perl中pack函数的实例

$foo = pack("WWWW",65,66,67,68); # foo eq "ABCD" $foo = pack("W4",65,66,67,68); # same thing $foo = pack("W4",0x24b6,0x24b7,0x24b8,0x24b9); # same thing with Unicode circled letters. $foo = pack("U4",0x24b6,0x24b7,0x24b8,0x24b9); # same thing with Unicode circled letters. You don't get the UTF-8 # bytes because the U at the start of the format caused a switch to # U0-mode, so the UTF-8 bytes get joined into characters $foo = pack("C0U4",0x24b6,0x24b7,0x24b8,0x24b9); # foo eq "/xe2/x92/xb6/xe2/x92/xb7/xe2/x92/xb8/xe2/x92/xb9" # This is the UTF-8 encoding of the string in the previous example $foo = pack("ccxxcc",65,66,67,68); # foo eq "AB/0/0CD" # NOTE: The examples above featuring "W" and "c" are true # only on ASCII and ASCII-derived systems such as ISO Latin 1 # and UTF-8. On EBCDIC systems, the first example would be # $foo = pack("WWWW",193,194,195,196); $foo = pack("s2",1,2); # "/1/0/2/0" on little-endian # "/0/1/0/2" on big-endian $foo = pack("a4","abcd","x","y","z"); # "abcd" $foo = pack("aaaa","abcd","x","y","z"); # "axyz" $foo = pack("a14","abcdefg"); # "abcdefg/0/0/0/0/0/0/0" $foo = pack("i9pl", gmtime); # a real struct tm (on my system anyway) $utmp_template = "Z8 Z8 Z16 L"; $utmp = pack($utmp_template, @utmp1); # a struct utmp (BSDish) @utmp2 = unpack($utmp_template, $utmp); # "@utmp1" eq "@utmp2" sub bintodec { unpack("N", pack("B32", substr("0" x 32 . shift, -32))); } $foo = pack('sx2l', 12, 34); # short 12, two zero bytes padding, long 34 $bar = pack('s@4l', 12, 34); # short 12, zero fill to position 4, long 34 # $foo eq $bar $baz = pack('s.l', 12, 4, 34); # short 12, zero fill to position 4, long 34 $foo = pack('nN', 42, 4711); # pack big-endian 16- and 32-bit unsigned integers $foo = pack('S>L>', 42, 4711); # exactly the same $foo = pack('s<l<', -42, 4711); # pack little-endian 16- and 32-bit signed integers $foo = pack('(sl)<', -42, 4711); # exactly the same