解析用PHP读写音频文件信息的详解(支持WMA和MP3)
<div class="codetitle"><a style="CURSOR: pointer" data="47454" class="copybut" id="copybut47454" onclick="doCopy('code47454')"> 代码如下:
<div class="codebody" id="code47454">
<?
PHP// Au
dioExif.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 ('Au
dioExif.class.
PHP');
// $AE = new Au
dioExif;
// $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 Au
dioExif',E_USER_WARNING);
return true;
}
// the Main Class
class Au
dioExif
{
// public vars
var $_wma = false;
var $_mp3 = false;
// Construct
function Au
dioExif()
{
//
nothing to do
}
// check the filesize
function CheckSize($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('Au
dioExif: 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
{ // unk
Nown
trigger_error('Au
dioExif not supported
' . $ext . ' file.',E_USER_WARNING);
}
return $ret;
}
}
// DBCS => gb2312
function dbcs_gbk($str)
{
// strip the last ""
$str = substr($str,-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 _Au
dioExif
{
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('Au
dioExif:
' . $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,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($this->fd,SEEK_SET);
fwrite($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 = $olen;
// read f
irst buffer
flock($this->fd,$roff,SEEK_SET);
$buf = fread($this->fd,4096);
// seek to start
fseek($this->fd,$woff,$nlen);
$woff += $nlen;
// seek to woff & write the data
do
{
$buf2 = $buf;
$roff += 4096;
if ($roff < $fsize)
{
fseek($this->fd,4096);
}
// save last buffer
$len2 = strlen($buf2);
fseek($this->fd,$buf2,$len2);
$woff += $len2;
}
while ($roff < $fsize);
ft
runcate($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 _Au
dioExif
{
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);
$et_body .= pack('v',$vlen) . $vbuf;
}
}
// left buf?
if ($tmp['len'] > 0) $et_body .= $this->_read_head_buf($tmp['len']);
// save to head_body
$head_body .= pack('H32VH8v',strlen($et_body)+26,$tmp['unused'],$inum2);
$head_body .= $et_body;
}
else
{
// just keep other head frame
$head_body .= pack('H32VH8',$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','');
$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)) . $nbuf . pack('vv',strlen($vbuf)) . $vbuf;
$inum++;
}
$head_body .= pack('H32Va4v','40a4d0d207e3d21197f000a0c95ea850','',$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;
$head_buf = pack('H32VVVH4',$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,$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,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 _Au
dioExif
{
var $head1;
var $genres = array('Blues','Classic Rock','Country','Dance','
disco','Funk','Grunge','Hip-Hop','Jazz','
Metal','New Age','Oldies','Other','Pop','R&B','Rap','Reggae','Rock','Techno','Industrial','Alternative','Ska','Death
Metal','Pranks','Soundtrack','Euro-Techno','Ambient','Trip-Hop','Vocal','Jazz+Funk','Fusion','Trance','Classical','Instrumental','Acid','House','Game','Sound Clip','Gospel','Noise','AlternRock','Bass','Soul','Punk','Space','Meditative','Instrumental Pop','Instrumental Rock','Ethnic','Gothic','Darkwave','Techno-Industrial','Electronic','Pop-Folk','Eurodance','Dream','Southern Rock','Comedy','Cult','Gangsta','Top 40','Christian Rap','Pop/Funk','Jungle','Native American','Cabaret','New Wave','Psychadelic','Rave','Showtu
nes','Trailer','Lo-Fi','Tribal','Acid Punk','Acid Jazz','
polka','Retro','Musical','Rock & Roll','Hard Rock','Unk
Nown');
// MP3 always return true
function check_size($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->
getMeta_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 f
irst 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;
$this->head = false;
// try to get ID3v1 f
irst
fseek($this->fd,-128,SEEK_END);
$buf = fread($this->fd,128);
if (strlen($buf) == 128 && substr($buf,3) == 'TAG')
{
$tmp = unpack('a3id/a30Title/a30Artist/a30AlbumTitle/a4Year/a28Description/CReserved/CTrack/CGenre',$buf);
$this->head1 = $tmp;
}
// try to get ID3v2
fseek($this->fd,10);
if (strlen($buf) == 10 && substr($buf,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();
$tmpa = array('Title','Year','AlbumTitle');
foreach ($tmpa as $tmp)
{
$ret[$tmp] = $this->head1[$tmp];
if ($pos = strpos($ret[$tmp],""))
$ret[$tmp] = substr($ret[$tmp],$pos);
}
// count the Genre,[Track]
if ($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'] = 'Unk
Nown';
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( 'T
cop'=>'
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 f
irst char is "",just skip
if (substr($tmp['dat'],1) == "") $tmp['dat'] = substr($tmp['dat'],1);
$ret[$k] = $tmp['dat'];
}
}
// reset the genre
if ($g = $ret['Genre'])
{
if (substr($g,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] : 'Unk
Nown');
}
}
$ret['ID3v1'] = 'no';
return $ret;
}
// get
Meta info of MP3
function
getMeta_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(0,48,56,80,112,
3 => array(0,40,0)
),
2 => array(
1 => array(0,144,176,8,16,24,0)
)
);
$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(44100,48000,32000,2=>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
$items = array('Title','AlbumTitle');
foreach ($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['Title'],$tmp['Artist'],$tmp['AlbumTitle'],
$tmp['Year'],$tmp['Description'],$tmp['Track'],$tmp['Genre']);
flock($this->fd,SEEK_END);
fwrite($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( 'T
cop'=>'
copyright','TRAC'=>'Track','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
// 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 ";
$head_buf = pack('a3CCCCCCC',$tmp['ver'],$tmp['rev'],$tmp['flag'],
$size[1],$size[2],$size[3],$size[4]);
$head_buf .= $head_body;
$this->_file_save($head_buf,$new_len);
}
}
?>
