github.com/d4l3k/go@v0.0.0-20151015000803-65fc379daeda/src/hash/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  package crc32
     6  
     7  // This file contains the code to call the SSE 4.2 version of the Castagnoli
     8  // CRC.
     9  
    10  // haveSSE42 is defined in crc_amd64p32.s and uses CPUID to test for SSE 4.2
    11  // support.
    12  func haveSSE42() bool
    13  
    14  // castagnoliSSE42 is defined in crc_amd64.s and uses the SSE4.2 CRC32
    15  // instruction.
    16  func castagnoliSSE42(crc uint32, p []byte) uint32
    17  
    18  var sse42 = haveSSE42()
    19  
    20  func updateCastagnoli(crc uint32, p []byte) uint32 {
    21  	if sse42 {
    22  		return castagnoliSSE42(crc, p)
    23  	}
    24  	return update(crc, castagnoliTable, p)
    25  }
    26  
    27  func updateIEEE(crc uint32, p []byte) uint32 {
    28  	// only use slicing-by-8 when input is >= 4KB
    29  	if len(p) >= 4096 {
    30  		iEEETable8Once.Do(func() {
    31  			iEEETable8 = makeTable8(IEEE)
    32  		})
    33  		return updateSlicingBy8(crc, iEEETable8, p)
    34  	}
    35  
    36  	return update(crc, IEEETable, p)
    37  }