4ec1e58aa6
We have an optimization for this specific pattern, but it's really just a hack. With the addition of unsafe.Add in Go 1.17 we can directly specify the intent instead and eventually remove this special case. The code is also easier to read.
40 строки
1 КиБ
Go
40 строки
1 КиБ
Go
package reflect
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import "unsafe"
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// Some of code here has been copied from the Go sources:
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// https://github.com/golang/go/blob/go1.15.2/src/reflect/swapper.go
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// It has the following copyright note:
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//
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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func Swapper(slice interface{}) func(i, j int) {
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v := ValueOf(slice)
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if v.Kind() != Slice {
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panic(&ValueError{Method: "Swapper"})
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}
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// Just return Nop func if nothing to swap.
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if v.Len() < 2 {
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return func(i, j int) {}
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}
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typ := v.typecode.Elem()
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size := typ.Size()
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header := (*sliceHeader)(v.value)
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tmp := unsafe.Pointer(&make([]byte, size)[0])
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return func(i, j int) {
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if uint(i) >= uint(header.len) || uint(j) >= uint(header.len) {
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panic("reflect: slice index out of range")
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}
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val1 := unsafe.Add(header.data, uintptr(i)*size)
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val2 := unsafe.Add(header.data, uintptr(j)*size)
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memcpy(tmp, val1, size)
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memcpy(val1, val2, size)
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memcpy(val2, tmp, size)
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}
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}
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