keyword_counting.c

/*
* Keywords counting program
*/

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

#define MAXWORD 100

struct key {
	char *word;
	int count;
} keytab[] = {
	"auto", 0,
	"break", 0,
	"case", 0,
	"char", 0,
	"const", 0,
	"continue", 0,
	"default", 0,
	"unsigned", 0,
	"void", 0,
	"volatile", 0,
	"while", 0
};


#define NKEYS	(sizeof keytab / sizeof(struct key))
int getword(char *, int);
int binsearch(char *, struct key *, int);

int main(void)
{
	int n;
	char word[MAXWORD];

	while (getword(word, MAXWORD) != EOF)
		if (isalpha(word[0]))
			keytab[n].count++;
	for (n = 0; n < NKEYS; n++)
		if (keytab[n].count > 0)
			printf("%4d %s\n", keytab[n].count, keytab[n].word);
	return 0;

}


/* binsearch: find word in tab[0]...tab[n-1] */
int binsearch(char *word, struct key tab[], int n)
{

	int cond;
	int low, mid, high;

	low = 0;
	high = n - 1;
	while (low <= high) {
		mid =(low + high) / 2;
		if ((cond = strcmp(word, tab[mid].word)) < 0)
			high = mid - 1;
		else if (cond > 0)
			low = mid + 1;
		else
			return mid;
	}
	return -1;
}

#define BUFSIZE  100
char buf[BUFSIZE];
int bufp = 0;

int getch(void)
{
	return (bufp > 0) ? buf[--bufp] : getchar();
}

void ungetch(int ch)
{
	if (bufp >= BUFSIZE)
		printf("too many characters\n");
	else
		buf[bufp++] = ch;
}


/* getword: get next word or character from input */
int getword(char *word, int lim)
{
	int c, getch(void);
	void ungetch(int);
	char *w = word;

	while (isspace(c = getch()))
		;
	if (c != EOF)
		*w++ = c;
	if (!isalpha(c)) {
		*w = '\0';
		return c;
	}
	for ( ; --lim > 0; w++)
		if (!isalnum(*w = getch())) {
			ungetch(*w);
			break;
		}
	*w = '\0';
	return word[0];
}