Decode.cpp

/****************************************************************************************************************************************************************
  Author:
  Vishal Dhiman

  Description:
  This program decodes huffman encoded file



****************************************************************************************************************************************************************/
#include<iostream>
#include<fstream>
#include<vector>
#include<time.h>
#include<stdlib.h>
using namespace std;
struct Node                                                                                     //Structure of a Node of a Huffman tree for decoding
{
    unsigned char character;
    Node* left;
    Node* right;
    Node(char c,Node* l=NULL,Node* r=NULL)
    {
        character=c;
        left=l;
        right=r;
    }

};
Node* Make_Huffman_tree(ifstream &input)                                                        //Make Tree using the compressed file
{
    char ch;
    input.get(ch);
    if(ch=='1')
    {
        input.get(ch);
        return (new Node(ch));
    }
    else
    {
        Node* left=Make_Huffman_tree(input);
        Node* right=Make_Huffman_tree(input);
        return(new Node(-1,left,right));
    }
}
void decode(ifstream &input,string filename,Node* Root,long long int Total_Freq)              //Decode each binary symbol according to the tree
{
    ofstream output((filename.erase(filename.size()-4)).c_str(),ios::binary);
    if(!output.good())
    {
        perror("Error:\t");
        exit(-1);
    }
    bool eof_flag=false;
    char bits_8;
    Node* pointer=Root;
    while(input.get(bits_8))
    {
        int counter=7;
        while(counter>=0)
        {
            if(!pointer->left&&!pointer->right)
            {
                output<<pointer->character;
                Total_Freq--;
                if(!Total_Freq)
                {
                    eof_flag=true;
                    break;
                }
                pointer=Root;
                continue;
            }
            if((bits_8&(1<<counter)))
            {
                pointer=pointer->right;
                counter--;
            }
            else
            {
                pointer=pointer->left;
                counter--;
            }
        }
        if(eof_flag)
            break;
    }
    output.close();
}
int main()
{
    string filename;
    //cout<<"Enter the Filename:\t";
     filename="";
    //cin>>filename;
    ifstream input_file(filename.c_str(),ios::binary);                                           //Open File
    if(!input_file.good())                                                                       //Check if stream is open
    {
        perror("Error:\t");
        exit(-1);
    }
    if(filename.find(".huf")==string::npos)                                                     //Check if file has .huf extension
    {
        cout<<"Error: File is already decompressed\n\n";
        exit(-1);
    }
    cout<<"\nDecompressing the file....";
    clock_t start_time=clock();
    long long int Total_freq=0;
    char ch;
    while(input_file.get(ch))                                                                  //read Original total frequency from file
    {
        if(ch==',')
            break;
        Total_freq*=10;
        Total_freq+=ch-'0';
    }
    Node* Huffman_tree=Make_Huffman_tree(input_file);                                         //Remake Huffman tree from file
    input_file.get(ch);                                                                       //Read Extra space between compressed data and tree from file
    decode(input_file,filename,Huffman_tree,Total_freq);
    input_file.close();
    clock_t stop_time=clock();
    if(remove(filename.c_str())!=0)                                                           //Delete compressed file
        perror("Error deleting the compressed file:\t");
    cout<<"\n\n****File Decompressed Successfully! :-)****\n\n";
    cout<<"Time taken to Compress:\t"<<double(stop_time-start_time)/CLOCKS_PER_SEC<<" seconds\n\n"; //Display timer after Decoding
}