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Prevent unnecessary string scanning. #16

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Prevent unnecessary string scanning. #16

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9935d19
Prevent unnecessary string scanning.
EdSchouten Aug 27, 2015
d1b11cd
Change name of lenSource to be more clear.
EdSchouten Aug 27, 2015
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18 changes: 8 additions & 10 deletions include/boost/regex/v4/regex_workaround.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,12 +46,6 @@
# include <locale>
#endif

#if defined(BOOST_NO_STDC_NAMESPACE)
namespace std{
using ::sprintf; using ::strcpy; using ::strcat; using ::strlen;
}
#endif

namespace boost{ namespace re_detail{
#ifdef BOOST_NO_STD_DISTANCE
template <class T>
Expand Down Expand Up @@ -83,6 +77,7 @@ namespace std{
using ::abs;
using ::memset;
using ::memcpy;
using ::strlen;
}

#endif
Expand Down Expand Up @@ -196,9 +191,10 @@ namespace boost{ namespace re_detail{
const char *strSource
)
{
if(std::strlen(strSource)+1 > sizeInBytes)
std::size_t lenSourceWithNull = std::strlen(strSource) + 1;
if(lenSourceWithNull > sizeInBytes)
return 1;
std::strcpy(strDestination, strSource);
std::memcpy(strDestination, strSource, lenSourceWithNull);
return 0;
}
inline std::size_t strcat_s(
Expand All @@ -207,9 +203,11 @@ namespace boost{ namespace re_detail{
const char *strSource
)
{
if(std::strlen(strSource) + std::strlen(strDestination) + 1 > sizeInBytes)
std::size_t lenSourceWithNull = std::strlen(strSource) + 1;
std::size_t lenDestination = std::strlen(strDestination);
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lenSource and lenDestination names are confusingly similar while one includes the terminating zero and the other doesn't.

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There two ways we can resolve this. Both ways are fine by me. Be sure to let me know which one you prefer.

  • Rename lenSource to something like lenSourceWithNull, or
  • Don't add the + 1 and add it in both places where we need it.

My only concern with the second approach is that it makes the arithmetic that's going on less obvious. Right now it is quite obvious that this will never access the buffer out of bounds.

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I think renaming would be better.

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Done!

if(lenSourceWithNull + lenDestination > sizeInBytes)
return 1;
std::strcat(strDestination, strSource);
std::memcpy(strDestination + lenDestination, strSource,lenSourceWithNull);
return 0;
}

Expand Down