PIEC.c

/*
Platform Independent Endian Converter

Copyright (c) 2010 Oliver Daids
3-clause BSD

Note: This was not designed for speed, nor cleanliness, it was just a quick experiment to see if I could get a platform independent endian converter.
*/

#include <stdint.h>

static uint64_t UInt64TwoToThe(uint64_t exponent){
	uint64_t x=1;
	for(uint64_t i=0;i<exponent;i++) x*=2;
	return x;
}

uint64_t UInt64From8Bytes(uint8_t* bytes, int bigendian){
	uint64_t integer=0;
	for(int i=0;i<8;i++){
		int byteID=i;
		if(bigendian) byteID=8-i-1;
		integer+=(uint64_t)bytes[byteID]*UInt64TwoToThe(8*i);
	}
	return integer;
}

void UInt64To8Bytes(uint64_t integer, uint8_t* bytes, int bigendian){
	for(int i=0;i<8;i++) bytes[i]=0;

	uint64_t quotient=integer;
	for(int i=0;i<8;i++){
		int byteID=i;
		if(bigendian) byteID=8-i-1;
		if(quotient==0) break;
		bytes[byteID]=quotient%256;
		quotient/=256;
	}
}