#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <setjmp.h>
#include "jpeglib.h"

struct my_errmgr
{
	struct jpeg_error_mgr pub;
	sigjmp_buf jmp;
	const char *fname;
};

typedef struct my_errmgr *my_errmgr_p;

METHODDEF (void)
my_output_message (j_common_ptr cinfo)
{
	my_errmgr_p err = (my_errmgr_p) cinfo->err;
	char    buffer[JMSG_LENGTH_MAX];

	(*cinfo->err->format_message) (cinfo, buffer);
	fprintf (stderr, "%s: %s: %s\n", program_invocation_short_name,
		 err->fname, buffer);
}

METHODDEF (void)
my_error_exit (j_common_ptr cinfo)
{
	my_errmgr_p err = (my_errmgr_p) cinfo->err;

	my_output_message (cinfo);
	siglongjmp (err->jmp, 1);
}

#define last_element(array) (sizeof ((array)) / sizeof (*(array)) - 1)

int
display_file (const char *fname)
{
	struct jpeg_decompress_struct cinfo;
	struct my_errmgr jerr;
	FILE   *fp;
	int     header;

	if (!(fp = fopen (fname, "rb")))
	{
		fprintf (stderr, "%s: %s: %s\n",
			 program_invocation_short_name, fname,
			 strerror (errno));
		return EXIT_FAILURE;
	}

	jerr.fname = fname;
	cinfo.err = jpeg_std_error (&jerr.pub);
	jerr.pub.error_exit = my_error_exit;
	jerr.pub.output_message = my_output_message;

	if (setjmp (jerr.jmp))
	{
		jpeg_destroy_decompress (&cinfo);
		fclose (fp);
		return EXIT_FAILURE;
	}

	jpeg_create_decompress (&cinfo);
	jpeg_stdio_src (&cinfo, fp);
	header = jpeg_read_header (&cinfo, FALSE);

	printf ("%s:\n", fname);
	printf ("  Datastream type: %s\n",
		(header ==
		 JPEG_HEADER_TABLES_ONLY) ? "abbreviated" : "image");
	printf ("  Image width: %u\n", (unsigned) cinfo.image_width);
	printf ("  Image height: %u\n", (unsigned) cinfo.image_height);

	unsigned jpeg_color_space = cinfo.jpeg_color_space;
	const char *colorspace[] = {
		"unspecified", "monochrome", "R/G/B", "Y/Cb/Cr",
		"C/M/Y/K", "Y/Cb/Cr/K", "unrecognized"
	};
	if (jpeg_color_space > last_element (colorspace))
		jpeg_color_space = last_element (colorspace);
	printf ("  Image colorspace: %d (%s)\n", cinfo.jpeg_color_space,
		colorspace[jpeg_color_space]);
	printf ("  Number of color components: %d\n", cinfo.num_components);

	if (cinfo.saw_JFIF_marker)
	{
		unsigned density_unit = cinfo.density_unit;
		const char *density[] =
			{ "", " dots/inch", " dots/cm", " units" };
		if (density_unit > last_element (density))
			density_unit = last_element (density);

		printf ("  JFIF version: %u.%u\n",
			(unsigned) cinfo.JFIF_major_version,
			(unsigned) cinfo.JFIF_minor_version);
		printf ("  X density: %u%s\n",
			(unsigned) cinfo.X_density, density[density_unit]);
		printf ("  Y density: %u%s\n",
			(unsigned) cinfo.Y_density, density[density_unit]);
	}
	if (cinfo.saw_Adobe_marker)
	{
		printf ("  Adobe_transform: %u\n",
			(unsigned) cinfo.Adobe_transform);
	}

	jpeg_destroy_decompress (&cinfo);
	fclose (fp);

	return EXIT_SUCCESS;
}

int
main (int ac, const char **av)
{
	int     rc = EXIT_SUCCESS, i;

	for (i = 1; i < ac; ++i)
		rc |= display_file (av[i]);
	return rc;
}