
 *  
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *  
 *  This program 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 General Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License
 *  along with this program; see the file COPYING.  If not, write to
 *  the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 *  Boston, MA 02111-1307, USA.
 *  
 *  Please send any comments/bug reports to
 *  mats_peterson@swipnet.se  (Mats Peterson)
 */

#include <Xm/Xm.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

#include "mp3info.h"
#include "msgbox.h"
#include "util.h"

static int bitrateTbl[2][3][16] = {
{
  /* MPEG 2 & 2.5 */
  {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160,0}, /* Layer III */
  {0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160,0}, /* Layer II */
  {0, 32, 48, 56, 64, 80, 96,112,128,144,160,176,192,224,256,0} /* Layer I  */
},
{
  /* MPEG 1 */
  {0, 32, 40, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,0}, /* Layer III */
  {0, 32, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,384,0}, /* Layer II */
  {0, 32, 64, 96,128,160,192,224,256,288,320,352,384,416,448,0}  /* Layer I */
}
};

static int freqTbl[4][3] = {
  {32000, 16000,  8000},  /* MPEG 2.5 */
  {    0,     0,     0},  /* reserved */
  {22050, 24000, 16000},  /* MPEG 2   */
  {44100, 48000, 32000}   /* MPEG 1   */
};


MP3INFO* MP3Info(String fileName)
{
    static MP3INFO *info = NULL;
    FILE *fd;
    char tmp[128], hdrSize[4];
    unsigned long bitHeader;
    int tryCount = 0, skip, fileSize, hdrSkip;
    float frameSize;

    if (! (fd = fopen(fileName, "r"))) {
	ErrMsg(strerror(errno));
	return NULL;
    }

    if (info)
	XtFree((char*)info);
    info = XtNew(MP3INFO);
    
    fseek(fd, 0, SEEK_END);
    fileSize = ftell(fd);
    fseek(fd, 0, SEEK_SET);

    fread(&tmp[1], 1, 3, fd);

    do {
	tmp[0]=tmp[1];
	tmp[1]=tmp[2];
	tmp[2]=tmp[3];

	fread(&tmp[3], 1, 1, fd);

	/* check for ID3v2 tag */
	if ((tryCount == 0) && (! strncmp(tmp, "ID3", 3))) {
	    /* skip id3v2 version and flags */
	    fread(tmp, 1, 2, fd);

	    /* read id3v2 header size */
	    fread(hdrSize, 1, 4, fd);

	    /* compute bytes to skip */

	    hdrSkip = ((int)hdrSize[3] |
		    ((int)hdrSize[2] << (8 - 1)) |
		    ((int)hdrSize[1] << (16 - 2)) |
		    ((int)hdrSize[0] << (24 - 3))) + 10;

	    /* skip */
	    fseek(fd, hdrSkip, SEEK_SET);

	    /* and get (hopefully) the first frame header */
	    fread(tmp, 1, 4, fd);
	}

	bitHeader = (unsigned long)(
	    ( (tmp[0] & 255) << 24) | ( (tmp[1] & 255) << 16) |
	    ( (tmp[2] & 255) <<  8) | ( (tmp[3] & 255)      )
	    );

	info->sync = (bitHeader >> 21)&0x7ff;
	info->version = ((bitHeader >> 19)&0x3);
	info->layer = ((bitHeader >> 17)&0x3);
	info->bitrate = ((bitHeader >> 12)&0xf);
	info->freq = ((bitHeader >> 10)&0x3);

	tryCount++;
	if (tryCount >= 500)
	    return NULL;
    } while (info->sync!=0x7ff || info->version==1 ||
	info->layer==0 || info->bitrate==0xf ||
	info->freq==3);
    
    info->protect = ((bitHeader >> 16)&0x1);

    /*  get index & calc brate from it */
    info->bitrate =
	bitrateTbl[info->version & 1][info->layer - 1][info->bitrate];

    info->freq = freqTbl[info->version][info->freq];

    info->padding = ((bitHeader >> 9)&0x1);
    info->channels = ((bitHeader >> 6)&0x3);
    info->ext = ((bitHeader >> 4)&0x3);
    info->copyright = ((bitHeader >> 3)&0x1);
    info->original = ((bitHeader >> 2)&0x1);
    info->emphasis = (bitHeader & 0x3);

    skip=0;

    /* is there a variable bit rate bit */
    if (info->version == 3 ) {    /* mpeg version 1 */
	if (info->channels == 3)
	    skip = 17;		    /* Single Channel */
	else
	    skip = 32;
    } else {			    /* mpeg version 2 or 2.5 */
	if (info->channels==3 )
	    skip = 9;		    /* Single Channel */
	else
	    skip = 17;
    }

    /* read next twelve bits in */
    fread(tmp, 1, skip, fd);
    fread(tmp, 1, 12, fd);

    if (! strncmp("Xing", tmp, 4)) {
	/* Got a varible bitrate */
	bitHeader = (unsigned long) (
	    (tmp[4] << 24) |
	    (tmp[5] << 16) |
	    (tmp[6] <<  8) |
	    (tmp[7]      )
	    );
	if (bitHeader & 1) {     /* there is frame data */
	    /* get the num of frames */
	    bitHeader = (unsigned long)(
		(tmp[8] << 24) |
		(tmp[9] << 16) |
		(tmp[10] <<  8) |
		(tmp[11]      )
		);

		frameSize = (float)fileSize / (float)bitHeader;
		info->bitrate =
		    (int)(( frameSize * (float)info->freq) /
		    ( 1000.0 * ( (info->layer==3) ? 12.0 : 144.0)) );
	}
    }

    info->seconds = (8 * fileSize) / 1000;
    if (info->bitrate)
	info->seconds = info->seconds/info->bitrate;
    else
	info->seconds=0;

    fclose(fd);
    return info;
}
.