aecunpack.c

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#include "grib2_int.h"
#include <stdio.h>
#include <stdlib.h>
 
static int
aecunpack_int(unsigned char *cpack, g2int len, g2int *idrstmpl, g2int ndpts,
              void *fld, int fld_is_double, int verbose)
{
    g2int *ifld;
    g2int j, ctemplen = 0, nbits;
    g2int ccsds_flags, ccsds_block_size, ccsds_rsi;
    //g2int ifld1 = 0;
    int ret = 0;
    float ref, bscale, dscale;
    float *ffld = fld;
    double *dfld = fld;
    unsigned char *ctemp;
    size_t nbytes = 0;
 
    LOG((2, "aecunpack_int len %ld ndpts %ld fld_is_double %d", len, ndpts, fld_is_double));
 
    /* Get compression parameters from data representation template array. */
    rdieee(idrstmpl, &ref, 1);
    bscale = int_power(2.0, idrstmpl[1]);
    dscale = int_power(10.0, -idrstmpl[2]);
    nbits = idrstmpl[3];
    ccsds_flags = idrstmpl[5];
    ccsds_block_size = idrstmpl[6];
    ccsds_rsi = idrstmpl[7];
 
    /* If nbits equals 0, we have a constant field where the reference
     * value is the data value at each gridpoint. */
    if (nbits != 0)
    {
        if (!(ifld = calloc(ndpts, sizeof(g2int))))
        {
            if (verbose)
                fprintf(stderr, "Could not allocate space in aecunpack.\n  Data field NOT upacked.\n");
            return G2C_ENOMEM;
        }
 
        /* Determine the number of bytes needed for each value, then allocate the
         * buffer for the decoded AEC stream. */
        nbytes = (nbits + 7) / 8;
        if (nbytes == 3)
            nbytes = 4;
        ctemplen = nbytes * ndpts;
        if ((ctemp = (unsigned char *)malloc(ctemplen)) == NULL)
        {
            if (verbose)
                fprintf(stderr, "Allocation error.\n");
            return G2C_ENOMEM;
        }
 
        /* Decode the AEC stream. */
        ret = dec_aec(cpack, len, nbits, ccsds_flags, ccsds_block_size, ccsds_rsi, ctemp, ctemplen);
        if (ret < 0)
            return ret;
 
        /* IMPORTANT: The decoded AEC stream is byte-aligned (not bit), so when extracting the data
         * values from the buffer via gbits, we need to pass the byte size in bits, not nbits. */
        gbits(ctemp, ifld, 0, nbytes * 8, 0, ndpts);
 
        /* Zero out all higher-order bits, preserving nbits. NOTE: This might be unecessary. */
        //for (j = 0; j < ndpts; j++)
        //    ifld1 = ifld[j];
        //    ifld1 = ifld1 << (sizeof(ifld1)*8-nbits);
        //    ifld1 = ifld1 >> (sizeof(ifld1)*8-nbits);
        //    ifld[j] = ifld1;
 
        /* Unscale data. */
        if (fld_is_double)
        {
            for (j = 0; j < ndpts; j++)
                dfld[j] = (((float)ifld[j] * bscale) + ref) * dscale;
        }
        else
        {
            for (j = 0; j < ndpts; j++)
                ffld[j] = (((float)ifld[j] * bscale) + ref) * dscale;
        }
 
        /* Clean up. */
        free(ctemp);
        free(ifld);
    }
    else
    {
        if (fld_is_double)
        {
            for (j = 0; j < ndpts; j++)
                dfld[j] = ref;
        }
        else
        {
            for (j = 0; j < ndpts; j++)
                ffld[j] = ref;
        }
    }
 
    return G2C_NOERROR;
}
 
g2int
aecunpack(unsigned char *cpack, g2int len, g2int *idrstmpl, g2int ndpts,
          float *fld)
{
    int ret;
 
    LOG((2, "g2c_aecunpack len %lld ndpts %lld", len, ndpts));
 
    ret = aecunpack_int(cpack, len, idrstmpl, ndpts, fld, 0, 1);
 
    return ret;
}
 
int
g2c_aecunpackf(unsigned char *cpack, size_t len, int *idrstmpl, size_t ndpts,
               float *fld)
{
    g2int idrstmpl8[G2C_AEC_DRS_TEMPLATE_LEN];
    g2int len8 = len, ndpts8 = ndpts;
    int i;
 
    LOG((2, "g2c_aecunpackf len %d ndpts %lld", len, ndpts));
 
    for (i = 0; i < G2C_AEC_DRS_TEMPLATE_LEN; i++)
        idrstmpl8[i] = idrstmpl[i];
 
    return aecunpack_int(cpack, len8, idrstmpl8, ndpts8, fld, 0, 0);
}
 
int
g2c_aecunpackd(unsigned char *cpack, size_t len, int *idrstmpl, size_t ndpts,
               double *fld)
{
    g2int idrstmpl8[G2C_AEC_DRS_TEMPLATE_LEN];
    g2int len8 = len, ndpts8 = ndpts;
    int i;
 
    LOG((2, "g2c_aecunpackd len %lld ndpts %lld", len, ndpts));
 
    for (i = 0; i < G2C_AEC_DRS_TEMPLATE_LEN; i++)
        idrstmpl8[i] = idrstmpl[i];
 
    return aecunpack_int(cpack, len8, idrstmpl8, ndpts8, fld, 1, 0);
}