/*
 * Copyright 2018, University Corporation for Atmospheric Research
 * See netcdf/COPYRIGHT file for copying and redistribution conditions.
 */


#include "config.h"
#include "netcdf_filter_build.h"

/*
Common utilities related to filters.
Taken from libdispatch/dfilters.c.
*/

#ifdef WORDS_BIGENDIAN
/* Byte swap an 8-byte integer in place */
static void
byteswap8(unsigned char* mem)
{
    unsigned char c;
    c = mem[0];
    mem[0] = mem[7];
    mem[7] = c;
    c = mem[1];
    mem[1] = mem[6];
    mem[6] = c;
    c = mem[2];
    mem[2] = mem[5];
    mem[5] = c;
    c = mem[3];
    mem[3] = mem[4];
    mem[4] = c;
}

/* Byte swap an 8-byte integer in place */
static void
byteswap4(unsigned char* mem)
{
    unsigned char c;
    c = mem[0];
    mem[0] = mem[3];
    mem[3] = c;
    c = mem[1];
    mem[1] = mem[2];
    mem[2] = c;
}
#endif /*WORDS_BIGENDIAN*/

void
NC_h5filterspec_fix8(void* mem0, int decode)
{
#ifdef WORDS_BIGENDIAN
    unsigned char* mem = mem0;
    if(decode) { /* Apply inverse of the encode case */
	byteswap4(mem); /* step 1: byte-swap each piece */
	byteswap4(mem+4);
	byteswap8(mem); /* step 2: convert to little endian format */
    } else { /* encode */
	byteswap8(mem); /* step 1: convert to little endian format */
	byteswap4(mem); /* step 2: byte-swap each piece */
	byteswap4(mem+4);
    }
#else /* Little endian */
    /* No action is necessary */
#endif
}