Commit 4d35ec65 authored by simonmar's avatar simonmar
Browse files

[project @ 2000-04-14 12:46:34 by simonmar]

Fix a bug in commitBuffer, and tweak the semantics of
commitBuffer/commitAndReleaseBuffer.

Add some comments on the algorithms used here.
parent cb9a82f5
......@@ -366,7 +366,8 @@ swapBuffers handle_ buf sz = do
setBuf fo buf sz
return (handle_{ haBuffers__ = fo_buf : haBuffers__ handle_ })
-- commitBuffer handle buf sz count flush
-----------------------------------------------------------------------------------
-- commitAndReleaseBuffer handle buf sz count flush
--
-- Write the contents of the buffer 'buf' ('sz' bytes long, containing
-- 'count' bytes of data) to handle (handle must be block or line buffered).
......@@ -392,6 +393,7 @@ commitAndReleaseBuffer
-> Int -- number of bytes of data in buffer
-> Bool -- flush the handle afterward?
-> IO ()
commitAndReleaseBuffer hdl@(Handle h) buf sz count flush = do
h_ <- takeMVar h
......@@ -418,18 +420,18 @@ commitAndReleaseBuffer hdl@(Handle h) buf sz count flush = do
let ok h_ = putMVar h h_ >> return ()
if (fo_bufSize - fo_wptr < count) -- not enough room in handle buffer?
if (flush || fo_bufSize - fo_wptr < count) -- not enough room in handle buffer?
then do rc <- mayBlock fo (flushFile fo)
if (rc < 0)
then constructErrorAndFail "commitBuffer"
then constructErrorAndFail "commitAndReleaseBuffer"
else
if flush || sz /= fo_bufSize
if (flush || sz /= fo_bufSize)
then do rc <- write_buf fo buf count
if (rc < 0)
then constructErrorAndFail "commitBuffer"
else do handle_ <- freeBuffer handle_ buf sz
ok handle_
then constructErrorAndFail "commitAndReleaseBuffer"
else do handle_ <- freeBuffer handle_ buf sz
ok handle_
-- don't have to flush, and the new buffer is the
-- same size as the old one, so just swap them...
......@@ -437,16 +439,26 @@ commitAndReleaseBuffer hdl@(Handle h) buf sz count flush = do
setBufWPtr fo count
ok handle_
-- not flushing, and there's enough room in the buffer:
-- just copy the data in and update bufWPtr.
else do memcpy (plusAddr fo_buf (AddrOff# fo_wptr)) buf count
setBufWPtr fo (fo_wptr + count)
if flush
then do rc <- mayBlock fo (flushFile fo)
if (rc < 0)
then constructErrorAndFail "commitBuffer"
else do handle_ <- freeBuffer handle_ buf sz
ok handle_
else do handle_ <- freeBuffer handle_ buf sz
ok handle_
handle_ <- freeBuffer handle_ buf sz
ok handle_
------------------------------------------------------------------------------------
-- commitBuffer handle buf sz count flush
--
-- Flushes 'count' bytes from the buffer 'buf' (size 'sz') to 'handle'.
-- There are several cases to consider altogether:
--
-- If flush,
-- - flush handle buffer,
-- - write out new buffer directly
--
-- else
-- - if there's enough room in the handle buffer, then copy new buf into it
-- else flush handle buffer, then copy new buffer into it
commitBuffer
:: Handle -- handle to commit to
......@@ -454,6 +466,7 @@ commitBuffer
-> Int -- number of bytes of data in buffer
-> Bool -- flush the handle afterward?
-> IO ()
commitBuffer handle buf sz count flush = do
wantWriteableHandle "commitBuffer" handle $ \handle_ -> do
let fo = haFO__ handle_
......@@ -463,19 +476,21 @@ commitBuffer handle buf sz count flush = do
fo_wptr <- getBufWPtr fo
fo_bufSize <- getBufSize fo
(if (fo_bufSize - fo_wptr < count) -- not enough room in handle buffer?
then mayBlock fo (flushFile fo)
else return 0)
new_wptr <- -- not enough room in handle buffer?
(if flush || (fo_bufSize - fo_wptr < count)
then do rc <- mayBlock fo (flushFile fo)
if (rc < 0) then constructErrorAndFail "commitBuffer"
else return 0
else return fo_wptr )
if (fo_bufSize < count) -- committed buffer too large?
if (flush || fo_bufSize < count) -- committed buffer too large?
then do rc <- write_buf fo buf count
if rc < 0 then constructErrorAndFail "commitBuffer"
else return ()
if (rc < 0) then constructErrorAndFail "commitBuffer"
else return ()
else do memcpy (plusAddr fo_buf (AddrOff# fo_wptr)) buf count
setBufWPtr fo (fo_wptr + count)
(if flush then mayBlock fo (flushFile fo) else return 0)
else do memcpy (plusAddr fo_buf (AddrOff# new_wptr)) buf count
setBufWPtr fo (new_wptr + count)
return ()
write_buf fo buf 0 = return 0
......
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