/*
	 * Copyright (C) 2013 Red Hat, Inc.
	 *
	 * All rights reserved.
	 *
	 * Author: Jan Friesse <jfriesse@redhat.com>
	 *
	 * libqb is free software: you can redistribute it and/or modify
	 * it under the terms of the GNU Lesser General Public License as published by
	 * the Free Software Foundation, either version 2.1 of the License, or
	 * (at your option) any later version.
	 *
	 * libqb is distributed in the hope that it will be useful,
	 * but WITHOUT ANY WARRANTY; without even the implied warranty of
	 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	 * GNU Lesser General Public License for more details.
	 *
	 * You should have received a copy of the GNU Lesser General Public License
	 * along with libqb.  If not, see <http://www.gnu.org/licenses/>.
	 */
	
	#include <sys/types.h>
	
	#include <assert.h>
	#include <err.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <time.h>
	#include <unistd.h>
	
	static void usage(void)
	{
		printf("Usage: [ -i input_file] [ -o output_file ] [ -n no_bytes]\n");
		printf("Changes no_bytes (default 1024) in input_file (default = - = stdin) and store\n");
		printf("result to output_file (default = - = stdout). It's possible to use same file\n");
		printf("as both input and output\n");
	
		exit(1);
	}
	
	static void init_rand(void) {
		unsigned int init_v;
	
		init_v = time(NULL) + getpid();
	
		srand(init_v);
	}
	
	int main(int argc, char *argv[])
	{
		FILE *fi, *fo;
		int i;
		const char *input_file_name;
		const char *output_file_name;
		int no_bytes;
		char *ep;
		int ch;
		unsigned char *data;
		size_t data_size;
		size_t data_pos;
		size_t input_data_size;
		unsigned char buf[1024];
	
		input_file_name = "-";
		output_file_name = "-";
		no_bytes = 1024;
	

		while ((ch = getopt(argc, argv, "hi:o:n:")) != -1) {

			switch (ch) {

			case 'i':
				input_file_name = optarg;

				break;

			case 'n':
				no_bytes = strtol(optarg, &ep, 10);

				if (no_bytes < 0 || *ep != '\0') {
					warnx("illegal number -- %s", argv[2]);
					usage();

				}

				break;

			case 'o':
				output_file_name = optarg;

				break;
			case 'h':
			case '?':
			default:
				usage();
				/* NOTREACHED */

			}

		}
	

		if (strcmp(input_file_name, "-") == 0) {
			fi = stdin;

		} else {
			fi = fopen(input_file_name, "rb");
			if (fi == NULL) {
				err(1, "%s", input_file_name);
			}

		}
	
		/*
		 * Open and fully read input file
		 */
		data = NULL;
		data_size = 0;

		data_pos = 0;

		while ((input_data_size = fread(buf, 1, sizeof(buf), fi)) != 0) {
			if (data_pos + input_data_size >= data_size) {
				data_size = (data_size + input_data_size) * 2;
				assert((data = realloc(data, data_size)) != NULL);
			}
			memcpy(data + data_pos, buf, input_data_size);
			data_pos += input_data_size;

		}
		fclose(fi);
	
		/*
		 * Change bytes
		 */
		init_rand();
	

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

			data[rand() % data_pos] = rand();
		}
	
		/*
		 * Fully write ouput file
		 */
		if (strcmp(output_file_name, "-") == 0) {
			fo = stdout;
		} else {
			fo = fopen(output_file_name, "wb");
			if (fo == NULL) {
				err(1, "%s", output_file_name);
			}
		}
		assert(fwrite(data, 1, data_pos, fo) == data_pos);
		fclose(fo);
	
		free(data);
	
		return (0);
	}