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Initial implementation of fix for dotnet#77835 - cloning files on macOS
• Use copyfile (with COPYFILE_CLONE_FORCE) when possible on macOS to clone the file while still keeping file locking logic intact • Split common Unix logic into multiple functions that the macOS implementation uses parts of at different times • Add string version of ResolveLinkTarget to save the allocation since part of the code needs it • Need to add tests to check the file is actually cloned so we know if it works or not
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141 changes: 141 additions & 0 deletions
141
src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.CopyFile.OSX.cs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,141 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
|
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| using System.Runtime.InteropServices; | ||
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| namespace System.IO | ||
| { | ||
| partial class FileSystem | ||
| { | ||
| public static unsafe void CopyFile(string sourceFullPath, string destFullPath, bool overwrite) | ||
| { | ||
| //Attempt to clone the file: | ||
|
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| //Get the full path of the source path | ||
| string fullSource = TryGetLinkTarget(sourceFullPath) ?? sourceFullPath; | ||
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| //Start the file copy and prepare for finalization | ||
| StartedCopyFileState startedCopyFile = StartCopyFile(fullSource, destFullPath, overwrite, openDst: false); | ||
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| //Attempt counter just in case we somehow loop infinite times e.g. on a | ||
| //filesystem that doesn't actually delete files but pretends it does. | ||
| //Declare error variable here since it can be used after some jumping around. | ||
| int attempts = 0; | ||
| int error; | ||
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| try | ||
| { | ||
| //Don't need to re-read the link on our first attempt | ||
| bool failOnRereadDoesntChange = false; | ||
| if (overwrite) | ||
| { | ||
| //Ensure file is deleted on first try. | ||
| //Get a lock to the dest file for compat reasons, and then delete it. | ||
| using SafeFileHandle? dstHandle = OpenCopyFileDstHandle(destFullPath, true, startedCopyFile, false); | ||
| File.Delete(destFullPath); | ||
| } | ||
| goto tryAgain; | ||
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| //We may want to re-read the link to see if its path has changed | ||
| tryAgainWithReadLink: | ||
| if (++attempts >= 5) goto throwError; | ||
| string fullSource2 = TryGetLinkTarget(sourceFullPath) ?? sourceFullPath; | ||
| if (fullSource != fullSource2) | ||
| { | ||
| //Path has changed | ||
| startedCopyFile.Dispose(); | ||
| startedCopyFile = StartCopyFile(fullSource, destFullPath, overwrite, openDst: false); | ||
| } | ||
| else if (failOnRereadDoesntChange) | ||
| { | ||
| //Path hasn't changed and we want to throw the error we got earlier | ||
| goto throwError; | ||
| } | ||
| failOnRereadDoesntChange = false; | ||
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| //Attempt to clone the file | ||
| tryAgain: | ||
| if (Interop.@libc.copyfile(fullSource, destFullPath, null, Interop.@libc.COPYFILE_CLONE_FORCE) == 0) | ||
| { | ||
| return; | ||
| } | ||
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| //Check the error | ||
| error = Marshal.GetLastWin32Error(); | ||
| const int ENOTSUP = 45; | ||
| const int EEXIST = 17; | ||
| const int ENOENT = 2; | ||
| bool directoryExist = false; | ||
| if ((error == ENOTSUP && FileOrDirectoryExists(destFullPath)) || error == EEXIST) | ||
| { | ||
| //This means the destination existed, try again with the destination deleted if appropriate | ||
| error = EEXIST; | ||
| if (Directory.Exists(destFullPath)) | ||
| { | ||
| directoryExist = true; | ||
| goto throwError; | ||
| } | ||
| if (overwrite) | ||
| { | ||
| //Get a lock to the dest file for compat reasons, and then delete it. | ||
| using SafeFileHandle dstHandle = OpenCopyFileDstHandle(destFullPath, true, startedCopyFile); | ||
| File.Delete(destFullPath); | ||
| goto tryAgainWithReadLink; | ||
| } | ||
| } | ||
| else if (error == ENOTSUP) | ||
| { | ||
| //This probably means cloning is not supported, try the standard implementation | ||
| goto fallback; | ||
| } | ||
| else if (error == ENOENT) | ||
| { | ||
| //This can happen if the source is a symlink and it has been changed to a different file, and the first has been deleted or renamed, for example. | ||
| //failOnRereadDoesntChange means we want to fail if the link didn't change, indicating the source actually doesn't exist. | ||
| failOnRereadDoesntChange = true; | ||
| goto tryAgainWithReadLink; | ||
| } | ||
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| //Throw an appropriate error | ||
| throwError: | ||
| if (directoryExist) | ||
| { | ||
| throw new IOException(SR.Format(SR.Arg_FileIsDirectory_Name, path)); | ||
| } | ||
| throw Interop.GetExceptionForIoErrno(new ErrorInfo(error)); | ||
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| //Fallback to the standard unix implementation for when cloning is not supported | ||
| fallback: | ||
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| //Open the dst handle | ||
| startedCopyFile.dst = OpenCopyFileDstHandle(destFullPath, overwrite, startedCopyFile, true); | ||
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| //Copy the file using the standard unix implementation | ||
| StandardCopyFile(startedCopyFile); | ||
| } | ||
| finally | ||
| { | ||
| startedCopyFile.Dispose(); | ||
| } | ||
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| //Attempts to read the path's link target, or returns null even if the path doesn't exist | ||
| static string? TryGetLinkTarget(string path) | ||
| { | ||
| try | ||
| { | ||
| return ResolveLinkTargetString(sourceFullPath, true, false); | ||
| } | ||
| catch | ||
| { | ||
| return null; | ||
| } | ||
| } | ||
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| //Checks if a file or directory exists without caring which it was | ||
| static bool FileOrDirectoryExists(string path) | ||
| { | ||
| return Interop.Sys.Stat(fullPath, out _) >= 0; | ||
| } | ||
| } | ||
| } | ||
| } |
17 changes: 17 additions & 0 deletions
17
src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.CopyFile.OtherUnix.cs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,17 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
|
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| namespace System.IO | ||
| { | ||
| partial class FileSystem | ||
| { | ||
| public static void CopyFile(string sourceFullPath, string destFullPath, bool overwrite) | ||
| { | ||
| //Start the file copy and prepare for finalization | ||
| using StartedCopyFileState startedCopyFile = StartCopyFile(sourceFullPath, destFullPath, overwrite); | ||
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| //Copy the file using the standard unix implementation | ||
| StandardCopyFile(startCopyFile); | ||
| } | ||
| } | ||
| } |
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