id3tag.cpp

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.7平台上编译为嵌入式图形界面操作系统。

/**********************************************************************
** Copyright (C) 2000-2002 Trolltech AS.  All rights reserved.
**
** This file is part of the Qtopia Environment.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
** See http://www.trolltech.com/gpl/ for GPL licensing information.
**
** Contact [e-mail] if any conditions of this licensing are
** not clear to you.
**
**********************************************************************/
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <ctype.h>
#include "id3tag.h"


ID3Tag::ID3Tag()
{
}


QString ID3Tag::toString()
{
    QString info;
    QString label[6] = { tr( "Title" ), tr( "Artist" ), tr( "Album" ), tr( "Year" ), tr( "Comment" ), tr( "Track" ) };
    bool first = TRUE;
    for ( int i = 0; i < 6; i++ ) {
	if ( !idFields[i].isEmpty() ) {
	    info += ( first ? "" : ", " ) + label[i] + ": " + (const char *)idFields[i];
	    first = FALSE;
	}
    }
    return info;
}


bool ID3Tag::read( int fd )
{
    uchar id3v1[128 + 1];
    bool isGood = TRUE;

    // get the original file position
    off_t originalPosition = ::lseek( fd, 0L, SEEK_CUR );

    // seek to the position in the file where an ID tag is expected
    if ( ::lseek( fd, -128, SEEK_END ) == -1 ) {
	qDebug( "error seeking to id3 tags" );
	isGood = FALSE;
    }

    // read in the id3 tag data
    if ( isGood && ::read( fd, id3v1, 128 ) != 128 ) {
	qDebug( "error reading id3 tags" );
	isGood = FALSE;
    }

    // check the tag header
    if ( isGood && ::strncmp( (const char *)id3v1, "TAG", 3 ) != 0 ) {
	// No id3 tags
	isGood = FALSE;
    } else if ( isGood ) {
        // parse the tag fields
	int len[5] = { 30, 30, 30, 4, 30 };
	char *ptr = (char *)id3v1 + 3, *ptr2 = ptr + len[0];
	for ( int i = 0; i < 5; ptr += len[i], i++, ptr2 += len[i] ) {
	    char push = *ptr2;
	    *ptr2 = '\0';
	    char *ptr3 = ptr2;
	    while ( ptr3-1 >= ptr && isspace(ptr3[-1]) ) ptr3--;
	    char push2 = *ptr3; *ptr3 = '\0';
	    if ( strcmp( ptr, "" ) ) 
		idFields[i] = ptr;
	    *ptr3 = push2;
	    *ptr2 = push;
	}
/*
	// Debug ID3 Tags
	// --------------
	for ( int i = 0; i < 64; i++ )
	    printf("%i", i % 10 );
	printf("\n");
	for ( int i = 0; i < 64; i++ )
	    printf("%c", ( isprint( id3v1[i] ) != 0 ) ? id3v1[i] : '-' );
	printf("\n");
	for ( int i = 0; i < 64; i++ )
	    printf("%i", i % 10 );
	printf("\n");
	for ( int i = 0; i < 64; i++ )
	    printf("%c", ( isprint( id3v1[i+64] ) != 0 ) ? id3v1[i+64] : '-' );
	printf("\n");
*/
	idFields[5] = (id3v1[127] == 255 && id3v1[126] != 0) ? QString::number( id3v1[126] ) : QString("");
    }

    // reset the file position to the original position 
    ::lseek( fd, originalPosition, SEEK_SET );
    return isGood;
}


bool ID3Tag::write( int fd )
{
    uchar id3v1[128 + 1];
    bool isGood = TRUE;

    // get the original file position
    off_t originalPosition = ::lseek( fd, 0L, SEEK_CUR );

    // seek to the position in the file where an ID tag is expected
    if ( ::lseek( fd, -128, SEEK_END ) == -1 || ::read( fd, id3v1, 128 ) != 128 ) {
	qDebug( "error reading id3 tags" );
	isGood = FALSE;
    } else {
	// check the tag header to see if it has tags, else we must append the new tags to the end
	if ( ::strncmp( (const char *)id3v1, "TAG", 3 ) != 0 ) {
	    if ( ::lseek( fd, 0, SEEK_END ) == -1 ) {
		qDebug( "error seeking to end of file to output new tags" );
		isGood = FALSE;
	    }
	} else {
	    // We have old tags, so rewind to where they start to overwrite them
	    if ( ::lseek( fd, -128, SEEK_END ) == -1 ) {
		qDebug( "error seeking to beginning of old tags to overwrite" );
		isGood = FALSE;
	    }
	}
    }

    if ( isGood ) {
	// build the id3 data structure
	id3v1[0] = 'T', id3v1[1] = 'A', id3v1[2] = 'G';
	uint i = 3;
	uint len[5] = { 30, 30, 30, 4, 30 };
	for ( uint t = 0; t < sizeof(len)/sizeof(len[0]); t++ ) {
	    int copyLength = QMIN( idFields[t].length(), len[t] );
	    int remaining = len[t] - copyLength;
	    strncpy( (char *)id3v1 + i, (const char *)idFields[t], copyLength );
	    memset( (char *)id3v1 + i + copyLength, 0, remaining ); // fill remaining with zeros
	    i += len[t];
	}
	// Track field
	id3v1[125] = 0;
	id3v1[126] = idFields[5].toUInt();
	id3v1[127] = 255;
	// Write it out
	::write( fd, id3v1, 128 );
    }

    // reset the file position to the original position 
    ::lseek( fd, originalPosition, SEEK_SET );
    return isGood;
}