#include <stdio.h>

#include <stdlib.h>

#include <limits.h>

#include "grib2.h"

#include "libaec.h"

// Cf https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-42.shtml

// and https://github.com/erget/wgrib2/commit/07b0f6fcb9669e0e3285318f50d516731b6956b2

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

                g2float *fld)

{

      g2int  iret = 0;

      g2float  refV;

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

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

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

      g2float bdscale = bscale * dscale;

      g2float refD = refV * dscale;

      g2int 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_per_sample = (nbits + 7) / 8;

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

         {

             return 1;

         }

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

         // Was checked just before

         // coverity[integer_overflow,overflow_sink]

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

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

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

                    "Data field NOT unpacked.\n");

            free(ifld);

            free(ctemp);

            return(1);

         }

         struct aec_stream strm = {0};

         strm.flags = idrstmpl[5]; // CCSDS compression options mask

         strm.bits_per_sample = nbits;

         strm.block_size = idrstmpl[6];

         strm.rsi = idrstmpl[7]; // Restart interval

         strm.next_in = cpack;

         strm.avail_in = len;

         strm.next_out = ctemp;

         strm.avail_out = (size_t)(ndpts) * nbytes_per_sample;

         // Note: libaec doesn't seem to be very robust to invalid inputs...

         int status = aec_buffer_decode(&strm);

         if (status != AEC_OK)

         {

             fprintf(stderr, "aec_buffer_decode() failed with return code %d", status);

             iret = 1;

         }

         else

         {

             gbits(ctemp,ndpts * nbytes_per_sample,ifld,0,nbytes_per_sample*8,0,ndpts);

             g2int j;

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

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

             }

         }

         free(ctemp);

         free(ifld);

      }

      else {

         g2int j;

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

      }

      return(iret);

}