exc/k&r/03-control-flow/03-03.c

#include <stdio.h>
#include <ctype.h>

#define SIZE 1000 

/* check if c1-c2 is valid range */
#define IS_RANGE(c1, c2) ( \
    (isdigit(c1) && isdigit(c2)) || \
    (islower(c1) && islower(c2)) || \
    (isupper(c1) && isupper(c2)) \
)

int getstr(char *s, int n);
void expand(char *s, char *t, int n);

/* copy stdin to string, run expand, print output */
int main()
{
    char s[SIZE], t[SIZE];
    if (getstr(s, SIZE) < 0)
        printf("warning : overlfow on input\n");
    expand(s, t, SIZE);
    printf("%s\n", t);
    return 0;
}

/* macro for checking overlfow of t in expand(s, t, n) */
#define CHECK_OVERFLOW(i, n) \
    do { \
    if (i >= n-1) { \
        printf("warning : overflow in expand\n"); \
        goto terminate; \
    } \
    } while (0)
       
/* expand: expand a-z from s to to abc...xyz in t (of size n), same for 
 * digits and uppercase letters */
void expand(char *s, char *t, int n)
{
    int i = 0;
    if (*s == '\0')
        goto terminate;
      
    int c; 
    for (t[i++] = *(s++); *s != '\0'; s++, i++) {
        if (*s == '-' && IS_RANGE(*(s-1), *(s+1))) {
            for (c = *(s-1) + 1; c < *(s+1); c++, i++) {
                CHECK_OVERFLOW(i, n);
                t[i] = c;
            }
            s++;
        }
        CHECK_OVERFLOW(i, n);
        t[i] = *s;
    }
terminate:
    t[i] = '\0';
}

/* getstr: copies stdin to array s of length n, returns size of string or 
 * -1 if overflow */
int getstr(char *s, int n)
{
    int i, c;

    for (i = 0; (c = getchar()) != EOF; i++) {
        if (i >= n-1) {
            s[i] = '\0';
            return -1;
        }
        s[i] = c;
    }
    s[i] = '\0';
    return i;
}