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Implement SunOS FileSystemWatcher using portfs event ports
This implementation uses SunOS portfs (event ports) to watch for directory changes. Unlike Linux inotify, portfs can only detect WHEN a directory changes, not WHAT changed. Therefore, this implementation: 1. Maintains a snapshot of each watched directory's contents 2. When portfs signals a change, re-reads the directory 3. Compares new vs old snapshots to detect creates/deletes/modifications 4. Generates appropriate FileSystemWatcher events Key implementation details: - Uses pinned GC.AllocateArray for file_obj structures required by portfs - When watching attributes or timestamps watches directory contents too - Each watched objct gets a unique cookie for identification - port_get returns the cookie to indicate which object changed - Optimized snapshot comparison with sorted single-pass algorithm - Supports IncludeSubdirectories by recursively watching child directories - Track mtime of the watched directory to avoid missing changes - Implement graceful cancellation using PortSend Native changes (pal_io.c): - SystemNative_PortCreate: Opens event port file descriptor - SystemNative_PortAssociate: Associates directory with port using file_obj - SystemNative_PortGet: Waits for events, returns cookie identifying directory - SystemNative_PortSend: Send an event (used in cancellation) - SystemNative_PortDissociate: Removes directory association Performance notes: - Less efficient than inotify (must re-read directories on each change) - Better than polling (blocks until change occurs) - Memory overhead for directory snapshots Passes all System.IO.FileSystem.Watcher.Tests --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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‎src/libraries/Common/src/Interop/SunOS/portfs/Interop.portfs.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// This implementation uses SunOS portfs (event ports) to watch directories.
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// portfs can detect when a directory's modification time changes via port_associate,
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// but cannot tell us WHAT changed in the directory. This makes it different from
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// Linux inotify or Windows ReadDirectoryChangesW.
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//
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// The FileSystemWatcher implementation must:
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// 1. Use port_associate to watch for FILE_MODIFIED events on directories
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// 2. When an event occurs, re-read the directory contents
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// 3. Compare with cached state to determine what actually changed
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//
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using System;
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using System.Runtime.InteropServices;
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using Microsoft.Win32.SafeHandles;
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internal static partial class Interop
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{
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internal static partial class PortFs
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{
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[LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_PortCreate",
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SetLastError = true)]
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internal static partial SafeFileHandle PortCreate();
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// pFileObj must point to pinned memory with size >= sizeof(file_obj)
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// because the address is used as an identifier in the kernel.
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// dirPath string is used while making the association but is
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// never referenced again after PortAssociate returns.
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// mtime is the directory modification time before reading the directory
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// cookie is returned by PortGet to identify which directory changed
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[LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_PortAssociate",
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SetLastError = true, StringMarshalling = StringMarshalling.Utf8)]
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internal static unsafe partial int PortAssociate(SafeFileHandle fd, IntPtr pFileObj, string dirPath, Interop.Sys.TimeSpec* mtime, int evmask, IntPtr cookie);
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// Returns the cookie value from PortAssociate in the cookie parameter
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[LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_PortGet",
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SetLastError = true)]
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internal static unsafe partial int PortGet(SafeFileHandle fd, int* events, IntPtr* cookie, Interop.Sys.TimeSpec* tmo);
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[LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_PortDissociate",
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SetLastError = true)]
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internal static partial int PortDissociate(SafeFileHandle fd, IntPtr pFileObj);
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// Send a synthetic event to wake up a blocked PortGet call
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// evflags can be any PortEvent value (e.g., FILE_NOFOLLOW for cancellation)
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// cookie is returned to PortGet to identify the event
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[LibraryImport(Libraries.SystemNative, EntryPoint = "SystemNative_PortSend",
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SetLastError = true)]
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internal static partial int PortSend(SafeFileHandle fd, int evflags, IntPtr cookie);
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[Flags]
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internal enum PortEvent
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{
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FILE_ACCESS = 0x00000001,
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FILE_MODIFIED = 0x00000002,
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FILE_ATTRIB = 0x00000004,
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FILE_TRUNC = 0x00100000,
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FILE_NOFOLLOW = 0x10000000,
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FILE_EXCEPTION = 0x20000000,
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// Exception events
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FILE_DELETE = 0x00000010,
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FILE_RENAME_TO = 0x00000020,
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FILE_RENAME_FROM = 0x00000040,
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// These are unused, and the duplicate value causes warnings.
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// UNMOUNTED = 0x20000000,
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// MOUNTEDOVER = 0x40000000,
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}
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// sizeof(file_obj) = 3*sizeof(timespec) + 3*sizeof(uintptr_t) + sizeof(char*)
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// On 64-bit: 3*16 + 3*8 + 8 = 80 bytes
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internal const int FileObjSize = 80;
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}
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}

‎src/libraries/System.IO.FileSystem.Watcher/src/Resources/Strings.resx‎

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<data name="FSW_BufferOverflow" xml:space="preserve">
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<value>Too many changes at once in directory:{0}.</value>
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</data>
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<data name="FSW_MaxFilesWatchedExceeded" xml:space="preserve">
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<value>Max file watch limit ({0}) exceeded for directory: {1}</value>
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</data>
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<data name="FSW_MaxSubdirectoriesExceeded" xml:space="preserve">
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<value>Max subdirectory watch limit ({0}) exceeded for directory: {1}</value>
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</data>
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<data name="InvalidDirName" xml:space="preserve">
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<value>The directory name {0} is invalid.</value>
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</data>

‎src/libraries/System.IO.FileSystem.Watcher/src/System.IO.FileSystem.Watcher.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)</TargetFrameworks>
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<TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-solaris;$(NetCoreAppCurrent)</TargetFrameworks>
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<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
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<UseCompilerGeneratedDocXmlFile>false</UseCompilerGeneratedDocXmlFile>
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</PropertyGroup>
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Link="Common\Interop\Unix\Interop.Stat.cs" />
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</ItemGroup>
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<ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'illumos' or '$(TargetPlatformIdentifier)' == 'solaris'">
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<Compile Include="System\IO\FileSystemWatcher.SunOS.cs" />
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<Compile Include="$(CommonPath)Interop\SunOS\portfs\Interop.portfs.cs"
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Link="Common\Interop\SunOS\portfs\Interop.portfs.cs" />
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<Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.UTimensat.cs"
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Link="Common\Interop\Unix\System.Native\Interop.UTimensat.cs" />
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<Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Poll.cs"
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Link="Common\Interop\Unix\Interop.Poll.cs" />
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<Compile Include="$(CommonPath)Interop\Unix\Interop.Poll.Structs.cs"
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Link="Common\Interop\Unix\Interop.Poll.Structs.cs" />
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<Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Stat.cs"
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Link="Common\Interop\Unix\Interop.Stat.cs" />
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</ItemGroup>
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<ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'maccatalyst'">
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<Compile Include="System\IO\FileSystemWatcher.OSX.cs" />
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<Compile Include="$(CoreLibSharedDir)System\IO\FileSystem.Exists.Unix.cs"

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