PHP获取音频文件的相关信息

项目需求：现在有一个音频文件上传的功能，在上传后PHP需要获取这个音频文件的相关信息，例如：时长等，由于这个文件是放在买的空间上的，没有像ffmpeg这样的扩展来处理，那么PHP能不能获取到这些信息？
下面是之前在项目中用到的一个用PHP进行音频文件头部信息的读取与写入操作的实现，主要针对 WMA 和 MP3 两种格式，供参考。
				?

									<?php

									// AudioExif.class.php

									// 用PHP进行音频文件头部信息的读取与写入

									// 目前只支持 WMA 和 MP3 两种格式, 只支持常用的几个头部信息

									//

									// 写入信息支持: Title(名称), Artist(艺术家), Copyright(版权), Description (描述)

									// Year(年代), Genre (流派), AlbumTitle (专辑标题)

									// 其中 mp3 和 wma 略有不同, 具体返回的信息还可能更多, 但只有以上信息可以被写入

									// mp3 还支持 Track (曲目编号写入)

									// 对于 MP3 文件支持 ID3v1也支持ID3v2, 读取时优先 v2, 写入时总是会写入v1, 必要时写入v2

									//

									// 用法说明: (由于 wma 使用 Unicode 存取, 故还需要 mb_convert_encoding() 扩展

									// 返回数据及写入数据均为 ANSI 编码, 即存什么就显示什么 (中文_GB2312)

									//

									// require ('AudioExif.class.php');

									// $AE = new AudioExif;

									// $file = '/path/to/test.mp3';

									//

									// 1. 检查文件是否完整 (only for wma, mp3始终返回 true)

									//

									// $AE->CheckSize($file);

									//

									// 2. 读取信息, 返回值由信息组成的数组, 键名解释参见上方

									//

									// print_r($AE->GetInfo($file));

									//

									// 3. 写入信息, 第二参数是一个哈希数组, 键->值, 支持的参见上方的, mp3也支持 Track

									// 要求第一参数的文件路径可由本程序写入

									// $pa = array('Title' => '新标题', 'AlbumTitle' => '新的专辑名称');

									// $AE->SetInfo($file, $pa);

									//

									// 其它: 该插件花了不少时间搜集查找 wma及mp3 的文件格式说明文档与网页, 希望对大家有用.

									// 其实网上已经有不少类似的程序, 但对 wma 实在太少了, 只能在 win 平台下通过 M$ 的

									// API 来操作, 而 MP3 也很少有可以在 unix/linux 命令行操作的, 所以特意写了这个模块

									//

									// 如果发现 bug 或提交 patch, 或加以改进使它更加健壮, 请告诉我.

									// (关于 ID3和Wma的文件格式及结构 在网上应该都可以找到参考资料)

									//

									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 "\0\0"

									$str = substr($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 .= "\0\0";

									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?) 应该不会 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;

									$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("\0", $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], "\0"))

									$ret[$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 "\0", just skip

									if (substr($tmp['dat'], 0, 1) == "\0") $tmp['dat'] = substr($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 <采样率>

									$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; // 没有就算了

									/**

									$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 "\0" [replace]

									$data = "\0" . $pa[$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) . "\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("\0", $old_len - $new_len);

									$new_len = $old_len;

									}

									// count the size1,2,3,4, no include the header

									// 较为变态的算法... :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\n";

									$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);

									}
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