ref: 5c448c618a89ab8933838da1b5b97ed7c4a42e08
dir: /sys/src/ape/lib/ap/gen/strtoul.c/
#include <stdlib.h> #include <errno.h> #include <limits.h> unsigned long strtoul(const char *nptr, char **endptr, int base) { const char *p; unsigned long n, nn; int c, ovfl, neg, v, ndig; p = (char*)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){ if(*p != '0') base = 10; else{ 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 */ 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; nn = n*base + v; if(nn < n) ovfl = 1; n = nn; } Return: if(ndig == 0) p = nptr; if(endptr) *endptr = (char *)p; if(ovfl){ errno = ERANGE; return ULONG_MAX; } if(neg) return -n; return n; }