From b9c2e999b4cccce3a942cd92469078045b03e36b Mon Sep 17 00:00:00 2001
From: Daniel Ryzhuk <daniel.ryzhuk@student.tuke.sk>
Date: Sun, 17 Jan 2021 17:21:21 +0000
Subject: [PATCH] Add 'sk1/program.c'

---
 sk1/program.c | 178 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 178 insertions(+)
 create mode 100644 sk1/program.c

diff --git a/sk1/program.c b/sk1/program.c
new file mode 100644
index 0000000..1b6a172
--- /dev/null
+++ b/sk1/program.c
@@ -0,0 +1,178 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct node{
+    struct node* children[256];
+    unsigned char size;
+    unsigned char character;
+    unsigned char pos;
+
+    //Not used in encoding
+    struct node* parent;
+};
+
+typedef struct node* node;
+
+void compress(FILE* in, FILE* out);
+void decompress(FILE* in, FILE* out);
+
+int main(int argc, char* argv[]){
+    if(argc < 4){
+        printf("Choose option and files!\n");
+        printf("Options:\n\tc for compress\n\td for decompress\n");
+        return 0;
+    }
+
+    FILE* in = fopen(argv[2], "r");
+    FILE* out = fopen(argv[3], "w");
+
+    if(argv[1][0] == 'c'){
+        compress(in, out);
+    }
+    else{
+        decompress(in, out);
+    }
+
+    fclose(in);
+    fclose(out);
+}
+
+
+node create_node(unsigned char character, unsigned char pos){
+    node new = malloc(sizeof(struct node));
+    new->character = character;
+    new->pos = pos;
+    new->size = 0;
+    return new;
+}
+
+
+node find_parent_enc(node root, unsigned char character){
+    for(int i = 0; i < root->size; i++){
+        if(root->children[i]->character == character){
+            return root->children[i];
+        }
+    }
+    return NULL;
+}
+
+
+void recursive_free(node tree){
+    if(tree != NULL){
+        for(int i = 0; i < tree->size; i++){
+            recursive_free(tree->children[i]);
+        }
+        free(tree);
+    }
+}
+
+void free_tree(node tree){
+    for(int i = 0; i < tree->size; i++){
+        recursive_free(tree->children[i]);
+    }
+    tree->size = 0;
+}
+
+
+void enc_write(unsigned char pos, char character, FILE* out){
+    fputc(pos, out);
+    fputc(character, out);
+}
+
+
+void compress(FILE* in, FILE* out){
+    node root = create_node(0, 0);
+
+    unsigned char pos = 1;
+    unsigned char character;
+
+    node parent = root;
+
+
+    while(fread(&character, 1, 1, in) > 0){
+        node parent_copy = parent;
+        parent = find_parent_enc(parent_copy, character);
+        if(parent == NULL){
+            node new = create_node(character, pos);
+            parent_copy->children[parent_copy->size] = new;
+            enc_write(parent_copy->pos, parent_copy->children[parent_copy->size]->character, out);
+            parent_copy->size += 1;
+            pos++;
+            if(pos >= 255){
+                pos = 1;
+                free_tree(root);
+            }
+            parent = root;
+        }
+    }
+
+    if(parent != root){
+        fputc(parent->pos, out);
+    }
+
+    free_tree(root);
+    free(root);
+}
+
+
+node find_parent_dec(unsigned char pos, node tree){
+    if(pos == 0 || tree == NULL){
+        return NULL;
+    }
+    else if(tree->pos == pos){
+        return tree;
+    }
+
+    for(int i = 0; i < tree->size; i++){
+        node child = find_parent_dec(pos, tree->children[i]);
+        if(child != NULL){
+            return child;
+        }
+    }
+    return NULL;
+}
+
+void dec_write(node element, FILE* out){
+    if(element->parent != NULL){
+        dec_write(element->parent, out);
+        fputc(element->character, out);
+    }
+}
+void decompress(FILE* in, FILE* out){
+    int res = 0;
+    node root = create_node(0, 0);
+    
+    unsigned short pos = 1;
+    unsigned char character;
+    unsigned char parent_pos;
+    
+    while(fread(&parent_pos, 1, 1, in) > 0 && fread(&character, 1, 1, in) > 0){
+        node parent = find_parent_dec(parent_pos, root);
+        if(parent == NULL){
+            parent = root;
+        }
+
+        node new = create_node(character, pos);
+        pos++;
+
+        new->parent = parent;
+        parent->children[parent->size] = new;
+        parent->size += 1;
+        parent_pos = 0;
+
+        dec_write(new, out);
+        if(pos >= 255){
+            free_tree(root);
+            res++;
+            pos = 1;
+        }
+    }
+
+    if(parent_pos != 0){
+        node last = find_parent_dec(parent_pos, root);
+        dec_write(last, out);
+    }
+
+    free_tree(root);
+    free(root);
+}
\ No newline at end of file