compress.cpp

/**
 * Christopher Yeh
 * cyeh@ucsd.edu
 * Main runner to compress a file with a huffman trie.
 * Compile and run with proper arguments.
 */
#include <algorithm>
#include "HCTree.hpp"

/**
 * Encodes a given file up to 1GB.
 * @param argc number of arguments
 * @param argv two arguments, file name to be compressed and output file name.
 * @return failure if wrong number of arguments. Success otherwise.
 */
int main(int argc, char** argv) {
    // Check for appropriate arguments. Does not account for invalid files.
    const int NUM_ARGS = 3;
    if (argc != NUM_ARGS) {
        cout << "Invalid number of arguments" << endl <<
             "Usage: ./compress <infile filename> <outfile filename>." << endl;
        return EXIT_FAILURE;
    }
    // Error "checking" done. Proceed with program.
    const string INFILE = argv[1];
    const string OUTFILE = argv[2];
    ifstream input;
    ofstream output;
    input.open(INFILE, ios_base::binary);
    output.open(OUTFILE, ios_base::trunc);
    unsigned char nextChar;
    int nextByte;
    // If file is empty, don't write anything.
    input.seekg(0, ios::end);
    if (input.tellg() == 0) {
        return EXIT_SUCCESS;
    }
    input.clear();
    input.seekg(0);
    // Initiate all vector to 0.
    vector<int> ascii_count(HCTree::TABLE_SIZE, 0);
    unsigned int numCharacters = 0;
    unsigned int numUniqueChars = 0;
    // Proceed to read bytes, and count number of characters.
    while ((nextByte = input.get()) != EOF) {
        ascii_count[nextByte]++;
        numCharacters++;
    }
    // Get our number of unique characters */
    for (int count : ascii_count) {
        if (count > 0) {
            numUniqueChars++;
        }
    }
    // Encode our tree.
    BitOutputStream bitOut = BitOutputStream(output);
    HCTree* ht = new HCTree();
    ht->build(ascii_count);
    // Write our header: count and pre-order traversal of tree.
    ht->writeHeader(bitOut, numCharacters, numUniqueChars);
//    cout << "Header size is: " << bitOut.getBytes() << " bytes" << endl;
    // Write our encoding.
    if (numUniqueChars > 1) {
        input.clear();
        input.seekg(0);
        while ((nextByte = input.get()) != EOF) {
            nextChar = (unsigned char) nextByte;
            ht->encode(nextChar, bitOut);
        }
    }
    // Padding for last.
    ht->pad(bitOut);
    delete ht;
    return EXIT_SUCCESS;
}