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os: fix race in ReadAt/WriteAt on Windows

Browse source 
R=bradfitzgo, rsc, peterGo
CC=golang-dev
https://golang.org/cl/4441051
This commit is contained in:
Alex Brainman 2011-04-26 18:09:46 +10:00
parent 2d99974ec5
commit b1deb3be7f
5 changed files with 147 additions and 46 deletions
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14
src/pkg/os/file.go
View file

@ -8,6 +8,7 @@ package os
import (
"runtime"
"sync"
"syscall"
)
@ -17,6 +18,7 @@ type File struct {
name string
dirinfo *dirInfo // nil unless directory being read
nepipe int // number of consecutive EPIPE in Write
l sync.Mutex // used to implement windows pread/pwrite
}
// Fd returns the integer Unix file descriptor referencing the open file.
@ -30,7 +32,7 @@ func NewFile(fd int, name string) *File {
if fd < 0 {
return nil
}
f := &File{fd, name, nil, 0}
f := &File{fd: fd, name: name}
runtime.SetFinalizer(f, (*File).Close)
return f
}
@ -85,7 +87,7 @@ func (file *File) Read(b []byte) (n int, err Error) {
if file == nil {
return 0, EINVAL
}
n, e := syscall.Read(file.fd, b)
n, e := file.read(b)
if n < 0 {
n = 0
}
@ -107,7 +109,7 @@ func (file *File) ReadAt(b []byte, off int64) (n int, err Error) {
return 0, EINVAL
}
for len(b) > 0 {
m, e := syscall.Pread(file.fd, b, off)
m, e := file.pread(b, off)
if m == 0 && !iserror(e) {
return n, EOF
}
@ -129,7 +131,7 @@ func (file *File) Write(b []byte) (n int, err Error) {
if file == nil {
return 0, EINVAL
}
n, e := syscall.Write(file.fd, b)
n, e := file.write(b)
if n < 0 {
n = 0
}
@ -150,7 +152,7 @@ func (file *File) WriteAt(b []byte, off int64) (n int, err Error) {
return 0, EINVAL
}
for len(b) > 0 {
m, e := syscall.Pwrite(file.fd, b, off)
m, e := file.pwrite(b, off)
if iserror(e) {
err = &PathError{"write", file.name, Errno(e)}
break
@ -167,7 +169,7 @@ func (file *File) WriteAt(b []byte, off int64) (n int, err Error) {
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an Error, if any.
func (file *File) Seek(offset int64, whence int) (ret int64, err Error) {
r, e := syscall.Seek(file.fd, offset, whence)
r, e := file.seek(offset, whence)
if !iserror(e) && file.dirinfo != nil && r != 0 {
e = syscall.EISDIR
}

33
src/pkg/os/file_plan9.go
View file

@ -117,6 +117,39 @@ func (f *File) Sync() (err Error) {
return nil
}
// read reads up to len(b) bytes from the File.
// It returns the number of bytes read and an error, if any.
func (f *File) read(b []byte) (n int, err syscall.Error) {
return syscall.Read(f.fd, b)
}
// pread reads len(b) bytes from the File starting at byte offset off.
// It returns the number of bytes read and the error, if any.
// EOF is signaled by a zero count with err set to nil.
func (f *File) pread(b []byte, off int64) (n int, err syscall.Error) {
return syscall.Pread(f.fd, b, off)
}
// write writes len(b) bytes to the File.
// It returns the number of bytes written and an error, if any.
func (f *File) write(b []byte) (n int, err syscall.Error) {
return syscall.Write(f.fd, b)
}
// pwrite writes len(b) bytes to the File starting at byte offset off.
// It returns the number of bytes written and an error, if any.
func (f *File) pwrite(b []byte, off int64) (n int, err syscall.Error) {
return syscall.Pwrite(f.fd, b, off)
}
// seek sets the offset for the next Read or Write on file to offset, interpreted
// according to whence: 0 means relative to the origin of the file, 1 means
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err syscall.Error) {
return syscall.Seek(f.fd, offset, whence)
}
// Truncate changes the size of the named file.
// If the file is a symbolic link, it changes the size of the link's target.
func Truncate(name string, size int64) Error {

33
src/pkg/os/file_unix.go
View file

@ -96,6 +96,39 @@ func (file *File) Readdir(count int) (fi []FileInfo, err Error) {
return
}
// read reads up to len(b) bytes from the File.
// It returns the number of bytes read and an error, if any.
func (f *File) read(b []byte) (n int, err int) {
return syscall.Read(f.fd, b)
}
// pread reads len(b) bytes from the File starting at byte offset off.
// It returns the number of bytes read and the error, if any.
// EOF is signaled by a zero count with err set to 0.
func (f *File) pread(b []byte, off int64) (n int, err int) {
return syscall.Pread(f.fd, b, off)
}
// write writes len(b) bytes to the File.
// It returns the number of bytes written and an error, if any.
func (f *File) write(b []byte) (n int, err int) {
return syscall.Write(f.fd, b)
}
// pwrite writes len(b) bytes to the File starting at byte offset off.
// It returns the number of bytes written and an error, if any.
func (f *File) pwrite(b []byte, off int64) (n int, err int) {
return syscall.Pwrite(f.fd, b, off)
}
// seek sets the offset for the next Read or Write on file to offset, interpreted
// according to whence: 0 means relative to the origin of the file, 1 means
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err int) {
return syscall.Seek(f.fd, offset, whence)
}
// Truncate changes the size of the named file.
// If the file is a symbolic link, it changes the size of the link's target.
func Truncate(name string, size int64) Error {

71
src/pkg/os/file_windows.go
View file

@ -165,6 +165,77 @@ func (file *File) Readdir(count int) (fi []FileInfo, err Error) {
return fi, nil
}
// read reads up to len(b) bytes from the File.
// It returns the number of bytes read and an error, if any.
func (f *File) read(b []byte) (n int, err int) {
f.l.Lock()
defer f.l.Unlock()
return syscall.Read(f.fd, b)
}
// pread reads len(b) bytes from the File starting at byte offset off.
// It returns the number of bytes read and the error, if any.
// EOF is signaled by a zero count with err set to 0.
func (f *File) pread(b []byte, off int64) (n int, err int) {
f.l.Lock()
defer f.l.Unlock()
curoffset, e := syscall.Seek(f.fd, 0, 1)
if e != 0 {
return 0, e
}
defer syscall.Seek(f.fd, curoffset, 0)
o := syscall.Overlapped{
OffsetHigh: uint32(off >> 32),
Offset: uint32(off),
}
var done uint32
e = syscall.ReadFile(int32(f.fd), b, &done, &o)
if e != 0 {
return 0, e
}
return int(done), 0
}
// write writes len(b) bytes to the File.
// It returns the number of bytes written and an error, if any.
func (f *File) write(b []byte) (n int, err int) {
f.l.Lock()
defer f.l.Unlock()
return syscall.Write(f.fd, b)
}
// pwrite writes len(b) bytes to the File starting at byte offset off.
// It returns the number of bytes written and an error, if any.
func (f *File) pwrite(b []byte, off int64) (n int, err int) {
f.l.Lock()
defer f.l.Unlock()
curoffset, e := syscall.Seek(f.fd, 0, 1)
if e != 0 {
return 0, e
}
defer syscall.Seek(f.fd, curoffset, 0)
o := syscall.Overlapped{
OffsetHigh: uint32(off >> 32),
Offset: uint32(off),
}
var done uint32
e = syscall.WriteFile(int32(f.fd), b, &done, &o)
if e != 0 {
return 0, e
}
return int(done), 0
}
// seek sets the offset for the next Read or Write on file to offset, interpreted
// according to whence: 0 means relative to the origin of the file, 1 means
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err int) {
f.l.Lock()
defer f.l.Unlock()
return syscall.Seek(f.fd, offset, whence)
}
// Truncate changes the size of the named file.
// If the file is a symbolic link, it changes the size of the link's target.
func Truncate(name string, size int64) Error {

38
src/pkg/syscall/syscall_windows.go
View file

@ -250,27 +250,6 @@ func Read(fd int, p []byte) (n int, errno int) {
return int(done), 0
}
// TODO(brainman): ReadFile/WriteFile change file offset, therefore
// i use Seek here to preserve semantics of unix pread/pwrite,
// not sure if I should do that
func Pread(fd int, p []byte, offset int64) (n int, errno int) {
curoffset, e := Seek(fd, 0, 1)
if e != 0 {
return 0, e
}
defer Seek(fd, curoffset, 0)
var o Overlapped
o.OffsetHigh = uint32(offset >> 32)
o.Offset = uint32(offset)
var done uint32
e = ReadFile(int32(fd), p, &done, &o)
if e != 0 {
return 0, e
}
return int(done), 0
}
func Write(fd int, p []byte) (n int, errno int) {
var done uint32
e := WriteFile(int32(fd), p, &done, nil)
@ -280,23 +259,6 @@ func Write(fd int, p []byte) (n int, errno int) {
return int(done), 0
}
func Pwrite(fd int, p []byte, offset int64) (n int, errno int) {
curoffset, e := Seek(fd, 0, 1)
if e != 0 {
return 0, e
}
defer Seek(fd, curoffset, 0)
var o Overlapped
o.OffsetHigh = uint32(offset >> 32)
o.Offset = uint32(offset)
var done uint32
e = WriteFile(int32(fd), p, &done, &o)
if e != 0 {
return 0, e
}
return int(done), 0
}
func Seek(fd int, offset int64, whence int) (newoffset int64, errno int) {
var w uint32
switch whence {