firstly, I have no idea now that I look at ti again, how I managed to get away with that.
I think I'll post a couple notes on what I noticed I did wrong, and then post a better version, with comments included (if you also want it in an email just ask, it might be a bit harder to read on here)
ok here goes for the errors I made yesterday(at least the ones I noticed):
first of all, adding the char at the beggining of buf was pointess since I only added a '-' to the beggining of b, never buf.
secondly, I was using j to keep track of which place I was in.. but how did that work?? j is only an int, so it's surprising i didn't get errors - i suppose I should have made sure the function could handle even large ints properly.
thirdly, I was putting a null terminator on the char *after* the end of b
and another thing - after using the first char of buf for something else, i never made buf long enough, so it was actually only using sizeint-1 chars, which means it couldn't handle a large int anyway.
Well, I don't know how that slipped past me, but here's a hopefully better solution:
edit {Code:/i is the int we want to convert, b is the string we'll put it into, //and sizeb is the length of string b //(actually since the string starts at 0, sizeb should be //the last element of b void myitoa(int i, char* b, int sizeb) { //if the string doesn't point to anything, //or if it's 0 length, return if(!b || !sizeb) return; //j is for the loops, r is the temp variable for getting the value out of i int j=0, r=i; //this tells us how many bits an int has (assuming a byte has 8 bits.. I *think* this is safe? I may be wrong tho) int szint = sizeof(int)*8; //buf is the string we'll use to work on, s will point to the current spot we're working on char* buf=0; char* s=0; //allocate enough memory to handle the size of an int.. + 1 for the /0 at the end try { buf = new char[szint+1]; } catch(...) { cout << "error allocating memory\n"; buf=0; } //this way if there was an error we won't go trying to write an invalid pointer if(buf) { int c; //initialize the string to be all '0's and slap a null terminator on it for(j=0;j<szint;j++) *(buf+j) = '0'; *(buf+szint) = '\0'; //now if i is a negative number, reverse the sign on r //and then just treat it as a normal positive number //this was a hack cause I totally forgot to include support for //negative numbers untill like 2 minutes before I was going to post the code ;) if(i < 0) { r = (-(i)); } //have no idea how the old way wokred at all.. //s starts at the end of buf and works backwards s=buf+szint; //until it hits the beggining while(s >= buf) { //make the char at s's current address = '0' + whatever is in the current place; //if r == 756 for instance, r%756 == 6; and '0' + 6 = '6' *s = (char)('0' + r%10); //then switch to the next place by dividing by ten r /= 10; //and switch to the next(or rather previous ^.^) char by decreasing s s--; } s=buf; c=0; //remove the leading 0s since they look stupid - //what I'm actually doing is just having s point to the first character that is not 0 - //unless it's the only one in the string, in which case it will just point to the last one while(*s == '0' && c++ < szint) s++; //now copy it into the string we were passed, making sure not to write too far strncpy(b, s, sizeb); //and, if i was a negative number, shift the characters in b over to the right and make the first one a '-' //(might be a more efficient way of doing this but like I said, I just hacked it in two minutes before posting :P //and it actually works too hehe) if(i<0) { for(j=sizeb;j>0;j--) *(b+j) = *(b+j-1); *b = '-'; } //now if the b string is long enough to hold our whole string, cap it at the end of our string, //so we won't have gibberish after the number if(c < sizeb) *(b+c) = '\0'; } //and also be sure to cap the end of b once we're done with it, even if it doesn't hold our whole string. *(b+sizeb) = '\0'; }
re:Hammer
quite correct, it was, which is part of the reason why I'm not sure how I got away with it ^.^
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