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HomeBackend DevelopmentPHP TutorialPHP pack and unpack template character character meaning_PHP tutorial

format 参数的可能值:
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
a一个填充空的字节串
A一个填充空格的字节串
b一个位串,在每个字节里位的顺序都是升序
B一个位串,在每个字节里位的顺序都是降序
c一个有符号char(8位整数)值
C一个无符号char(8位整数)值;关于Unicode参阅U
d本机格式的双精度浮点数
f本机格式的单精度浮点数
h一个十六进制串,低四位在前
H一个十六进制串,高四位在前
i一个有符号整数值,本机格式
I一个无符号整数值,本机格式
l一个有符号长整形,总是32位
L一个无符号长整形,总是32位
n一个16位短整形,“网络”字节序(大头在前)
N一个32位短整形,“网络”字节序(大头在前)
p一个指向空结尾的字串的指针
P一个指向定长字串的指针
q一个有符号四倍(64位整数)值
Q一个无符号四倍(64位整数)值
s一个有符号短整数值,总是16位
S一个无符号短整数值,总是16位,字节序跟机器芯片有关
u一个无编码的字串
U一个Unicode字符数字
v一个“VAX”字节序(小头在前)的16位短整数
V一个“VAX”字节序(小头在前)的32位短整数
w一个BER压缩的整数
x一个空字节(向前忽略一个字节)
X备份一个字节
Z一个空结束的(和空填充的)字节串
规则:
1.每个字母后面都可以跟着一个数字,表示count(计数),如果count是一个*表示剩下的所有东西。
2.如果你提供的参数比$format要求的少,pack假设缺的都是空值。如果你提供的参数比$format要求的多,那么多余的参数被忽略。

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