3.getword.c

#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 }, { "double", 0 }, { "else", 0 },
	{ "enum", 0 }, { "extern", 0 }, { "float", 0 }, { "for", 0 },
	{ "goto", 0 }, { "if", 0 }, { "int", 0 }, { "long", 0 },
	{ "register", 0 }, { "return", 0 }, { "short", 0 }, { "signed", 0 },
	{ "sizeof", 0 }, { "static", 0 }, { "struct", 0 }, { "switch", 0 },
	{ "typedef", 0 }, { "union", 0 }, { "unsigned", 0 }, { "void", 0 },
	{ "volatile", 0 }, { "while", 0 }
};

#define NKEYS (sizeof keytab / sizeof keytab[0])

int getword(char *, int);
int binsearch(char *, struct key *, int);

// gcc 3.getword.c getch.c
main()
{
	int n;
	char word[MAXWORD];

	while (getword(word, MAXWORD) != EOF) {
		if (isalpha(word[0]))
			if ((n = binsearch(word, keytab, NKEYS)) >= 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;
}

int binsearch(char *word, struct key tab[], int n)
{
	int cond;
	int low, high, mid;

	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;
}

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 (c == '/') {
		*w = getch();
		if (*w == '/') {
			for ( ; --lim > 0; w++) {
				if ((*w = getch()) == '\n') {
					*++w = '\0';
					return c;
				}
			}
		} else if (*w == '*') {
			for ( ; --lim > 0; w++) {
				if ((*w = getch()) == '*') {
					if ((*++w = getch()) == '/') {
						*++w = '\0';
						return c;
					}
				}
			}
		} else {
			ungetch(*w);
		}
	}

	if (c == '\'') {
		*w++ = getch();
		*w++ = getch();
		*w = '\0';
		return c;
	}

	if (c == '"')
		for ( ; --lim > 0; w++)
			if ((*w = getch()) == '"') {
				*++w = '\0';
				return c;
			}

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

// for test sizeof return int double register

/* sizeof struct void while break
*/