/*
 * Copyright (C) International Business Machines Corp., 2006
 * Author: Dan Smith <danms@us.ibm.com>
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License. See the file COPYING in the main directory
 * of this archive for more details.
 *
 */
/*
 * This example program demonstrates a trivial use of the dmu pieces
 * of the libdevmapper library for userspace orchestration of a
 * device-mapper pseudo-device.  To compile:
 *
 *  # gcc -ldevmapper -o dmu-example dmu-example.c
 *
 * Here, we simply map all reads and writes to the device given as the
 * first argument to the program.  For example:
 *
 *  # ./dmu-example /dev/ram0
 *
 * will create a device /dev/mapper/foo in which all accesses are
 * redirected to /dev/ram0.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <libdevmapper.h>

#include <dmu.h>

#define VERBOSE 0

dev_t destination_dev;

int count = 0;
unsigned int total = 0;

struct dmu_context *c;

int map_handler(void *data, struct dmu_map_data *map_data)
{
	/* We leave block pointing to the original location, but
	 * change the destination device 
	 */
	dmu_map_set_dest_dev(map_data, destination_dev);
	
#if VERBOSE
	printf("[%llu] Mapping %llu -> 0x%llx\n",
	       dmu_map_get_id(map_data),
	       dmu_map_get_block(map_data),
	       destination_dev);
#endif

	count++;
	total++;

	/* Return 1 to signal that the mapping has been performed and
	 * should be sent to the kernel
	 */
	return 1;
}

int map_done_handler(void *data, struct dmu_map_data *map_data)
{
#if VERBOSE
	printf("[%llu] Completing IO to block %llu\n",
	       dmu_map_get_id(map_data),
	       dmu_map_get_block(map_data));
#endif

	/* Return 1 to signal that the IO can be completed */
	return 1;
}

int main(int argc, char **argv)
{
	struct stat s;
	char cmd[256];

	if (argc != 2) {
		printf("Usage: %s <device>\n", argv[0]);
		exit(1);
	}

	printf("I'm creating a device-mapper device called 'foo'.  \n"
	       "Be sure to remove it when you're done with this example\n"
	       "program! (run 'dmsetup remove foo')\n");

	/* Determine and record our destination device for mappings */
	stat(argv[1], &s);
	destination_dev = s.st_rdev;

	/* Create a very simple device-mapper device with a small
	 * section of sectors mapped to dm-userspace, at 512-byte
	 * blocks
	 */
	sprintf(cmd,
		"echo 0 1048576 userspace foo 4096 %i:%i | dmsetup create foo",
		(unsigned)(destination_dev & 0xFF00) >> 8,
		(unsigned)(destination_dev & 0x00FF));
	system(cmd);

	/* Open the control device for the device-mapper device 'foo' */
	c = dmu_ctl_open("foo", 0);
	if (!c) {
		printf("Failed to get control device\n");
		exit(1);
	}

	/* Register our callback function for handling map events */
	dmu_register_map_handler(c, map_handler, NULL);
	dmu_register_map_done_handler(c, map_done_handler, NULL);

	while (1) {
		if (dmu_events_pending(c, 1000)) {
			//printf("Processing events...\n");
			dmu_process_events(c);
			printf("Processed %i events\n", count);
			count = 0;
		} else {
			printf("Nothing to do\n");
		}
		printf("Total: %u\n", total);
	}
}