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src/crc.bend checks

raw source on the hub · import 0x57618559b9b26dd8415f821176a3e692/src/crc.bend as Crc

src/crc: CRC-32. PNG covers the chunk type and the chunk data with the ISO 3309 / ITU-T V.42 polynomial (ISO/IEC 15948 / W3C PNG).

1 import
import Base

Definitions

def crc.poly source · line 6 · raw

U32

the reflected polynomial

def crc.bit source · line 10 · raw

@nn:Nat -> @odd:Bool -> @+cc:U32 -> U32

eight shifts, one per bit, low bit first. The Nat shrinks, so it is first.

def crc.byte source · line 22 · raw

@+cc:U32 -> @+bb:U32 -> U32

fold one byte into the register

def crc.fold source · line 27 · raw

@xs:List<&2, U32> -> @+cc:U32 -> U32

fold every byte, register still inverted. The list shrinks, so it is first.

def crc32 source · line 35 · raw

@xs:List<&2, U32> -> U32

CRC-32 of the bytes, init and final xor all ones