// Seek to a new position on a file descriptor.
public static long __syscall_lseek(int fd, long offset, int whence)
{
// Get the stream and validate it.
byte[] buffer;
Stream stream = FileTable.GetStreamAndBuffer(fd, out buffer);
if (stream == null)
{
return(-9); /* EBADF */
}
else if (!stream.CanSeek)
{
return(-29); /* ESPIPE */
}
// Validate the "whence" argument.
if (whence < 0 || whence > 2)
{
return(-22); /* EINVAL */
}
// Seek to the new position. We lock down the buffer
// to synchronize descriptor accesses with pread/pwrite.
try
{
lock (buffer)
{
return(stream.Seek(offset, (SeekOrigin)whence));
}
}
catch (NotSupportedException)
{
return(-29); /* ESPIPE */
}
catch (ObjectDisposedException)
{
return(-9); /* EBADF */
}
catch (EndOfStreamException)
{
return(-22); /* EINVAL */
}
}
// Read data from a file descriptor.
public static int __syscall_read(int fd, IntPtr buf, uint count)
{
// Get the stream and validate it.
byte[] buffer;
Stream stream = FileTable.GetStreamAndBuffer(fd, out buffer);
if (stream == null)
{
return(-9); /* EBADF */
}
else if (count == 0)
{
return(0);
}
else if (buf == IntPtr.Zero)
{
return(-14); /* EFAULT */
}
// Read data from the stream. We lock down the buffer
// to prevent other threads from accessing the stream
// until we have finished with it.
int result = 0;
int templen;
try
{
lock (buffer)
{
while (count > 0)
{
templen = buffer.Length;
if (((uint)templen) > count)
{
templen = (int)count;
}
templen = stream.Read(buffer, 0, templen);
if (templen > 0)
{
Marshal.Copy(buffer, 0, buf, templen);
buf = new IntPtr(buf.ToInt64() + templen);
result += templen;
count -= (uint)templen;
}
else
{
break;
}
}
}
}
catch (IOException)
{
return(-5); /* EIO */
}
catch (ObjectDisposedException)
{
return(-9); /* EBADF */
}
catch (NotSupportedException)
{
return(-22); /* EINVAL */
}
catch (SocketException)
{
return(-11); /* EAGAIN */
}
return(result);
}
