Greg Hartman | 76d05dc | 2016-11-23 15:51:27 -0800 | [diff] [blame] | 1 | /* |
| 2 | * strntoumax.c |
| 3 | * |
| 4 | * The strntoumax() function and associated |
| 5 | */ |
| 6 | |
| 7 | #include <stddef.h> |
| 8 | #include <stdint.h> |
| 9 | #include <ctype.h> |
| 10 | |
| 11 | static inline int digitval(int ch) |
| 12 | { |
| 13 | if (ch >= '0' && ch <= '9') { |
| 14 | return ch - '0'; |
| 15 | } else if (ch >= 'A' && ch <= 'Z') { |
| 16 | return ch - 'A' + 10; |
| 17 | } else if (ch >= 'a' && ch <= 'z') { |
| 18 | return ch - 'a' + 10; |
| 19 | } else { |
| 20 | return -1; |
| 21 | } |
| 22 | } |
| 23 | |
| 24 | uintmax_t strntoumax(const char *nptr, char **endptr, int base, size_t n) |
| 25 | { |
| 26 | int minus = 0; |
| 27 | uintmax_t v = 0; |
| 28 | int d; |
| 29 | |
| 30 | while (n && isspace((unsigned char)*nptr)) { |
| 31 | nptr++; |
| 32 | n--; |
| 33 | } |
| 34 | |
| 35 | /* Single optional + or - */ |
| 36 | if (n && *nptr == '-') { |
| 37 | minus = 1; |
| 38 | nptr++; |
| 39 | n--; |
| 40 | } else if (n && *nptr == '+') { |
| 41 | nptr++; |
| 42 | } |
| 43 | |
| 44 | if (base == 0) { |
| 45 | if (n >= 2 && nptr[0] == '0' && (nptr[1] == 'x' || nptr[1] == 'X')) { |
| 46 | n -= 2; |
| 47 | nptr += 2; |
| 48 | base = 16; |
| 49 | } else if (n >= 1 && nptr[0] == '0') { |
| 50 | n--; |
| 51 | nptr++; |
| 52 | base = 8; |
| 53 | } else { |
| 54 | base = 10; |
| 55 | } |
| 56 | } else if (base == 16) { |
| 57 | if (n >= 2 && nptr[0] == '0' && (nptr[1] == 'x' || nptr[1] == 'X')) { |
| 58 | n -= 2; |
| 59 | nptr += 2; |
| 60 | } |
| 61 | } |
| 62 | |
| 63 | while (n && (d = digitval(*nptr)) >= 0 && d < base) { |
| 64 | v = v * base + d; |
| 65 | n--; |
| 66 | nptr++; |
| 67 | } |
| 68 | |
| 69 | if (endptr) |
| 70 | *endptr = (char *)nptr; |
| 71 | |
| 72 | return minus ? -v : v; |
| 73 | } |