#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <err.h>
#include <getopt.h>
#include <time.h>
#include <libutil.h>

#define swab16(x) (u_int16_t)__builtin_bswap16((u_int16_t)(x))

/*
 * smart helpers
 */
void fd_close(int *fd)
{
	close(*fd);
	*fd = -1;
}
#define _smartfd __attribute((cleanup(fd_close)))

void file_close(FILE **fd)
{
	fclose(*fd);
	*fd = NULL;
}
#define _smartfile __attribute((cleanup(file_close)))

__attribute__((noreturn)) static int usage(void)
{
	fputs("swap16 [--input] file\n", stderr);
	exit (EXIT_SUCCESS);
}

/*
 * Print human readable numbers
 *
 * @width: spaces
 * @bytes: value in bytes
 */
static void printsize(size_t width, off_t bytes)
{
	/*
	 * Reserve one space before the size and allocate room for
	 * the trailing '\0'.
	 */
	char buf[5];

	humanize_number(buf, sizeof(buf), (int64_t)bytes, "",
			HN_AUTOSCALE, HN_B | HN_NOSPACE | HN_DECIMAL);
	(void)printf("%*s", (u_int)width, buf);
}

int main(int argc, char *argv[])
{
	static struct option longopts[] = {
		{ "input",   required_argument, NULL, 'i' },
		{ NULL,	0, NULL, 0 }
	};

	int ch;
	_smartfd int fd = -1;
	char *inputfile = NULL;

	while ((ch = getopt_long(argc, argv, "hi:", longopts, NULL)) != -1) {
		switch (ch) {
			case 'i':
				inputfile = optarg;
				break;
			case 0:
				/* long option */
				break;
			default:
				usage();
		}
	}

	argc -= optind;
	argv += optind;

	/* if not already set, get the last arguments as the input filename */
	if (!inputfile && argv) {
		inputfile = *argv;
		argv++;
	}

	/* sanity checks */
	if (*argv || (inputfile == NULL))
		usage();

	fd = open(inputfile, O_RDWR);
	if (fd < 0) {
		err(EXIT_FAILURE, "failed to open %s:", inputfile);
	}

	/* File analysis */
	struct stat statbuf = { 0 };
	fstat(fd, & statbuf);

	printf("Parsing:");
	printsize(10, statbuf.st_size);
	puts(".");

	char *addr = (char *)mmap(NULL, (size_t)statbuf.st_size, PROT_WRITE | PROT_READ, MAP_SHARED, fd, 0);
	if (addr == NULL)
		err(EXIT_FAILURE, "Failed to map file %s:\n", inputfile);

	u_int16_t *sbmax=(u_int16_t *)(addr + statbuf.st_size);
	u_int16_t *sb=(u_int16_t *)addr;


	clock_t t1, t0;

	t0 = clock();
	for (;sb < sbmax; sb++)
		*(sb)=swab16(*sb);
	t1 = clock();
	printf("Swab   : %6.3f ms.\n", 1000.0 * (double)(t1 - t0) / CLOCKS_PER_SEC);

	munmap(addr, (size_t)statbuf.st_size);

	return EXIT_SUCCESS;
}