id3.c

一款MP3 Player Firmware 的原代码,非常有参考价值

/*
 * MP3 Player, ID3 Tag Processing, http://www.pjrc.com/tech/mp3
 * Copyright (c) 2000, PJRC.COM, LLC
 *
 * 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; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * As a specific exception to the GPL, the executable object code built
 * from this source code may be combined with hardware configuration data
 * files.  A hardware configuration data file is a set of data that is
 * transmitted to an intergrated circuit that is not a general purpose
 * microprocessor or microcontroller, in order to establish its normal
 * operation.  The process of combining the executable ojbect code built
 * from the GPL licensed source code with the hardware configuration data
 * shall be considered an aggregation of another work not based on the
 * Program.  While the GPL does not restrict use of the program, any
 * use restriction associated with the hardware configuration data (for
 * example, that it only be used with particular hardware) shall apply
 * to the combined file which includes a copy of the hardware configuration
 * data.
 *
 * Contact: [e-mail]
 */


#include "as31glue.h"
#include "printf.h"
#include "display.h"
#include "dirlist.h"
#include "playlist.h"
#include "stricmp.h"


#include "id3.h"




// TODO: someday make process_id3 read in just one 128 byte
// file_read to fill this struct, and have display.c reference
// the elements of this struct.  Write nulls at the 24th byte
// of each string, and use %24s in display.c instead of doing
// all this space padding stuff.

// id3_tag_struct id3_tag; // Structure moved to display.h so we have
// a prayer of making the above TODO come true... -ZSB 13-Aug-2001 2:41 PM


// NOGCSE = No Common Global Subexpression Elimination 
// Turning this optimization off SOMETIMES results in less
// DSEG usage... sometimes it makes things worse.  It can
// be turned back on with a RESTORE pragma if you did a
// SAVE pragma before turning it off.
#pragma SAVE
// #pragma NOGCSE

void process_id3(char fd, unsigned long size)
//
//	process_id3
//
//	Capture id3 tag info from file
//
{
	xdata char id3[11];
	xdata unsigned long cur_pos;
	
	/*unsigned char a;     file_read seems to return number of bytes read,
                               not 0 or 1 as specified in drivers.asm??? */

	if (size == 0xFFFFFFFF) return;

	string_init(id3, ' ', sizeof(id3));	// fill id3 string with spaces

	printf("##### Inside process_id3 for file %d of size %ld\r\n", (int)fd, (long)size);

	// search for id3v1 tag at end of file
	cur_pos=file_tell(fd);
	file_seek(fd,size-128);	
	file_read(fd, (xdata char *)(id3_tag.id3), 3);

	if(id3_tag.id3[0] == 'T' && id3_tag.id3[1] == 'A' && id3_tag.id3[2] == 'G') {
		print("Found ID3v1 tag\r\n");
		file_read(fd, (xdata char *)(id3_tag.title), 30);				
		file_read(fd, (xdata char *)(id3_tag.artist),30);		
		file_read(fd, (xdata char *)(id3_tag.album), 30);		
		file_read(fd, (xdata char *)(id3_tag.year), 4);		
		file_read(fd, (xdata char *)(id3_tag.comment), 30);
		/* id3v1.1 specifies that if the last byte but one in the comment
		  field is zero, the last byte is to be used to identify the track
		  number - this is not implemented here, it's complicated ;) */
		if(id3_tag.comment[28] == 0 && id3_tag.comment[29] != 0) {
			id3_tag.track_number = id3_tag.comment[29];
		} else {
			id3_tag.track_number = 0;
		}
				
		lcd_display_id3_struct();
#if 0
		printf("Tag Value: [%s]\r\n", id3_tag.id3);		
		printf("Title:     [%s]\r\n", id3_tag.title);
		printf("Artist:    [%s]\r\n", id3_tag.artist);
		printf("Album:     [%s]\r\n", id3_tag.album);
		printf("Comment:   [%s]\r\n", id3_tag.comment);
#endif
		// printf("Track #:   [%d]\r\n", track_number);
	} else {
		lcd_display_id3_none();
	}
	file_seek(fd,cur_pos);

#if 0
	// search for ID3v2 tag as specified at
	// http://www.id3.org/id3v2.4.0-structure.txt and
	// http://www.id3.org/id3v2.4.0-frames.txt
	cur_pos=file_tell(fd);
	file_seek(fd,0);
	file_read(fd, id3, 10);
	file_seek(fd,cur_pos);

	//printf("*** Got %c,%c,%c,%c,%c and returning %d for id3v2\r\n",
	//	(char)b[0], (char)b[1], (char)b[2], (char)b[3],
	//	(char)b[4], (int)a);

	if(id3[0] == 'I' && id3[1] == 'D' && id3[2] == '3') {
	  // found ID3v2 tag at start of file, further ID3v2 tag locations
          // can be determined from first one

	  // header - 10 bytes
	  //   identifier: "ID3"
	  //   version:    $04 00
	  //   flags:      %abcd0000
	  //   size:   4 * %0xxxxxxx

	  /*
          printf("Found ID3v2 tag. version=%d %d flags=%d size=%x %x %x %x\r\n",
                 (char)id3[3], (char)id3[4], (char)id3[5],
                 (char)id3[6], (char)id3[7], (char)id3[8], (char)id3[9]);
	  */
	} else {
	  // look for tag at end of file - BEFORE ID3v1 tag if present
	  // tags at END of file, must have FOOTER part, format:
	  //   identifier: "3DI"
	  //   version:    $04 00
	  //   flags:      %abcd0000
	  //   size:   4 * %0xxxxxxx
	}
#endif

}


#pragma RESTORE