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sk2a/readme.md
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sk2a/readme.md
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// najprv robim kompresiu algoritmu runlength a potom lz78, ak sa robi nasledne dekompresia je to naopak najprv dekompresia lz78 a potom runlength.
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "compressor.h"
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#define BUFSIZE 1024
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#define SIZE 256
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#define MAX_WORDS 100000
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// One codeword is previous index - new index -character
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// Trie (a.k.a prefix tree)
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struct dict {
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int index;
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// Character is encoded as non zero value in characters
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struct dict* characters[SIZE];
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};
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// Free trie
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void delete(struct dict* tree){ //skopirovane z lz78, vymaze strukturu co sa pouziva v lz78
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if (tree == NULL){ //maze to pamat stromu
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return;
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}
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for (int i = 0 ;i < SIZE; i++){
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delete(tree-> characters[i]);
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}
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}
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void get_words (struct dict* tree,char* words[]){ //posielam cely strom a smernik na dvojrozmerne pole
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if (tree == NULL){
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return;
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}
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for (int i = 0 ;i < SIZE; i++){ //prejdeme vsetkych potomkov
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if (tree-> characters[i] > 0){ //zistime ci tam je nieco naalokovane
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int need_size = snprintf(NULL,0,"-%d-%c\n",tree->index,i); //kolko pamate
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words[tree->characters[i]->index] = calloc(need_size + 1,sizeof(char)); //naalokujeme pamat
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memset(words[tree->characters[i]->index],0,need_size + 1);
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sprintf(words[tree->characters[i]->index],"-%d-%c\n",tree->index,i); //napise sa vo formate -index predosleho notu - aktualny znak
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get_words(tree-> characters[i],words); //zavolam na kazdeho potomka a potom na dalsich potomkov alebo syna
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}
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}
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}
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int mylz78compress(char* buff,int size,char** outbuf){
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// https://medium.com/@dbudhrani/how-data-compression-works-exploring-lz78-e97e539138
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// The trie represents the current phrase
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// The first node represents the empty string with index 0
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struct dict* root = calloc(1,sizeof(struct dict));
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struct dict* current = root;
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int index = 1;
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int c = 0;
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char *last = NULL;
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for(int i = 0; i < size; i++){
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c = buff[i];
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// Current character is in dictionary, continue searching
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if (current->characters[c] > 0){
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// ak este nieco ostalo a toto je koniec
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if (i == size - 1){ // pridem na koniec suboru a musim si to zapamatat, inac to stratim
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int sz_needed = snprintf(NULL,0,"-%d-%c\n",current->index,c); //kolko bajtov to bude zaberat
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last = calloc(sz_needed + 1,sizeof(char)); //alokuje do do last
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sprintf(last,"-%d-%c\n",current->index,c); //
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}
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current = current->characters[c];
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}
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else {
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current->characters[c] = calloc(1,sizeof(struct dict));
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current->characters[c]->index = index;
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index += 1;
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current = root;
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}
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}
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char **words = calloc(index,sizeof(char*)); // z stromu vytvori format
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get_words(root,words);
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int size_needed = 0;
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for(int i=1; i < index; i++){ //nastavime velkost aku bude mat vystupny buffer
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if(words[i] != NULL){
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size_needed += strlen(words[i]); //poscitavame velkosti vsetkych stringov
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}
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}
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if (last != NULL){ //mame string last?
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size_needed += strlen(last); //priratam
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}
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char *temp = calloc(size_needed + 10,sizeof(char)); //alokujem velkost, padalo mi to ked som mal mensie cislo ako 10
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int pos = 0; //pamatam kde som to uz vypisal
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for(int i=0; i < index; i++){
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if (words[i] != NULL){
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strcpy(temp + pos,words[i]); //nebude sa to pisat na zaciatok ale az za tym
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pos += strlen(words[i]);
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}
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}
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if (last != NULL){ // zapisem aj last
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strcpy(temp + pos,last);
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pos += strlen(last);
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}
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delete(root); //nepotrebujeme strom, uvolnime pamat
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*outbuf = temp; //adresa sa zapise do outbuffer
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return strlen(temp);
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}
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int myrlcompress(char* buff,int size,char** outbuf){
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// 2 * size je urcite dost, kedze v najhorsom pripade bude kazdy znak osamote
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*outbuf = calloc(2 * size + 1,sizeof(char)); //smernik na smernik, napisem adresu novej pamate
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memset(*outbuf,0,size + 1); //vymaze
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int head = -1;
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int length = 0;
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int pos = 0;
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for(int i = 0; i < size; i++){
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int c = buff[i];
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if (c == head){
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length += 1;
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if (i == size - 1){ //posledne pismenko
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(*outbuf)[pos] = head;
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(*outbuf)[pos + 1] = length;
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pos += 2; //aby som vedel kde to zapisovat
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break;
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}
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}
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else {
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if (head != -1){
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(*outbuf)[pos] = head;
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(*outbuf)[pos + 1] = length;
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pos += 2;
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}
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if (i == size - 1){ //posledne pismenko
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(*outbuf)[pos] = c;
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(*outbuf)[pos + 1] = 1;
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pos += 2;
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break;
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}
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head = c;
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length = 1;
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}
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// ak sme blizko preteceniu, vypiseme aktualny znak
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if (length == 255){ //nemozme ist viac, vynulujem a idem od nuly
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(*outbuf)[pos] = head;
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(*outbuf)[pos + 1] = length;
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pos += 2;
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head = -1;
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length = 0;
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}
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}
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return pos; //velkost vystupneho buffera
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}
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void compress(FILE* infile,FILE* outfile){
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fseek(infile, 0, SEEK_END); //vstupny subor, a chceme presunut kurzor na konci suboru
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int insize = ftell(infile) + 1; // na akej pozicii je kurzor, zistime velkost suboru
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rewind(infile); //vrati kurzor na zaciatok
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char *buffer = calloc(insize,sizeof(char)); //alokuje pamat
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memset(buffer,0,insize);
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insize = fread(buffer,sizeof(char),insize - 1,infile); //nacita obsah do bufferu
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if (insize == 0){
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assert(!ferror(infile));
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}
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char *tempbuf = NULL; // az vo funkcii to alokujem
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int tempsize = myrlcompress(buffer,insize,&tempbuf); //vstupny buffer, velkost a adresu bufferu
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char *outbuf = NULL;
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int outsize = mylz78compress(tempbuf,tempsize,&outbuf);
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if (outsize > 0){
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fwrite(outbuf,sizeof(char),outsize,outfile); //napise sa do suboru, z akeho buffera do akeho suboru
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}
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}
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int myrldecompress(char* buff,int size,char** outbuf){
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*outbuf = calloc(size + 1,sizeof(char));
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memset(*outbuf,0,size + 1);
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int pos = 0;
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for(int i = 0; i < size; i+=2){
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char c = buff[i];
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char length = buff[i + 1];
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// ak nam nebude stacit miesto v *outbuf, treba allocovat viac
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while((length + pos) > (size - 1)){
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size *= 2;
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char *tempbuf = calloc(size,sizeof(char));
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memset(tempbuf,'\0',size);
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strcpy(tempbuf,*outbuf);
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*outbuf = tempbuf;
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}
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for (int j = 0; j < length; j++){ //tolko krat ho pridavam, kolko mam cisielko
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(*outbuf)[pos] = c;
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pos += 1;
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}
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}
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return pos;
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}
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int mylz78decompress(char* buff,int size,char** outbuf){ //nepotrebujem pouzivat strom
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*outbuf = calloc(size,sizeof(char)); //taka ista velkost ako vstup
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memset(*outbuf,0,size);
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char *words[MAX_WORDS]; //dvojrozmerne pole
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words[0] = "";
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char c;
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int index = 1;
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int number;
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int pos = 0;
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int bytes_read, bytes_read_all = 0; //citame vstupny buffer, necitame po bajtoch, viac ciferne cisla
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while (sscanf(buff + bytes_read_all,"-%d-%c\n%n",&number,&c,&bytes_read) == 2){ //formatovacie citanie, pusaveme o bajty, ktore sa precitali ak vrati ine cislo ako 2 tak je nakocni
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bytes_read_all += bytes_read; //o tolko sme sa posunuli
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words[index] = calloc(strlen(words[number]) + 2,sizeof(char*)); //vo words sa vytvoria prefixi
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strcpy(words[index],words[number]); //nakopirujeme words number a pridame nakoniec c
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words[index][strlen(words[number])] = c;
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// ak nam nebude stacit miesto v *outbuf, treba allocovat viac
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while((strlen(words[index]) + pos) > (size - 1)){
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size *= 2;
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char *tempbuf = calloc(size,sizeof(char));
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memset(tempbuf,'\0',size);
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strcpy(tempbuf,*outbuf);
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*outbuf = tempbuf;
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}
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strcpy(*outbuf + pos,words[index]); //nakopiruje najnovsie slovo
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pos += strlen(words[index]);
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index += 1;
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}
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return strlen(*outbuf); //vratim velkost
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}
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void decompress(FILE* infile,FILE* outfile){
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fseek(infile, 0, SEEK_END);
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int insize = ftell(infile) + 1;
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rewind(infile);
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char *buffer = calloc(insize,sizeof(char));
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memset(buffer,0,insize);
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insize = fread(buffer,sizeof(char),insize - 1,infile);
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if (insize == 0){
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assert(!ferror(infile));
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}
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char *tempbuf = NULL;
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int tempsize = mylz78decompress(buffer,insize,&tempbuf); //najprv lz78
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char *outbuf = NULL;
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int outsize = myrldecompress(tempbuf,tempsize,&outbuf);
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if (outsize > 0){
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fwrite(outbuf,sizeof(char),outsize,outfile);
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}
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}
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