https://bugs.freedesktop.org/show_bug.cgi?id=79941
Priority: medium
Bug ID: 79941
Assignee: libreoffice-bugs@lists.freedesktop.org
Summary: com.sun.star.io.TextInputStream incorrectly detects
permanent EOF when working with partial reads from
readSomeBytes
Severity: major
Classification: Unclassified
OS: Windows (All)
Reporter: sztej...@yahoo.com
Hardware: x86 (IA32)
Status: UNCONFIRMED
Version: 4.1.6.2 release
Component: sdk
Product: LibreOffice
When "com.sun.star.io.TextInputStream" service is used with XInputStream which
return partial read (that is reads less bytes than required) from its
readSomeBytes com.sun.star.io.TextInputStream assumes that it's a permanent End
Of File condition and never attempts to read any data again.
This is an important fault when reading data from dynamic resources built on
request like network sockets or similar connections - in may case a remote
measuring equipment.
For an example one may attempt to send a request to a server using self made
XOutputStream implementation and then may like to retrieve response with
com.sun.star.io.TextInputStream.readLine
The com.sun.star.io.TextInputStream.readLine will request readSomeBytes(....,
256), what means it is trying to read some data ahead. Obviously if server
response is shorter than that XInputStream will either timeout or return only
what can be returned immediately. The result will be that readSomeBytes will
return less bytes than requires. Or even a zero. It doesn't mean link is
broken, it just has no more data at the moment.
The current implementation of com.sun.star.io.TextInputStream.readLine fills
data in a buffer and detects that this is an eof. I sets mbReachedEOF in
TextInputStream.cxx to true.
line 295:
sal_Int32 nRead = mxStream->readSomeBytes( mSeqSource, nBytesToRead );
sal_Int32 nTotalRead = nRead;
if( nRead < nBytesToRead )
mbReachedEOF = true;
Later any attempt to call implReadString returns without updating buffer
content due to check in line 214:
// Already reached EOF? Then we can't read any more
if( mbReachedEOF )
break;
Effectively it prevents using TextInputStream to read anything from sources
other than a fast, blocking read, local files.
Please, do not make EOF condition permanent. Personally I don't feel capable
enough to tinker with this code and fix it. It seems than mbReachedEOF is
tested in many places and there is too less comments for me to grasp what's
going on.
I mark it as a "major" since this renders this service unusable. A work around
is possible by writing own UNO service which doing it correctly.
Best regards,
Tomasz Sztejka
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