github.com/insionng/yougam@v0.0.0-20170714101924-2bc18d833463/libraries/klauspost/crc32/crc32_amd64p32.go (about)

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // +build !appengine,!gccgo
     6  
     7  package crc32
     8  
     9  // This file contains the code to call the SSE 4.2 version of the Castagnoli
    10  // CRC.
    11  
    12  // haveSSE42 is defined in crc_amd64p32.s and uses CPUID to test for SSE 4.2
    13  // support.
    14  func haveSSE42() bool
    15  
    16  // castagnoliSSE42 is defined in crc_amd64.s and uses the SSE4.2 CRC32
    17  // instruction.
    18  //go:noescape
    19  func castagnoliSSE42(crc uint32, p []byte) uint32
    20  
    21  var sse42 = haveSSE42()
    22  
    23  func updateCastagnoli(crc uint32, p []byte) uint32 {
    24  	if sse42 {
    25  		return castagnoliSSE42(crc, p)
    26  	}
    27  	return update(crc, castagnoliTable, p)
    28  }
    29  
    30  func updateIEEE(crc uint32, p []byte) uint32 {
    31  	// only use slicing-by-8 when input is >= 4KB
    32  	if len(p) >= 4096 {
    33  		ieeeTable8Once.Do(func() {
    34  			ieeeTable8 = makeTable8(IEEE)
    35  		})
    36  		return updateSlicingBy8(crc, ieeeTable8, p)
    37  	}
    38  
    39  	return update(crc, IEEETable, p)
    40  }