compack.c

Go to the documentation of this file.

 
#include "grib2_int.h"
#include <math.h>
#include <stdlib.h>
 
void
compack(float *fld, g2int ndpts, g2int idrsnum, g2int *idrstmpl,
        unsigned char *cpack, g2int *lcpack)
{
 
    static g2int zero = 0;
    g2int *ifld, *gref, *glen, *gwidth;
    g2int *jmin, *jmax, *lbit;
    g2int i, j, n, imin, imax, left;
    g2int isd, itemp, ilmax, ngwidthref = 0, nbitsgwidth = 0;
    g2int nglenref = 0, nglenlast = 0, iofst, ival1, ival2;
    g2int minsd, nbitsd = 0, maxorig, nbitorig, ngroups;
    g2int lg, ng, igmax, iwmax, nbitsgref;
    g2int glength, grpwidth, nbitsglen = 0;
    g2int kfildo, minpk, inc, maxgrps, ibit, jbit, kbit, novref, lbitref;
    g2int missopt, miss1, miss2, ier;
    float bscale, dscale, rmax, rmin, temp;
    static float alog2 = ALOG2; /*  ln(2.0) */
    static g2int one = 1;
 
    bscale = int_power(2.0, -idrstmpl[1]);
    dscale = int_power(10.0, idrstmpl[2]);
 
    /* Find max and min values in the data. */
    rmax = fld[0];
    rmin = fld[0];
    for (j = 1; j < ndpts; j++)
    {
        if (fld[j] > rmax)
            rmax = fld[j];
        if (fld[j] < rmin)
            rmin = fld[j];
    }
 
    /* If max and min values are not equal, pack up field. If they are
     * equal, we have a constant field, and the reference value (rmin)
     * is the value for each point in the field and set nbits to 0. */
    if (rmin != rmax)
    {
        iofst = 0;
        ifld = calloc(ndpts, sizeof(g2int));
        gref = calloc(ndpts, sizeof(g2int));
        gwidth = calloc(ndpts, sizeof(g2int));
        glen = calloc(ndpts, sizeof(g2int));
 
        /* Scale original data. */
        if (idrstmpl[1] == 0)
        { /* No binary scaling. */
            imin = (g2int)rint(rmin * dscale);
            /*imax = (g2int)rint(rmax*dscale); */
            rmin = (float)imin;
            for (j = 0; j < ndpts; j++)
                ifld[j] = (g2int)rint(fld[j] * dscale) - imin;
        }
        else
        { /*  Use binary scaling factor */
            rmin = rmin * dscale;
            /*rmax = rmax*dscale; */
            for (j = 0; j < ndpts; j++)
                ifld[j] = (g2int)rint(((fld[j] * dscale) - rmin) * bscale);
        }
 
        /* Calculate Spatial differences, if using DRS Template
         * 5.3. */
        if (idrsnum == 3)
        { /* spatial differences */
            if (idrstmpl[16] != 1 && idrstmpl[16] != 2)
                idrstmpl[16] = 1;
            if (idrstmpl[16] == 1)
            { /* first order */
                ival1 = ifld[0];
                for (j = ndpts - 1; j > 0; j--)
                    ifld[j] = ifld[j] - ifld[j - 1];
                ifld[0] = 0;
            }
            else if (idrstmpl[16] == 2)
            { /* second order */
                ival1 = ifld[0];
                ival2 = ifld[1];
                for (j = ndpts - 1; j > 1; j--)
                    ifld[j] = ifld[j] - (2 * ifld[j - 1]) + ifld[j - 2];
                ifld[0] = 0;
                ifld[1] = 0;
            }
 
            /* Subtract min value from spatial diff field. */
            isd = idrstmpl[16];
            minsd = ifld[isd];
            for (j = isd; j < ndpts; j++)
                if (ifld[j] < minsd)
                    minsd = ifld[j];
            for (j = isd; j < ndpts; j++)
                ifld[j] = ifld[j] - minsd;
 
            /* Find num of bits need to store minsd and add 1 extra bit to indicate sign. */
            temp = log((double)(abs(minsd) + 1)) / alog2;
            nbitsd = (g2int)ceil(temp) + 1;
 
            /* Find num of bits need to store ifld[0] (and ifld[1] if
             * using 2nd order differencing). */
            maxorig = ival1;
            if (idrstmpl[16] == 2 && ival2 > ival1)
                maxorig = ival2;
            temp = log((double)(maxorig + 1)) / alog2;
            nbitorig = (g2int)ceil(temp) + 1;
            if (nbitorig > nbitsd)
                nbitsd = nbitorig;
 
            /* Increase number of bits to even multiple of 8 (octet). */
            if ((nbitsd % 8) != 0)
                nbitsd = nbitsd + (8 - (nbitsd % 8));
 
            /* Store extra spatial differencing info into the packed
             * data section. */
            if (nbitsd != 0)
            {
                /* pack first original value */
                if (ival1 >= 0)
                {
                    sbit(cpack, &ival1, iofst, nbitsd);
                    iofst = iofst + nbitsd;
                }
                else
                {
                    sbit(cpack, &one, iofst, 1);
                    iofst = iofst + 1;
                    itemp = abs(ival1);
                    sbit(cpack, &itemp, iofst, nbitsd - 1);
                    iofst = iofst + nbitsd - 1;
                }
                if (idrstmpl[16] == 2)
                {
                    /*  pack second original value */
                    if (ival2 >= 0)
                    {
                        sbit(cpack, &ival2, iofst, nbitsd);
                        iofst = iofst + nbitsd;
                    }
                    else
                    {
                        sbit(cpack, &one, iofst, 1);
                        iofst = iofst + 1;
                        itemp = abs(ival2);
                        sbit(cpack, &itemp, iofst, nbitsd - 1);
                        iofst = iofst + nbitsd - 1;
                    }
                }
 
                /*  pack overall min of spatial differences */
                if (minsd >= 0)
                {
                    sbit(cpack, &minsd, iofst, nbitsd);
                    iofst = iofst + nbitsd;
                }
                else
                {
                    sbit(cpack, &one, iofst, 1);
                    iofst = iofst + 1;
                    itemp = abs(minsd);
                    sbit(cpack, &itemp, iofst, nbitsd - 1);
                    iofst = iofst + nbitsd - 1;
                }
            }
        } /*  end of spatial diff section */
 
        /* Use Dr. Glahn's algorithm for determining grouping. */
        kfildo = 6;
        minpk = 10;
        inc = 1;
        maxgrps = (ndpts / minpk) + 1;
        jmin = calloc(maxgrps, sizeof(g2int));
        jmax = calloc(maxgrps, sizeof(g2int));
        lbit = calloc(maxgrps, sizeof(g2int));
        missopt = 0;
        pack_gp(&kfildo, ifld, &ndpts, &missopt, &minpk, &inc, &miss1, &miss2,
                jmin, jmax, lbit, glen, &maxgrps, &ngroups, &ibit, &jbit,
                &kbit, &novref, &lbitref, &ier);
        for (ng = 0; ng < ngroups; ng++)
            glen[ng] = glen[ng] + novref;
        free(jmin);
        free(jmax);
        free(lbit);
 
        /* For each group, find the group's reference value and the
         * number of bits needed to hold the remaining values. */
        n = 0;
        for (ng = 0; ng < ngroups; ng++)
        {
            /* find max and min values of group */
            gref[ng] = ifld[n];
            imax = ifld[n];
            j = n + 1;
            for (lg = 1; lg < glen[ng]; lg++)
            {
                if (ifld[j] < gref[ng])
                    gref[ng] = ifld[j];
                if (ifld[j] > imax)
                    imax = ifld[j];
                j++;
            }
 
            /* calc num of bits needed to hold data */
            if (gref[ng] != imax)
            {
                temp = log((double)(imax - gref[ng] + 1)) / alog2;
                gwidth[ng] = (g2int)ceil(temp);
            }
            else
                gwidth[ng] = 0;
            /* Subtract min from data */
            j = n;
            for (lg = 0; lg < glen[ng]; lg++)
            {
                ifld[j] = ifld[j] - gref[ng];
                j++;
            }
            /* increment fld array counter */
            n = n + glen[ng];
        }
 
        /* Find max of the group references and calc num of bits
         * needed to pack each groups reference value, then pack up
         * group reference values. */
        igmax = gref[0];
        for (j = 1; j < ngroups; j++)
            if (gref[j] > igmax)
                igmax = gref[j];
        if (igmax != 0)
        {
            temp = log((double)(igmax + 1)) / alog2;
            nbitsgref = (g2int)ceil(temp);
            sbits(cpack, gref, iofst, nbitsgref, 0, ngroups);
            itemp = nbitsgref * ngroups;
            iofst = iofst + itemp;
            /* Pad last octet with Zeros, if necessary. */
            if ((itemp % 8) != 0)
            {
                left = 8 - (itemp % 8);
                sbit(cpack, &zero, iofst, left);
                iofst = iofst + left;
            }
        }
        else
            nbitsgref = 0;
 
        /* Find max/min of the group widths and calc num of bits
         * needed to pack each groups width value, then pack up group
         * width values. */
        iwmax = gwidth[0];
        ngwidthref = gwidth[0];
        for (j = 1; j < ngroups; j++)
        {
            if (gwidth[j] > iwmax)
                iwmax = gwidth[j];
            if (gwidth[j] < ngwidthref)
                ngwidthref = gwidth[j];
        }
        if (iwmax != ngwidthref)
        {
            temp = log((double)(iwmax - ngwidthref + 1)) / alog2;
            nbitsgwidth = (g2int)ceil(temp);
            for (i = 0; i < ngroups; i++)
                gwidth[i] = gwidth[i] - ngwidthref;
            sbits(cpack, gwidth, iofst, nbitsgwidth, 0, ngroups);
            itemp = nbitsgwidth * ngroups;
            iofst = iofst + itemp;
            /* Pad last octet with Zeros, if necessary. */
            if ((itemp % 8) != 0)
            {
                left = 8 - (itemp % 8);
                sbit(cpack, &zero, iofst, left);
                iofst = iofst + left;
            }
        }
        else
        {
            nbitsgwidth = 0;
            for (i = 0; i < ngroups; i++)
                gwidth[i] = 0;
        }
 
        /* Find max/min of the group lengths and calc num of bits
         * needed to pack each groups length value, then pack up group
         * length values. */
        ilmax = glen[0];
        nglenref = glen[0];
        for (j = 1; j < ngroups - 1; j++)
        {
            if (glen[j] > ilmax)
                ilmax = glen[j];
            if (glen[j] < nglenref)
                nglenref = glen[j];
        }
        nglenlast = glen[ngroups - 1];
        if (ilmax != nglenref)
        {
            temp = log((double)(ilmax - nglenref + 1)) / alog2;
            nbitsglen = (g2int)ceil(temp);
            for (i = 0; i < ngroups - 1; i++)
                glen[i] = glen[i] - nglenref;
            sbits(cpack, glen, iofst, nbitsglen, 0, ngroups);
            itemp = nbitsglen * ngroups;
            iofst = iofst + itemp;
            /*         Pad last octet with Zeros, if necessary, */
            if ((itemp % 8) != 0)
            {
                left = 8 - (itemp % 8);
                sbit(cpack, &zero, iofst, left);
                iofst = iofst + left;
            }
        }
        else
        {
            nbitsglen = 0;
            for (i = 0; i < ngroups; i++)
                glen[i] = 0;
        }
 
        /* For each group, pack data values. */
        n = 0;
        for (ng = 0; ng < ngroups; ng++)
        {
            glength = glen[ng] + nglenref;
            if (ng == (ngroups - 1))
                glength = nglenlast;
            grpwidth = gwidth[ng] + ngwidthref;
            if (grpwidth != 0)
            {
                sbits(cpack, ifld + n, iofst, grpwidth, 0, glength);
                iofst = iofst + (grpwidth * glength);
            }
            n = n + glength;
        }
        /* Pad last octet with Zeros, if necessary. */
        if ((iofst % 8) != 0)
        {
            left = 8 - (iofst % 8);
            sbit(cpack, &zero, iofst, left);
            iofst = iofst + left;
        }
        *lcpack = iofst / 8;
 
        if (ifld)
            free(ifld);
        if (gref)
            free(gref);
        if (gwidth)
            free(gwidth);
        if (glen)
            free(glen);
    }
    else
    { /*   Constant field (max = min) */
        *lcpack = 0;
        nbitsgref = 0;
        ngroups = 0;
    }
 
    /* Fill in ref value and number of bits in Template 5.2. */
 
    /* Ensure reference value is IEEE format. */
    mkieee(&rmin, idrstmpl, 1);
    idrstmpl[3] = nbitsgref;
    idrstmpl[4] = 0;            /* original data were reals */
    idrstmpl[5] = 1;            /* general group splitting */
    idrstmpl[6] = 0;            /* No internal missing values */
    idrstmpl[7] = 0;            /* Primary missing value */
    idrstmpl[8] = 0;            /* secondary missing value */
    idrstmpl[9] = ngroups;      /* Number of groups */
    idrstmpl[10] = ngwidthref;  /* reference for group widths */
    idrstmpl[11] = nbitsgwidth; /* num bits used for group widths */
    idrstmpl[12] = nglenref;    /* Reference for group lengths */
    idrstmpl[13] = 1;           /* length increment for group lengths */
    idrstmpl[14] = nglenlast;   /* True length of last group */
    idrstmpl[15] = nbitsglen;   /* num bits used for group lengths */
    if (idrsnum == 3)
    {
        idrstmpl[17] = nbitsd / 8; /* num bits used for extra spatial */
        /* differencing values */
    }
}