Util/FileAdvise.cs

   1 //
   2 // FileAdvise.cs
   3 //
   4 // Copyright (C) 2004 Novell, Inc.
   5 //
   6
   7 //
   8 // Permission is hereby granted, free of charge, to any person obtaining a
   9 // copy of this software and associated documentation files (the "Software"),
  10 // to deal in the Software without restriction, including without limitation
  11 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12 // and/or sell copies of the Software, and to permit persons to whom the
  13 // Software is furnished to do so, subject to the following conditions:
  14 //
  15 // The above copyright notice and this permission notice shall be included in
  16 // all copies or substantial portions of the Software.
  17 //
  18 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  21 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  23 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  24 // DEALINGS IN THE SOFTWARE.
  25 //
  26
  27 // FIXME: This is not portable to Win32
  28
  29 using System;
  30 using System.IO;
  31 using System.Text;
  32 using System.Runtime.InteropServices;
  33 using Mono.Posix;
  34
  35 using Beagle.Util;
  36
  37 namespace Beagle.Util {
  38
  39         public class FileAdvise {
  40
  41                 // FIXME: On 64-bit architectures, we need to use "long" not "int" here for
  42                 // "offset" and "len"
  43                 [DllImport ("libc", SetLastError=true)]
  44                 static extern int posix_fadvise (int fd, int offset, int len, int advice);
  45
  46                 // The following are from /usr/include/linux/fadvise.h and will not change
  47                 private const int AdviseNormal = 0;     // POSIX_FADV_NORMAL
  48                 private const int AdviseRandom = 1;     // POSIX_FADV_RANDOM
  49                 private const int AdviseSequential = 2; // POSIX_FADV_SEQUENTIAL
  50                 private const int AdviseWillNeed = 3;   // POSIX_FADV_WILLNEED
  51                 private const int AdviseDontNeed = 4;   // POSIX_FADV_DONTNEED
  52                 private const int AdviseNoReUse = 5;    // POSIX_FADV_NOREUSE
  53
  54                 static private int GiveAdvice (FileStream file, int advice)
  55                 {
  56                         int fd = file.Handle.ToInt32 ();
  57                         return posix_fadvise (fd, 0, 0, advice);
  58                 }
  59
  60                 static public void FlushCache (FileStream file)
  61                 {
  62                         GiveAdvice (file, AdviseDontNeed);
  63                 }
  64
  65                 static public void PreLoad (FileStream file)
  66                 {
  67                         GiveAdvice (file, AdviseWillNeed);
  68                 }
  69
  70                 static public void IncreaseReadAhead (FileStream file)
  71                 {
  72                         GiveAdvice (file, AdviseSequential);
  73                 }
  74
  75                 static public void DisableReadAhead (FileStream file)
  76                 {
  77                         GiveAdvice (file, AdviseRandom);
  78                 }
  79
  80                 static public void NormalReadAhead (FileStream file)
  81                 {
  82                         GiveAdvice (file, AdviseNormal);
  83                 }
  84
  85                 static public void WillAccessOnlyOnce (FileStream file)
  86                 {
  87                         GiveAdvice (file, AdviseNoReUse);
  88                 }
  89
  90                 static public void TestAdvise ()
  91                 {
  92                         try {
  93                                 FileStream file = new FileStream ("/etc/fstab",
  94                                                                   System.IO.FileMode.Open,
  95                                                                   FileAccess.Read);
  96
  97                                 int ret = GiveAdvice (file, AdviseNormal);
  98                                 if (ret != 0) {
  99                                         Logger log = Logger.Get ("FileAdvise");
 100                                         log.Error ("FileAdvise failed: " +
 101                                                    Syscall.strerror (Marshal.GetLastWin32Error()));
 102                                 }
 103
 104                                 file.Close ();
 105                         } catch { }
 106                 }
 107         }
 108 }