github.com/gopherd/gonum@v0.0.4/mat/offset_appengine.go (about)

     1  // Copyright ©2015 The Gonum 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  //go:build safe
     6  // +build safe
     7  
     8  package mat
     9  
    10  import "reflect"
    11  
    12  var sizeOfFloat64 = int(reflect.TypeOf(float64(0)).Size())
    13  
    14  // offset returns the number of float64 values b[0] is after a[0].
    15  func offset(a, b []float64) int {
    16  	va0 := reflect.ValueOf(a).Index(0)
    17  	vb0 := reflect.ValueOf(b).Index(0)
    18  	if va0.Addr() == vb0.Addr() {
    19  		return 0
    20  	}
    21  	// This expression must be atomic with respect to GC moves.
    22  	// At this stage this is true, because the GC does not
    23  	// move. See https://golang.org/issue/12445.
    24  	return int(vb0.UnsafeAddr()-va0.UnsafeAddr()) / sizeOfFloat64
    25  }
    26  
    27  var sizeOfComplex128 = int(reflect.TypeOf(complex128(0)).Size())
    28  
    29  // offsetComplex returns the number of complex128 values b[0] is after a[0].
    30  func offsetComplex(a, b []complex128) int {
    31  	va0 := reflect.ValueOf(a).Index(0)
    32  	vb0 := reflect.ValueOf(b).Index(0)
    33  	if va0.Addr() == vb0.Addr() {
    34  		return 0
    35  	}
    36  	// This expression must be atomic with respect to GC moves.
    37  	// At this stage this is true, because the GC does not
    38  	// move. See https://golang.org/issue/12445.
    39  	return int(vb0.UnsafeAddr()-va0.UnsafeAddr()) / sizeOfComplex128
    40  }