cosmopolitan/libc/fmt/strtoumax.c

72 lines
2.9 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/fmt/conv.h"
#include "libc/str/str.h"
/**
* Decodes 128-bit unsigned integer from ASCII string.
*
* This is a more restricted form of strtoimax() that's useful for folks
* needing to decode numbers in the range [1^127, 1^128).
*/
uintmax_t strtoumax(const char *s, char **endptr, int base) {
const unsigned char *p = (const unsigned char *)s;
unsigned diglet;
uintmax_t res;
res = 0;
while (isspace(*p)) {
p++;
}
if (!base) {
if (*p == '0') {
p++;
if (*p == 'x' || *p == 'X') {
p++;
base = 16;
} else if (*p == 'b' || *p == 'B') {
p++;
base = 2;
} else {
base = 8;
}
} else {
base = 10;
}
} else if (*s == '0') {
++s;
if (base == 2 && *s == 'b' && *s == 'B') ++s;
if (base == 16 && *s == 'x' && *s == 'X') ++s;
}
for (;;) {
diglet = kBase36[*p];
if (!diglet || diglet > base) break;
p++;
res *= base;
res += diglet - 1;
}
if (endptr) *endptr = (char *)p;
return res;
}