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decompressing.cpp
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decompressing.cpp
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#include <iostream>
#include <vector>
#include <string>
#include <queue>
#include <map>
#include <fstream>
#include <stdexcept>
using namespace std;
const int AND8 = 255;
const int INT_SZ_IN_CHAR = 4;
const int SZ_CHAR = 8 * sizeof(char);
class HuffmanTreeNode
{
public:
bool isEOF, isChar;
char character;
int frequency;
HuffmanTreeNode *leftChild = nullptr;
HuffmanTreeNode *rightChild = nullptr;
HuffmanTreeNode(char inputChar, bool isEOF, int frequency)
{
this->character = inputChar;
this->isEOF = isEOF;
this->isChar = !isEOF;
this->frequency = frequency;
}
HuffmanTreeNode(int frequency)
{
this->frequency = frequency;
this->isChar = false;
this->isEOF = false;
}
void makeLeftChild(HuffmanTreeNode *child)
{
this->leftChild = child;
}
void makeRightChild(HuffmanTreeNode *child)
{
this->rightChild = child;
}
void generateCharacterCodes(string &characterCode, map<char, string> &characterCodeMap, string &eofCode)
{
if (isChar)
{
characterCodeMap[character] = characterCode;
return;
}
if (isEOF)
{
eofCode = characterCode;
return;
}
if (leftChild != nullptr)
{
characterCode.push_back('0');
(*this->leftChild).generateCharacterCodes(characterCode, characterCodeMap, eofCode);
characterCode.pop_back();
}
if (rightChild != nullptr)
{
characterCode.push_back('1');
(*this->rightChild).generateCharacterCodes(characterCode, characterCodeMap, eofCode);
characterCode.pop_back();
}
}
};
class HuffmanNodePointer
{
public:
HuffmanTreeNode *nodePointer;
HuffmanNodePointer(HuffmanTreeNode *nodePointer)
{
this->nodePointer = nodePointer;
}
};
bool operator>(const HuffmanNodePointer &node1, const HuffmanNodePointer &node2)
{
return node1.nodePointer->frequency > node2.nodePointer->frequency;
}
HuffmanTreeNode *buildHuffmanTree(map<char, int> &frequencyMap)
{
priority_queue<HuffmanNodePointer, vector<HuffmanNodePointer>, greater<HuffmanNodePointer>> pq;
for (auto it : frequencyMap)
{
HuffmanTreeNode *newNode = new HuffmanTreeNode(it.first, false, it.second);
HuffmanNodePointer newPointer = HuffmanNodePointer(newNode);
pq.push(newPointer);
}
HuffmanTreeNode *newNode = new HuffmanTreeNode('~', true, 1);
HuffmanNodePointer newPointer = HuffmanNodePointer(newNode);
pq.push(newPointer);
while (pq.size() > 1)
{
HuffmanNodePointer node1 = pq.top();
pq.pop();
HuffmanNodePointer node2 = pq.top();
pq.pop();
HuffmanTreeNode *newNode = new HuffmanTreeNode(node1.nodePointer->frequency + node2.nodePointer->frequency);
(*newNode).makeLeftChild(node1.nodePointer);
(*newNode).makeRightChild(node2.nodePointer);
HuffmanNodePointer newPointer = HuffmanNodePointer(newNode);
pq.push(newPointer);
}
return pq.top().nodePointer;
}
int makeInt(char chArr[])
{
int result = 0;
for (int i = 0; i < INT_SZ_IN_CHAR; i++)
{
result |= ((chArr[i] & AND8) << ((INT_SZ_IN_CHAR - i - 1) * SZ_CHAR));
}
return result;
}
void createFrequencyMap(map<char, int> &frequencyMap, fstream &HeaderFile)
{
char ch;
char chArr[INT_SZ_IN_CHAR];
while (HeaderFile >> noskipws >> ch)
{
for (int i = 0; i < INT_SZ_IN_CHAR; i++)
{
try
{
HeaderFile >> chArr[i];
}
catch (...)
{
cerr << "Error reading header file\n";
exit(1);
}
}
frequencyMap[ch] = makeInt(chArr);
}
}
void getBinaryString(vector<int> &binaryString, fstream &BodyFile)
{
char ch;
while (BodyFile >> noskipws >> ch)
{
for (int i = 7; i >= 0; i--)
{
binaryString.push_back((ch >> i) & 1);
}
}
return;
}
void generateSourceFile(vector<int> &binaryString, fstream &DestinationFile, HuffmanTreeNode *root)
{
HuffmanTreeNode *ptr = root;
char ch;
if (root->isEOF)
{
return;
}
for (auto it : binaryString)
{
if (it == 1)
{
ptr = ptr->rightChild;
}
else
{
ptr = ptr->leftChild;
}
if (ptr->isEOF)
{
break;
}
if (ptr->isChar)
{
DestinationFile << ptr->character;
ptr = root;
}
}
}
int main()
{
fstream DestinationFile, HeaderFile, BodyFile;
try
{
DestinationFile.open("destination.txt", ios::trunc | ios::out | ios::binary);
HeaderFile.open("header.huffh", ios::in | ios::binary);
BodyFile.open("body.huffb", ios::in | ios::binary);
}
catch (...)
{
cerr << "Error opening files" << endl;
exit(1);
}
map<char, int> frequencyMap;
vector<int> bodyFileBinaryString;
try
{
createFrequencyMap(frequencyMap, HeaderFile);
}
catch (...)
{
cerr << "Error reading Header file: file may be corrupted\n";
exit(1);
}
getBinaryString(bodyFileBinaryString, BodyFile);
HuffmanTreeNode *root = buildHuffmanTree(frequencyMap);
generateSourceFile(bodyFileBinaryString, DestinationFile, root);
DestinationFile.close();
HeaderFile.close();
BodyFile.close();
return 0;
}