\begin{code}
-{-# OPTIONS -fcompiling-prelude -fno-implicit-prelude -#include "cbits/stgio.h" #-}
+{-# OPTIONS -fno-implicit-prelude -#include "cbits/stgio.h" #-}
module PrelIO where
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).
-> 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
- -- First deal with any possible exceptions by freeing the buffer.
+ -- First deal with any possible exceptions, by freeing the buffer.
-- Async exceptions are blocked, but there are still some interruptible
-- ops below.
let ok h_ = putMVar h h_ >> return ()
- if (fo_bufSize - fo_wptr < count) -- not enough room in handle buffer?
+ -- enough room in handle buffer for the new data?
+ if (flush || fo_bufSize - fo_wptr <= count)
+
+ -- The <= is to be sure that we never exactly fill up the
+ -- buffer, which would require a flush. So if copying the
+ -- new data into the buffer would make the buffer full, we
+ -- just flush the existing buffer and the new data immediately,
+ -- rather than copying before flushing.
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 || count == sz)
then do rc <- write_buf fo buf count
if (rc < 0)
- then constructErrorAndFail "commitBuffer"
- 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...
+ then constructErrorAndFail "commitAndReleaseBuffer"
+ else do handle_ <- freeBuffer handle_ buf sz
+ ok handle_
+
+ -- if: (a) we don't have to flush, and
+ -- (b) size(new buffer) == size(old buffer), and
+ -- (c) new buffer is not full,
+ -- we can just just swap them over...
else do handle_ <- swapBuffers handle_ buf sz
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
+--
+-- Make sure that we maintain the invariant that the handle buffer is never
+-- left in a full state. Several functions rely on this (eg. filePutc), so
+-- if we're about to exactly fill the buffer then we make sure we do a flush
+-- here (also see above in commitAndReleaseBuffer).
commitBuffer
:: Handle -- handle to commit to
-> 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_
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
then write_buf fo buf (count - rc) -- partial write
else return rc
+-- a version of commitBuffer that will free the buffer if an exception is
+-- received. DON'T use this if you intend to use the buffer again!
+checkedCommitBuffer handle buf sz count flush
+ = catchException (commitBuffer handle buf sz count flush)
+ (\e -> do withHandle__ handle (\h_ -> freeBuffer h_ buf sz)
+ throw e)
+
foreign import "memcpy" unsafe memcpy :: Addr -> Addr -> Int -> IO ()
\end{code}
let next_n = n + 1
if next_n == bufLen || x == '\n'
then do
- commitBuffer hdl buf len next_n True{-needs flush-}
+ checkedCommitBuffer hdl buf len next_n True{-needs flush-}
shoveString 0 xs
else
shoveString next_n xs
let next_n = n +# 1#
if next_n ==# bufLen || x `eqChar#` '\n'#
then do
- commitBuffer hdl buf len (I# next_n) True{-needs flush-}
+ checkedCommitBuffer hdl buf len (I# next_n) True{-needs flush-}
shoveString 0# xs
else
shoveString next_n xs
let next_n = n + 1
if next_n == bufLen
then do
- commitBuffer hdl buf len next_n True{-needs flush-}
+ checkedCommitBuffer hdl buf len next_n True{-needs flush-}
shoveString 0 xs
else
shoveString next_n xs
let next_n = n +# 1#
if next_n ==# bufLen
then do
- commitBuffer hdl buf len (I# next_n) True{-needs flush-}
+ checkedCommitBuffer hdl buf len (I# next_n) True{-needs flush-}
shoveString 0# xs
else
shoveString next_n xs
projects / ghc-hetmet.git / blobdiff