php使用pack处理二进制文件的方法

来源：文书网 2.2W

文章主要介绍了php使用pack处理二进制文件的方法,需要的朋友可以参考下读写二进制文件可以使用pack和unpack函数。天要处理一个二进制文件的问题，所以需要用一下，特意了解一下pack的用法，unpack用法与此类似。

简单来说，pack函数就是给一个目标格式，和相应的参数，就可以返回二进制数据了。

　　下面举例加以说明，对于四个整数：

pack("L4", 0,1,2,3)

pack("LLLL", 0,1,2,3)

pack("L", 0)("L", 1)("L", 2)("L", 3)

上面的处理结果是一样的，也就是说，format是描述后面的数据的格式。

至于具体format可以用什么，看看format characters就知道了。

比如一个30字符的 pack("a30", "") ，就是这个意思，很简单

pack函数的官方声明如下：

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)