CRC32 Calculation

Monkey Forums/Monkey Code/CRC32 Calculation

Goodlookinguy(Posted 2012) [#1]
I made this crc32 calculation for simple various verification. I thought it might be of use to others.

Requirements: You need my Lsr function from this post http://www.monkeycoder.co.nz/Community/posts.php?topic=1707#28645 which is included in the zip file I provided ready-to-go.

Full ZIP: http://dump.nrgs.org/monkey/moremojo.zip

[monkeycode]Global CRC32Table:Int[] = [
$00000000, $77073096, $ee0e612c, $990951ba, $076dc419, $706af48f, $e963a535,
$9e6495a3, $0edb8832, $79dcb8a4, $e0d5e91e, $97d2d988, $09b64c2b, $7eb17cbd,
$e7b82d07, $90bf1d91, $1db71064, $6ab020f2, $f3b97148, $84be41de, $1adad47d,
$6ddde4eb, $f4d4b551, $83d385c7, $136c9856, $646ba8c0, $fd62f97a, $8a65c9ec,
$14015c4f, $63066cd9, $fa0f3d63, $8d080df5, $3b6e20c8, $4c69105e, $d56041e4,
$a2677172, $3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b, $35b5a8fa, $42b2986c,
$dbbbc9d6, $acbcf940, $32d86ce3, $45df5c75, $dcd60dcf, $abd13d59, $26d930ac,
$51de003a, $c8d75180, $bfd06116, $21b4f4b5, $56b3c423, $cfba9599, $b8bda50f,
$2802b89e, $5f058808, $c60cd9b2, $b10be924, $2f6f7c87, $58684c11, $c1611dab,
$b6662d3d, $76dc4190, $01db7106, $98d220bc, $efd5102a, $71b18589, $06b6b51f,
$9fbfe4a5, $e8b8d433, $7807c9a2, $0f00f934, $9609a88e, $e10e9818, $7f6a0dbb,
$086d3d2d, $91646c97, $e6635c01, $6b6b51f4, $1c6c6162, $856530d8, $f262004e,
$6c0695ed, $1b01a57b, $8208f4c1, $f50fc457, $65b0d9c6, $12b7e950, $8bbeb8ea,
$fcb9887c, $62dd1ddf, $15da2d49, $8cd37cf3, $fbd44c65, $4db26158, $3ab551ce,
$a3bc0074, $d4bb30e2, $4adfa541, $3dd895d7, $a4d1c46d, $d3d6f4fb, $4369e96a,
$346ed9fc, $ad678846, $da60b8d0, $44042d73, $33031de5, $aa0a4c5f, $dd0d7cc9,
$5005713c, $270241aa, $be0b1010, $c90c2086, $5768b525, $206f85b3, $b966d409,
$ce61e49f, $5edef90e, $29d9c998, $b0d09822, $c7d7a8b4, $59b33d17, $2eb40d81,
$b7bd5c3b, $c0ba6cad, $edb88320, $9abfb3b6, $03b6e20c, $74b1d29a, $ead54739,
$9dd277af, $04db2615, $73dc1683, $e3630b12, $94643b84, $0d6d6a3e, $7a6a5aa8,
$e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1, $f00f9344, $8708a3d2, $1e01f268,
$6906c2fe, $f762575d, $806567cb, $196c3671, $6e6b06e7, $fed41b76, $89d32be0,
$10da7a5a, $67dd4acc, $f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5, $d6d6a3e8,
$a1d1937e, $38d8c2c4, $4fdff252, $d1bb67f1, $a6bc5767, $3fb506dd, $48b2364b,
$d80d2bda, $af0a1b4c, $36034af6, $41047a60, $df60efc3, $a867df55, $316e8eef,
$4669be79, $cb61b38c, $bc66831a, $256fd2a0, $5268e236, $cc0c7795, $bb0b4703,
$220216b9, $5505262f, $c5ba3bbe, $b2bd0b28, $2bb45a92, $5cb36a04, $c2d7ffa7,
$b5d0cf31, $2cd99e8b, $5bdeae1d, $9b64c2b0, $ec63f226, $756aa39c, $026d930a,
$9c0906a9, $eb0e363f, $72076785, $05005713, $95bf4a82, $e2b87a14, $7bb12bae,
$0cb61b38, $92d28e9b, $e5d5be0d, $7cdcefb7, $0bdbdf21, $86d3d2d4, $f1d4e242,
$68ddb3f8, $1fda836e, $81be16cd, $f6b9265b, $6fb077e1, $18b74777, $88085ae6,
$ff0f6a70, $66063bca, $11010b5c, $8f659eff, $f862ae69, $616bffd3, $166ccf45,
$a00ae278, $d70dd2ee, $4e048354, $3903b3c2, $a7672661, $d06016f7, $4969474d,
$3e6e77db, $aed16a4a, $d9d65adc, $40df0b66, $37d83bf0, $a9bcae53, $debb9ec5,
$47b2cf7f, $30b5ffe9, $bdbdf21c, $cabac28a, $53b39330, $24b4a3a6, $bad03605,
$cdd70693, $54de5729, $23d967bf, $b3667a2e, $c4614ab8, $5d681b02, $2a6f2b94,
$b40bbe37, $c30c8ea1, $5a05df1b, $2d02ef8d ]

Function CalculateCRC32:String( str:String, byteOrder:Bool = BigEndian, crc:Int = 0 )
crc = crc ~ (-1)

Local length:Int = str.Length

For Local index:Int = 0 Until length Step 1
crc = Lsr(crc, 8) ~ CRC32Table[(crc ~ str[index]) & $FF]
Next

Return DecimalToHex(crc ~ (-1), byteOrder)
End

Const LittleEndian:Bool = False
Const BigEndian:Bool = True

Function DecimalToHex:String( number:String, byteOrder:Bool = BigEndian )
Local charlist:String = "0123456789ABCDEF"
Local char:Int, ret:String, digitOne:Int, digitTwo:Int
Local num:Int = Int(number)

For Local index:Int = 0 Until 4
If byteOrder
char = Lsr(num, 8 * (3 - index)) & $FF
Else
char = Lsr(num, 8 * index) & $FF
End
digitOne = Lsr(char, 4) & 15
digitTwo = char & 15

ret += charlist[digitOne..digitOne + 1] + charlist[digitTwo..digitTwo + 1]
Next

Return ret
End[/monkeycode]

Example Code

[monkeycode]Function Main()
Print CalculateCRC32("Hello World!")
End[/monkeycode]


Rushino(Posted 2012) [#2]
Thanks you Goodlookinguy! Offcourse i think this gonna be really useful! I find this useful for sending out requests to a server and verify if the requests havent been changed.