Hi
I am trying to make function which returns a substring as a char* , but string::substr returns a const char* . So I have managed to make a function that will return a substring as char* , except when I was comparing the speed of the two, I found that string::substr was much faster than the one I made. But its not actually to do with the technique I used to retrieve a substring, I found that just allocating the memory takes about twice as long than string::substr to manage everything.
Here is the code that compares the two functions:
#include<iostream>
unsigned __int64 start;
unsigned __int64 end;
inline __declspec(naked) unsigned __int64 GetCycleCount() {
_asm rdtsc;
_asm ret;
}
inline void StartMeasure() {
start = GetCycleCount();
}
inline void EndMeasure() {
end = GetCycleCount();
}
inline unsigned __int64 GetMeasure() {
return (end - start);
}
#define SpeedTest(event, loops)\
StartMeasure();\
for(unsigned __int64 _i = 0; _i < loops; _i++) {\
event;\
}\
EndMeasure();\
start /= loops, end /= loops;\
std::cout << GetMeasure();
char *SubStr(char *text, unsigned int beg, unsigned int fin) {
unsigned int len = fin - beg;
char *sub = new char[len];
memcpy(sub, &text[beg], len);
sub[len] = '\0';
return sub;
}
int main() {
char text[] = "0123456789";
std::string text_s = text;
/* SubStr */
std::cout << "\n SubStr:\t ";
SpeedTest(
SubStr(text, 0, 5),
1000000);
std::cout << "\tCPU Cycles";
/* string::substr */
std::cout << "\n\n string::substr: ";
SpeedTest(
text_s.substr(0, 5),
1000000);
std::cout << "\tCPU Cycles";
std::cin.ignore();
return 0;
}If anybody has any ideas on how to speed up my SubStr function / memory allocating to a similar speed as string::substr, please tell me :)
Thanks.
