golang outbuf_windows 代码
文件路径：/src/cmd/link/internal/ld/outbuf_windows.go
/ Copyright 2019 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package ld
import (
"reflect"
"syscall"
"unsafe"
)
/ Mmap maps the output file with the given size. It unmaps the old mapping
/ if it is already mapped. It also flushes any in-heap data to the new
/ mapping.
func (out *OutBuf) Mmap(filesize uint64) error {
oldlen := len(out.buf)
if oldlen != 0 {
out.munmap()
}
err := out.f.Truncate(int64(filesize))
if err != nil {
Exitf("resize output file failed: %v", err)
}
low, high := uint32(filesize), uint32(filesize>>32)
fmap, err := syscall.CreateFileMapping(syscall.Handle(out.f.Fd()), nil, syscall.PAGE_READWRITE, high, low, nil)
if err != nil {
return err
}
defer syscall.CloseHandle(fmap)
ptr, err := syscall.MapViewOfFile(fmap, syscall.FILE_MAP_READ|syscall.FILE_MAP_WRITE, 0, 0, uintptr(filesize))
if err != nil {
return err
}
bufHdr := (*reflect.SliceHeader)(unsafe.Pointer(&out.buf))
bufHdr.Data = ptr
bufHdr.Len = int(filesize)
bufHdr.Cap = int(filesize)
/ copy heap to new mapping
if uint64(oldlen+len(out.heap)) > filesize {
panic("mmap size too small")
}
copy(out.buf[oldlen:], out.heap)
out.heap = out.heap[:0]
return nil
}
func (out *OutBuf) munmap() {
if out.buf == nil {
return
}
/ Apparently unmapping without flush may cause ACCESS_DENIED error
/ (see issue 38440).
err := syscall.FlushViewOfFile(uintptr(unsafe.Pointer(&out.buf[0])), 0)
if err != nil {
Exitf("FlushViewOfFile failed: %v", err)
}
/ Issue 44817: apparently the call below may be needed (according
/ to the Windows docs) in addition to the FlushViewOfFile call
/ above, " ... to flush all the dirty pages plus the metadata for
/ the file and ensure that they are physically written to disk".
/ Windows DOC links:
/
/ https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-flushviewoffile
/ https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-flushfilebuffers
err = syscall.FlushFileBuffers(syscall.Handle(out.f.Fd()))
if err != nil {
Exitf("FlushFileBuffers failed: %v", err)
}
err = syscall.UnmapViewOfFile(uintptr(unsafe.Pointer(&out.buf[0])))
out.buf = nil
if err != nil {
Exitf("UnmapViewOfFile failed: %v", err)
}
}