File: grib_bits_fast_big_endian.c

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/*
 * Copyright 2005-2018 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 *
 * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
 * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
 */

/***************************************************************************
 *   Enrico Fucile  - 19.06.2007                                           *
 *                                                                         *
 ***************************************************************************/


typedef struct bits_all_one_t {
    int inited;
    int size;
    long v[128];
} bits_all_one_t;

static bits_all_one_t bits_all_one={0,0,{0,}};

static void init_bits_all_one()
{
    int size=sizeof(long)*8;
    long* v=0;
    unsigned long cmask=-1;
    bits_all_one.size=size;
    bits_all_one.inited=1;
    v=bits_all_one.v+size;
    *v= cmask << size;
    while (size>0)  *(--v)= ~(cmask << --size);
}

int grib_is_all_bits_one(long val, long nbits)
{
    if (!bits_all_one.inited) init_bits_all_one();
    return bits_all_one.v[nbits]==val;
}

int grib_encode_string(unsigned char *bitStream, long *bitOffset, size_t numberOfCharacters, const char *string)
{
    size_t i;
    int err=0;
    long byteOffset = *bitOffset / 8;
    int remainder = *bitOffset % 8;
    unsigned char* p;
    int remainderComplement=8-remainder;
    const char *s=string;

    Assert(numberOfCharacters<512 && (numberOfCharacters == 0 || string));

    /* if (remainder) byteOffset++; */

    if (numberOfCharacters > 0) {
        unsigned char *restrict p = bitStream+byteOffset;
        if ( remainder == 0 )  {
            memcpy(p, string, numberOfCharacters);
        } else {
            unsigned char mask = (unsigned char)(0xFF00 >> remainder);
            unsigned char accum = p[0];
            for (size_t i=0; i < numberOfCharacters; ++i) {
                accum |= (s[i] >>remainder) & ~mask;
                p[i] = accum;
                accum = (s[i] << remainderComplement) & mask;
            }
            p[numberOfCharacters] = accum;
        }
    }
    *bitOffset+=numberOfCharacters*8;
    return err;
}

char* grib_decode_string(const unsigned char* bitStream, long *bitOffset, size_t numberOfCharacters,char* string)
{
    size_t i;
    long byteOffset = *bitOffset / 8;
    int remainder = *bitOffset % 8;
    unsigned char c;
    unsigned char* p;
    char* s=string;
    unsigned char mask[] ={ 0, 0x80, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC, 0xFE };
    int remainderComplement=8-remainder;

    if (numberOfCharacters==0) return string;

    p=(unsigned char*)bitStream+byteOffset;

    if ( remainder == 0 )  {
        memcpy(string,bitStream+byteOffset,numberOfCharacters);
        *bitOffset+=numberOfCharacters*8;
        return string;
    }

    for (i=0;i<numberOfCharacters;i++) {
        c=(*p)<<remainder;
        p++;
        *s = ( c | ( (*p) & mask[remainder] )>>remainderComplement );
        s++;
    }
    *bitOffset+=numberOfCharacters*8;
    return string;
}


unsigned long grib_decode_unsigned_long(const unsigned char* p, long *bitp, long nbits)
{
    long countOfLeftmostBits=0,leftmostBits=0;
    long startBit= *bitp ;
    long remainingBits = nbits;
    long *pp=(long*)p;
    unsigned long val=0;

    if (startBit >= max_nbits) {
        pp += startBit/max_nbits;
        startBit %= max_nbits;
    }

    countOfLeftmostBits = startBit + remainingBits;
    if (countOfLeftmostBits > max_nbits) {
        countOfLeftmostBits = max_nbits - startBit;
        remainingBits -= countOfLeftmostBits;
        leftmostBits=(VALUE(*pp,startBit,countOfLeftmostBits)) << remainingBits;
        startBit = 0;
        pp++;
    } else
        leftmostBits = 0;

    val=leftmostBits+(VALUE(*pp,startBit,remainingBits));

    *bitp += nbits;

    return val;
}

int grib_encode_unsigned_long(unsigned char* p, unsigned long val ,long *bitp, long nbits)
{
    long* destination = (long*)p;
    long countOfLeftmostBits=0,nextWord=0,startBit=0,remainingBits=0,rightmostBits=0;

    startBit = *bitp;
    remainingBits = nbits;

    if (startBit >= max_nbits) {
        nextWord = startBit / max_nbits;
        startBit %= max_nbits;
    } else
        nextWord = 0;

    countOfLeftmostBits = startBit + remainingBits;
    if (countOfLeftmostBits > max_nbits) {
        countOfLeftmostBits = max_nbits - startBit;
        startBit = max_nbits - remainingBits;
        remainingBits -= countOfLeftmostBits;
	if (countOfLeftmostBits < max_nbits)
	  {
	    destination[nextWord] =
	      ((destination[nextWord] >> countOfLeftmostBits) << countOfLeftmostBits)
	      + (VALUE(val,startBit,countOfLeftmostBits));
	  }
	else
	  {
	    destination[nextWord] = (VALUE(val,startBit,countOfLeftmostBits));
	  }
        startBit = 0;
        nextWord++;
    }

    rightmostBits = VALUE(val,max_nbits-remainingBits,remainingBits);
    destination[nextWord] =
            (destination[nextWord] & ~MASKVALUE(startBit,remainingBits))
            + (rightmostBits << max_nbits-(remainingBits+startBit));

    *bitp+=nbits;
    return GRIB_SUCCESS;
}

int grib_encode_unsigned_longb(unsigned char* p, unsigned long val ,long *bitp, long nbits)
{
    return grib_encode_unsigned_long(p,val ,bitp, nbits);
}

#if VECTOR
 #include "grib_bits_fast_big_endian_vector.c"
#elif OMP
 #include "grib_bits_fast_big_endian_omp.c"
#else
 #include "grib_bits_fast_big_endian_simple.c"
#endif