1 /*
2 FUNCTION
3 <<itoa>>---integer to string
4
5 INDEX
6 itoa
7
8 SYNOPSIS
9 #include <stdlib.h>
10 char *itoa(int <[value]>, char *<[str]>, int <[base]>);
11 char *__itoa(int <[value]>, char *<[str]>, int <[base]>);
12
13 DESCRIPTION
14 <<itoa>> converts the integer <[value]> to a null-terminated string
15 using the specified base, which must be between 2 and 36, inclusive.
16 If <[base]> is 10, <[value]> is treated as signed and the string will be
17 prefixed with '-' if negative. For all other bases, <[value]> is treated as
18 unsigned. <[str]> should be an array long enough to contain the converted
19 value, which in the worst case is sizeof(int)*8+1 bytes.
20
21 RETURNS
22 A pointer to the string, <[str]>, or NULL if <[base]> is invalid.
23
24 PORTABILITY
25 <<itoa>> is non-ANSI.
26
27 No supporting OS subroutine calls are required.
28 */
29
30 #include <stdlib.h>
31
32 char *
__itoa(int value,char * str,int base)33 __itoa (int value,
34 char *str,
35 int base)
36 {
37 unsigned uvalue;
38 int i = 0;
39
40 /* Check base is supported. */
41 if ((base < 2) || (base > 36))
42 {
43 str[0] = '\0';
44 return NULL;
45 }
46
47 /* Negative numbers are only supported for decimal.
48 * Cast to unsigned to avoid overflow for maximum negative value. */
49 if ((base == 10) && (value < 0))
50 {
51 str[i++] = '-';
52 uvalue = (unsigned)-value;
53 }
54 else
55 uvalue = (unsigned)value;
56
57 __utoa (uvalue, &str[i], base);
58 return str;
59 }
60
61 char *
itoa(int value,char * str,int base)62 itoa (int value,
63 char *str,
64 int base)
65 {
66 return __itoa (value, str, base);
67 }
68