source: liacs/da/opdr2b/decompressie.cc@ 144

/* Author    : Rick van der Zwet
 * S-number  : 0433373
 * Version   : $Id: decompressie.cc 457 2008-01-08 22:24:08Z rick $
 * Copyright : FreeBSD Licence
 */
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <sysexits.h>
#include <string>
#include "trie.cc"
#include "fileio.h"
#include "constants.h"
using namespace std;



/* lookup table to quickly convert key into string */
struct keypair {
    int value;
    int next;
};
keypair * lookup[MAX_KNOB];

/* global trie */
Trie<int> * lwz;


/* find string of certain key, return empty if none found */
void
getstring (int * output, const int key) {
    int temp[MAX_KNOB + 1];
    for (int i = 0; i <= MAX_KNOB + 1; i++) {
        output[i] = -2;
        temp[i] = -2;
    }

    if (lookup[key] == NULL) {
        output[0] = ROOT;
        return;
    }

    int walker = key;
    int count = 0;
    while (walker != ROOT) {
        temp[count] = lookup[walker]->value;
        walker = lookup[walker]->next;
        count++;
    }

    /* reverse the whole string */
    count--;
    walker = 0;
    for (; count >= 0; count--) {
        output[walker] = temp[count];
        //fprintf(stderr, "Value %i\n", temp[count]);
        walker++;
    }
    /* put a custom end on the string */
    output[walker] = ROOT;
}


void decode (FILE * input, FILE *output)
{
    /* character storage */
    int numbers[2];
    /* string storage of word to find */
    int string[2][MAX_KNOB + 1];

    /* temp */
    int count = 0; /* temp variable, loop counter */
    int knob = START_KNOB;  /* knob to be added */
    int code = 0;   /* temp variable, loop counter */
    Trie<int> * lwz;

    /* initialiseer Trie voor ZLW codering */
    lwz = new Trie<int>;

    for (code = 0; code <= 0xFF; code++) {
        lwz->GoRoot();
        lwz->AddChild(code);
        lwz->GoChild(code);
        lwz->PutInfo(knob);
        /* Put data into lookup array */
        lookup[knob] = new keypair;
        lookup[knob]->value = code;
        lookup[knob]->next = ROOT;

        knob++;
    }

    /* initial input Letter */
    numbers[1] = fetchnumber(input);
    while (1) {
        numbers[0] = numbers[1];
        numbers[1] = fetchnumber(input);

        /* no need to write any other strings, cause
         * last knob exists for sure
         */
        if (numbers[1] == FILE_END) {
            getstring(string[0], numbers[0]);
            for (count = 0; string[0][count] != ROOT; count++)
                fprintf(output,"%c",string[0][count]);
            break;
        }

        /* find potential string */
        #ifdef DEBUG
            fprintf(stderr, "Find numbers %i and %i\n", numbers[0], numbers[1]);
        #endif
        getstring(string[0], numbers[0]);
        getstring(string[1], numbers[1]);
 
        /* string1 not exits, find special letter */
        if (string[1][0] == ROOT) {
            #ifdef DEBUG
                fprintf(stderr, "Special find '%i'\n", string[0][0]);
            #endif
            string[1][0] = string[0][0];
        }

        /* find parent */
        lwz->GoRoot();
        for (count = 0; string[0][count] != ROOT; count++) {
            lwz->GoChild(string[0][count]);
            #ifdef DEBUG
                fprintf(stderr, "Addon Position: %i\n", lwz->GetInfo());
            #endif
        }
 
        /* add child */
        if (knob < MAX_KNOB) {
            lookup[knob] = new keypair;
            lookup[knob]->value = string[1][0];
            lookup[knob]->next = lwz->GetInfo();

            #ifdef DEBUG
             fprintf(stderr, "Knob add: %i, value: %i, next %i\n", knob,
                string[1][0], lwz->GetInfo());
            #endif
 
            lwz->AddChild(string[1][0]);
            lwz->GoChild(string[1][0]);
            lwz->PutInfo(knob);
            knob++;
        }
 
        for (count = 0; string[0][count] != ROOT; count++) {
            fprintf(output,"%c",string[0][count]);
        }
    }

    /* free trie memory */
    delete lwz;

    /* free keypair allocations */
    for ( ; knob <= 0; knob--) {
        delete lookup[knob];
    }

}



/* XXX: File are only checked at creation time, not during execution */
int
main(int argc, char ** argv) {
    FILE * input;
    FILE * output;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s <infile> [<outfile>]\n",argv[0]);
        return(EX_USAGE);
    }

    input = fopen(argv[1], "r");
    if (input == NULL) {
        fprintf(stderr,"Error: Unable to use `%s', errno: %i\n",
            argv[1], errno);
        return(EX_NOINPUT);
    }

    if (argc == 3) {
        output = fopen(argv[2], "w");
        if (output == NULL)
        {
            fprintf(stderr,"Error: Unable to use `%s', errno: %i\n",
                argv[2], errno);
            return(EX_CANTCREAT);
        }
    } else
        output = stdout;

    /* call actual program */
    decode(input,output);

    fclose(input);
    fclose(output);
    return(EX_OK);
}