c++ - Return char * instead of string -

i trying use 'user434507''s unsigned solution here:

c++ performance challenge: integer std::string conversion

but instead want return char * , not accept in string.

i have been playing around awhile , have got, returns nothing/garbage - limited c , pointer knowledge not helping me. think using malloc right, in original code it's if uses internal char* , changed elements of string , returns string. figured if allocated via malloc have same effect :

char * itostr(unsigned val) {      const char digit_pairs[201] = {       "00010203040506070809"       "10111213141516171819"       "20212223242526272829"       "30313233343536373839"       "40414243444546474849"       "50515253545556575859"       "60616263646566676869"       "70717273747576777879"       "80818283848586878889"       "90919293949596979899"     };      int size;     if(val>=10000) {         if(val>=10000000) {             if(val>=1000000000) {                 size=10;             } else if(val>=100000000) {                 size=9;             } else {                 size=8;             }         } else {             if(val>=1000000) {                 size=7;             } else if(val>=100000) {                 size=6;             } else {                 size=5;             }         }     } else {         if(val>=100) {             if(val>=1000) {                 size=4;             } else {                 size=3;             }         } else {             if(val>=10) {                 size=2;             } else {                 size=1;             }         }     }      char * c = (char *)malloc(size + 1);     c[size] = '\0';      //char* c = &s[size-1];     while(val>=100)     {        int pos = val % 100;        val /= 100;        *(short*)(c-1)=*(short*)(digit_pairs+2*pos);         c-=2;     }     while(val>0)     {         *c--='0' + (val % 10);         val /= 10;     }       return c; } 

c += size-1; 

you need line before first while loop. 2 loops write digits right left. it's needed writing starts @ right end of string.