Perl pack()函數

perl pack()函數例子，pack()函數實例代碼 - 計算該表達式在列表中，包成一個指定的EXPR的二元結構。

語法

pack EXPR, LIST

定義和用法

計算該表達式在列表中，包成一個指定的EXPR的二元結構。使用下表中所示的字符格式指定：

每個字符可以被後麵可以跟一個數字，指定重複次數的類型被包裝的的值。是半字節，字符，或偶數比特，根據該格式。*重複值，為儘可能多的價值保留在LIST中。值可以解壓縮與解壓縮功能。

例如，A5預期表示五個字母。B32表示，預期32位。為h8表示預期8 nybbles（或4個字節）。P10表示的結構是10個字節長。

返回值

• 包（packed）的版本使用模板來確定它是如何編碼的數據列表。

下麵是表，它給出在TEMPLATE要使用的值。

Character	Description
a	ASCII character string padded with null characters
A	ASCII character string padded with spaces
b	String of bits, lowest first
B	String of bits, highest first
c	A signed character (range usually -128 to 127)
C	An unsigned character (usually 8 bits)
d	A double-precision floating-point number
f	A single-precision floating-point number
h	Hexadecimal string, lowest digit first
H	Hexadecimal string, highest digit first
i	A signed integer
I	An unsigned integer
l	A signed long integer
L	An unsigned long integer
n	A short integer in network order
N	A long integer in network order
p	A pointer to a string
s	A signed short integer
S	An unsigned short integer
u	Convert to uuencode format
v	A short integer in VAX (little-endian) order
V	A long integer in VAX order
x	A null byte
X	Indicates "go back one byte"
@	Fill with nulls (ASCII 0)

例子

試試下麵的例子：

#!/usr/bin/perl -w
#by www.gitbook.net

$bits = pack("c", 65);
# prints A, which is ASCII 65.
print "bits are $bits\n";
$bits = pack( "x" );
# $bits is now a null chracter.
print "bits are $bits\n";
$bits = pack( "sai", 255, "T", 30 );
# creates a seven charcter string on most computers'
print "bits are $bits\n";

@array = unpack( "sai", "$bits" );

#Array now contains three elements: 255, T and 30.
print "Array $array[0]\n";
print "Array $array[1]\n";
print "Array $array[2]\n";

這將產生以下這些二進製結果：

bits are A
bits are
bits are �T
Array 255
Array T
Array 30

請查看Socket編程會話，看看 pack 函數的使用。