/* Copyright 2005, Tresys Technology */

#include <stdio.h>

typedef unsigned char bool_t;

/* file_context_node

 * A node used in a linked list of file contexts.

 * Each node contains the regular expression, the type and 

 *  the context, as well as information about the regular

 *  expression. The regular expression data (meta, stem_len

 *  and str_len) can be filled in by using the fc_fill_data

 *  function after the regular expression has been loaded.

 * next points to the next node in the linked list.

 */

typedef struct file_context_node {

	char *regex;

	char *file_type;

	char *context;

	bool_t meta;

	int stem_len;

	int str_len;

	struct file_context_node *next;

} file_context_node_t;

void file_context_node_destroy(file_context_node_t *x)

{

	free(x->regex);

	free(x->file_type);

	free(x->context);

}

/* file_context_bucket

 * A node used in a linked list of buckets that contain

 *  file_context_node's.

 * Each node contains a pointer to a file_context_node which

 *  is the header of its linked list. This linked list is the

 *  content of this bucket.

 * next points to the next bucket in the linked list.

 */

typedef struct file_context_bucket {

	file_context_node_t *data;

	struct file_context_bucket *next;

} file_context_bucket_t;

/* fc_merge

 * Merges two sorted file context linked lists into one

 *  sorted one.

 * Pass two lists a and b, and after the completion of fc_merge,

 *  the final list is contained in a, and b is empty.

 */

file_context_node_t *fc_merge(file_context_node_t *a,

				   file_context_node_t *b)

{

	file_context_node_t *a_current;

	file_context_node_t *b_current;

	file_context_node_t *temp;

	file_context_node_t *jumpto;

	/* If a is a empty list, and b is not,

	 *  set a as b and proceed to the end. */

	if (!a && b)

		a = b;

	/* If b is an empty list, leave a as it is. */

	else if (!b) {

	} else {

		/* Make it so the list a has the lesser

		 *  first element always. */

		if (fc_compare(a, b) == 1) {

			temp = a;

			a = b;

			b = temp;

		}

		a_current = a;

		b_current = b;

		/* Merge by inserting b's nodes inbetween a's nodes. */

		while (a_current->next && b_current) {

			jumpto = a_current->next;

			/* Insert b's nodes inbetween the current a node

			 *  and the next a node.*/

			while (b_current && a_current->next &&

			       fc_compare(a_current->next,

					  b_current) != -1) {

				temp = a_current->next;

				a_current->next = b_current;

				b_current = b_current->next;

				a_current->next->next = temp;

				a_current = a_current->next;

			}

			/* Skip all the inserted node from b to the

			 *  next node in the original a. */

			a_current = jumpto;

		}

		/* if there is anything left in b to be inserted,

		   put it on the end */

		if (b_current) {

			a_current->next = b_current;

		}

	}

	b = NULL;

	return a;

}

/* fc_merge_sort

 * Sorts file contexts from least specific to more specific.

 * The bucket linked list is passed and after the completion

 *  of the fc_merge_sort function, there is only one bucket

 *  (pointed to by master) that contains a linked list

 *  of all the file contexts, in sorted order.

 * Explanation of the algorithm:

 *  The algorithm implemented in fc_merge_sort is an iterative

 *   implementation of merge sort.

 *  At first, each bucket has a linked list of file contexts

 *   that are 1 element each.

 *  Each pass, each odd numbered bucket is merged into the bucket

 *   before it. This halves the number of buckets each pass.

 *  It will continue passing over the buckets (as described above)

 *   until there is only  one bucket left, containing the list of

 *   file contexts, sorted.

 */

void fc_merge_sort(file_context_bucket_t *master)

{

	int i;

	file_context_bucket_t *current;

	file_context_bucket_t *temp;

	file_context_node_t *ncurrent;

	file_context_node_t *ntemp;

	/* Loop until master is the only bucket left

	 * so that this will stop when master contains

	 * the sorted list. */

	while (master->next) {

		current = master;

		/* This loop merges buckets two-by-two. */

		while (current) {

			if (current->next) {

				/* Merge the next one into the current one. */

				current->data =

				    fc_merge(current->data,

					     current->next->data);

				/* remove the next bucket that is now empty. */

				temp = current->next;

				current->next = current->next->next;

				free(temp);

			}

			current = current->next;

		}

	}

}

/* fc_compare

 * Compares two file contexts' regular expressions and returns:

 *    -1 if a is less specific than b

 *     0 if a and be are equally specific

 *     1 if a is more specific than b

 * The comparison is based on the following statements,

 *  in order from most important to least important, given a and b:

 *     If a is a regular expression and b is not,

 *      -> a is less specific than b.

 *     If a's stem length is shorter than b's stem length,

 *      -> a is less specific than b.

 *     If a's string length is shorter than b's string length,

 *      -> a is less specific than b.

 *     If a does not have a specified type and b does not,

 *      -> a is less specific than b.

 */

int fc_compare(file_context_node_t *a, file_context_node_t *b)

{

	/* Check to see if either a or b have meta characters

	 *  and the other doesn't. */

	if (a->meta && !b->meta)

		return -1;

	if (b->meta && !a->meta)

		return 1;

	/* Check to see if either a or b have a shorter stem

	 *  length than the other. */

	if (a->stem_len < b->stem_len)

		return -1;

	if (b->stem_len < a->stem_len)

		return 1;

	/* Check to see if either a or b have a shorter string

	 *  length than the other. */

	if (a->str_len < b->str_len)

		return -1;

	if (b->str_len < b->str_len)

		return 1;

	/* Check to see if either a or b has a specified type

	 *  and the other doesn't. */

	if (!a->type && b->type)

		return -1;

	if (!b->type && a->type)

		return 1;

	/* If none of the above conditions were satisfied, 

	 * then a and b are equally specific. */

	return 0;

}

/* fc_fill_data

 * This processes a regular expression in a file context

 *  and sets the data held in file_context_node, namely

 *  meta, str_len and stem_len. 

 * The following changes are made to fc_node after the

 *  the completion of the function:

 *     fc_node->meta =		1 if regex has a meta character,

 *                       	0 if not.

 *     fc_node->str_len =	The string length of the regular

 *                               expression.

 *     fc_node->stem_len = 	The number of characters up until

 *				 the first meta character.

 */

void fc_fill_data(file_context_node_t *fc_node)

{

	int c = 0;

	fc_node->meta = 0;

	fc_node->stem_len = 0;

	fc_node->str_len = 0;

	/* Process until the string termination character

	 *  has been reached.

	 * Note: this while loop has been adapted from

	 *  spec_hasMetaChars in matchpathcon.c from

	 *  libselinux-1.22. */

	while (fc_node->regex[c] != 0) {

		switch (fc_node->regex[c]) {

		case '.':

		case '^':

		case '$':

		case '?':

		case '*':

		case '+':

		case '|':

		case '[':

		case '(':

		case '{':

			/* If a meta character is found,

			 *  set meta to one */

			fc_node->meta = 1;

			break;

		case '\\':

			/* If a escape character is found,

			 *  skip the next character. */

			c++;

		default:

			/* If no meta character has been found yet,

			 *  add one to the stem length. */

			if (!fc_node->meta)

				fc_node->stem_len++;

			break;

		}

		fc_node->str_len++;

		c++;

	}

}

/* main

 * This program takes in two arguments, the input filename and the

 *  output filename. The input file should be syntactically correct.

 * Overall what is done in the main is read in the file and store each

 *  line of code, sort it, then output it to the output file.

 */

int main(int argc, char *argv[])

{

	int lines;

	size_t start, finish, regex_len;

	size_t line_len, i, j;

	char *str, *input_name, *output_name, *line_buf;

	file_context_node_t *temp;

	file_context_node_t *head;

	file_context_node_t *current;

	file_context_node_t *array;

	file_context_bucket_t *master;

	file_context_bucket_t *bcurrent;

	FILE *in_file, *out_file;

	/* Check for the correct number of command line arguments. */

	if (argc != 3) {

		fprintf(stderr, "Error: invalid number of command line arguments.\n");

		return 1;

	}

	input_name = argv[1];

	output_name = argv[2];

	i = j = lines = 0;

	/* Make sure to have a terminating character, always. */

	line_buf[BUF_SIZE - 1] = '\0';

	/* Open the input file. */

	if (!(in_file = fopen(input_name), "r")) {

		fprintf(stderr, "Error: failure opening input file for read.\n");

		return 1;

	}

	/* Parse the file into a file_context linked list. */

	buf = NULL;

	while (getline(&line_buf, &line_len, in_file) {

		/* Get rid of whitespace from the front of the line. */

		for (i = 0; i < line_len; i++) {

			if (line_buf[i] != ' ' || line_buf[i] != '\t')

				break;

		}

		if (i >= line_len)

			continue;

		/* Check if the line isn't empty and isn't a comment */

		if (line_buf[i] == '#')

			continue;

		/* We have a valid line - allocate a new node. */

		temp = (file_context_node_t *)malloc(sizeof(file_context_node_t));

		if (!temp) {

			fprintf(stderr, "Error: failure allocating memory.\n");

			return 1;

		}

		memset(temp, 0, sizeof(file_context_node_t));

		/* Parse out the regular expression from the line. */

		start = i;

		while (i < line_len && (line_buf[i] != ' ' || line_buf[i] != '\t'))

			i++;

		finish = i;

		regex_len = start - finish;

		if (regex_len == 0) {

			file_context_node_destroy(temp);

			free(temp);

			continue;

		}

		temp->path = strndup(&line_buf[start], regex_len);

		if (!temp->path) {

			file_context_node_destroy(temp);

			free(temp);

			fprintf(stderr, "Memory error\n");

			return 1;

		}

		/* Get rid of whitespace after the regular expression. */

		for (; i < line_len; i++) {

			if (line_buf[i] != ' ' || line_buf[i] != '\t')

				break;

		}

		if (i == line_len) {

			file_context_node_destroy(temp);

			free(temp);

			continue;

		}

		/* Parse out the type from the line (if it 

			*  is there). */

		if (line_buf[i] == '-') {

			temp->type = (char *)malloc(sizeof(char) * 3);

			if (!(temp->type)) {

				fprintf(stderr, "Error: failure allocating memory.\n");

				return 1;

			}

			/* Fill the type into the array. */

			temp->type[0] = line_buf[i];

			temp->type[1] = line_buf[i + 1];

			i += 2;

			temp->type[2] = 0;

			/* Get rid of whitespace after the type. */

			while (line_buf[i] <= ' ')

				i++;

		}

		/* Parse out the context from the line. */

		start = i;

		while (line_buf[i] > ' ')

			i++;

		finish = i;

		/* Allocate a character array to hold the context. */

		temp->context =

			(char *) malloc(sizeof(char) *

					(finish - start + 1));

		if (!(temp->context)) {

			printf

				("Error: failure allocating memory.\n");

			return -1;

		}

		temp->context[0] = 0;

		/* Fill the context array. */

		temp->context[(finish - start)] = 0;

		for (j = 0; j < finish - start; j++) {

			temp->context[j] = line_buf[j + start];

		}

		/* Set all the data about the regular

			*  expression. */

		fc_fill_data(temp);

		/* Link this line of code at the end of

			*  the linked list. */

		current->next = temp;

		current = current->next;

		lines++;

	}

	free(buf);

	fclose(path);

	/* Create the bucket linked list from the earlier linked list. */

	current = head->next;

	bcurrent = master =

	    (file_context_bucket_t *)

	    malloc(sizeof(file_context_bucket_t));

	/* Go until all the nodes have been put in individual buckets. */

	while (current) {

		/* Copy over the file context line into the bucket. */

		bcurrent->data = current;

		current = current->next;

		/* Detatch the node in the bucket from the old list. */

		bcurrent->data->next = NULL;

		/* If there should be another bucket, put one at the end. */

		if (current) {

			bcurrent->next =

			    (file_context_bucket_t *)

			    malloc(sizeof(file_context_bucket_t));

			if (!(bcurrent->next)) {

				printf

				    ("Error: failure allocating memory.\n");

				return -1;

			}

			/* Make sure the new bucket thinks it's the end of the

			 *  list. */

			bcurrent->next->next = NULL;

			bcurrent = bcurrent->next;

		}

	}

	/* Sort the bucket list. */

	fc_merge_sort(master);

	/* Open the output file. */

	if (!(path = fopen(argv[2], "w"))) {

		printf("Error: failure opening output file for write.\n");

		return -1;

	}

	/* Output the sorted file_context linked list to the output file. */

	current = master->data;

	while (current) {

		/* Output the regular expression. */

		i = 0;

		while (current->regex[i] != 0) {

			fprintf(path, "%c", current->regex[i]);

			i++;

		}

		fprintf(path, "\t");

		/* Output the type, if there is one. */

		if (current->type) {

			i = 0;

			while (current->type[i] != 0) {

				fprintf(path, "%c", current->type[i]);

				i++;

			}

			fprintf(path, "\t");

		}

		/* Output the context. */

		i = 0;

		while (current->context[i] != 0) {

			fprintf(path, "%c", current->context[i]);

			i++;

		}

		fprintf(path, "\n");

		/* Remove the node. */

		temp = current;

		current = current->next;

		free(temp->regex);

		if (temp->type)

			free(temp->type);

		free(temp->context);

		free(temp);

	}

	free(master);

	fclose(path);

	return 0;

}