7.7
crc32c
Tetsumi <testumi@protonmail.com>
| (require crc32c) | package: crc32c |
This package provides an implementation of CRC32-C.
CRC32-C is specified as the CRC that uses the iSCSI polynomial (#x1edc6f41) in RFC 3720. The polynomial was introduced by G. Castagnoli, S. Braeuer and M. Herrmann.
1 Basic Generation
procedure
(crc32c-bytes bytes) → fixnum?
bytes : bytes?
Generates a checksum from a bytes? object.
Example:
> (crc32c-bytes #"Lorem ipsum dolor sit amet") 3993763883
procedure
(crc32c-string/utf8 string) → fixnum?
string : string? (crc32c-string/latin-1 string) → fixnum? string : string? (crc32c-string/locale string) → fixnum? string : string?
Generates a checksum from a string? object.
Example:
> (crc32c-string/utf8 "Lorem ipsum dolor sit amet") 3993763883
procedure
(crc32c-input-port [in]) → fixnum?
in : input-port? = (current-input-port)
Generates a checksum reading bytes from an input-port? object.
Examples:
> (crc32c-input-port (open-input-bytes #"Lorem ipsum dolor sit amet")) 3993763883
> (crc32c-input-port (open-input-string "Lorem ipsum dolor sit amet")) 3993763883
2 Incremental Generation
The following procedures generate a checksum incrementally, one byte at a time.
value
crc32c-initial-value : fixnum? = 4294967295
Initial value to use to start the generation of a checksum.
procedure
(crc32c-update acc byte) → fixnum?
acc : fixnum? byte : byte?
Returns updated acc after using byte.
Example:
> (crc32c-update crc32c-initial-value 123) 1167283096
procedure
(crc32c-finalize acc) → fixnum?
acc : fixnum?
Finalizes the generation by applying the final XOR operation to acc.
Examples:
> (crc32c-finalize (crc32c-update crc32c-initial-value 123)) 3127684199
> (for/fold ([acc crc32c-initial-value] #:result (crc32c-finalize acc)) ([ch "Lorem ipsum dolor sit amet"]) (crc32c-update acc (char->integer ch))) 3993763883