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Improve perfomance by replacing sscanf with strto* functions #1074

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Improve perfomance by replacing sscanf with strto* functions #1074

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85 changes: 33 additions & 52 deletions tinyxml2.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,11 +25,13 @@ distribution.

#include <new> // yes, this one new style header, is in the Android SDK.
#if defined(ANDROID_NDK) || defined(__BORLANDC__) || defined(__QNXNTO__) || defined(__CC_ARM)
# include <stddef.h>
# include <errno.h>
# include <stdarg.h>
# include <stddef.h>
#else
# include <cstddef>
# include <cerrno>
# include <cstdarg>
# include <cstddef>
#endif

// Handle fallthrough attribute for different compilers
Expand Down Expand Up @@ -78,12 +80,10 @@ distribution.
}

#define TIXML_VSCPRINTF _vscprintf
#define TIXML_SSCANF sscanf_s
#elif defined _MSC_VER
// Microsoft Visual Studio 2003 and earlier or WinCE
#define TIXML_SNPRINTF _snprintf
#define TIXML_VSNPRINTF _vsnprintf
#define TIXML_SSCANF sscanf
#if (_MSC_VER < 1400 ) && (!defined WINCE)
// Microsoft Visual Studio 2003 and not WinCE.
#define TIXML_VSCPRINTF _vscprintf // VS2003's C runtime has this, but VC6 C runtime or WinCE SDK doesn't have.
Expand Down Expand Up @@ -121,7 +121,6 @@ distribution.
TIXMLASSERT( len >= 0 );
return len;
}
#define TIXML_SSCANF sscanf
#endif

#if defined(_WIN64)
Expand Down Expand Up @@ -157,6 +156,20 @@ static const unsigned char TIXML_UTF_LEAD_2 = 0xbfU;
namespace tinyxml2
{

namespace {

template<typename T, typename Fn>
bool StrTo(const char* str, size_t skip, T* value, Fn fn) {
char* endptr = nullptr;
errno = 0;
auto v = fn(str + skip, &endptr);
if (endptr == str + skip || errno == ERANGE) { return false; }
*value = static_cast<T>(v);
return true;
}

} // anonymous namespace

struct Entity {
const char* pattern;
int length;
Expand Down Expand Up @@ -626,27 +639,16 @@ void XMLUtil::ToStr( uint64_t v, char* buffer, int bufferSize )

bool XMLUtil::ToInt(const char* str, int* value)
{
if (IsPrefixHex(str)) {
unsigned v;
if (TIXML_SSCANF(str, "%x", &v) == 1) {
*value = static_cast<int>(v);
return true;
}
}
else {
if (TIXML_SSCANF(str, "%d", value) == 1) {
return true;
}
}
return false;
NumPrefix pfx = GetNumPrefix(str);
if ( pfx.base == NumPrefix::Hex )
return StrTo(str, pfx.skip, value, [](const char* s, char** e) { return strtoul(s, e, NumPrefix::Hex); });
return StrTo(str, pfx.skip, value, [](const char* s, char** e) { return strtol(s, e, NumPrefix::Dec); });
}

bool XMLUtil::ToUnsigned(const char* str, unsigned* value)
{
if (TIXML_SSCANF(str, IsPrefixHex(str) ? "%x" : "%u", value) == 1) {
return true;
}
return false;
NumPrefix pfx = GetNumPrefix(str);
return StrTo(str, pfx.skip, value, [pfx](const char* s, char** e) { return strtoul(s, e, pfx.base); });
}

bool XMLUtil::ToBool( const char* str, bool* value )
Expand Down Expand Up @@ -677,49 +679,28 @@ bool XMLUtil::ToBool( const char* str, bool* value )

bool XMLUtil::ToFloat( const char* str, float* value )
{
if ( TIXML_SSCANF( str, "%f", value ) == 1 ) {
return true;
}
return false;
return StrTo(str, 0, value, strtof);
}


bool XMLUtil::ToDouble( const char* str, double* value )
{
if ( TIXML_SSCANF( str, "%lf", value ) == 1 ) {
return true;
}
return false;
return StrTo(str, 0, value, strtod);
}


bool XMLUtil::ToInt64(const char* str, int64_t* value)
{
if (IsPrefixHex(str)) {
unsigned long long v = 0; // horrible syntax trick to make the compiler happy about %llx
if (TIXML_SSCANF(str, "%llx", &v) == 1) {
*value = static_cast<int64_t>(v);
return true;
}
}
else {
long long v = 0; // horrible syntax trick to make the compiler happy about %lld
if (TIXML_SSCANF(str, "%lld", &v) == 1) {
*value = static_cast<int64_t>(v);
return true;
}
}
return false;
NumPrefix pfx = GetNumPrefix(str);
if ( pfx.base == NumPrefix::Hex )
return StrTo(str, pfx.skip, value, [](const char* s, char** e) { return strtoull(s, e, NumPrefix::Hex); });
return StrTo(str, pfx.skip, value, [](const char* s, char** e) { return strtoll(s, e, NumPrefix::Dec); });
}


bool XMLUtil::ToUnsigned64(const char* str, uint64_t* value) {
unsigned long long v = 0; // horrible syntax trick to make the compiler happy about %llu
if(TIXML_SSCANF(str, IsPrefixHex(str) ? "%llx" : "%llu", &v) == 1) {
*value = static_cast<uint64_t>(v);
return true;
}
return false;
NumPrefix pfx = GetNumPrefix(str);
return StrTo(str, pfx.skip, value, [pfx](const char* s, char** e) { return strtoull(s, e, pfx.base); });
}


Expand Down Expand Up @@ -2649,7 +2630,7 @@ void XMLPrinter::Print( const char* format, ... )
va_start( va, format );
TIXMLASSERT( _buffer.Size() > 0 && _buffer[_buffer.Size() - 1] == 0 );
char* p = _buffer.PushArr( len ) - 1; // back up over the null terminator.
TIXML_VSNPRINTF( p, len+1, format, va );
TIXML_VSNPRINTF( p, static_cast<size_t>(len)+1, format, va );
}
va_end( va );
}
Expand Down
22 changes: 19 additions & 3 deletions tinyxml2.h
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Original file line number Diff line number Diff line change
Expand Up @@ -302,7 +302,10 @@ class DynArray
const size_t newAllocated = cap * 2;
T* newMem = new T[newAllocated];
TIXMLASSERT( newAllocated >= _size );
memcpy( newMem, _mem, sizeof(T) * _size ); // warning: not using constructors, only works for PODs
// Intermediate variable avoids bugprone-sizeof-expression false positive
// when T is a pointer type (checker suspects sizeof(ptr) is unintentional).
const size_t bytesToCopy = _size * sizeof(T);
memcpy( newMem, _mem, bytesToCopy ); // not using constructors, only works for PODs
if ( _mem != _pool ) {
delete [] _mem;
}
Expand Down Expand Up @@ -586,9 +589,22 @@ class TINYXML2_LIB XMLUtil
|| ch == '-';
}

inline static bool IsPrefixHex( const char* p) {
struct NumPrefix {
enum Base { Dec = 10, Hex = 16 };
size_t skip;
Base base;
};

inline static NumPrefix GetNumPrefix( const char* p) {
const char* start = p;
p = SkipWhiteSpace(p, 0);
return p && *p == '0' && ( *(p + 1) == 'x' || *(p + 1) == 'X');
size_t wsLen = static_cast<size_t>(p - start);
if ( p && *p == '0' && ( *(p + 1) == 'x' || *(p + 1) == 'X') ) {
NumPrefix r = { wsLen + 2, NumPrefix::Hex };
return r;
}
NumPrefix r = { wsLen, NumPrefix::Dec };
return r;
}

inline static bool StringEqual( const char* p, const char* q, int nChar=INT_MAX ) {
Expand Down