/*---------------------------------------------------------------------------
 
   File name 	:	flipx.c
   Author 		:	N. Devillard
   Created on	:	July 2001
   Description	:	flip x axis in a FITS image.

   This is an example use of the qfits library. This program expects
   a list of FITS file names in input. For each input file, it will
   flip the image contained in the main data section in the X direction,
   i.e. pixel (i,j) is swapped with pixel (lx-i, j).
   
   The pixel loading mechanism is independent from endian-ness of the
   local host or FITS pixel type. This program offers a good overview
   of how to use qfits for pixel-level operations.

   Notice that this program does not support cubes or image extensions,
   but could be easily extended to support that case.

 *--------------------------------------------------------------------------*/

/*
	$Id: flipx.c,v 1.1 2001/12/14 09:53:21 ndevilla Exp $
	$Author: ndevilla $
	$Date: 2001/12/14 09:53:21 $
	$Revision: 1.1 $
*/

/*---------------------------------------------------------------------------
   								Includes
 ---------------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>

#include "qfits.h"


/*---------------------------------------------------------------------------
   								Macros
 ---------------------------------------------------------------------------*/

#define ERRMSG(s)	fprintf(stderr, "\tflipx error: %s\n", s)

/*---------------------------------------------------------------------------
							Private functions
 ---------------------------------------------------------------------------*/

/*
 * Swap pixels between position p1 and p2, regardless of the pixel
 * type and endian-ness of the local host.
 */
static void swap_pix(char * buf, int p1, int p2, int psize)
{
	int	 i ;
	char c ;

	for (i=0 ; i<psize ; i++) {
		c = buf[p1+i] ;
		buf[p1+i] = buf[p2+i];
		buf[p2+i] = c ;
	}
}

/*
 * Main processing function. It expects one only file name
 * and will flip pixels on the input frame.
 */
static int fits_flip(char * pname, char * filename)
{
	char		*	sval ;
	int				dstart;
	int				lx, ly ;
	int				bpp ;
	int				i, j ;
	char		*	buf ;
	char		*	fbuf ;
	int				psize;
	struct stat		fileinfo ;
	int				fd ;

	printf("%s: processing %s\n", pname, filename);

	if (stat(filename, &fileinfo)!=0) {
		return -1 ;
	}
	if (fileinfo.st_size<1) {
		ERRMSG("cannot stat file");
		return -1 ;
	}

	/* Retrieve image attributes */
	if (is_fits_file(filename)!=1) {
		ERRMSG("not a FITS file");
		return -1 ;
	}

	sval = qfits_query_hdr(filename, "NAXIS1");
	if (sval==NULL) {
		ERRMSG("cannot read NAXIS1");
		return -1 ;
	}
	lx = atoi(sval);
	sval = qfits_query_hdr(filename, "NAXIS2");
	if (sval==NULL) {
		ERRMSG("cannot read NAXIS2");
		return -1 ;
	}
	ly = atoi(sval);
	sval = qfits_query_hdr(filename, "BITPIX");
	if (sval==NULL) {
		ERRMSG("cannot read BITPIX");
		return -1 ;
	}
	bpp = atoi(sval);

	psize = bpp/8 ;
	if (psize<0) psize=-psize ;

	/* Retrieve start of first data section */
	if (qfits_get_hdrinfo(filename, 0, &dstart, NULL)!=0) {
		ERRMSG("reading header information");
		return -1 ;
	}

	/* Map the input file in read/write mode (input file is modified) */
	if ((fd=open(filename, O_RDWR))==-1) {
		perror("open");
		ERRMSG("reading file");
		return -1 ;
	}
	fbuf = (char*)mmap(0,
					   fileinfo.st_size,
					   PROT_READ | PROT_WRITE,
					   MAP_SHARED,
					   fd,
					   0);
	if (fbuf==(char*)-1) {
		perror("mmap");
		ERRMSG("mapping file");
		return -1 ;
	}
	buf = fbuf + dstart ;

	/* Double loop */
	for (j=0 ; j<ly ; j++) {
		for (i=0 ; i<lx/2 ; i++) {
			/* Swap bytes */
			swap_pix(buf, i*psize, (lx-i-1)*psize, psize);
		}
		buf += lx * psize ;
	}
	if (munmap(fbuf, fileinfo.st_size)!=0) {
		ERRMSG("unmapping file");
		return -1 ;
	}
	return 0 ;
}

/*---------------------------------------------------------------------------
								main()
 ---------------------------------------------------------------------------*/

int main(int argc, char * argv[])
{
	int i ;
	int err ;

	if (argc<2) {
		printf("use: %s <list of FITS files...>\n", argv[0]);
		return 1 ;
	}
	err=0 ;
	for (i=1 ; i<argc ; i++) {
		err += fits_flip(argv[0], argv[i]) ;
	}
	if (err>0) {
		fprintf(stderr, "%s: %d error(s) occurred\n", argv[0], err);
		return -1 ;
	}
	return 0 ;
}