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lib/file: reimplement os.OpenFile allowing rename/delete open files under Windows

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Normally os.OpenFile under Windows does not allow renaming or deleting
open file handles.  This package provides equivelents for os.OpenFile,
os.Open and os.Create which do allow that.
This commit is contained in:
Nick Craig-Wood 2019-01-07 14:47:19 +00:00
parent 571b4c060b
commit 42d997f639
4 changed files with 257 additions and 0 deletions
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66
lib/file/file_windows.go Normal file
View file

@ -0,0 +1,66 @@
//+build windows
package file
import (
"os"
"syscall"
)
// OpenFile is the generalized open call; most users will use Open or Create
// instead. It opens the named file with specified flag (O_RDONLY etc.) and
// perm (before umask), if applicable. If successful, methods on the returned
// File can be used for I/O. If there is an error, it will be of type
// *PathError.
//
// Under both Unix and Windows this will allow open files to be
// renamed and or deleted.
func OpenFile(path string, mode int, perm os.FileMode) (*os.File, error) {
// This code copied from syscall_windows.go in the go source and then
// modified to support renaming and deleting open files by adding
// FILE_SHARE_DELETE.
//
// https://docs.microsoft.com/en-us/windows/desktop/api/fileapi/nf-fileapi-createfilea#file_share_delete
if len(path) == 0 {
return nil, syscall.ERROR_FILE_NOT_FOUND
}
pathp, err := syscall.UTF16PtrFromString(path)
if err != nil {
return nil, err
}
var access uint32
switch mode & (syscall.O_RDONLY | syscall.O_WRONLY | syscall.O_RDWR) {
case syscall.O_RDONLY:
access = syscall.GENERIC_READ
case syscall.O_WRONLY:
access = syscall.GENERIC_WRITE
case syscall.O_RDWR:
access = syscall.GENERIC_READ | syscall.GENERIC_WRITE
}
if mode&syscall.O_CREAT != 0 {
access |= syscall.GENERIC_WRITE
}
if mode&syscall.O_APPEND != 0 {
access &^= syscall.GENERIC_WRITE
access |= syscall.FILE_APPEND_DATA
}
sharemode := uint32(syscall.FILE_SHARE_READ | syscall.FILE_SHARE_WRITE | syscall.FILE_SHARE_DELETE)
var createmode uint32
switch {
case mode&(syscall.O_CREAT|syscall.O_EXCL) == (syscall.O_CREAT | syscall.O_EXCL):
createmode = syscall.CREATE_NEW
case mode&(syscall.O_CREAT|syscall.O_TRUNC) == (syscall.O_CREAT | syscall.O_TRUNC):
createmode = syscall.CREATE_ALWAYS
case mode&syscall.O_CREAT == syscall.O_CREAT:
createmode = syscall.OPEN_ALWAYS
case mode&syscall.O_TRUNC == syscall.O_TRUNC:
createmode = syscall.TRUNCATE_EXISTING
default:
createmode = syscall.OPEN_EXISTING
}
h, e := syscall.CreateFile(pathp, access, sharemode, nil, createmode, syscall.FILE_ATTRIBUTE_NORMAL, 0)
if e != nil {
return nil, e
}
return os.NewFile(uintptr(h), path), nil
}