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HPCC-32795 Additional optimizations to replaceString #19239

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HPCC-32795 Additional optimizations to replaceString #19239

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6f71021
HPCC-32795 Additional optimizations to replaceString
jackdelv Oct 25, 2024
4bb7a82
Directly copy newStr to buffer in special case.
jackdelv Oct 25, 2024
98315c6
Fix memory corruption issue
jackdelv Oct 28, 2024
19984dd
Optimize for case where no matches are found
jackdelv Oct 28, 2024
b6dc378
Optimize for case where target is less than or equal to source string.
jackdelv Oct 29, 2024
e3364e7
Change return type of replaceString function
jackdelv Oct 30, 2024
b57c932
Remove extra line
jackdelv Oct 30, 2024
45800b0
Remove duplicate code.
jackdelv Oct 30, 2024
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24 changes: 19 additions & 5 deletions system/jlib/jstring.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1056,13 +1056,27 @@ StringBuffer &replaceStringNoCase(StringBuffer & result, size_t lenSource, const
// this method will replace all occurrences of "oldStr" with "newStr"
StringBuffer & StringBuffer::replaceString(const char* oldStr, const char* newStr)
{
if (curLen)
if (curLen && oldStr)
{
StringBuffer temp;
size_t oldlen = oldStr ? strlen(oldStr) : 0;
size_t oldlen = strlen(oldStr);
if (oldlen > curLen)
return *this;

size_t newlen = newStr ? strlen(newStr) : 0;
::replaceString(temp, curLen, buffer, oldlen, oldStr, newlen, newStr);
swapWith(temp);
if (oldlen == curLen)
{
if (memcmp(buffer, oldStr, oldlen) == 0)
{
memcpy(buffer, newStr, newlen);
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If I was reviewing this code (I am not because of general review comments) - this has a serious memory corruption if newlen > oldlen

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Fixed. I added ensureCapacity(newlen).

curLen = newlen;
}
}
else
{
StringBuffer temp;
::replaceString(temp, curLen, buffer, oldlen, oldStr, newlen, newStr);
swapWith(temp);
}
}
return *this;
}
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10 changes: 10 additions & 0 deletions testing/unittests/jlibtests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -913,6 +913,16 @@ void testEncodeCSVColumn()
source.set("abbabab");
source.replaceString("ab", "xxx");
CPPUNIT_ASSERT_EQUAL_STR("xxxbxxxxxx", source.str());

// Search String has same length as source string and matches
source.set("ababab");
source.replaceString("ababab", "xxxxxx");
CPPUNIT_ASSERT_EQUAL_STR("xxxxxx", source.str());

// Search String has same length as source string and does not match
source.set("ababab");
source.replaceString("ababac", "xxxxxx");
CPPUNIT_ASSERT_EQUAL_STR("ababab", source.str());
}
};

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