itoa.cpp

00001 #include <string.h>
00002 #include "itoa.h"
00003 using namespace std;
00004 
00005 // Implementation of itoa()
00006 char* itoa(int num, char* str, int base)
00007 {
00008     int i = 0;
00009     bool isNegative = false;
00010  
00011     /* Handle 0 explicitely, otherwise empty string is printed for 0 */
00012     if (num == 0)
00013     {
00014         str[i++] = '0';
00015         str[i] = '\0';
00016         return str;
00017     }
00018  
00019     // In standard itoa(), negative numbers are handled only with 
00020     // base 10. Otherwise numbers are considered unsigned.
00021     if (num < 0 && base == 10)
00022     {
00023         isNegative = true;
00024         num = -num;
00025     }
00026  
00027     // Process individual digits
00028     while (num != 0)
00029     {
00030         int rem = num % base;
00031         str[i++] = (rem > 9)? (rem-10) + 'a' : rem + '0';
00032         num = num/base;
00033     }
00034  
00035     // If number is negative, append '-'
00036     if (isNegative)
00037         str[i++] = '-';
00038  
00039     str[i] = '\0'; // Append string terminator
00040  
00041     // Reverse the string
00042     reverse(str);
00043  
00044     return str;
00045 }
00046 
00047 /*
00048 ** reverse string in place 
00049 */
00050 void reverse(char *s){
00051 char *j;
00052 int c;
00053  
00054   j = s + strlen(s) - 1;
00055   while(s < j) {
00056     c = *s;
00057     *s++ = *j;
00058     *j-- = c;
00059   }
00060 }