Huffman.cpp

#include <string>
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
#include "Huffman.h"

//--- Definition of buildDecodingTree()

void Huffman::buildDecodingTree(ifstream & codeIn)
{
	char ch; // a character
	string code; // its code
	for (;;)
	{
		codeIn >> ch >> code;
		if (codeIn.eof()) return;
		insert(ch, code);
	}
}
//--- Definition of insert()
void Huffman::insert(char ch, string code)
{
	Huffman::BinNodePointer p = myRoot; // pointer to move down the tree
	for (int i = 0; i < code.length(); i++)
	{
		switch (code[i])
		{
		case '0': // descend left
			if (p->left == 0) // create node along path
				p->left = new Huffman::BinNode('*');
			p = p->left;
			break;
		case '1': // descend right
			if (p->right == 0) // create node along path
				p->right = new Huffman::BinNode('*');
			p = p->right;
			break;
		default:
			cerr << "*** Illegal character in code ***\n";
			exit(1);
		}
	}
	p->data = ch;
}
//--- Definition of decode()
void Huffman::decode(ifstream & messageIn)
{
	char bit; // next message bit
	Huffman::BinNodePointer p; // pointer to trace path in decoding tree
	for (;;)
	{
		p = myRoot;
		while (p->left != 0 || p->right != 0)
		{
			messageIn >> bit;
			if (messageIn.eof()) return;
			cout << bit;
			if (bit == '0')
				p = p->left;
			else if (bit == '1')
				p = p->right;
			else
				cerr << "Illegal bit: " << bit << " -- ignored\n";
		}
		cout << "--" << p->data << endl;
	}
}
//--- Definition of printTree()
void Huffman::printTree(ostream & out, Huffman::BinNodePointer root,
	int indent)
{
	if (root != 0)
	{
		printTree(out, root->right, indent + 8);
		out << setw(indent) << " " << root->data << endl;
		printTree(out, root->left, indent + 8);
	}
}