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php使用pack處理二進(jìn)制文件的方法
文章主要介紹了php使用pack處理二進(jìn)制文件的方法,需要的朋友可以參考下.php讀寫(xiě)二進(jìn)制文件可以使用pack和unpack函數(shù)。天要處理一個(gè)二進(jìn)制文件的問(wèn)題，所以需要用一下，特意了解一下pack的用法，unpack用法與此類(lèi)似。
簡(jiǎn)單來(lái)說(shuō)，pack函數(shù)就是給一個(gè)目標(biāo)格式，和相應(yīng)的參數(shù)，就可以返回二進(jìn)制數(shù)據(jù)了。
下面舉例加以說(shuō)明，對(duì)于四個(gè)整數(shù)：
pack("L4", 0,1,2,3)
pack("LLLL", 0,1,2,3)
pack("L", 0).pack("L", 1).pack("L", 2).pack("L", 3)
上面的處理結(jié)果是一樣的，也就是說(shuō)，format是描述后面的數(shù)據(jù)的格式。
至于具體format可以用什么，看看format characters就知道了。
比如一個(gè)30字符的 pack("a30", "http://www.jb51.net") ，就是這個(gè)意思，很簡(jiǎn)單
pack函數(shù)的官方聲明如下：
引用
pack
(PHP 3, PHP 4, PHP 5)
pack -- Pack data into binary string
Description
string pack ( string format [, mixed args [, mixed ...]] )
Pack given arguments into binary string according to format. Returns binary string containing data.
The idea to this function was taken from Perl and all formatting codes work the same as there, however, there are some formatting codes that are missing such as Perl's "u" format code. The format string consists of format codes followed by an optional repeater argument. The repeater argument can be either an integer value or * for repeating to the end of the input data. For a, A, h, H the repeat count specifies how many characters of one data argument are taken, for @ it is the absolute position where to put the next data, for everything else the repeat count specifies how many data arguments are consumed and packed into the resulting binary string. Currently implemented are
表格 1. pack() format characters
Code Description
a NUL-padded string
A SPACE-padded string
h Hex string, low nibble first
H Hex string, high nibble first
c signed char
C unsigned char
s signed short (always 16 bit, machine byte order)
S unsigned short (always 16 bit, machine byte order)
n unsigned short (always 16 bit, big endian byte order)
v unsigned short (always 16 bit, little endian byte order)
i signed integer (machine dependent size and byte order)
I unsigned integer (machine dependent size and byte order)
l signed long (always 32 bit, machine byte order)
L unsigned long (always 32 bit, machine byte order)
N unsigned long (always 32 bit, big endian byte order)
V unsigned long (always 32 bit, little endian byte order)
f float (machine dependent size and representation)
d double (machine dependent size and representation)
x NUL byte
X Back up one byte
@ NUL-fill to absolute position
看累了英文，下面來(lái)看看對(duì)應(yīng)的中文解釋?zhuān)?/p>
引用
pack()函數(shù)的作用是：將數(shù)據(jù)壓縮成一個(gè)二進(jìn)制字符串。
a - NUL-padded string
a - NUL- 字符串填滿(mǎn)[padded string]
A - SPACE-padded string
A - SPACE- 字符串填滿(mǎn)[padded string]
h - Hex string, low nibble first
h – 十六進(jìn)制字符串，低“四位元”[low nibble first]
H - Hex string, high nibble first
H - 十六進(jìn)制字符串，高“四位元”[high nibble first]
c - signed char
c – 帶有符號(hào)的字符
C - unsigned char
C – 不帶有符號(hào)的字符
s - signed short (always 16 bit, machine byte order)
s – 帶有符號(hào)的短模式[short]（通常是16位，按機(jī)器字節(jié)順序）
S - unsigned short (always 16 bit, machine byte order)
S – 不帶有符號(hào)的短模式[short]（通常是16位，按機(jī)器字節(jié)排序）
n - unsigned short (always 16 bit, big endian byte order)
n -不帶有符號(hào)的短模式[short]（通常是16位，按大endian字節(jié)排序）
v - unsigned short (always 16 bit, little endian byte order)
v -不帶有符號(hào)的短模式[short]（通常是16位，按小endian字節(jié)排序）
i - signed integer (machine dependent size and byte order)
i – 帶有符號(hào)的整數(shù)（由大小和字節(jié)順序決定）
I - unsigned integer (machine dependent size and byte order)
I – 不帶有符號(hào)的整數(shù)（由大小和字節(jié)順序決定）
l - signed long (always 32 bit, machine byte order)
l– 帶有符號(hào)的長(zhǎng)模式[long]（通常是32位，按機(jī)器字節(jié)順序）
L - unsigned long (always 32 bit, machine byte order)
L – 不帶有符號(hào)的長(zhǎng)模式[long]（通常是32位，按機(jī)器字節(jié)順序）
N - unsigned long (always 32 bit, big endian byte order)
N – 不帶有符號(hào)的長(zhǎng)模式[long]（通常是32位，按大edian字節(jié)順序）
V - unsigned long (always 32 bit, little endian byte order)
V– 不帶有符號(hào)的長(zhǎng)模式[long]（通常是32位，按小edian字節(jié)順序）
f - float (machine dependent size and representation)
f –浮點(diǎn)（由大小和字節(jié)順序決定）
d - double (machine dependent size and representation)
d – 雙精度（由大小和字節(jié)順序決定）
x - NUL byte
x – 空字節(jié)[NUL byte]
X - Back up one byte
X- 后面一個(gè)字節(jié)[Back up one byte]
@ - NUL-fill to absolute position
@ - NUL- 添加到一個(gè)絕對(duì)位置[absolute position]
示例代碼如下：
?
<?php
$code=array(
"username"=>array("A7","張三adfb12"),
"pass"=>array("A10","asdf*#1"),
"age"=>array("C","23"),
"birthday"=>array("I","19900101"),
"email"=>array("A50","www.jb51.net"));
$stream=join("\0",parkByArr($code));
echo $stream,strlen($stream);
file_put_contents("1.txt",$stream);//將流保存起來(lái)便于下面讀取
function parkByArr($arr)
{
$atArr=array();
foreach ($arr as $k=>$v)
{
$atArr[]=pack($v[0],$v[1]);
}
return $atArr;
}
function getAscill($str)
{
$arr=str_split($str);
foreach ($arr as $v)
{
echo $v,"=",ord($v),"\n";
}
}
$code=array(
"username"=>array("A20"),
"pass"=>array("A10"),
"age"=>array("C"),
"birthday"=>array("I"),
"email"=>array("A50"));
$stream=file_get_contents("1.txt");
var_dump(parkByArr($stream,$code));
function parkByArr($str,$code)
{
$Arr=explode("\0",$str);
$atArr=array();
$i=0;
foreach ($code as $k=>$v)
{
$atArr[$k]=unpack($v[0],$Arr[$i]);
$i++;
}
return $atArr;
}
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