Extract comments from the comment area of a binary DAS file. 

   DAS 

   Variable  I/O  Description 
   --------  ---  -------------------------------------------------- 
   handle     I   Handle of binary DAS file open with read access. 
   bufsiz     I   Maximum size, in lines, of buffer. 
   buflen     I   Line length associated with buffer.
   n          O   Number of comments extracted from the DAS file. 
   buffer     O   Buffer in which extracted comments are placed. 
   done       O   Indicates whether all comments have been extracted. 

   handle   The file handle of a binary DAS file which has been 
            opened with read access. 

   bufsiz   The maximum number of comments that may be placed into 
            buffer. This would typically be the declared array size 
            for the C character string array passed into this 
            routine. 

   buflen   is the common length of the strings in buffer, including the 
            terminating nulls.

   n        The number of comment lines extracted from the comment area
            of the binary DAS file attached to handle. This number will
            be <= bufsiz on output. If n == bufsiz and done !=
            SPICETRUE then there are more comments left to extract. If
            n == 0, then done == SPICETRUE, i.e., there were no
            comments in the comment area. If there are comments in the
            comment area, or comments remaining after the extraction
            process has begun, n > 0, always.

   buffer   A list of at most bufsiz comments which have been 
            extracted from the comment area of the binary DAS 
            file attached to handle.  buffer should be declared as 
            follows:

               ConstSpiceChar   buffer [bufsiz][buflen]

            Each string in buffer is null-terminated.

   done     A boolean flag indicating whether or not all of the 
            comment lines from the comment area of the DAS file have 
            been read. This variable has the value SPICETRUE after the 
            last comment line has been read. It will have the value 
            SPICEFALSE otherwise. 

            If there are no comments in the comment area, this 
            variable will have the value SPICETRUE, and n == 0. 

   None. 

   Binary DAS files contain an area which is reserved for storing 
   annotations or descriptive textual information describing the data 
   contained in a file. This area is referred to as the "comment 
   area" of the file. The comment area of a DAS file is a line 
   oriented medium for storing textual information. The comment 
   area preserves any leading or embedded white space in the line(s) 
   of text which are stored, so that the appearance of the of 
   information will be unchanged when it is retrieved (extracted) at 
   some other time. Trailing blanks, however, are NOT preserved, 
   due to the way that character strings are represented in 
   standard Fortran 77. 

   This routine will read the comments from the comment area of 
   a binary DAS file, placing them into a line buffer. If the line 
   buffer is not large enough to hold the entire comment area, 
   the portion read will be returned to the caller, and the done 
   flag will be set to SPICEFALSE. This allows the comment area to be 
   read in "chunks," a buffer at a time. After all of the comment 
   lines have been read, the done flag will be set to SPICETRUE. 

   After all of the comments in DAS file have been read, the next
   call to this routine will start reading comments at the start
   of the comment area.

   This routine can be used to "simultaneously" extract comments 
   from the comment areas of multiple binary DAS files. 

   1) The following example will extract the entire comment area of a 
      binary DAS file attached to HANDLE, displaying the comments on 
      the terminal screen. 

         #include <stdio.h>
         #include "SpiceUsr.h"

         int main( int argc, char ** argv )
         {

            #define LNSIZE          81
            #define MAXBUF          25

            SpiceBoolean            done;

            SpiceChar               buffer [MAXBUF][LNSIZE];
            SpiceChar             * filename;

            SpiceInt                handle;
            SpiceInt                i;
            SpiceInt                n;


            filename = argv[1];     

            dasopr_ ( filename, &handle, (ftnlen)strlen(filename) );

            done = SPICEFALSE;

            while ( !done )
            {
               dasec_c( handle, MAXBUF, LNSIZE, &n, buffer, &done );

               for ( i = 0;  i < n;  i++ )
               {
                  printf ( "%s\n", buffer[i] );
               }
            } 

            return ( 0 );
         }

   1) The comment area may consist only of printing ASCII characters, 
      decimal values 32 - 126. 

   2) There is NO maximum length imposed on the significant portion 
      of a text line that may be placed into the comment area of a 
      DAS file. The maximum length of a line stored in the comment 
      area should be kept reasonable, so that they may be easily 
      extracted. A good value for this would be 255 characters, as 
      this can easily accommodate "screen width" lines as well as 
      long lines which may contain some other form of information. 

   1) If the size of the output line buffer is is not positive, 
      the error SPICE(INVALIDARGUMENT) will be signaled. 

   2) If a comment line in a DAS file is longer than the length 
      of a character string array element of BUFFER, the error 
      SPICE(COMMENTTOOLONG) will be signaled. 

   3) If there is a mismatch between the number of comment 
      characters found and the number of comment characters 
      expected, the error SPICE(BADDASCOMMENTAREA) will be 
      signaled. 

   4) If the binary DAS file attached to HANDLE is not open for 
      reading, an error will be signaled by a routine called by 
      this routine. 

   5) If the input buffer pointer is null, the error SPICE(NULLPOINTER) 
      will be signaled.

   6) If the input buffer string length buflen is not at least 2, 
      the error SPICE(STRINGTOOSHORT) will be signaled.

   See argument handle in $ Detailed_Input. 

   N.J. Bachman   (JPL)
   K.R. Gehringer (JPL) 

   None. 

   -CSPICE Version 1.0.0, 24-FEB-2003 (NJB) (KRG)

    extract comments from a das file