const IEEE, Castagnoli, Koopman
Common reversed polynomials.
v0 source pure
Package crc32 implements the CRC-32 checksum as a pure, reusable package.
View source
gno.land/p/moul/x/daily/crc32/v0
CRC-32 checksum — Checksum, ChecksumHex, ChecksumWith, Verify,
MakeTable, Update, Finalize, Hex, Split.
Treats a message as one enormous binary number and takes the remainder of dividing it by a fixed polynomial. The bit-reflected, table-driven form — the one zip, gzip, PNG and Ethernet actually use.
1import "gno.land/p/moul/x/daily/crc32/v0"
2
3crc32.ChecksumHex("123456789") // "cbf43926" — the standard check value
4crc32.Checksum("abc") // 0x352441C2
5crc32.Verify("abc", 0x352441C2) // true
Three polynomials: IEEE (zip/gzip/PNG, the default), Castagnoli
(iSCSI/btrfs, better error detection) and Koopman. MakeTable builds the
256-entry table once — that is the whole point of the table-driven form, trading
1 KiB for eight bit-shifts per byte.
Update/Finalize take and return the raw register, not the finished
checksum, so a long message can be fed in chunks. Chaining on final values would
be wrong; there is a test asserting chunked equals one-shot.
⚠️ A CRC detects accidents, not tampering. It is linear, so anyone can craft a different message with the same checksum. Never use it to authenticate anything.
Live demo: r/moul/x/daily/crc32demo
· render it at /r/moul/x/daily/crc32demo/v0.
Part of moul/gno-contracts — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.
🧪 Highly experimental — potentially vibe-coded. Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: DISCLAIMER.
Package crc32 implements the CRC-32 checksum as a pure, reusable package.
CRC-32 treats a message as one enormous binary number and takes the remainder of dividing it by a fixed polynomial. The bit-reflected, table-driven form implemented here is the one everything actually uses — zip, gzip, PNG, and Ethernet all speak IEEE.
Three polynomials are provided:
- IEEE (0xEDB88320) — zip/gzip/PNG. The default.
- Castagnoli (0x82F63B78) — iSCSI/btrfs; better error detection.
- Koopman (0xEB31D82E)
A CRC is an ACCIDENT detector, not a security primitive: it is linear, so anyone can craft a different message with the same checksum. Never use it to authenticate anything.
A live demo of this package is at r/moul/x/daily/crc32demo(/r/moul/x/daily/crc32demo/v0).
1
9
func Checksum
Checksum returns the IEEE CRC-32 of s — the one zip, gzip and PNG use.
func ChecksumHex
ChecksumHex is Checksum rendered with Hex.
func ChecksumWith
ChecksumWith returns the CRC-32 of s under the given table.
func Finalize
Finalize turns a running register into the checksum.
func Hex
Hex renders a checksum as eight lowercase hex digits, zero-padded, which is how CRCs are conventionally shown.
func Split
Split returns the checksum of each line of s, in order.
func Update
Update adds the bytes of s to a running checksum.
Takes and returns the RAW register, not the final value: the caller-visible checksum is the register XOR 0xFFFFFFFF, so chaining Update calls on final values would be wrong. Start from 0 and finish with Finalize.
func Verify
Verify reports whether s has the expected checksum.
func MakeTable
MakeTable builds the lookup table for a reversed polynomial. Building it once and reusing it is the whole point of the table-driven form: it trades 1 KiB for eight bit-shifts per byte.
1
Imports 1
/p/g1magld5ptgzaktqcexxq0pgq5lmdf0kz6re8hlv/x/daily/crc32/v0
