ref: 04c4a9ca8b06e34a203f7ddacc2263cf2077e1aa
dir: /sys/src/libc/port/strtoull.c/
#include <u.h> #include <libc.h> #define UVLONG_MAX (1LL<<63) uvlong strtoull(char *nptr, char **endptr, int base) { char *p; uvlong n, nn, m; int c, ovfl, v, neg, ndig; p = nptr; neg = 0; n = 0; ndig = 0; ovfl = 0; /* * White space */ for(;; p++) { switch(*p) { case ' ': case '\t': case '\n': case '\f': case '\r': case '\v': continue; } break; } /* * Sign */ if(*p == '-' || *p == '+') if(*p++ == '-') neg = 1; /* * Base */ if(base == 0) { base = 10; if(*p == '0') { base = 8; if(p[1] == 'x' || p[1] == 'X'){ p += 2; base = 16; } } } else if(base == 16 && *p == '0') { if(p[1] == 'x' || p[1] == 'X') p += 2; } else if(base < 0 || 36 < base) goto Return; /* * Non-empty sequence of digits */ m = UVLONG_MAX/base; for(;; p++,ndig++) { c = *p; v = base; if('0' <= c && c <= '9') v = c - '0'; else if('a' <= c && c <= 'z') v = c - 'a' + 10; else if('A' <= c && c <= 'Z') v = c - 'A' + 10; if(v >= base) break; if(n > m) ovfl = 1; nn = n*base + v; if(nn < n) ovfl = 1; n = nn; } Return: if(ndig == 0) p = nptr; if(endptr) *endptr = p; if(ovfl) return UVLONG_MAX; if(neg) return -n; return n; }