1 // Licensed to the .NET Foundation under one or more agreements. 2 // The .NET Foundation licenses this file to you under the MIT license. 3 // See the LICENSE file in the project root for more information. 4 5 using System.Runtime.InteropServices; 6 using Microsoft.Win32.SafeHandles; 7 8 internal static partial class Interop 9 { 10 internal static partial class Sys 11 { 12 internal enum FileAdvice : int 13 { 14 POSIX_FADV_NORMAL = 0, /* no special advice, the default value */ 15 POSIX_FADV_RANDOM = 1, /* random I/O access */ 16 POSIX_FADV_SEQUENTIAL = 2, /* sequential I/O access */ 17 POSIX_FADV_WILLNEED = 3, /* will need specified pages */ 18 POSIX_FADV_DONTNEED = 4, /* don't need the specified pages */ 19 POSIX_FADV_NOREUSE = 5, /* data will only be accessed once */ 20 } 21 22 /// <summary> 23 /// Notifies the OS kernel that the specified file will be accessed in a particular way soon; this allows the kernel to 24 /// potentially optimize the access pattern of the file. 25 /// </summary> 26 /// <param name="fd">The file descriptor of the file</param> 27 /// <param name="offset">The start of the region to advise about</param> 28 /// <param name="length">The number of bytes of the region (until the end of the file if 0)</param> 29 /// <param name="advice">The type of advice to give the kernel about the specified region</param> 30 /// <returns> 31 /// Returns 0 on success; otherwise, the error code is returned 32 /// </returns> 33 [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_PosixFAdvise", SetLastError = false /* this is explicitly called out in the man page */)] PosixFAdvise(SafeFileHandle fd, long offset, long length, FileAdvice advice)34 internal static extern int PosixFAdvise(SafeFileHandle fd, long offset, long length, FileAdvice advice); 35 } 36 } 37