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
  34 using Beagle.Util;
  35
  36 namespace Beagle.Util {
  37
  38         public class FileAdvise {
  39
  40                 // FIXME: On 64-bit architectures, we need to use "long" not "int" here for
  41                 // "offset" and "len"
  42                 [DllImport ("libc", SetLastError=true)]
  43                 static extern int posix_fadvise (int fd, int offset, int len, int advice);
  44
  45                 // The following are from /usr/include/linux/fadvise.h and will not change
  46                 private const int AdviseNormal = 0;     // POSIX_FADV_NORMAL
  47                 private const int AdviseRandom = 1;     // POSIX_FADV_RANDOM
  48                 private const int AdviseSequential = 2; // POSIX_FADV_SEQUENTIAL
  49                 private const int AdviseWillNeed = 3;   // POSIX_FADV_WILLNEED
  50                 private const int AdviseDontNeed = 4;   // POSIX_FADV_DONTNEED
  51                 private const int AdviseNoReUse = 5;    // POSIX_FADV_NOREUSE
  52
  53                 static private int GiveAdvice (FileStream file, int advice)
  54                 {
  55                         int fd = file.Handle.ToInt32 ();
  56                         return posix_fadvise (fd, 0, 0, advice);
  57                 }
  58
  59                 static public void FlushCache (FileStream file)
  60                 {
  61                         GiveAdvice (file, AdviseDontNeed);
  62                 }
  63
  64                 static public void PreLoad (FileStream file)
  65                 {
  66                         GiveAdvice (file, AdviseWillNeed);
  67                 }
  68
  69                 static public void IncreaseReadAhead (FileStream file)
  70                 {
  71                         GiveAdvice (file, AdviseSequential);
  72                 }
  73
  74                 static public void DisableReadAhead (FileStream file)
  75                 {
  76                         GiveAdvice (file, AdviseRandom);
  77                 }
  78
  79                 static public void NormalReadAhead (FileStream file)
  80                 {
  81                         GiveAdvice (file, AdviseNormal);
  82                 }
  83
  84                 static public void WillAccessOnlyOnce (FileStream file)
  85                 {
  86                         GiveAdvice (file, AdviseNoReUse);
  87                 }
  88
  89                 static public void TestAdvise ()
  90                 {
  91                         try {
  92                                 FileStream file = new FileStream ("/etc/fstab",
  93                                                                   System.IO.FileMode.Open,
  94                                                                   FileAccess.Read);
  95                                 int ret = GiveAdvice (file, AdviseNormal);
  96                                 if (ret != 0)
  97                                         Log.Error ("FileAdvise failed: {0}", Mono.Unix.Native.Stdlib.strerror (Mono.Unix.Native.Stdlib.GetLastError()));
  98                                 file.Close ();
  99                         } catch { }
 100                 }
 101         }
 102 }