#include "shgetc.h"
#include <ctype.h>
#include <errno.h>
#include <limits.h>

/* Lookup table for digit values. -1==255>=36 -> invalid */
static const unsigned char table[] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15,
    16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1,
    -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
    32, 33, 34, 35, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};

unsigned long long __intscan(FILE* f, unsigned base, int pok, unsigned long long lim) {
    const unsigned char* val = table + 1;
    int c, neg = 0;
    unsigned x;
    unsigned long long y;
    if (base > 36) {
        errno = EINVAL;
        return 0;
    }
    while (isspace((c = shgetc(f))))
        ;
    if (c == '+' || c == '-') {
        neg = -(c == '-');
        c = shgetc(f);
    }
    if ((base == 0 || base == 16) && c == '0') {
        c = shgetc(f);
        if ((c | 32) == 'x') {
            c = shgetc(f);
            if (val[c] >= 16) {
                shunget(f);
                if (pok)
                    shunget(f);
                else
                    shlim(f, 0);
                return 0;
            }
            base = 16;
        } else if (base == 0) {
            base = 8;
        }
    } else {
        if (base == 0)
            base = 10;
        if (val[c] >= base) {
            shunget(f);
            shlim(f, 0);
            errno = EINVAL;
            return 0;
        }
    }
    if (base == 10) {
        for (x = 0; c >= '0' && c <= '9' && x <= UINT_MAX / 10 - 1; c = shgetc(f))
            x = x * 10 + (c - '0');
        for (y = x; c >= '0' && c <= '9' && y <= ULLONG_MAX / 10 && 10 * y <= ULLONG_MAX - (c - '0');
             c = shgetc(f))
            y = y * 10 + (c - '0');
        if (c < '0' || c > '9')
            goto done;
    } else if (!(base & (base - 1))) {
        int bs = "\0\1\2\4\7\3\6\5"[(0x17 * base) >> 5 & 7];
        for (x = 0; val[c] < base && x <= UINT_MAX / 32; c = shgetc(f))
            x = x << bs | val[c];
        for (y = x; val[c] < base && y <= ULLONG_MAX >> bs; c = shgetc(f))
            y = y << bs | val[c];
    } else {
        for (x = 0; val[c] < base && x <= UINT_MAX / 36 - 1; c = shgetc(f))
            x = x * base + val[c];
        for (y = x; val[c] < base && y <= ULLONG_MAX / base && base * y <= ULLONG_MAX - val[c];
             c = shgetc(f))
            y = y * base + val[c];
    }
    if (val[c] < base) {
        for (; val[c] < base; c = shgetc(f))
            ;
        errno = ERANGE;
        y = lim;
        if (lim & 1)
            neg = 0;
    }
done:
    shunget(f);
    if (y >= lim) {
        if (!(lim & 1) && !neg) {
            errno = ERANGE;
            return lim - 1;
        } else if (y > lim) {
            errno = ERANGE;
            return lim;
        }
    }
    return (y ^ neg) - neg;
}