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