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