解析用PHP讀寫音頻文件信息的詳解(支持WMA和MP3)_PHP教程

<?php
// AudioExif.class.php
// 用PHP進行音頻文件頭部信息的讀取與寫入
// 目前只支持 WMA 和 MP3 兩種格式, 只支持常用的幾個頭部信息
//
// 寫入信息支持: Title(名稱), Artist(藝術家), Copyright(版權), Description (描述)
// Year(年代), Genre (流派), AlbumTitle (專輯標題)
// 其中 mp3 和 wma 略有不同, 具體返回的信息還可能更多, 但只有以上信息可以被寫入
// mp3 還支持 Track (曲目編號寫入)
// 對于 MP3 文件支持 ID3v1也支持ID3v2, 讀取時優先 v2, 寫入時總是會寫入v1, 必要時寫入v2
//
// 用法說明: (由于 wma 使用 Unicode 存取, 故還需要 mb_convert_encoding() 擴展
// 返回數據及寫入數據均為 ANSI 編碼, 即存什么就顯示什么 (中文_GB2312)
//
// require ('AudioExif.class.php');
// $AE = new AudioExif;
// $file = '/path/to/test.mp3';
//
// 1. 檢查文件是否完整 (only for wma, mp3始終返回 true)
//
// $AE->CheckSize($file);
//
// 2. 讀取信息, 返回值由信息組成的數組, 鍵名解釋參見上方
//
// print_r($AE->GetInfo($file));
//
// 3. 寫入信息, 第二參數是一個哈希數組, 鍵->值, 支持的參見上方的, mp3也支持 Track
// 要求第一參數的文件路徑可由本程序寫入
// $pa = array('Title' => '新標題', 'AlbumTitle' => '新的專輯名稱');
// $AE->SetInfo($file, $pa);
//
//
// 其它: 該插件花了不少時間搜集查找 wma及mp3 的文件格式說明文檔與網頁, 希望對大家有用.
// 其實網上已經有不少類似的程序, 但對 wma 實在太少了, 只能在 win 平臺下通過 M$ 的
// API 來操作, 而 MP3 也很少有可以在 unix/linux 命令行操作的, 所以特意寫了這個模塊
//
// 如果發現 bug 或提交 patch, 或加以改進使它更加健壯, 請告訴我.
// (關于 ID3和Wma的文件格式及結構 在網上應該都可以找到參考資料)
//
if (!extension_loaded('mbstring'))
{
trigger_error('PHP Extension module `mbstring` is required for AudioExif', E_USER_WARNING);
return true;
}
// the Main Class
class AudioExif
{
// public vars
var $_wma = false;
var $_mp3 = false;
// Construct
function AudioExif()
{
// nothing to do
}
// check the filesize
function CheckSize($file)
{
$handler = &$this->_get_handler($file);
if (!$handler) return false;
return $handler->check_size($file);
}
// get the infomations
function GetInfo($file)
{
$handler = &$this->_get_handler($file);
if (!$handler) return false;
return $handler->get_info($file);
}
// write the infomations
function SetInfo($file, $pa)
{
if (!is_writable($file))
{
trigger_error('AudioExif: file `' . $file . '` can not been overwritten', E_USER_WARNING);
return false;
}
$handler = &$this->_get_handler($file);
if (!$handler) return false;
return $handler->set_info($file, $pa);
}
// private methods
function &_get_handler($file)
{
$ext = strtolower(strrchr($file, '.'));
$ret = false;
if ($ext == '.mp3')
{ // MP3
$ret = &$this->_mp3;
if (!$ret) $ret = new _Mp3Exif();
}
else if ($ext == '.wma')
{ // wma
$ret = &$this->_wma;
if (!$ret) $ret = new _WmaExif();
}
else
{ // unknown
trigger_error('AudioExif not supported `' . $ext . '` file.', E_USER_WARNING);
}
return $ret;
}
}
// DBCS => gb2312
function dbcs_gbk($str)
{
// strip the last ""
$str = substr($str, 0, -2);
return mb_convert_encoding($str, 'GBK', 'UCS-2LE');
}
// gb2312 => DBCS
function gbk_dbcs($str)
{
$str = mb_convert_encoding($str, 'UCS-2LE', 'GBK');
$str .= "";
return $str;
}
// file exif
class _AudioExif
{
var $fd;
var $head;
var $head_off;
var $head_buf;

// init the file handler
function _file_init($fpath, $write = false)
{
$mode = ($write ? 'rb+' : 'rb');
$this->fd = @fopen($fpath, $mode);
if (!$this->fd)
{
trigger_error('AudioExif: `' . $fpath . '` can not be opened with mode `' . $mode . '`', E_USER_WARNING);
return false;
}
$this->head = false;
$this->head_off = 0;
$this->head_buf = '';
return true;
}
// read buffer from the head_buf & move the off pointer
function _read_head_buf($len)
{
if ($len <= 0) return NULL;
$buf = substr($this->head_buf, $this->head_off, $len);
$this->head_off += strlen($buf);
return $buf;
}
// read one short value
function _read_head_short()
{
$ord1 = ord(substr($this->head_buf, $this->head_off, 1));
$ord2 = ord(substr($this->head_buf, $this->head_off+1, 1));
$this->head_off += 2;
return ($ord1 + ($ord2<<8));
}
// save the file head
function _file_save($head, $olen, $nlen = 0)
{
if ($nlen == 0) $nlen = strlen($head);
if ($nlen == $olen)
{
// shorter
flock($this->fd, LOCK_EX);
fseek($this->fd, 0, SEEK_SET);
fwrite($this->fd, $head, $nlen);
flock($this->fd, LOCK_UN);
}
else
{
// longer, buffer required
$stat = fstat($this->fd);
$fsize = $stat['size'];
// buf required (4096?) 應該不會 nlen - olen > 4096 吧
$woff = 0;
$roff = $olen;
// read first buffer
flock($this->fd, LOCK_EX);
fseek($this->fd, $roff, SEEK_SET);
$buf = fread($this->fd, 4096);
// seek to start
fseek($this->fd, $woff, SEEK_SET);
fwrite($this->fd, $head, $nlen);
$woff += $nlen;
// seek to woff & write the data
do
{
$buf2 = $buf;
$roff += 4096;
if ($roff < $fsize)
{
fseek($this->fd, $roff, SEEK_SET);
$buf = fread($this->fd, 4096);
}
// save last buffer
$len2 = strlen($buf2);
fseek($this->fd, $woff, SEEK_SET);
fwrite($this->fd, $buf2, $len2);
$woff += $len2;
}
while ($roff < $fsize);
ftruncate($this->fd, $woff);
flock($this->fd, LOCK_UN);
}
}
// close the file
function _file_deinit()
{
if ($this->fd)
{
fclose($this->fd);
$this->fd = false;
}
}
}
// wma class
class _WmaExif extends _AudioExif
{
var $items1 = array('Title', 'Artist', 'Copyright', 'Description', 'Reserved');
var $items2 = array('Year', 'Genre', 'AlbumTitle');
// check file size (length) maybe invalid file
function check_size($file)
{
$ret = false;
if (!$this->_file_init($file)) return true;
if ($this->_init_header())
{
$buf = fread($this->fd, 24);
$tmp = unpack('H32id/Vlen/H8unused', $buf);
if ($tmp['id'] == '3626b2758e66cf11a6d900aa0062ce6c')
{
$stat = fstat($this->fd);
$ret = ($stat['size'] == ($this->head['len'] + $tmp['len']));
}
}
$this->_file_deinit();
return $ret;
}
// set info (save the infos)
function set_info($file, $pa)
{
// check the pa
settype($pa, 'array');
if (!$this->_file_init($file, true)) return false;
if (!$this->_init_header())
{
$this->_file_deinit();
return false;
}

// parse the old header & generate the new header
$head_body = '';
$st_found = $ex_found = false;
$head_num = $this->head['num'];
while (($tmp = $this->_get_head_frame()) && ($head_num > 0))
{
$head_num--;
if ($tmp['id'] == '3326b2758e66cf11a6d900aa0062ce6c')
{ // Standard Info
// 1-4
$st_found = true;
$st_body1 = $st_body2 = '';
$lenx = unpack('v5', $this->_read_head_buf(10));
$tmp['len'] -= 34; // 10 + 24
for ($i = 0; $i < count($this->items1); $i++)
{
$l = $lenx[$i+1];
$k = $this->items1[$i];
$tmp['len'] -= $l;
$data = $this->_read_head_buf($l);
if (isset($pa[$k])) $data = gbk_dbcs($pa[$k]);
$st_body2 .= $data;
$st_body1 .= pack('v', strlen($data));
}
// left length
if ($tmp['len'] > 0) $st_body2 .= $this->_read_head_buf($tmp['len']);
// save to head_body
$head_body .= pack('H32VH8', $tmp['id'], strlen($st_body1 . $st_body2)+24, $tmp['unused']);
$head_body .= $st_body1 . $st_body2;
}
else if ($tmp['id'] == '40a4d0d207e3d21197f000a0c95ea850')
{ // extended info
$ex_found = true;

$inum = $this->_read_head_short();
$inum2 = $inum;
$tmp['len'] -= 26; // 24 + 2
$et_body = '';
while ($tmp['len'] > 0 && $inum > 0)
{
// attribute name
$nlen = $this->_read_head_short();
$nbuf = $this->_read_head_buf($nlen);
// the flag & value length
$flag = $this->_read_head_short();
$vlen = $this->_read_head_short();
$vbuf = $this->_read_head_buf($vlen);
// set the length
$tmp['len'] -= (6 + $nlen + $vlen);
$inum--;
// save the data?
$name = dbcs_gbk($nbuf);
$k = substr($name, 3);
if (in_array($k, $this->items2) && isset($pa[$k]))
{
$vbuf = gbk_dbcs($pa[$k]);
$vlen = strlen($vbuf);
unset($pa[$k]);
}
$et_body .= pack('v', $nlen) . $nbuf . pack('vv', $flag, $vlen) . $vbuf;
}
// new tag insert??
foreach ($this->items2 as $k)
{
if (isset($pa[$k]))
{
$inum2++;
$nbuf = gbk_dbcs('WM/' . $k);
$nlen = strlen($nbuf);
$vbuf = gbk_dbcs($pa[$k]);
$vlen = strlen($vbuf);
$et_body .= pack('v', $nlen) . $nbuf . pack('vv', 0, $vlen) . $vbuf;
}
}
// left buf?
if ($tmp['len'] > 0) $et_body .= $this->_read_head_buf($tmp['len']);
// save to head_body
$head_body .= pack('H32VH8v', $tmp['id'], strlen($et_body)+26, $tmp['unused'], $inum2);
$head_body .= $et_body;
}
else
{
// just keep other head frame
$head_body .= pack('H32VH8', $tmp['id'], $tmp['len'], $tmp['unused']);
if ($tmp['len'] > 24) $head_body .= $this->_read_head_buf($tmp['len']-24);
}
}
// st not found?
if (!$st_found)
{
$st_body1 = $st_body2 = '';
foreach ($this->items1 as $k)
{
$data = (isset($pa[$k]) ? gbk_dbcs($pa[$k]) : "");
$st_body1 .= pack('v', strlen($data));
$st_body2 .= $data;
}

// save to head_body
$head_body .= pack('H32Va4', '3326b2758e66cf11a6d900aa0062ce6c', strlen($st_body1 . $st_body2)+24, '');
$head_body .= $st_body1 . $st_body2;
$this->head['num']++;
}
// ex not found?
if (!$ex_found)
{
$inum = 0;
$et_body = '';
foreach ($this->items2 as $k)
{
$nbuf = gbk_dbcs('WM/' . $k);
$vbuf = (isset($pa[$k]) ? gbk_dbcs($pa[$k]) : "");
$et_body .= pack('v', strlen($nbuf)) . $nbuf . pack('vv', 0, strlen($vbuf)) . $vbuf;
$inum++;
}
$head_body .= pack('H32Va4v', '40a4d0d207e3d21197f000a0c95ea850', strlen($et_body)+26, '', $inum);
$head_body .= $et_body;
$this->head['num']++;
}
// after save
$new_len = strlen($head_body) + 30;
$old_len = $this->head['len'];
if ($new_len < $old_len)
{
$head_body .= str_repeat("", $old_len - $new_len);
$new_len = $old_len;
}
$tmp = $this->head;
$head_buf = pack('H32VVVH4', $tmp['id'], $new_len, $tmp['len2'], $tmp['num'], $tmp['unused']);
$head_buf .= $head_body;
$this->_file_save($head_buf, $old_len, $new_len);
// close the file & return
$this->_file_deinit();
return true;
}
// get info
function get_info($file)
{
$ret = array();
if (!$this->_file_init($file)) return false;
if (!$this->_init_header())
{
$this->_file_deinit();
return false;
}
// get the data from head_buf
$head_num = $this->head['num']; // num of head_frame
while (($tmp = $this->_get_head_frame()) && $head_num > 0)
{
$head_num--;
if ($tmp['id'] == '3326b2758e66cf11a6d900aa0062ce6c')
{ // Standard Info
$lenx = unpack('v*', $this->_read_head_buf(10));
for ($i = 1; $i <= count($this->items1); $i++)
{
$k = $this->items1[$i-1];
$ret[$k] = dbcs_gbk($this->_read_head_buf($lenx[$i]));
}
}
else if ($tmp['id'] == '40a4d0d207e3d21197f000a0c95ea850')
{ // Extended Info
$inum = $this->_read_head_short();
$tmp['len'] -= 26;
while ($inum > 0 && $tmp['len'] > 0)
{
// attribute name
$nlen = $this->_read_head_short();
$nbuf = $this->_read_head_buf($nlen);
// the flag & value length
$flag = $this->_read_head_short();
$vlen = $this->_read_head_short();
$vbuf = $this->_read_head_buf($vlen);
// update the XX
$tmp['len'] -= (6 + $nlen + $vlen);
$inum--;
$name = dbcs_gbk($nbuf);
$k = substr($name, 3);
if (in_array($k, $this->items2))
{ // all is string value (refer to falg for other tags)
$ret[$k] = dbcs_gbk($vbuf);
}
}
}
else
{ // skip only
if ($tmp['len'] > 24) $this->head_off += ($tmp['len'] - 24);
}
}
$this->_file_deinit();
return $ret;
}
// get the header?
function _init_header()
{
fseek($this->fd, 0, SEEK_SET);
$buf = fread($this->fd, 30);
if (strlen($buf) != 30) return false;
$tmp = unpack('H32id/Vlen/Vlen2/Vnum/H4unused', $buf);
if ($tmp['id'] != '3026b2758e66cf11a6d900aa0062ce6c')
return false;
$this->head_buf = fread($this->fd, $tmp['len'] - 30);
$this->head = $tmp;
return true;
}
// _get_head_frame()
function _get_head_frame()
{
$buf = $this->_read_head_buf(24);
if (strlen($buf) != 24) return false;
$tmp = unpack('H32id/Vlen/H8unused', $buf);
return $tmp;
}
}
// mp3 class (if not IDv2 then select IDv1)
class _Mp3Exif extends _AudioExif
{
var $head1;
var $genres = array('Blues','Classic Rock','Country','Dance','Disco','Funk','Grunge','Hip-Hop','Jazz','Metal','New Age','Oldies','Other','Pop','R&B','Rap','Reggae','Rock','Techno','Industrial','Alternative','Ska','Death Metal','Pranks','Soundtrack','Euro-Techno','Ambient','Trip-Hop','Vocal','Jazz+Funk','Fusion','Trance','Classical','Instrumental','Acid','House','Game','Sound Clip','Gospel','Noise','AlternRock','Bass','Soul','Punk','Space','Meditative','Instrumental Pop','Instrumental Rock','Ethnic','Gothic','Darkwave','Techno-Industrial','Electronic','Pop-Folk','Eurodance','Dream','Southern Rock','Comedy','Cult','Gangsta','Top 40','Christian Rap','Pop/Funk','Jungle','Native American','Cabaret','New Wave','Psychadelic','Rave','Showtunes','Trailer','Lo-Fi','Tribal','Acid Punk','Acid Jazz','Polka','Retro','Musical','Rock & Roll','Hard Rock','Unknown');
// MP3 always return true
function check_size($file)
{
return true;
}
// get info
function get_info($file)
{
if (!$this->_file_init($file)) return false;
$ret = false;
if ($this->_init_header())
{
$ret = ($this->head ? $this->_get_v2_info() : $this->_get_v1_info());
$ret['meta'] = $this->_get_meta_info();
}
$this->_file_deinit();
return $ret;
}
// set info
function set_info($file, $pa)
{
if (!$this->_file_init($file, true)) return false;
if ($this->_init_header())
{
// always save v1 info
$this->_set_v1_info($pa);
// set v2 first if need
$this->_set_v2_info($pa);
}
$this->_file_deinit();
return true;
}
// get the header information[v1+v2], call after file_init
function _init_header()
{
$this->head1 = false;
$this->head = false;
// try to get ID3v1 first
fseek($this->fd, -128, SEEK_END);
$buf = fread($this->fd, 128);
if (strlen($buf) == 128 && substr($buf, 0, 3) == 'TAG')
{
$tmp = unpack('a3id/a30Title/a30Artist/a30AlbumTitle/a4Year/a28Description/CReserved/CTrack/CGenre', $buf);
$this->head1 = $tmp;
}
// try to get ID3v2
fseek($this->fd, 0, SEEK_SET);
$buf = fread($this->fd, 10);
if (strlen($buf) == 10 && substr($buf, 0, 3) == 'ID3')
{
$tmp = unpack('a3id/Cver/Crev/Cflag/C4size', $buf);
$tmp['size'] = ($tmp['size1']<<21)|($tmp['size2']<<14)|($tmp['size3']<<7)|$tmp['size4'];
unset($tmp['size1'], $tmp['size2'], $tmp['size3'], $tmp['size4']);
$this->head = $tmp;
$this->head_buf = fread($this->fd, $tmp['size']);
}
return ($this->head1 || $this->head);
}
// get v1 info
function _get_v1_info()
{
$ret = array();
$tmpa = array('Title', 'Artist', 'Copyright', 'Description', 'Year', 'AlbumTitle');
foreach ($tmpa as $tmp)
{
$ret[$tmp] = $this->head1[$tmp];
if ($pos = strpos($ret[$tmp], ""))
$ret[$tmp] = substr($ret[$tmp], 0, $pos);
}
// count the Genre, [Track]
if ($this->head1['Reserved'] == 0) $ret['Track'] = $this->head1['Track'];
else $ret['Description'] .= chr($ret['Reserved']) . chr($ret['Track']);
// Genre_idx
$g = $this->head1['Genre'];
if (!isset($this->genres[$g])) $ret['Genre'] = 'Unknown';
else $ret['Genre'] = $this->genres[$g];
// return the value
$ret['ID3v1'] = 'yes';
return $ret;
}
// get v2 info
function _get_v2_info()
{
$ret = array();
$items = array( 'TCOP'=>'Copyright', 'TPE1'=>'Artist', 'TIT2'=>'Title', 'TRCK'=> 'Track',
'TCON'=>'Genre', 'COMM'=>'Description', 'TYER'=>'Year', 'TALB'=>'AlbumTitle');
while (true)
{
$buf = $this->_read_head_buf(10);
if (strlen($buf) != 10) break;
$tmp = unpack('a4fid/Nsize/nflag', $buf);
if ($tmp['size'] == 0) break;
$tmp['dat'] = $this->_read_head_buf($tmp['size']);
// 0x6000 (11000000 00000000)
if ($tmp['flag'] & 0x6000) continue;
// mapping the data
if ($k = $items[$tmp['fid']])
{ // If first char is "", just skip
if (substr($tmp['dat'], 0, 1) == "") $tmp['dat'] = substr($tmp['dat'], 1);
$ret[$k] = $tmp['dat'];
}
}
// reset the genre
if ($g = $ret['Genre'])
{
if (substr($g,0,1) == '(' && substr($g,-1,1) == ')') $g = substr($g, 1, -1);
if (is_numeric($g))
{
$g = intval($g);
$ret['Genre'] = (isset($this->genres[$g]) ? $this->genres[$g] : 'Unknown');
}
}
$ret['ID3v1'] = 'no';
return $ret;
}
// get meta info of MP3
function _get_meta_info()
{
// seek to the lead buf: 0xff
$off = 0;
if ($this->head) $off = $this->head['size'] + 10;
fseek($this->fd, $off, SEEK_SET);
while (!feof($this->fd))
{
$skip = ord(fread($this->fd, 1));
if ($skip == 0xff) break;
}
if ($skip != 0xff) return false;
$buf = fread($this->fd, 3);
if (strlen($buf) != 3) return false;
$tmp = unpack('C3', $buf);
if (($tmp[1] & 0xf0) != 0xf0) return false;
// get the meta info
$meta = array();
// get mpeg version
$meta['mpeg'] = ($tmp[1] & 0x08 ? 1 : 2);
$meta['layer'] = ($tmp[1] & 0x04) ? (($tmp[1] & 0x02) ? 1 : 2) : (($tmp[1] & 0x02) ? 3 : 0);
$meta['epro'] = ($tmp[1] & 0x01) ? 'no' : 'yes';
// bit rates
$bit_rates = array(
1 => array(
1 => array(0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,0),
2 => array(0,32,48,56,64,80,96,112,128,160,192,224,256,320,384,0),
3 => array(0,32,40,48,56,64,80,96,112,128,160,192,224,256,320,0)
),
2 => array(
1 => array(0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,0),
2 => array(0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0),
3 => array(0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0)
)
);
$i = $meta['mpeg'];
$j = $meta['layer'];
$k = ($tmp[2]>>4);
$meta['bitrate'] = $bit_rates[$i][$j][$k];
// sample rates <采樣率>
$sam_rates = array(1=>array(44100,48000,32000,0), 2=>array(22050,24000,16000,0));
$meta['samrate'] = $sam_rates[$i][$k];
$meta["padding"] = ($tmp[2] & 0x02) ? 'on' : 'off';
$meta["private"] = ($tmp[2] & 0x01) ? 'on' : 'off';
// mode & mode_ext
$k = ($tmp[3]>>6);
$channel_modes = array('stereo', 'joint stereo', 'dual channel', 'single channel');
$meta['mode'] = $channel_modes[$k];
$k = (($tmp[3]>>4) & 0x03);
$extend_modes = array('MPG_MD_LR_LR', 'MPG_MD_LR_I', 'MPG_MD_MS_LR', 'MPG_MD_MS_I');
$meta['ext_mode'] = $extend_modes[$k];
$meta['copyright'] = ($tmp[3] & 0x08) ? 'yes' : 'no';
$meta['original'] = ($tmp[3] & 0x04) ? 'yes' : 'no';
$emphasis = array('none', '50/15 microsecs', 'rreserved', 'CCITT J 17');
$k = ($tmp[3] & 0x03);
$meta['emphasis'] = $emphasis[$k];
return $meta;
}
// set v1 info
function _set_v1_info($pa)
{
// ID3v1 (simpled)
$off = -128;
if (!($tmp = $this->head1))
{
$off = 0;
$tmp['id'] = 'TAG';
$tmp['Title'] = $tmp['Artist'] = $tmp['AlbumTitle'] = $tmp['Year'] = $tmp['Description'] = '';
$tmp['Reserved'] = $tmp['Track'] = $tmp['Genre'] = 0;
}

// basic items
$items = array('Title', 'Artist', 'Copyright', 'Description', 'Year', 'AlbumTitle');
foreach ($items as $k)
{
if (isset($pa[$k])) $tmp[$k] = $pa[$k];
}
// genre index
if (isset($pa['Genre']))
{
$g = 0;
foreach ($this->genres as $gtmp)
{
if (!strcasecmp($gtmp, $pa['Genre']))
break;
$g++;
}
$tmp['Genre'] = $g;
}
if (isset($pa['Track'])) $tmp['Track'] = intval($pa['Track']);
// pack the data
$buf = pack('a3a30a30a30a4a28CCC', $tmp['id'], $tmp['Title'], $tmp['Artist'], $tmp['AlbumTitle'],
$tmp['Year'], $tmp['Description'], 0, $tmp['Track'], $tmp['Genre']);
flock($this->fd, LOCK_EX);
fseek($this->fd, $off, SEEK_END);
fwrite($this->fd, $buf, 128);
flock($this->fd, LOCK_UN);
}
// set v2 info
function _set_v2_info($pa)
{
if (!$this->head)
{ // insert ID3
return; // 沒有就算了
/**
$tmp = array('id'=>'ID3','ver'=>3,'rev'=>0,'flag'=>0);
$tmp['size'] = -10; // +10 => 0
$this->head = $tmp;
$this->head_buf = '';
$this->head_off = 0;
**/
}
$items = array( 'TCOP'=>'Copyright', 'TPE1'=>'Artist', 'TIT2'=>'Title', 'TRAC'=>'Track',
'TCON'=>'Genre', 'COMM'=>'Description', 'TYER'=>'Year', 'TALB'=>'AlbumTitle');
$head_body = '';
while (true)
{
$buf = $this->_read_head_buf(10);
if (strlen($buf) != 10) break;
$tmp = unpack('a4fid/Nsize/nflag', $buf);
if ($tmp['size'] == 0) break;
$data = $this->_read_head_buf($tmp['size']);
if (($k = $items[$tmp['fid']]) && isset($pa[$k]))
{
// the data should prefix by "" [replace]
$data = "" . $pa[$k];
unset($pa[$k]);
}
$head_body .= pack('a4Nn', $tmp['fid'], strlen($data), $tmp['flag']) . $data;
}
// reverse the items & set the new tags
$items = array_flip($items);
foreach ($pa as $k => $v)
{
if ($fid = $items[$k])
{
$head_body .= pack('a4Nn', $fid, strlen($v) + 1, 0) . "" . $v;
}
}
// new length
$new_len = strlen($head_body) + 10;
$old_len = $this->head['size'] + 10;
if ($new_len < $old_len)
{
$head_body .= str_repeat("", $old_len - $new_len);
$new_len = $old_len;
}
// count the size1,2,3,4, no include the header
// 較為變態的算法... :p (28bytes integer)
$size = array();
$nlen = $new_len - 10;
for ($i = 4; $i > 0; $i--)
{
$size[$i] = ($nlen & 0x7f);
$nlen >>= 7;
}
$tmp = $this->head;
//echo "old_len : $old_len new_len: $new_len ";
$head_buf = pack('a3CCCCCCC', $tmp['id'], $tmp['ver'], $tmp['rev'], $tmp['flag'],
$size[1], $size[2], $size[3], $size[4]);
$head_buf .= $head_body;
$this->_file_save($head_buf, $old_len, $new_len);
}
}
?>