实例分析：实现一个PHPWAV接合方案

WAV PCM文件的最大优点在于，你无需进行任何绑定操作，就能将来自两个文件的二进制音频数据连接起来。你只需把其中一个文件的二进制数据粘合到另一个文件的末尾，再调整一下Subchunk2Size值，即可实现两个文件的接合。唯一的缺点是这两个文件的格式必须相同；在本例中，不涉及问题。

当解析音频文件时，先将二进制音频数据读入一个缓冲数组中，然后再将另一个文件的数据读到这个数组的末端。重复这一过程直到所有的文件都被读取完毕。创建一个FILESTRUCT结构，填入格式信息，调整Subchunk2Size值，将Data成员设为缓冲数组，将FILESTRUCT写为需要的输出格式。对于基于PHP的Web发布系统，其输出为标准输出。以下为示范代码：

function StitchFiles(&$fsFile, &$sFiles) {

$fsFiles = array(); //FILESTRUCT

$lFileSize = 0;

$lOffset = 0;

$bData = array(); //byte

for ($i = 0; $i < count($sFiles); $i++) {

$fsFiles[$i] = new FILESTRUCT();

SetFile($fsFiles[$i], $sFiles[$i]);

$lSize = CalcLittleEndianValue($fsFiles[$i]-Subchunk2Size);

$lFileSize = $lFileSize + $lSize;

$bData = array_merge($bData, $fsFiles[$i]-Data);

$lOffset = $lOffset + $lSize;

}

$fsFile-ChunkID = $GLOBALS["ChunkID_"];

$fsFile-ChunkSize = GetLittleEndianByteArray(36 + $lFileSize);

$fsFile-Format = $GLOBALS["FileFormat_"];

$fsFile-Subchunk1ID = $GLOBALS["Subchunk1ID_"];

$fsFile-Subchunk1Size = array(0x10, 0x0, 0x0, 0x0);

$fsFile-AudioFormat = $GLOBALS["AudioFormat_"];

$fsFile-NumChannels = $GLOBALS["Stereo_"];

$fsFile-SampleRate = $GLOBALS["SampleRate_"];

$fsFile-ByteRate = GetLittleEndianByteArray(

CalcLittleEndianValue($GLOBALS["SampleRate_"]) *

CalcLittleEndianValue($GLOBALS["Stereo_"]) *

(CalcLittleEndianValue($GLOBALS["BitsPerSample_"]) / 8));

$fsFile-BlockAlign =

array_splice(GetLittleEndianByteArray(CalcLittleEndianValue($GLOBALS["Stereo_"]

) * (CalcLittleEndianValue($GLOBALS["BitsPerSample_"]) / 8)), 0, 2);

$fsFile-BitsPerSample = $GLOBALS["BitsPerSample_"];

$fsFile-Subchunk2ID = $GLOBALS["Subchunk2ID_"];

$fsFile-Subchunk2Size = GetLittleEndianByteArray($lFileSize);

$fsFile-Data = $bData;

}

本调用的第一个参数是对FILESTRUCT对象的引用。第二个参数是对一列文件名字符串的引用。在每次for循环中，我都将列表中的一个文件名载入一个FILESTRUCT中，然后再将每一个FILESTRUCT的Data属性提取出来，并合并到一个现有的缓冲区中。完成以上操作后，我通过一个事先声明的全局变量对FILESTRUCT参数对象的属性进行设定，然后改变Subchunk2Size属性，并将Data属性设为新的缓冲区。

你可能注意到，我使用了一些功能函数来填充FILESTRUCT结构、计算来自little endian字节数组的数值、创建little endian字节数组和拆分字符串为二进制数组。以下为这些函数：

function SetFile(&$fsFile_, $sFileName) {

$lSize = 1;

if (file_exists($sFileName)) {

$fil = fopen($sFileName, "rb");

$contents = fread($fil, count($fsFile_-ChunkID));

$fsFile_-ChunkID = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-ChunkSize));

$fsFile_-ChunkSize = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-Format));

$fsFile_-Format = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-Subchunk1ID));

$fsFile_-Subchunk1ID = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-Subchunk1Size));

$fsFile_-Subchunk1Size = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-AudioFormat));

$fsFile_-AudioFormat = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-NumChannels));

$fsFile_-NumChannels = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-SampleRate));

$fsFile_-SampleRate = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-ByteRate));

$fsFile_-ByteRate = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-BlockAlign));

$fsFile_-BlockAlign = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-BitsPerSample));

$fsFile_-BitsPerSample = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-Subchunk2ID));

$fsFile_-Subchunk2ID = bin_split($contents, 1);

$contents = fread($fil, count($fsFile_-Subchunk2Size));

$fsFile_-Subchunk2Size = bin_split($contents, 1);

$lSize = CalcLittleEndianValue($fsFile_-Subchunk2Size);

$contents = fread($fil, $lSize);

$fsFile_-Data = bin_split($contents, 1);

fclose($fil);

}

}

function CalcLittleEndianValue(&$bValue) {

$lSize_ = 0;

for ($iByte = 0; $iByte < count($bValue); $iByte++) {

$lSize_ += ($bValue[$iByte] * pow(16, ($iByte * 2)));

}

return $lSize_;

}

function GetLittleEndianByteArray($lValue) {

$running = 0;

$b = array(0, 0, 0, 0);

$running = $lValue / pow(16,6);

$b[3] = floor($running);

$running -= $b[3];

$running *= 256;

$b[2] = floor($running);

$running -= $b[2];

$running *= 256;

$b[1] = floor($running);

$running -= $b[1];

$running *= 256;

$b[0] = round($running);

return $b;

}

function bin_split($text, $c)

{

$arr = array();

$len = strlen($text);

$a = 0;

while($a < $len)

{

if ($a + $c $len)

{

$c = $len - $a;

}

$arr[$a] = ord(substr($text, $a, $c));

$a += $c;

}

return $arr;

}

为了实现这个类的功能，你可以创建一个CStitcher实例并调用StitchFiles()方法，以传递合适的参数：

$ChunkID_ = array(0x52, 0x49, 0x46, 0x46); //"RIFF" big endian

$FileFormat_ = array(0x57, 0x41, 0x56, 0x45); //"WAVE" big endian

$Subchunk1ID_ = array(0x66, 0x6D, 0x74, 0x20); //"fmt" big endian

$AudioFormat_ = array(0x1, 0x0); //PCM = 1 little endian

$Stereo_ = array(0x2, 0x0); //Stereo = 2 little endian

$Mono_ = array(0x1, 0x0); //Mono = 1 little endian

$SampleRate_ = array(0x44, 0xAC, 0x0, 0x0); //44100 little endian

$BitsPerSample_ = array(0x10, 0x0); //16 little endian

$Subchunk2ID_ = array(0x64, 0x61, 0x74, 0x61); //"data" big endian

$files = array("C:\\Inetpub\\wwwroot\\Test\\PHP\\1.wav",

"C:\\Inetpub\\wwwroot\\Test\\PHP\\2.wav");

$Stitcher = new CStitcher();

$file = new FILESTRUCT();

$Stitcher-StitchFiles($file, $files);

可用以下代码将二进制数据写到HTTP输出中：

header('Content-type: audio/x-wav', true);

header('Content-Disposition: attachment;filename=stitch.wav');

foreach($file-ChunkID as $val) {

print chr($val);

}

foreach($file-ChunkSize as $val) {

print chr($val);

}

foreach($file-Format as $val) {

print chr($val);

}

foreach($file-Subchunk1ID as $val) {

print chr($val);

}

foreach($file-Subchunk1Size as $val) {

print chr($val);

}

foreach($file-AudioFormat as $val) {

print chr($val);

}

foreach($file-NumChannels as $val) {

print chr($val);

}

foreach($file-SampleRate as $val) {

print chr($val);

}

foreach($file-ByteRate as $val) {

print chr($val);

}

foreach($file-BlockAlign as $val) {

print chr($val);

}

foreach($file-BitsPerSample as $val) {

print chr($val);

}

foreach($file-Subchunk2ID as $val) {

print chr($val);

}

foreach($file-Subchunk2Size as $val) {

print chr($val);

}

foreach($file-Data as $val) {

print chr($val);

}

以下是一段HTML代码，用于测试结果：

<html

<head

<sc

• ·Apache服务器Log分析应用实例
• ·分析PHP比ASP优秀的七个理由
• ·教您如何应用PHP开发出安全的应用程序
• ·成功迈向诺贝尔之路：诺贝尔文学奖获得者篇|报价
• ·举例说明：在PHP中运行XPath查询
• ·芝麻开门(附盘)|报价￥21.50|图书,英语
• ·用PHP实现通过Web执行C/C++程序
• ·亲密接触：在PHP下实现持久化
• ·提升PHP执行速度全攻略分析
• ·Windows服务器安装多套PHP的解决方案