swab.cpp

#include <stdlib.h>

#include <iostream>
#include <fstream>

int main(int argc, char* argv[]) {
    
    if(argc < 4 || argc > 5){
        std::cout << "swab: Mirrors <word-size> bytes, in the case of 2, it swaps adjacent bytes" << std::endl;
        std::cout << "Usage: swab  <word-size>  <infile> <outfile>  <block size in MByte (opt.)>" << std::endl;
        exit(0);
    }
    
    char *temp1,*temp2;
    unsigned long n_bytes;
    unsigned long block_size,i,k,n_data,j;
    std::ofstream out_data;
    
    n_bytes = atoi(argv[1]);
    std::ifstream in_data(argv[2],std::ios::in|std::ios::binary);
    if(in_data == NULL){
        std::cerr << "swab: ERROR: can't open file " << argv[2] << std::endl;
        exit(1);
    }
    in_data.seekg(0,std::ios::end);
    if(argc == 5) block_size = (unsigned)atol(argv[4])*1000000;
    else block_size = in_data.tellg();
    block_size-= block_size%n_bytes;
    n_data=in_data.tellg();
    if(block_size > n_data){
//      std::cerr << "swab: block size exceeding file size !" << std::endl
//           << "setting block size to file size (=" << n_data/1000000. << "MB)" << std::endl;
        block_size = n_data;
    }
    in_data.seekg(0,std::ios::beg);
    
    if((float)n_data/(float)n_bytes-n_data/n_bytes){
        std::cerr << "swab: ERROR: swab: size of \n" << argv[2] << 
                "not a multiple of no. of swap bytes (" << n_bytes << ")" << std::endl;
        exit(1);
    }
    
    temp1=new char[block_size];
    temp2=new char[block_size];
    
    for(k=0;k<n_data/block_size;k++){
        if(k == 0){
            out_data.open(argv[3],std::ios::out|std::ios::binary);
            if(out_data == NULL){
                std::cerr << "swab: ERROR: can't open file " << argv[3] << std::endl;
                exit(1);
            }
        }else{
            out_data.open(argv[3],std::ios::out|std::ios::binary|std::ios::app);
            if(out_data == NULL){
                std::cerr << "swab: ERROR: can't open file " << argv[3] << std::endl;
                exit(1);
            }
        }
        std::cout << "swab: reading block "<< k+1 << " of " <<n_data/block_size
             << " blocks" << std::endl;
        in_data.read(temp1,block_size);
        std::cout << "swab: swabbing block "<< k+1 <<" ..." << std::endl;
        for(i=0;i<block_size/n_bytes;i++)
            for(j=0;j<n_bytes;j++)temp2[i*n_bytes+j]=temp1[(i+1)*n_bytes-1-j];
        out_data.write(temp2,block_size);
        out_data.close();
        std::cout << "swab: block "<< k+1 << " written to file " << argv[3] << std::endl;
    }
    
    temp1=new char[n_data%block_size];
    temp2=new char[n_data%block_size];
        std::cout << "swab: reading rest block of size " << n_data%block_size/1000 << " KByte" << std::endl;
    in_data.read(temp1,n_data%block_size);
        std::cout << "swab: swabbing rest block ... "<< std::endl;
    for(i=0;i<n_data%block_size/n_bytes;i++)
        for(j=0;j<n_bytes;j++)temp2[i*n_bytes+j]=temp1[(i+1)*n_bytes-1-j];
    out_data.open(argv[3],std::ios::out|std::ios::binary|std::ios::app);
    out_data.write(temp2,n_data%block_size);
    out_data.close();
    std::cout << "swab: rest block written to file " << argv[3] << std::endl;
    
    
    in_data.close();
    return 0;
}

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