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ICU-278 Catch infinite loops in RBT rules

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X-SVN-Rev: 752
This commit is contained in:
Alan Liu 2000-02-12 02:05:36 +00:00
parent bb2611b517
commit 77749b5b8d
1 changed files with 19 additions and 1 deletions
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20
icu4c/source/i18n/rbt.cpp
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@ -91,9 +91,26 @@ RuleBasedTransliterator::handleTransliterate(Replaceable& text, Position& index,
int32_t limit = index.limit;
int32_t cursor = index.cursor;
/* A rule like
* a>b|a
* creates an infinite loop. To prevent that, we put an arbitrary
* limit on the number of iterations that we take, one that is
* high enough that any reasonable rules are ok, but low enough to
* prevent a server from hanging. The limit is 16 times the
* number of characters n, unless n is so large that 16n exceeds a
* uint32_t.
*/
uint32_t loopCount = 0;
uint32_t loopLimit = limit - cursor;
if (loopLimit >= 0x10000000) {
loopLimit = 0xFFFFFFFF;
} else {
loopLimit <<= 4;
}
bool_t isPartial = FALSE;
while (cursor < limit) {
while (cursor < limit && loopCount <= loopLimit) {
TransliterationRule* r = isIncremental ?
data->ruleSet.findIncrementalMatch(text, start, limit, cursor,
*data, isPartial,
@ -121,6 +138,7 @@ RuleBasedTransliterator::handleTransliterate(Replaceable& text, Position& index,
r->getOutput());
limit += r->getOutput().length() - r->getKeyLength();
cursor += r->getCursorPos();
++loopCount;
}
}