/******************************************************************************
*
* read_hdr
*
*   Fills the passed std_hdr header structure with header data 
*   read from the specified file.
*
* LAST UPDATE: 26 November 1997 
*
* ARGUMENTS: 
*
*   Name      Type                 Description
*   ----      ----                 -----------
*   infile   *FILE                 Opened input data file pointer
*   hdr      *struct std_hdr       Pointer to std_hdr structure 
*
* ORIGINAL AUTHORS:
*   Don Anderson and Wesley Berg, CIRES/CDC, November 1997
*
* RETURNS:   0  If successful
*           -1  If error allocating space 
*           -2  If error returned from fread  
* 
* NOTES:
*   (1) The passed file descriptor ("infile") must be for a file which
*       has already been opened
*   (2) Binary read (fread) stops at the 1000th byte of the file
*       (end of header)
*   (3) Example of use:
*       To print the 0th field description from the calling routine,
*       printf ("Description of field 0 is %s\n", hdrstruct.description[0]); 
*
***************************************************************************/

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

 int read_hdr ( FILE *infile, struct std_hdr *hdr )

 {

 char  buff[5000] ;          /* Buffer for filler bytes              */
 int   error_flag ;          /* Error flag                           */
 short fields ;              /* Number of fields                     */ 
 int   i,n ;                   /* Generic counter                      */

 error_flag = 0 ;

 if ((n=fread ( hdr->filename, 1, 80, infile )) != 80)
   {
   error_flag = -2 ;
   goto outta_here ;
   }
 fread ( hdr->satellite, 1, 20, infile ) ;
 fread ( hdr->sensor, 1, 20, infile ) ;
 fread ( &hdr->satid, 2, 1, infile ) ;
 fread ( &hdr->fields, 2, 1, infile ) ;
 fread ( &hdr->pixperscan, 2, 1, infile ) ;
 fread ( &hdr->hifields, 2, 1, infile ) ;
 fread ( &hdr->hipixperscan, 2, 1, infile ) ;
 fread ( &hdr->missing_val, 2, 1, infile ) ;

 fields = hdr->fields + hdr->hifields ; 


 /** Allocate space for variable-length records **/

 hdr->scale = 
 ( float * ) malloc ( ( hdr->fields + hdr->hifields ) * sizeof ( float ) ) ;
 hdr->offset = 
 ( float * ) malloc ( ( hdr->fields + hdr->hifields ) * sizeof ( float ) ) ;
 hdr->units = 
 ( struct units_text * ) 
 malloc ( ( hdr->fields + hdr->hifields ) * sizeof ( struct units_text ) ) ;
 hdr->description = 
 ( struct describe_text * ) 
 malloc ( ( hdr->fields + hdr->hifields ) * sizeof ( struct describe_text ) ) ;

 if ( hdr->scale == NULL || hdr->offset == NULL || hdr->units == NULL ||
      hdr->description == NULL )
   {
   error_flag = -1 ;
   goto outta_here ;
   }

 for ( i = 0 ; i < ( hdr->fields + hdr->hifields ) ; i++ )
   {
   fread ( &hdr->scale[i], 4, 1, infile ) ;
   fread ( &hdr->offset[i], 4, 1, infile ) ;
   fread ( &hdr->units[i], 40, 1, infile ) ;
   fread ( &hdr->description[i], 80, 1, infile ) ;
   }

 /** Read past additional bytes to get to 5000 **/

 if ( ! fread ( buff, 5000 - 132 - ( fields * 128 ), 1, infile ) )
   error_flag = -2 ;

 outta_here :
 return ( error_flag ) ;

 }