23 lines
610 B
Nim
23 lines
610 B
Nim
import unsigned, strutils
|
|
|
|
type TCrc32* = uint32
|
|
const InitCrc32* = TCrc32(-1)
|
|
|
|
proc createCrcTable(): array[0..255, TCrc32] =
|
|
for i in 0..255:
|
|
var rem = TCrc32(i)
|
|
for j in 0..7:
|
|
if (rem and 1) > 0: rem = (rem shr 1) xor TCrc32(0xedb88320)
|
|
else: rem = rem shr 1
|
|
result[i] = rem
|
|
|
|
# Table created at compile time
|
|
const crc32table = createCrcTable()
|
|
|
|
proc crc32(s: string): TCrc32 =
|
|
result = InitCrc32
|
|
for c in s:
|
|
result = (result shr 8) xor crc32table[(result and 0xff) xor ord(c)]
|
|
result = not result
|
|
|
|
echo crc32("The quick brown fox jumps over the lazy dog").int64.toHex(8)
|