#include <stdio.h>

#include <stdlib.h>

#include <limits.h>

#include "grib2.h"

g2int pngunpack(unsigned char *cpack,g2int len,g2int *idrstmpl,g2int ndpts,

                g2float *fld)

//$$$  SUBPROGRAM DOCUMENTATION BLOCK

//                .      .    .                                       .

// SUBPROGRAM:    pngunpack

//   PRGMMR: Gilbert          ORG: W/NP11    DATE: 2003-08-27

//

// ABSTRACT: This subroutine unpacks a data field that was packed into a

//   PNG image format

//   using info from the GRIB2 Data Representation Template 5.41 or 5.40010.

//

// PROGRAM HISTORY LOG:

// 2003-08-27  Gilbert

//

// USAGE:    pngunpack(unsigned char *cpack,g2int len,g2int *idrstmpl,g2int ndpts,

//                     g2float *fld)

//   INPUT ARGUMENT LIST:

//     cpack    - The packed data field (character*1 array)

//     len      - length of packed field cpack().

//     idrstmpl - Pointer to array of values for Data Representation

//                Template 5.41 or 5.40010

//     ndpts    - The number of data values to unpack

//

//   OUTPUT ARGUMENT LIST:

//     fld[]    - Contains the unpacked data values

//

// REMARKS: None

//

// ATTRIBUTES:

//   LANGUAGE: C

//   MACHINE:  IBM SP

//

//$$$

{

      g2int  *ifld;

      g2int  j,nbits,iret = 0,width,height;

      g2float  refD, refV,bscale,dscale, bdscale;

      unsigned char *ctemp;

      rdieee(idrstmpl+0,&refV,1);

      bscale = (g2float)int_power(2.0,idrstmpl[1]);

      dscale = (g2float)int_power(10.0,-idrstmpl[2]);

      bdscale = bscale * dscale;

      refD = refV * dscale;

      nbits = idrstmpl[3];

//

//  if nbits equals 0, we have a constant field where the reference value

//  is the data value at each gridpoint

//

      if (nbits != 0) {

         int nbytes = nbits/8;

         if( ndpts != 0 && nbytes > INT_MAX / ndpts )

         {

             return 1;

         }

         ifld=(g2int *)calloc(ndpts,sizeof(g2int));

         // Was checked just before

         // coverity[integer_overflow,overflow_sink]

         ctemp=(unsigned char *)calloc((size_t)(ndpts)*nbytes,1);

         if ( ifld == NULL || ctemp == NULL) {

            fprintf(stderr, "Could not allocate space in jpcunpack.\n"

                    "Data field NOT unpacked.\n");

            free(ifld);

            free(ctemp);

            return(1);

         }

         iret=(g2int)dec_png(cpack,len,&width,&height,ctemp, ndpts, nbits);

         gbits(ctemp,ndpts*nbytes,ifld,0,nbits,0,ndpts);

         for (j=0;j<ndpts;j++) {

            fld[j] = refD + bdscale*(g2float)(ifld[j]);

         }

         free(ctemp);

         free(ifld);

      }

      else {

         for (j=0;j<ndpts;j++) fld[j]=refD;

      }

      return(iret);

}