crc32c

8.16.0.1

crc32c🔗ℹ

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🔗ℹ

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🔗ℹ

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