/*----------------------------------------------------------------------------*/
/**
   @file	fits_md5.c
   @author	N. Devillard
   @date	May 2001
   @version	$Revision: 1.8 $
   @brief	FITS data block MD5 computation routine.

   This module offers MD5 computation over all data areas of a FITS file.
*/
/*----------------------------------------------------------------------------*/

/*
	$Id: fits_md5.c,v 1.8 2003/01/23 09:13:18 yjung Exp $
	$Author: yjung $
	$Date: 2003/01/23 09:13:18 $
	$Revision: 1.8 $
*/

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

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

#include "md5.h"
#include "fits_std.h"
#include "qerror.h"

/*-----------------------------------------------------------------------------
   								Defines
 -----------------------------------------------------------------------------*/

/** Size of an MD5 hash in bytes (32 bytes are 128 bits) */
#define MD5HASHSZ	32

/*-----------------------------------------------------------------------------
  							Function code
 -----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------*/
/**
  @brief	Compute the MD5 hash of data zones in a FITS file.
  @param	filename	Name of the FITS file to examine.
  @return	1 statically allocated character string, or NULL.

  This function expects the name of a FITS file.
  It will compute the MD5 hash on all data blocks in the main data section
  and possibly extensions (including zero-padding blocks if necessary) and
  return it as a string suitable for inclusion into a FITS keyword.

  The returned string is statically allocated inside this function,
  so do not free it or modify it. This function returns NULL in case
  of error.
 */
/*----------------------------------------------------------------------------*/
char *
qfits_datamd5 (char *filename)
{
  static char datamd5[MD5HASHSZ + 1];
  struct MD5Context ctx;
  unsigned char digest[16];
  FILE *in;
  char buf[FITS_BLOCK_SIZE];
  char *buf_c;
  int i;
  int in_header;
  int check_fits;

  /* Check entries */
  if (filename == NULL)
    return NULL;
  /* Open input file */
  if ((in = fopen (filename, "r")) == NULL)
    {
      qfits_error ("cannot open file %s", filename);
      return NULL;
    }
  /* Initialize all variables */
  MD5Init (&ctx);
  in_header = 1;
  check_fits = 0;
  /* Loop over input file */
  while (fread (buf, 1, FITS_BLOCK_SIZE, in) == FITS_BLOCK_SIZE)
    {
      /* First time in the loop: check the file is FITS */
      if (check_fits == 0)
	{
	  /* Examine first characters in block */
	  if (buf[0] != 'S' ||
	      buf[1] != 'I' ||
	      buf[2] != 'M' ||
	      buf[3] != 'P' ||
	      buf[4] != 'L' ||
	      buf[5] != 'E' ||
	      buf[6] != ' ' || buf[7] != ' ' || buf[8] != '=')
	    {
	      qfits_error ("file [%s] is not FITS\n", filename);
	      fclose (in);
	      return NULL;
	    }
	  else
	    {
	      check_fits = 1;
	    }
	}
      if (in_header)
	{
	  buf_c = buf;
	  for (i = 0; i < FITS_NCARDS; i++)
	    {
	      if (buf_c[0] == 'E' &&
		  buf_c[1] == 'N' && buf_c[2] == 'D' && buf_c[3] == ' ')
		{
		  in_header = 0;
		  break;
		}
	      buf_c += FITS_LINESZ;
	    }
	}
      else
	{
	  /* If current block is a data block */
	  /* Try to locate an extension header */
	  if (buf[0] == 'X' &&
	      buf[1] == 'T' &&
	      buf[2] == 'E' &&
	      buf[3] == 'N' &&
	      buf[4] == 'S' &&
	      buf[5] == 'I' &&
	      buf[6] == 'O' && buf[7] == 'N' && buf[8] == '=')
	    {
	      in_header = 1;
	      buf_c = buf;
	      for (i = 0; i < FITS_NCARDS; i++)
		{
		  /* Try to find an END marker in this block */
		  if (buf_c[0] == 'E' &&
		      buf_c[1] == 'N' && buf_c[2] == 'D' && buf_c[3] == ' ')
		    {
		      /* Found END marker in same block as XTENSION */
		      in_header = 0;
		      break;
		    }
		  buf_c += FITS_LINESZ;
		}
	    }
	  else
	    {
	      MD5Update (&ctx, (unsigned char *) buf, FITS_BLOCK_SIZE);
	    }
	}
    }
  fclose (in);
  if (check_fits == 0)
    {
      /* Never went through the read loop: file is not FITS */
      qfits_error ("file [%s] is not FITS", filename);
      return NULL;
    }
  /* Got to the end of file: summarize */
  MD5Final (digest, &ctx);
  /* Write digest into a string */
  sprintf (datamd5,
	   "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
	   digest[0],
	   digest[1],
	   digest[2],
	   digest[3],
	   digest[4],
	   digest[5],
	   digest[6],
	   digest[7],
	   digest[8],
	   digest[9],
	   digest[10],
	   digest[11], digest[12], digest[13], digest[14], digest[15]);
  return datamd5;
}

/* vim: set ts=4 et sw=4 tw=75 */