Copyright 2011 The Go Authors. All rights reserved. Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
This file contains CRC32 algorithms that are not specific to any architecture and don't use hardware acceleration. The simple (and slow) CRC32 implementation only uses a 256*4 bytes table. The slicing-by-8 algorithm is a faster implementation that uses a bigger table (8*256*4 bytes).

package crc32
simpleMakeTable allocates and constructs a Table for the specified polynomial. The table is suitable for use with the simple algorithm (simpleUpdate).
func ( uint32) *Table {
	 := new(Table)
	simplePopulateTable(, )
	return 
}
simplePopulateTable constructs a Table for the specified polynomial, suitable for use with simpleUpdate.
func ( uint32,  *Table) {
	for  := 0;  < 256; ++ {
		 := uint32()
		for  := 0;  < 8; ++ {
			if &1 == 1 {
				 = ( >> 1) ^ 
			} else {
				 >>= 1
			}
		}
		[] = 
	}
}
simpleUpdate uses the simple algorithm to update the CRC, given a table that was previously computed using simpleMakeTable.
func ( uint32,  *Table,  []byte) uint32 {
	 = ^
	for ,  := range  {
		 = [byte()^] ^ ( >> 8)
	}
	return ^
}
Use slicing-by-8 when payload >= this value.
const slicing8Cutoff = 16
slicing8Table is array of 8 Tables, used by the slicing-by-8 algorithm.
type slicing8Table [8]Table
slicingMakeTable constructs a slicing8Table for the specified polynomial. The table is suitable for use with the slicing-by-8 algorithm (slicingUpdate).
func ( uint32) *slicing8Table {
	 := new(slicing8Table)
	simplePopulateTable(, &[0])
	for  := 0;  < 256; ++ {
		 := [0][]
		for  := 1;  < 8; ++ {
			 = [0][&0xFF] ^ ( >> 8)
			[][] = 
		}
	}
	return 
}
slicingUpdate uses the slicing-by-8 algorithm to update the CRC, given a table that was previously computed using slicingMakeTable.
func ( uint32,  *slicing8Table,  []byte) uint32 {
	if len() >= slicing8Cutoff {
		 = ^
		for len() > 8 {
			 ^= uint32([0]) | uint32([1])<<8 | uint32([2])<<16 | uint32([3])<<24
			 = [0][[7]] ^ [1][[6]] ^ [2][[5]] ^ [3][[4]] ^
				[4][>>24] ^ [5][(>>16)&0xFF] ^
				[6][(>>8)&0xFF] ^ [7][&0xFF]
			 = [8:]
		}
		 = ^
	}
	if len() == 0 {
		return 
	}
	return simpleUpdate(, &[0], )