Exercise 5.16 - -d makes comparison on letters, numbers, blanks¶

/**
 * Add the -d ("Directory option") which makes comparison only on letters, numbers and blanks.
 * Make sure it works in conjunction with -f
 **/

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

#define NUMERIC 1    /* numeric sort */
#define DECR    2    /* sort in decreasing order */
#define FOLD    4    /* fold upper and lower cases */
#define MDIR    8    /* directory order */
#define LINES    100    /* maximum number of lines to be sorted */
#define MAXLEN    1000    /* max length of any input line */
#define ALLOCSIZE 10000    /* size of available space */

static char allocbuf[ALLOCSIZE];    /* storage for alloc */
static char *allocp = allocbuf;        /* next free position */
static char option = 0;

void swap(void *v[], int i, int j) {
    void *temp;

    temp = v[i];
    v[i] = v[j];
    v[j] = temp;
}

/* mgetline: read a line s, return length */
int mgetline(char s[], int lim) {
    int c, i;

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

    s[i] = '\0';
    return i;
}

char *alloc(int n)        /* return pointer to n characters */
{
    if (allocbuf + ALLOCSIZE - allocp >= n) {
        allocp += n;
        return allocp - n;
    } else
        return 0;
}

void afree(char *p)    /* free storage pointed to by p */
{
    if (p >= allocbuf && p < allocbuf + ALLOCSIZE)
        allocp = p;
}

/* myqsort: sort v[left] ... v[right] into increasing order */
void myqsort(void *v[], int left, int right, int (*comp)(void *, void *)) {
    int i, last;
    void swap(void *v[], int, int);

    if (left >= right)    /* do nothing if array contains */
        return;        /* fewer than two elements */

    swap(v, left, (left + right) / 2);
    last = left;

    for (i = left + 1; i <= right; i++)
        if ((*comp)(v[i], v[left]) < 0)
            swap(v, ++last, i);

    swap(v, left, last);

    myqsort(v, left, last - 1, comp);
    myqsort(v, last + 1, right, comp);
}

/* readlines: read input lines */
int readlines(char *lineptr[], int maxlines) {
    int len, nlines;
    char *p, line[MAXLEN];

    nlines = 0;

    while ((len = mgetline(line, MAXLEN)) > 0)
        if (nlines >= maxlines || (p = alloc(len)) == NULL)
            return -1;
        else {
            line[len - 1] = '\0';
            strcpy(p, line);
            lineptr[nlines++] = p;
        }
    return nlines;
}

/* writelines: write output lines */
void writelines(char *lineptr[], int nlines, int order) {
    int i;

    if (order)
        for (i = nlines - 1; i >= 0; i--)
            printf("%s\n", lineptr[i]);
    else
        for (i = 0; i < nlines; i++)
            printf("%s\n", lineptr[i]);
}

/* numcmp: compare s1 and s2 numerically */
int numcmp(char *s1, char *s2) {
    double v1, v2;

    v1 = atof(s1);
    v2 = atof(s2);

    if (v1 < v2)
        return -1;
    else if (v1 > v2)
        return 1;
    else
        return 0;
}

/* charcmp: return <0 if s < t, 0 if s ==t, >0 if s > t */
int charcmp(char *s, char *t) {
    char a, b;
    int fold = (option & FOLD) ? 1 : 0;
    int dir = (option & MDIR) ? 1 : 0;

    do {
        if (dir) {
            while (!isalnum(*s) && *s != ' ' && *s != '\0')
                s++;
            while (!isalnum(*t) && *t != ' ' && *t != '\0')
                t++;
        }
        a = fold ? tolower(*s) : *s;
        s++;
        b = fold ? tolower(*t) : *t;
        t++;

        if (a == b && a == '\0')
            return 0;
    } while (a == b);

    return a - b;
}


/* sort input lines */
int main(int argc, char *argv[]) {
    char *lineptr[LINES];    /* pointer to text line */
    int nlines;
    int c, rc = 0;

    while (--argc > 0 && (*++argv)[0] == '-')
        while (c = *++argv[0])
            switch (c) {
                case 'd':    /* directory order */
                    option |= MDIR;
                    break;
                case 'f':
                    option |= FOLD;
                    break;
                case 'n':
                    option |= NUMERIC;
                    break;
                case 'r':
                    option |= DECR;
                    break;
                default:
                    printf("sort: illegal option %c\n", c);
                    argc = 1;
                    rc = -1;
                    break;
            }

    if (argc)
        printf("Usage: sort -dfnr \n");
    else {
        if ((nlines = readlines(lineptr, LINES)) > 0) {
            if (option & NUMERIC)
                myqsort((void **) lineptr, 0, nlines - 1, (int (*)(void *, void *)) numcmp);
            else
                myqsort((void **) lineptr, 0, nlines - 1, (int (*)(void *, void *)) charcmp);

            writelines(lineptr, nlines, option & DECR);
        } else {
            printf("input too big to sort \n");
            rc = -1;
        }
    }

    return rc;
}