*** readimage.c.orig	Tue May 25 09:12:39 1999
--- readimage.c	Wed Apr 17 08:53:37 2002
***************
*** 28,33 ****
--- 28,36 ----
  #include	"astrom.h"
  #include	"weight.h"
  
+ /* added by DMW */
+ void findextension(FILE *file, char *filename, int which);
+ 
  /******************************* loadstrip ***********************************/
  /*
  Load a new strip of pixel data into the buffer.
***************
*** 555,563 ****
--- 558,586 ----
     int		j,l, n;
     char		*buf, st[80], str[80], *point;
  
+    /* added by DMW */
+    int extension=-1;
+    char *base;
+ 
+    /* parse name[extension].  name,extension is not allowed because SE already
+       uses commas to separate multiple image filenames. */
+    base = strdup(field->filename); /* cheap way of allocing enough space for base */
+    if(sscanf(field->filename,"%[^[][%d]",base,&extension)==2){
+      fprintf(stderr,"base: %s, extension: %d\n",base,extension);
+      strcpy(field->filename,base);
+    }
+    free(base);
+ 
  /* Open the file */
    if (!(field->file = fopen(field->filename, "rb")))
      error(EXIT_FAILURE,"*Error*: cannot open ", field->filename);
+ 
+   if(extension>0){
+     /* fast-forward to that extension */
+     findextension(field->file,field->filename,extension);
+   }
+ 
+ 
    buf = readfitshead(field->file, field->filename, &n);
    if(FITSTOI("NAXIS   ", 0) < 2)
      error(EXIT_FAILURE, field->filename, " does NOT contain 2D-data!");
***************
*** 791,797 ****
        error(EXIT_FAILURE, filename, " is NOT a FITS file!");
      else
        {
!       memset(buf, ' ', 80);
        strncpy(buf,
  	"SIMPLE  =                    T / Decompressed by SExtractor", 59);
        }
--- 814,820 ----
        error(EXIT_FAILURE, filename, " is NOT a FITS file!");
      else
        {
! 
        strncpy(buf,
  	"SIMPLE  =                    T / Decompressed by SExtractor", 59);
        }
***************
*** 809,811 ****
--- 832,887 ----
    }
  
  
+ /**** findextension added by DMW *****/
+ 
+ void findextension(FILE *file, char *filename, int which)
+ {
+   char *primarybuf;
+   int nseek,bitpix,bytepix,naxis1,naxis2;  /* refer to pixels or bytes */
+   int this,nextend;  /* refer to extension numbers */
+   int n,nprimary,nblocks; /* refer to FITS blocks */
+   char *buf, st[80], *point;	/* necessary to make FITSTOI work */
+ 
+   
+   /* find number of extensions in this file. the buf/primarybuf switch
+      is required because FITSTOI only works on buf. */
+   buf = readfitshead(file, filename, &n);
+   primarybuf=buf;
+   nprimary=n;
+   
+   /* assume this primary hdu has no extension--I'm not sure if that
+    is part of the fits standard, but it is common practice at least. 
+    Go straight to the next hdu and cycle thru to the desired one. */
+   for(this=1;this<which;this++){
+ 
+     buf = readfitshead(file, filename, &n);
+     bitpix = FITSTOI("BITPIX  ", 0);
+     bytepix = abs(bitpix)/8;
+     naxis1 = FITSTOI("NAXIS1  ", 0);
+     naxis2 = FITSTOI("NAXIS2  ", 0);
+     nseek = bytepix*naxis1*naxis2;
+     if(nseek==0){
+       error(EXIT_FAILURE, "*Error*: Can't calculate extension size ", "findextension()");
+       /* NB. A more robust (but very slow) backup plan is to read in each
+ 	 2880-byte block and see if it is the start of a new hdu. Also, we may in fact
+ 	 want to allow hdus with no extensions. */
+     }
+     nblocks = nseek/FBSIZE;
+     if(nseek%FBSIZE != 0)
+       nblocks += 1;
+     /*fprintf(stderr,"seeking %d blocks...",nblocks);*/
+     if(fseek(file,nblocks*FBSIZE,SEEK_CUR)<0){
+       error(EXIT_FAILURE, "*Error*: fseek failed in ", "findextension()");
+     }
+     free(buf);
+   }
+   
+   /* we should be at the desired extension.  Return, because the
+      calling function (readimagehead) will now read the header as
+      normal.  primarybuf still exists because in theory we can do
+      something fancy with inheritance, but for now I'll just free
+      it. */
+   free(primarybuf);
+ 
+   return;
+ }