Dan PV created XERCESC-1984:
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Summary: TranscodeToStr::transcode throws an exception when
transcoding to UTF-8
Key: XERCESC-1984
URL: https://issues.apache.org/jira/browse/XERCESC-1984
Project: Xerces-C++
Issue Type: Bug
Components: Utilities
Affects Versions: 3.2.0, 4.0.0
Environment: Bug reproducible on a Red Hat 5 based platform. The bug
doesn't seem to be platform specific though.
Reporter: Dan PV
This issue relates to the bug fix for issue XERCESC-1947. There are still cases
where the method will fail in providing a transcoded version without throwing
an exception. See the attached "transtest2.cpp" to reproduce the issue.
The cause seems to come from the added "if((allocSize - fBytesWritten) < (len -
charsDone))" condition in "TranscodeToStr::transcode" . In my provided test
case I have a string composed of 6 Japanese characters (i.e. "絞り込み検索"). Once
the first call to "XMLUTF8Transcoder::transcodeTo" is done, "charsRead" will
return a count of 5 XMLCh readed. Since the initial allocated buffer for this
string was set to 16 bytes, the condition will check against the following
values "if((16 - 15) < (6 - 5))" which avoids the reallocation of a larger
buffer for the UTF-8 encoded version of the string.
Since the reallocation doesn't take place, the code will recall
"XMLUTF8Transcoder::transcodeTo" but this time the "charsRead" count will be
set to 0 because there is insufficient space in the buffer and this will
trigger an exception of type "Trans_BadSrcSeq".
I suppose that the goal of this added condition was to avoid an unnecessary
reallocation of a buffer but unfortunately it doesn’t work when transcoding to
variable length encoding like UTF-8. The solution is probably to simply replace
the condition with "if(charsDone < len)".
Regards,
Dan
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