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Ayke van Laethem
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.
41 lines
1.0 KiB
Go
41 lines
1.0 KiB
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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