Number parsing using C11 _Generic

parse-number.c

/* parse_number() using C11 _Generic */
/* @lafp, 2015-06-07 */
#include <stdlib.h>
#include <stdbool.h>
#include <stdio.h>
#include <errno.h>

#define parse_number(Input, Output) \
    _Generic((*Output), \
        int: parse_number_strtoint, \
        unsigned int: parse_number_strtouint, \
        long: parse_number_strtol, \
        long long: parse_number_strtoll, \
        unsigned long: parse_number_strtoul, \
        unsigned long long: parse_number_strtoull, \
        float: parse_number_strtof, \
        double: parse_number_strtod, \
        long double: parse_number_strtold)(Input, Output)

#define DECLARE_INT_PARSE_FN(Type, ParseFn) \
    bool \
    parse_number_ ## ParseFn(const char *input, Type *output) \
    { \
        char *endptr = NULL; \
        errno = 0; \
        *output = ParseFn(input, &endptr, 0); \
        return errno == 0 && endptr && *endptr == '\0'; \
    }

int
strtoint(const char *input, char **endptr, int base)
{
    if (sizeof(int) == sizeof(long long)) {
        long long output = strtoll(input, endptr, base);
        if ((long long)(int)output != output)
            errno = ERANGE;
        return (int)output;
    }

    long output = strtol(input, endptr, base);
    if ((long)(int)output != output)
        errno = ERANGE;
    return (int)output;
}

unsigned int
strtouint(const char *input, char **endptr, int base)
{
    if (sizeof(unsigned int) == sizeof(unsigned long long)) {
        unsigned long long output = strtoull(input, endptr, base);
        if ((unsigned long long)(unsigned int)output != output)
            errno = ERANGE;
        return (unsigned int)output;
    }

    unsigned long output = strtoul(input, endptr, base);
    if ((unsigned long)(unsigned int)output != output)
        errno = ERANGE;
    return (unsigned int)output;
}

DECLARE_INT_PARSE_FN(long, strtol)
DECLARE_INT_PARSE_FN(long long, strtoll)
DECLARE_INT_PARSE_FN(unsigned long, strtoul)
DECLARE_INT_PARSE_FN(unsigned long long, strtoull)
DECLARE_INT_PARSE_FN(int, strtoint)
DECLARE_INT_PARSE_FN(unsigned int, strtouint)

#undef DECLARE_INT_PARSE_FN

#define DECLARE_FLOAT_PARSE_FN(Type, ParseFn) \
    bool \
    parse_number_ ## ParseFn(const char *input, Type *output) \
    { \
        char *endptr = NULL; \
        errno = 0; \
        *output = ParseFn(input, &endptr); \
        return errno == 0 && endptr && *endptr == '\0'; \
    }

DECLARE_FLOAT_PARSE_FN(float, strtof)
DECLARE_FLOAT_PARSE_FN(double, strtod)
DECLARE_FLOAT_PARSE_FN(long double, strtold)

#undef DECLARE_FLOAT_PARSE_FN

int
main(void)
{
    long loutput;
    long long lloutput;
    unsigned long uloutput;
    unsigned long long ulloutput;
    size_t soutput;
    int ioutput;
    unsigned int uioutput;
    float foutput;
    double doutput;
    long double ldoutput;

    if (!parse_number("0", &loutput))
        return 1;
    if (!parse_number("0", &lloutput))
        return 1;
    if (!parse_number("0", &uloutput))
        return 1;
    if (!parse_number("0", &ulloutput))
        return 1;
    if (!parse_number("0", &soutput))
        return 1;
    if (!parse_number("0", &ioutput))
        return 1;
    if (!parse_number("0", &uioutput))
        return 1;
    if (!parse_number("0", &foutput))
        return 1;
    if (!parse_number("0", &doutput))
        return 1;
    if (!parse_number("0", &ldoutput))
        return 1;
    printf("done!\n");
    return 0;
}