chrisg220 / huffmancompression Goto Github PK

This program compresses files by reducing the necessary number of bits per character by using a Huffman coding scheme that is generated from a Huffman Tree structure. Using a priority queue our program constructs a tree that always has nodes with the lowest frequencies farthest down the tree, and nodes with high frequencies up near the root of the tree. Left subtree paths have a “0” value, and right subtrees have a “1” value. The unique structure that is created is exactly what is needed to make path codes, which exhibit the prefix property. Our program is able to output our tree, in standard order, to a given code file. It is also able to take encoded files and decode them back into their original 8-bit character format using the code file.

post: constructs the initial Huffman structure with the given frequency counts of ASCII characters. An extra node is added to account for our special pseudo-eof character

public HuffmanBinaryTree(int[] count)

pre : Scanner contains a tree stored in standard format post: constructs a Huffman structure from the given code file. Uses each binary value in the Huffman code to reconstruct a pathway from the top of the tree to each character node. A binary value of 0 means we shall progress left down the tree, and a value of 1 means we progress downward to the right. A dummy(empty) root will be instantiated.

public HuffmanBinaryTree(Scanner input)

post: writes the tree to the given output file in standard format which consists of line pairs that describe the ASCII value code for each character in the structure. Codes will appear in traversal order.

public void write(PrintStream output)

post: returns the current sum of letter counts in the LetterInventory instance

public void write(PrintStream output)

pre : input stream contains a legal encoding of characters for this tree’s Huffman code post: reads individual bits from the input stream and writes corresponding characters to the given output file. This method stops reading if it encounters our pseudo-eof character.

public void decode(BitInputStream input, PrintStream output, int eof)