Endian.h

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#ifndef ENDIAN_H
#define ENDIAN_H

#include <iostream>

//Is this architecture little endian?
inline
bool IsLittleEndian(){
    long l=1;
    return ((*(char*)&l));
}

//Is this architecture big endian?
inline
bool IsBigEndian(){
    return !IsLittleEndian();
}

//Old, incorrect implementation. 
/*inline
void ByteSwap(char* b, int n){
    int i=0;
    int j=n-1;
    while(i,j){
        std::swap(b[i],b[j]);
            i++; j--;
    }
}*/

inline
void ByteSwap(char* b, int n){
    for (int i = 0; i <  n/2; i++) {
        std::swap(b[i], b[n-1-i]);
    }
}

inline
void ReadFromBigEndian(char* ptr, int nelem, int bytesPerElem, std::istream &is){
        is.read(ptr, nelem*bytesPerElem);
        if(IsLittleEndian()){
            //Swap byte order
            for(int i= 0; i<nelem*bytesPerElem; i+=bytesPerElem){
                ByteSwap(&ptr[i],bytesPerElem); 
            }
        }
}

inline
void WriteToBigEndian(char* ptr, int nelem, int bytesPerElem, std::ostream &os){
    if(IsBigEndian()){
        os.write(ptr, nelem*bytesPerElem);
    }
    else{
        //Swap byte order
        for(int i= 0; i<nelem*bytesPerElem; i+=bytesPerElem){
            ByteSwap(&ptr[i],bytesPerElem); 
        }

        os.write(ptr, nelem*bytesPerElem);

        //Restore byte order
        for(int i= 0; i<nelem*bytesPerElem; i+=bytesPerElem){
            ByteSwap(&ptr[i],bytesPerElem); 
        }
    }
}

inline
void ReadFromLittleEndian(char* ptr, int nelem, int bytesPerElem, std::istream &is){
        is.read(ptr, nelem*bytesPerElem);
        if(IsBigEndian()){
            //Swap byte order
            for(int i= 0; i<nelem*bytesPerElem; i+=bytesPerElem){
                ByteSwap(&ptr[i],bytesPerElem); 
            }
        }
}

inline
void WriteToLittleEndian(char* ptr, int nelem, int bytesPerElem, std::ostream &os){
    if(IsLittleEndian()){
        os.write(ptr, nelem*bytesPerElem);
    }
    else{
        //Swap byte order
        for(int i= 0; i<nelem*bytesPerElem; i+=bytesPerElem){
            ByteSwap(&ptr[i],bytesPerElem); 
        }

        os.write(ptr, nelem*bytesPerElem);

        //Restore byte order
        for(int i= 0; i<nelem*bytesPerElem; i+=bytesPerElem){
            ByteSwap(&ptr[i],bytesPerElem); 
        }
    }
}



#endif