void compress(ibstream& infile, obstream& outfile) {
    Map<ext_char, int> frequencies = getFrequencyTable(infile);
    Node* tree = buildEncodingTree(frequencies);
    writeFileHeader(outfile, frequencies);
    infile.rewind();
    encodeFile(infile, tree, outfile);
    freeTree(tree);
}

/* Function: decompress
 * Usage: decompress(infile, outfile);
 * --------------------------------------------------------
 * Main entry point for the Huffman decompressor.
 * Decompresses the file whose contents are specified by the
 * input ibstream, then writes the decompressed version of
 * the file to the stream specified by outfile.  Your final
 * task in this assignment will be to combine all of the
 * previous functions together to implement this function,
 * which should not require much logic of its own and should
 * primarily be glue code.
 */
void decompress(ibstream& infile, ostream& outfile) {
    Map<ext_char, int> frequenceTable = readFileHeader(infile);
    Node* tree = buildEncodingTree(frequenceTable);
    decodeFile(infile, tree, outfile);
    freeTree(tree);
}