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adamsitnik wants to merge 2 commits into from
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Alternative solution #3

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732d00f
revert the fallback
adamsitnik Oct 8, 2021
11eb480
alternative solution
adamsitnik Oct 8, 2021
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34 changes: 19 additions & 15 deletions src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ public sealed partial class SafeFileHandle : SafeHandleZeroOrMinusOneIsInvalid

// not using bool? as it's not thread safe
private volatile NullableBool _canSeek = NullableBool.Undefined;
private volatile NullableBool _supportsRandomAccess = NullableBool.Undefined;
private volatile NullableBool _isRegularFile = NullableBool.Undefined;
private bool _deleteOnClose;
private bool _isLocked;

Expand All @@ -34,20 +34,7 @@ private SafeFileHandle(bool ownsHandle)

internal bool CanSeek => !IsClosed && GetCanSeek();

internal bool SupportsRandomAccess
{
get
{
NullableBool supportsRandomAccess = _supportsRandomAccess;
if (supportsRandomAccess == NullableBool.Undefined)
{
_supportsRandomAccess = supportsRandomAccess = GetCanSeek() ? NullableBool.True : NullableBool.False;
}

return supportsRandomAccess == NullableBool.True;
}
set => _supportsRandomAccess = value ? NullableBool.True : NullableBool.False;
}
internal bool IsRegularFile => GetIsRegularFile();

internal ThreadPoolBoundHandle? ThreadPoolBinding => null;

Expand Down Expand Up @@ -112,8 +99,13 @@ private static SafeFileHandle Open(string path, Interop.Sys.OpenFlags flags, int
// and for regular files (most common case)
// avoid one extra sys call for determining whether file can be seeked
handle._canSeek = NullableBool.True;
handle._isRegularFile = NullableBool.True;
Debug.Assert(Interop.Sys.LSeek(handle, 0, Interop.Sys.SeekWhence.SEEK_CUR) >= 0);
}
else
{
handle._isRegularFile = NullableBool.False;
}
}

return handle;
Expand Down Expand Up @@ -405,6 +397,18 @@ private bool GetCanSeek()
return canSeek == NullableBool.True;
}

private bool GetIsRegularFile()
{
NullableBool isRegularFile = _isRegularFile;
if (isRegularFile == NullableBool.Undefined)
{
_isRegularFile = isRegularFile = (Interop.Sys.FStat(this, out Interop.Sys.FileStatus status) == 0
&& (status.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFREG) ? NullableBool.True : NullableBool.False;
}

return isRegularFile == NullableBool.True;
}

private enum NullableBool
{
Undefined = 0,
Expand Down
53 changes: 6 additions & 47 deletions src/libraries/System.Private.CoreLib/src/System/IO/RandomAccess.Unix.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,30 +33,9 @@ internal static unsafe int ReadAtOffset(SafeFileHandle handle, Span<byte> buffer
// The Windows implementation uses ReadFile, which ignores the offset if the handle
// isn't seekable. We do the same manually with PRead vs Read, in order to enable
// the function to be used by FileStream for all the same situations.
int result;
if (handle.SupportsRandomAccess)
{
// Try pread for seekable files.
result = Interop.Sys.PRead(handle, bufPtr, buffer.Length, fileOffset);
if (result == -1)
{
// We need to fallback to the non-offset version for certain file types
// e.g: character devices (such as /dev/tty), pipes, and sockets.
Interop.ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();

if (errorInfo.Error == Interop.Error.ENXIO ||
errorInfo.Error == Interop.Error.ESPIPE)
{
handle.SupportsRandomAccess = false;
result = Interop.Sys.Read(handle, bufPtr, buffer.Length);
}
}
}
else
{
result = Interop.Sys.Read(handle, bufPtr, buffer.Length);
}

int result = handle.IsRegularFile ?
Interop.Sys.PRead(handle, bufPtr, buffer.Length, fileOffset) :
Interop.Sys.Read(handle, bufPtr, buffer.Length);
FileStreamHelpers.CheckFileCall(result, handle.Path);
return result;
}
Expand Down Expand Up @@ -111,29 +90,9 @@ internal static unsafe void WriteAtOffset(SafeFileHandle handle, ReadOnlySpan<by
// The Windows implementation uses WriteFile, which ignores the offset if the handle
// isn't seekable. We do the same manually with PWrite vs Write, in order to enable
// the function to be used by FileStream for all the same situations.
int bytesToWrite = GetNumberOfBytesToWrite(buffer.Length);
int bytesWritten;
if (handle.SupportsRandomAccess)
{
bytesWritten = Interop.Sys.PWrite(handle, bufPtr, bytesToWrite, fileOffset);
if (bytesWritten == -1)
{
// We need to fallback to the non-offset version for certain file types
// e.g: character devices (such as /dev/tty), pipes, and sockets.
Interop.ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();

if (errorInfo.Error == Interop.Error.ENXIO ||
errorInfo.Error == Interop.Error.ESPIPE)
{
handle.SupportsRandomAccess = false;
bytesWritten = Interop.Sys.Write(handle, bufPtr, bytesToWrite);
}
}
}
else
{
bytesWritten = Interop.Sys.Write(handle, bufPtr, bytesToWrite);
}
int bytesWritten = handle.IsRegularFile ?
Interop.Sys.PWrite(handle, bufPtr, GetNumberOfBytesToWrite(buffer.Length), fileOffset) :
Interop.Sys.Write(handle, bufPtr, GetNumberOfBytesToWrite(buffer.Length));

FileStreamHelpers.CheckFileCall(bytesWritten, handle.Path);
if (bytesWritten == buffer.Length)
Expand Down