91 lines
2.2 KiB
Go
91 lines
2.2 KiB
Go
// +build windows
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/*
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* Copyright 2017 Dgraph Labs, Inc. and Contributors
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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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*/
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package y
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import (
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"fmt"
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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(fd *os.File, write bool, size int64) ([]byte, error) {
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protect := syscall.PAGE_READONLY
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access := syscall.FILE_MAP_READ
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if write {
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protect = syscall.PAGE_READWRITE
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access = syscall.FILE_MAP_WRITE
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}
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fi, err := fd.Stat()
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if err != nil {
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return nil, err
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}
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// Truncate the database to the size of the mmap.
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if fi.Size() < size {
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if err := fd.Truncate(size); err != nil {
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return nil, fmt.Errorf("truncate: %s", err)
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}
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}
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// Open a file mapping handle.
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sizelo := uint32(size >> 32)
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sizehi := uint32(size) & 0xffffffff
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handler, err := syscall.CreateFileMapping(syscall.Handle(fd.Fd()), nil,
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uint32(protect), sizelo, sizehi, nil)
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if err != nil {
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return nil, os.NewSyscallError("CreateFileMapping", err)
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}
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// Create the memory map.
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addr, err := syscall.MapViewOfFile(handler, uint32(access), 0, 0, uintptr(size))
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if addr == 0 {
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return nil, os.NewSyscallError("MapViewOfFile", err)
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}
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// Close mapping handle.
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if err := syscall.CloseHandle(syscall.Handle(handler)); err != nil {
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return nil, os.NewSyscallError("CloseHandle", err)
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}
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// Slice memory layout
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// Copied this snippet from golang/sys package
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var sl = struct {
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addr uintptr
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len int
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cap int
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}{addr, int(size), int(size)}
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// Use unsafe to turn sl into a []byte.
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data := *(*[]byte)(unsafe.Pointer(&sl))
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return data, nil
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}
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func Munmap(b []byte) error {
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return syscall.UnmapViewOfFile(uintptr(unsafe.Pointer(&b[0])))
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}
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func Madvise(b []byte, readahead bool) error {
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// Do Nothing. We don’t care about this setting on Windows
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return nil
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}
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