usaa25/sk1/compressor.c

#include <stdio.h>
#include <stdlib.h>
#include "compressor.h"

struct node {
    unsigned char znak;
    int pocet;
    struct node *left;
    struct node *right;
};

struct node* vytvor_node(unsigned char c, int p) {
    struct node* n = malloc(sizeof(struct node));
    n->znak = c;
    n->pocet = p;
    n->left = NULL;
    n->right = NULL;
    return n;
}

int compress_file(char *input, char *output) {
    FILE *f = fopen(input, "rb");
    if(!f) {
        printf("Neviem otvorit subor\n");
        return 1;
    }

    fseek(f, 0, SEEK_END);
    long velkost = ftell(f);
    fseek(f, 0, SEEK_SET);

    unsigned char *data = malloc(velkost);
    fread(data, 1, velkost, f);
    fclose(f);

    int frekvencia[256];
    int i;
    for(i=0;i<256;i++) frekvencia[i]=0;
    for(i=0;i<velkost;i++) frekvencia[data[i]]++;

    struct node* pole[256];
    int n=0;
    for(i=0;i<256;i++){
        if(frekvencia[i]>0){
            pole[n] = vytvor_node(i, frekvencia[i]);
            n++;
        }
    }

    for(i=0;i<n-1;i++){
        for(int j=0;j<n-i-1;j++){
            if(pole[j]->pocet > pole[j+1]->pocet){
                struct node* tmp = pole[j];
                pole[j] = pole[j+1];
                pole[j+1] = tmp;
            }
        }
    }

    while(n>1){
        struct node* left = pole[0];
        struct node* right = pole[1];

        struct node* parent = vytvor_node(0, left->pocet + right->pocet);
        parent->left = left;
        parent->right = right;

        for(i=0;i<n-2;i++){
            pole[i] = pole[i+2];
        }
        n = n-2;

        int vlozene=0;
        for(i=0;i<n;i++){
            if(parent->pocet < pole[i]->pocet){
                for(int j=n;j>i;j--){
                    pole[j] = pole[j-1];
                }
                pole[i] = parent;
                vlozene=1;
                break;
            }
        }
        if(!vlozene) pole[n] = parent;
        n++;
    }

    struct node* root = pole[0];

    unsigned int kody[256];
    unsigned char dlzky[256];
    for(i=0;i<256;i++){
        kody[i]=0;
        dlzky[i]=0;
    }
    struct node* zasobnik[512];
    unsigned int kod_zasobnik[512];
    unsigned char dlzka_zasobnik[512];
    int top=0;

    zasobnik[top] = root;
    kod_zasobnik[top] = 0;
    dlzka_zasobnik[top] = 0;
    top++;

    while(top>0){
        top--;
        struct node* aktualny = zasobnik[top];
        unsigned int kod = kod_zasobnik[top];
        unsigned char dlzka = dlzka_zasobnik[top];

        if(!aktualny->left && !aktualny->right){
            kody[aktualny->znak] = kod;
            dlzky[aktualny->znak] = dlzka>0 ? dlzka : 1;
        }else{
            if(aktualny->left){
                zasobnik[top] = aktualny->left;
                kod_zasobnik[top] = kod<<1;
                dlzka_zasobnik[top] = dlzka+1;
                top++;
            }
            if(aktualny->right){
                zasobnik[top] = aktualny->right;
                kod_zasobnik[top] = (kod<<1)|1;
                dlzka_zasobnik[top] = dlzka+1;
                top++;
            }
        }
    }
    unsigned char* vystup = malloc(velkost*2);
    long pos=0;
    unsigned char bajt=0;
    int bit_pos=0;

    for(i=0;i<velkost;i++){
        unsigned int kod = kody[data[i]];
        unsigned char dlzka = dlzky[data[i]];

        for(int j=dlzka-1;j>=0;j--){
            if((kod>>j)&1){
                bajt |= (1<<(7-bit_pos));
            }
            bit_pos++;
            if(bit_pos==8){
                vystup[pos++] = bajt;
                bajt=0;
                bit_pos=0;
            }
        }
    }
    if(bit_pos>0) vystup[pos++]=bajt;

    FILE *fout = fopen(output, "wb");
    fwrite(&velkost, sizeof(long), 1, fout);
    fwrite(frekvencia, sizeof(int), 256, fout);
    fwrite(vystup, 1, pos, fout);
    fclose(fout);

    printf("Komprimovane: %ld -> %ld\n", velkost, pos+sizeof(long)+256*sizeof(int));

    free(data);
    free(vystup);
    return 0;
}

int decompress_file(char *input, char *output) {
    FILE *f = fopen(input, "rb");
    if(!f){
        printf("Neviem otvorit subor\n");
        return 1;
    }
    long velkost;
    int frekvencia[256];
    fread(&velkost, sizeof(long), 1, f);
    fread(frekvencia, sizeof(int), 256, f);

    struct node* pole[256];
    int n=0;
    int i;
    for(i=0;i<256;i++){
        if(frekvencia[i]>0){
            pole[n] = vytvor_node(i, frekvencia[i]);
            n++;
        }
    }
    for(i=0;i<n-1;i++){
        for(int j=0;j<n-i-1;j++){
            if(pole[j]->pocet > pole[j+1]->pocet){
                struct node* tmp = pole[j];
                pole[j] = pole[j+1];
                pole[j+1] = tmp;
         }
      }
   }

    while(n>1){
        struct node* left = pole[0];
        struct node* right = pole[1];

        struct node* parent = vytvor_node(0, left->pocet + right->pocet);
        parent->left = left;
        parent->right = right;

        for(i=0;i<n-2;i++){
            pole[i] = pole[i+2];
        }
        n = n-2;

        int vlozene=0;
        for(i=0;i<n;i++){
            if(parent->pocet < pole[i]->pocet){
                for(int j=n;j>i;j--){
                    pole[j] = pole[j-1];
                }
                pole[i] = parent;
                vlozene=1;
                break;
            }
        }
        if(!vlozene) pole[n] = parent;
        n++;
    }

    struct node* root = pole[0];

    fseek(f, 0, SEEK_END);
    long total = ftell(f);
    long komp_velkost = total - sizeof(long) - 256*sizeof(int);
    fseek(f, sizeof(long) + 256*sizeof(int), SEEK_SET);

    unsigned char *komp_data = malloc(komp_velkost);
    fread(komp_data, 1, komp_velkost, f);
    fclose(f);

    unsigned char *vystup = malloc(velkost);
    long vystup_pos=0;
    struct node* aktualny = root;

    for(i=0;i<komp_velkost && vystup_pos<velkost;i++){
        for(int bit=7;bit>=0 && vystup_pos<velkost;bit--){
            if((komp_data[i]>>bit)&1){
                aktualny = aktualny->right;
            }else{
                aktualny = aktualny->left;
            }

            if(!aktualny->left && !aktualny->right){
                vystup[vystup_pos++] = aktualny->znak;
                aktualny = root;
            }
        }
    }

    FILE *fout = fopen(output, "wb");
    fwrite(vystup, 1, velkost, fout);
    fclose(fout);

    printf("Dekomprimovane: %ld\n", velkost);

    free(komp_data);
    free(vystup);
    return 0;
}