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47 lines
1.4 KiB
47 lines
1.4 KiB
6 years ago
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// Copyright 2017 The Prometheus Authors
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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 fileutil
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import (
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"os"
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"syscall"
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"unsafe"
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)
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func mmap(f *os.File, size int) ([]byte, error) {
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low, high := uint32(size), uint32(size>>32)
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h, errno := syscall.CreateFileMapping(syscall.Handle(f.Fd()), nil, syscall.PAGE_READONLY, high, low, nil)
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if h == 0 {
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return nil, os.NewSyscallError("CreateFileMapping", errno)
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}
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addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(size))
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if addr == 0 {
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return nil, os.NewSyscallError("MapViewOfFile", errno)
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}
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if err := syscall.CloseHandle(syscall.Handle(h)); err != nil {
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return nil, os.NewSyscallError("CloseHandle", err)
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}
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return (*[maxMapSize]byte)(unsafe.Pointer(addr))[:size], nil
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}
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func munmap(b []byte) error {
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if err := syscall.UnmapViewOfFile((uintptr)(unsafe.Pointer(&b[0]))); err != nil {
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return os.NewSyscallError("UnmapViewOfFile", err)
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}
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return nil
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}
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