示例类注册为流封装器

下面的示例实现了一个 var:// 协议处理程序,允许使用诸如 fread() 之类的标准文件系统流函数对有名称的全局变量进行读写访问。下面实现的 var:// 协议,指定的 URL “var://foo” 将从 $GLOBALS["foo"] 读写数据。

示例 #1 用于读写全局变量的流

<?php

class VariableStream {
var
$position;
var
$varname;

function
stream_open($path, $mode, $options, &$opened_path)
{
$url = parse_url($path);
$this->varname = $url["host"];
$this->position = 0;

return
true;
}

function
stream_read($count)
{
$ret = substr($GLOBALS[$this->varname], $this->position, $count);
$this->position += strlen($ret);
return
$ret;
}

function
stream_write($data)
{
$left = substr($GLOBALS[$this->varname], 0, $this->position);
$right = substr($GLOBALS[$this->varname], $this->position + strlen($data));
$GLOBALS[$this->varname] = $left . $data . $right;
$this->position += strlen($data);
return
strlen($data);
}

function
stream_tell()
{
return
$this->position;
}

function
stream_eof()
{
return
$this->position >= strlen($GLOBALS[$this->varname]);
}

function
stream_seek($offset, $whence)
{
switch (
$whence) {
case
SEEK_SET:
if (
$offset < strlen($GLOBALS[$this->varname]) && $offset >= 0) {
$this->position = $offset;
return
true;
} else {
return
false;
}
break;

case
SEEK_CUR:
if (
$offset >= 0) {
$this->position += $offset;
return
true;
} else {
return
false;
}
break;

case
SEEK_END:
if (
strlen($GLOBALS[$this->varname]) + $offset >= 0) {
$this->position = strlen($GLOBALS[$this->varname]) + $offset;
return
true;
} else {
return
false;
}
break;

default:
return
false;
}
}

function
stream_metadata($path, $option, $var)
{
if(
$option == STREAM_META_TOUCH) {
$url = parse_url($path);
$varname = $url["host"];
if(!isset(
$GLOBALS[$varname])) {
$GLOBALS[$varname] = '';
}
return
true;
}
return
false;
}
}

stream_wrapper_register("var", "VariableStream")
or die(
"Failed to register protocol");

$myvar = "";

$fp = fopen("var://myvar", "r+");

fwrite($fp, "line1\n");
fwrite($fp, "line2\n");
fwrite($fp, "line3\n");

rewind($fp);
while (!
feof($fp)) {
echo
fgets($fp);
}
fclose($fp);
var_dump($myvar);

?>

以上示例会输出:

line1
line2
line3
string(18) "line1
line2
line3
"

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