[project @ 2003-04-30 08:36:21 by simonmar]

When doing hGetChar on a block-buffered handle, don't wait for the
buffer to be completely full before returning a character.  This
behaviour seems more useful, and matches what hGetLine and
hGetContents do.

Without this, to do an unbuffered read you have to set the buffering
on the Handle to NoBuffering, which adversely affects the performance
of writes.  With this change, there is now no difference between line
buffering and block buffering for read operations.

Possibly fillReadBuffer can now be simplified, since the is_line
parameter is always True.  However, this is a delicate part of the IO
library, and I don't want to remove the possiblity of forcing a
complete buffer-fill in the future.

diff --git a/GHC/IO.hs b/GHC/IO.hs
index 4b0fa9f..914a55a 100644 (file)
--- a/GHC/IO.hs
+++ b/GHC/IO.hs
@@ -98,7 +98,9 @@ hGetChar handle =
        new_buf <- fillReadBuffer fd True (haIsStream handle_) buf
        hGetcBuffered fd ref new_buf
     BlockBuffering _ -> do
-       new_buf <- fillReadBuffer fd False (haIsStream handle_) buf
+       new_buf <- fillReadBuffer fd True (haIsStream handle_) buf
+               --                   ^^^^
+               -- don't wait for a completely full buffer.
        hGetcBuffered fd ref new_buf
     NoBuffering -> do
        -- make use of the minimal buffer we already have