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// Copyright (c) 2014 The fileutil Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build !arm
package fileutil
import (
"bytes"
"io"
"io/ioutil"
"os"
"strconv"
"syscall"
)
const hasPunchHole = true
func n(s []byte) byte {
for i, c := range s {
if c < '0' || c > '9' {
s = s[:i]
break
}
}
v, _ := strconv.Atoi(string(s))
return byte(v)
}
func init() {
b, err := ioutil.ReadFile("/proc/sys/kernel/osrelease")
if err != nil {
panic(err)
}
tokens := bytes.Split(b, []byte("."))
if len(tokens) > 3 {
tokens = tokens[:3]
}
switch len(tokens) {
case 3:
// Supported since kernel 2.6.38
if bytes.Compare([]byte{n(tokens[0]), n(tokens[1]), n(tokens[2])}, []byte{2, 6, 38}) < 0 {
puncher = func(*os.File, int64, int64) error { return nil }
}
case 2:
if bytes.Compare([]byte{n(tokens[0]), n(tokens[1])}, []byte{2, 7}) < 0 {
puncher = func(*os.File, int64, int64) error { return nil }
}
default:
puncher = func(*os.File, int64, int64) error { return nil }
}
}
var puncher = func(f *os.File, off, len int64) error {
const (
/*
/usr/include/linux$ grep FL_ falloc.h
*/
_FALLOC_FL_KEEP_SIZE = 0x01 // default is extend size
_FALLOC_FL_PUNCH_HOLE = 0x02 // de-allocates range
)
_, _, errno := syscall.Syscall6(
syscall.SYS_FALLOCATE,
uintptr(f.Fd()),
uintptr(_FALLOC_FL_KEEP_SIZE|_FALLOC_FL_PUNCH_HOLE),
uintptr(off),
uintptr(len),
0, 0)
if errno != 0 {
return os.NewSyscallError("SYS_FALLOCATE", errno)
}
return nil
}
// PunchHole deallocates space inside a file in the byte range starting at
// offset and continuing for len bytes. No-op for kernels < 2.6.38 (or < 2.7).
func PunchHole(f *os.File, off, len int64) error {
return puncher(f, off, len)
}
// Fadvise predeclares an access pattern for file data. See also 'man 2
// posix_fadvise'.
func Fadvise(f *os.File, off, len int64, advice FadviseAdvice) error {
_, _, errno := syscall.Syscall6(
syscall.SYS_FADVISE64,
uintptr(f.Fd()),
uintptr(off),
uintptr(len),
uintptr(advice),
0, 0)
return os.NewSyscallError("SYS_FADVISE64", errno)
}
// IsEOF reports whether err is an EOF condition.
func IsEOF(err error) bool { return err == io.EOF }
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