48 lines
1.7 KiB
Go
48 lines
1.7 KiB
Go
// Copyright 2016 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package main
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import (
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"os"
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"unsafe"
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)
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func existFileOrDir(name string) bool {
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_, err := os.Stat(name)
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return err == nil
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}
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func unsafeAdd(base unsafe.Pointer, offset uintptr) unsafe.Pointer {
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return unsafe.Pointer(uintptr(base) + offset)
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}
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func unsafeIndex(base unsafe.Pointer, offset uintptr, elemsz uintptr, n int) unsafe.Pointer {
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return unsafe.Pointer(uintptr(base) + offset + uintptr(n)*elemsz)
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}
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func unsafeByteSlice(base unsafe.Pointer, offset uintptr, i, j int) []byte {
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// See: https://github.com/golang/go/wiki/cgo#turning-c-arrays-into-go-slices
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//
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// This memory is not allocated from C, but it is unmanaged by Go's
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// garbage collector and should behave similarly, and the compiler
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// should produce similar code. Note that this conversion allows a
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// subslice to begin after the base address, with an optional offset,
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// while the URL above does not cover this case and only slices from
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// index 0. However, the wiki never says that the address must be to
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// the beginning of a C allocation (or even that malloc was used at
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// all), so this is believed to be correct.
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return (*[pageMaxAllocSize]byte)(unsafeAdd(base, offset))[i:j:j]
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}
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