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#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
/* The C Programming Language: 2nd Edition
*
* Exercise 6-2: Write a program that reads a C program and prints in
* alphabetical order each group of variable names that are identical in the
* first 6 characters, but different somewhere thereafter. Don't count words
* within string and comments. Make 6 a parameter that can be set from the
* command line.
*
* Notes: First off, "variable names" should be "words". It doesn't make sense
* otherwise.
*
* The trick to this is we can traverse the tree with no problem, but to do
* comparisons on the words, we need to know the last one we worked with. With
* two additional static variables in treeprint(), we have all we need to
* manipulate what we're outputting.
*/
#define BUFSIZE 1000
#define MAXWORD 100
#define DEF_PRE_LEN 6
struct key {
char *word;
int count;
};
struct tnode {
char *word;
int count;
struct tnode *left;
struct tnode *right;
};
enum states {
NORMAL,
INQUOTE,
INCOMMENT
};
char buf[BUFSIZE];
int bufp = 0;
int state = NORMAL;
int minlen;
int getch(void);
void ungetch(int);
int getword(char *, int);
struct key *binsearch(char *, struct key *, int);
struct tnode *addtree(struct tnode *, char *);
void treeprint(struct tnode *, int);
struct tnode *talloc(void);
char *mystrdup(char *);
int check_prefix(char *, char *, int);
int main(int argc, char *argv[]) {
switch (argc) {
case 1:
minlen = DEF_PRE_LEN;
break;
case 2:
minlen = strtol(argv[1], NULL, 10);
break;
default:
printf("Too many arguments.\n");
return 1;
}
struct tnode *root;
char word[MAXWORD];
root = NULL;
while (getword(word, MAXWORD) != EOF) {
/* Only add the words we need to the tree */
if (isalpha(word[0]) && strlen(word) > minlen) {
root = addtree(root, word);
if (root == NULL) {
printf("No words at that length or greater were found.\n");
return 1;
}
}
}
treeprint(root, minlen);
return 0;
}
int getword(char *word, int lim) {
int c;
char *w = word;
while (isspace(c = getch())) {
}
if (c != EOF && c != '#' && c != '"' && c != '/' && c != '*') {
*w++ = c;
}
if (c == '*' && state == INCOMMENT) {
if ((c = getch()) == '/') {
state == NORMAL;
return '/';
}
}
/* Ignore comments */
if (c == '/') {
c = getch();
if (c == '/') {
while ((c = getch()) != EOF && c != '\n') {
}
return '*';
}
if (c == '*') {
state = INCOMMENT;
return '*';
}
}
/* Handle quotes */
if (c == '"') {
state = INQUOTE;
}
if (state == INQUOTE) {
while ((c = getch()) != '"' && c != EOF) {
}
state = NORMAL;
}
/* Ignore preprocessor lines */
if (c == '#') {
while ((c = getch()) != '\n' && c != EOF) {
}
}
/* Add exceptions for underscores */
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];
}
struct key *binsearch(char *word, struct key *tab, int n) {
int cond;
struct key *low = &tab[0];
struct key *high = &tab[n];
struct key *mid;
while (low < high) {
mid = low + (high - low) / 2;
if ((cond = strcmp(word, mid->word)) < 0) {
high = mid;
} else if (cond > 0) {
low = mid + 1;
} else {
return mid;
}
}
return NULL;
}
int getch(void) {
return (bufp > 0) ? buf[--bufp] : getchar();
}
void ungetch(int c) {
if (bufp >= BUFSIZE) {
printf("ungetch: Too many characters.\n");
} else {
buf[bufp++] = c;
}
}
struct tnode *addtree(struct tnode *p, char *w) {
int cond;
if (p == NULL) {
p = talloc();
p->word = mystrdup(w);
p->count = 1;
p->left = p->right = NULL;
} else if ((cond = strcmp(w, p->word)) == 0) {
p->count++;
} else if (cond < 0) {
p->left = addtree(p->left, w);
} else {
p->right = addtree(p->right, w);
}
return p;
}
int check_prefix(char *s1, char *s2, int len) {
int i;
if (len == 0) {
return 1;
}
for (i == 0; *s1 == *s2 && *s1 != '\0' && i < len; i++, *s1++, *s2++) {
}
if (i == len) {
return 1;
}
return 0;
}
void treeprint(struct tnode *p, int len) {
static struct tnode *last; /* The last word we saw */
static int output = 1; /* Controls whether we output 'last' or not */
if (p != NULL) {
treeprint(p->left, len);
if (len == 0) {
printf("%4d %s\n", p->count, p->word);
} else {
if (last != NULL) {
if (check_prefix(last->word, p->word, len)) {
if (output) {
printf("%4d %s\n", last->count, last->word);
output = 0;
}
printf("%4d %s\n", p->count, p->word);
} else {
output = 1;
}
}
last = p;
}
treeprint(p->right, len);
}
}
struct tnode *talloc(void) {
return (struct tnode *) malloc(sizeof(struct tnode));
}
char *mystrdup(char *s) {
char *p;
p = (char *) malloc(strlen(s) + 1);
if (p != NULL) {
strcpy(p , s);
}
return p;
}
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