Module crc

Public because a checksum is a checksum. copy verifies a file it has just written with the same CRC-32 routine Ogg pages are checked with, rather than growing a second implementation of the same polynomial next door. The three cyclic redundancy checks the audio containers carry.

Each is defined by its polynomial and by whether the bits are reflected, and the three used here disagree on both counts — so they are written out rather than derived from one another.

Where	Width	Polynomial	Covers
FLAC frame header	8	0x07	the header, up to the byte before the CRC
FLAC frame	16	0x8005	the whole frame, up to the two bytes before the CRC
Ogg page	32	0x04C11DB7	the page, its own CRC field read as zero

Tables are built at first use rather than written out: 256 entries computed in a few microseconds are easier to trust than 256 constants copied by hand.

Functions

crc8

CRC-8 as FLAC uses it: polynomial 0x07, no reflection, zero seed.

crc16

CRC-16 as FLAC uses it: polynomial 0x8005, no reflection, zero seed.

crc32_ogg

CRC-32 as Ogg uses it: polynomial 0x04C11DB7, no reflection and no final inversion — which is what sets it apart from the CRC-32 of zip and PNG, and why a general-purpose implementation cannot be reused here.