private unsafe int ReadCoreWithCancellation(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
{
DebugAssertReadWriteArgs(buffer, offset, count, _handle);
Debug.Assert(cancellationToken.CanBeCanceled, "ReadCoreNoCancellation should be used if cancellation can't happen");
// Register for a cancellation request. This will throw if cancellation has already been requested,
// and otherwise will write to the cancellation pipe if/when cancellation has been requested.
using (DescriptorCancellationRegistration cancellation = RegisterForCancellation(cancellationToken))
{
bool gotRef = false;
try
{
cancellation.Poll.DangerousAddRef(ref gotRef);
fixed (byte* bufPtr = buffer)
{
const int CancellationSentinel = -42;
int rv = (int)SysCall(_handle, (fd, ptr, len, cancellationFd) =>
{
// Wait for data to be available on either the pipe we want to read from
// or on the cancellation pipe, which would signal a cancellation request.
Interop.libc.pollfd* fds = stackalloc Interop.libc.pollfd[2];
fds[0] = new Interop.libc.pollfd { fd = fd, events = Interop.libc.PollFlags.POLLIN, revents = 0 };
fds[1] = new Interop.libc.pollfd { fd = (int)cancellationFd, events = Interop.libc.PollFlags.POLLIN, revents = 0 };
while (Interop.CheckIo(Interop.libc.poll(fds, 2, -1))) ;
// If we woke up because of a cancellation request, bail.
if ((fds[1].revents & Interop.libc.PollFlags.POLLIN) != 0)
{
return CancellationSentinel;
}
// Otherwise, we woke up because data is available on the pipe. Read it.
Debug.Assert((fds[0].revents & Interop.libc.PollFlags.POLLIN) != 0);
long result = (long)Interop.libc.read(fd, (byte*)ptr, (IntPtr)len);
Debug.Assert(result <= len);
return result;
}, (IntPtr)(bufPtr + offset), count, cancellation.Poll.DangerousGetHandle());
Debug.Assert(rv >= 0 || rv == CancellationSentinel);
// If cancellation was requested, waking up the read, throw.
if (rv == CancellationSentinel)
{
Debug.Assert(cancellationToken.IsCancellationRequested);
throw new OperationCanceledException(cancellationToken);
}
// Otherwise return what we read.
return rv;
}
}
finally
{
if (gotRef)
cancellation.Poll.DangerousRelease();
}
}
}
private unsafe int ReadCoreWithCancellation(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
{
DebugAssertReadWriteArgs(buffer, offset, count, _handle);
Debug.Assert(cancellationToken.CanBeCanceled, "ReadCoreNoCancellation should be used if cancellation can't happen");
// Register for a cancellation request. This will throw if cancellation has already been requested,
// and otherwise will write to the cancellation pipe if/when cancellation has been requested.
using (DescriptorCancellationRegistration cancellation = RegisterForCancellation(cancellationToken))
{
bool gotRef = false;
try
{
cancellation.Poll.DangerousAddRef(ref gotRef);
fixed(byte *bufPtr = buffer)
{
const int CancellationSentinel = -42;
int rv = (int)SysCall(_handle, (fd, ptr, len, cancellationFd) =>
{
// Wait for data to be available on either the pipe we want to read from
// or on the cancellation pipe, which would signal a cancellation request.
Interop.libc.pollfd *fds = stackalloc Interop.libc.pollfd[2];
fds[0] = new Interop.libc.pollfd {
fd = fd, events = Interop.libc.PollFlags.POLLIN, revents = 0
};
fds[1] = new Interop.libc.pollfd {
fd = (int)cancellationFd, events = Interop.libc.PollFlags.POLLIN, revents = 0
};
while (Interop.CheckIo(Interop.libc.poll(fds, 2, -1)))
{
;
}
// If we woke up because of a cancellation request, bail.
if ((fds[1].revents & Interop.libc.PollFlags.POLLIN) != 0)
{
return(CancellationSentinel);
}
// Otherwise, we woke up because data is available on the pipe. Read it.
Debug.Assert((fds[0].revents & Interop.libc.PollFlags.POLLIN) != 0);
long result = (long)Interop.libc.read(fd, (byte *)ptr, (IntPtr)len);
Debug.Assert(result <= len);
return(result);
}, (IntPtr)(bufPtr + offset), count, cancellation.Poll.DangerousGetHandle());
Debug.Assert(rv >= 0 || rv == CancellationSentinel);
// If cancellation was requested, waking up the read, throw.
if (rv == CancellationSentinel)
{
Debug.Assert(cancellationToken.IsCancellationRequested);
throw new OperationCanceledException(cancellationToken);
}
// Otherwise return what we read.
return(rv);
}
}
finally
{
if (gotRef)
{
cancellation.Poll.DangerousRelease();
}
}
}
}
