atoi源码

isspace(int x) { if(x==' '||x=='/t'||x=='/n'||x=='/f'||x=='/b'||x=='/r') return 1; else return 0; } isdigit(int x) { if(x<='9'&&x>='0') return 1; else return 0; } int atoi(const char *nptr) { int c; /* current char */ int total; /* current total */ int sign; /* if '-', then negative, otherwise positive */ /* skip whitespace */ while ( isspace((int)(unsigned char)*nptr) ) ++nptr; c = (int)(unsigned char)*nptr++; sign = c; /* save sign indication */ if (c == '-' || c == '+') c = (int)(unsigned char)*nptr++; /* skip sign */ total = 0; while (isdigit(c)) { total = 10 * total + (c - '0'); /* accumulate digit */ c = (int)(unsigned char)*nptr++; /* get next char */ } if (sign == '-') return -total; else return total; /* return result, negated if necessary */ }