source: trunk/WRF.COMMON/WRFV3/external/io_grib1/WGRIB/bds.h

/* 
 * version 1.2.1 of grib headers  w. ebisuzaki 
 *         1.2.2 added access to spectral reference value l. kornblueh
 */

#ifndef INT2
#define INT2(a,b)   ((1-(int) ((unsigned) (a & 0x80) >> 6)) * (int) (((a & 0x7f) << 8) + b))
#endif

#define BDS_LEN(bds)            ((int) ((bds[0]<<16)+(bds[1]<<8)+bds[2]))
#define BDS_Flag(bds)           (bds[3])

#define BDS_Grid(bds)           ((bds[3] & 128) == 0)
#define BDS_Harmonic(bds)       (bds[3] & 128)

#define BDS_Packing(bds)        ((bds[3] & 64) != 0)
#define BDS_SimplePacking(bds)  ((bds[3] & 64) == 0)
#define BDS_ComplexPacking(bds) ((bds[3] & 64) != 0)

#define BDS_OriginalType(bds)   ((bds[3] & 32) != 0)
#define BDS_OriginalFloat(bds)  ((bds[3] & 32) == 0)
#define BDS_OriginalInt(bds)    ((bds[3] & 32) != 0)

#define BDS_MoreFlags(bds)      ((bds[3] & 16) != 0)
#define BDS_UnusedBits(bds)     ((int) (bds[3] & 15))

#define BDS_BinScale(bds)       INT2(bds[4],bds[5])

#define BDS_RefValue(bds)       (ibm2flt(bds+6))
#define BDS_NumBits(bds)        ((int) bds[10])

#define BDS_Harmonic_RefValue(bds) (ibm2flt(bds+11))

#define BDS_DataStart(bds)      ((int) (11 + BDS_MoreFlags(bds)*3))

/* breaks if BDS_NumBits(bds) == 0 */
#define BDS_NValues(bds)        (((BDS_LEN(bds) - BDS_DataStart(bds))*8 - \
                                BDS_UnusedBits(bds)) / BDS_NumBits(bds))

/*
#define BDS_NValues(bds)        ((BDS_NumBits(bds) == 0) ? 0 : \
                                (((BDS_LEN(bds) - BDS_DataStart(bds))*8 - \
                                BDS_UnusedBits(bds)) / BDS_NumBits(bds)))
*/


/* undefined value -- if bitmap */
#define UNDEFINED               9.999e20