37 lines
1.4 KiB
Go
37 lines
1.4 KiB
Go
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// Copyright 2018 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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//go:build purego
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// +build purego
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// Package subtle implements functions that are often useful in cryptographic
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// code but require careful thought to use correctly.
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package subtle // import "golang.org/x/crypto/internal/subtle"
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// This is the Google App Engine standard variant based on reflect
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// because the unsafe package and cgo are disallowed.
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import "reflect"
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// AnyOverlap reports whether x and y share memory at any (not necessarily
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// corresponding) index. The memory beyond the slice length is ignored.
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func AnyOverlap(x, y []byte) bool {
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return len(x) > 0 && len(y) > 0 &&
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reflect.ValueOf(&x[0]).Pointer() <= reflect.ValueOf(&y[len(y)-1]).Pointer() &&
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reflect.ValueOf(&y[0]).Pointer() <= reflect.ValueOf(&x[len(x)-1]).Pointer()
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}
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// InexactOverlap reports whether x and y share memory at any non-corresponding
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// index. The memory beyond the slice length is ignored. Note that x and y can
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// have different lengths and still not have any inexact overlap.
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//
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// InexactOverlap can be used to implement the requirements of the crypto/cipher
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// AEAD, Block, BlockMode and Stream interfaces.
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func InexactOverlap(x, y []byte) bool {
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if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
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return false
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}
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return AnyOverlap(x, y)
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}
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