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syscall: make Seek use SetFilePointerEx on Windows, allowing large se…

…ek offsets

Fixes #21681
Updates #21728

Change-Id: I79cf4564c1355ecab891102d4215cbbffd8eb0ce
Reviewed-on: https://go-review.googlesource.com/82535
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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bradfitz committed Dec 6, 2017
1 parent 9ce6b5c commit 7c46b62d0a6e2353db68da963c390b094e359a92
Showing with 39 additions and 11 deletions.
  1. +16 −4 src/os/os_test.go
  2. +23 −7 src/syscall/syscall_windows.go
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@@ -1362,14 +1362,26 @@ func TestSeek(t *testing.T) {
{-1, io.SeekEnd, int64(len(data)) - 1},
{1 << 33, io.SeekStart, 1 << 33},
{1 << 33, io.SeekEnd, 1<<33 + int64(len(data))},
// Issue 21681, Windows 4G-1, etc:
{1<<32 - 1, io.SeekStart, 1<<32 - 1},
{0, io.SeekCurrent, 1<<32 - 1},
{2<<32 - 1, io.SeekStart, 2<<32 - 1},
{0, io.SeekCurrent, 2<<32 - 1},
}
for i, tt := range tests {
if runtime.GOOS == "nacl" && tt.out > 1<<30 {
t.Logf("skipping test case #%d on nacl; https://golang.org/issue/21728", i)
continue
}
off, err := f.Seek(tt.in, tt.whence)
if off != tt.out || err != nil {
if e, ok := err.(*PathError); ok && e.Err == syscall.EINVAL && tt.out > 1<<32 {
// Reiserfs rejects the big seeks.
// https://golang.org/issue/91
break
if e, ok := err.(*PathError); ok && e.Err == syscall.EINVAL && tt.out > 1<<32 && runtime.GOOS == "linux" {
mounts, _ := ioutil.ReadFile("/proc/mounts")
if strings.Contains(string(mounts), "reiserfs") {
// Reiserfs rejects the big seeks.
t.Skipf("skipping test known to fail on reiserfs; https://golang.org/issue/91")
}
}
t.Errorf("#%d: Seek(%v, %v) = %v, %v want %v, nil", i, tt.in, tt.whence, off, err, tt.out)
}
@@ -332,6 +332,27 @@ func Write(fd Handle, p []byte) (n int, err error) {
var ioSync int64
var procSetFilePointerEx = modkernel32.NewProc("SetFilePointerEx")
const ptrSize = unsafe.Sizeof(uintptr(0))
// setFilePointerEx calls SetFilePointerEx.
// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365542(v=vs.85).aspx
func setFilePointerEx(handle Handle, distToMove int64, newFilePointer *int64, whence uint32) error {
var e1 Errno
if ptrSize == 8 {
_, _, e1 = Syscall6(procSetFilePointerEx.Addr(), 4, uintptr(handle), uintptr(distToMove), uintptr(unsafe.Pointer(newFilePointer)), uintptr(whence), 0, 0)
} else {
// distToMove is a LARGE_INTEGER:
// https://msdn.microsoft.com/en-us/library/windows/desktop/aa383713(v=vs.85).aspx
_, _, e1 = Syscall6(procSetFilePointerEx.Addr(), 5, uintptr(handle), uintptr(distToMove), uintptr(distToMove>>32), uintptr(unsafe.Pointer(newFilePointer)), uintptr(whence), 0)
}
if e1 != 0 {
return errnoErr(e1)
}
return nil
}
func Seek(fd Handle, offset int64, whence int) (newoffset int64, err error) {
var w uint32
switch whence {
@@ -342,18 +363,13 @@ func Seek(fd Handle, offset int64, whence int) (newoffset int64, err error) {
case 2:
w = FILE_END
}
hi := int32(offset >> 32)
lo := int32(offset)
// use GetFileType to check pipe, pipe can't do seek
ft, _ := GetFileType(fd)
if ft == FILE_TYPE_PIPE {
return 0, ESPIPE
}
rlo, e := SetFilePointer(fd, lo, &hi, w)
if e != nil {
return 0, e
}
return int64(hi)<<32 + int64(rlo), nil
err = setFilePointerEx(fd, offset, &newoffset, w)
return
}
func Close(fd Handle) (err error) {

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