From 183e166d8bb30ccce816400689d5161aad29060f Mon Sep 17 00:00:00 2001
From: Yevhen Kozirovskyi <yevhen.kozirovskyi@student.tuke.sk>
Date: Mon, 27 Jan 2025 15:08:53 +0000
Subject: [PATCH] =?UTF-8?q?=D0=9E=D0=B1=D0=BD=D0=BE=D0=B2=D0=B8=D1=82?=
 =?UTF-8?q?=D1=8C=20sk1/compressor.c?=
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---
 sk1/compressor.c | 369 ++++++++++++++++++-----------------------------
 1 file changed, 141 insertions(+), 228 deletions(-)

diff --git a/sk1/compressor.c b/sk1/compressor.c
index 70ee497..98dd1b6 100644
--- a/sk1/compressor.c
+++ b/sk1/compressor.c
@@ -1,224 +1,157 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <ctype.h>
+#include "compressor.h"
 
-#define MAX_TREE_NODES 256
+#define BUFFER_SIZE 4096
+#define MAX_SYMBOLS 257
 
-// Structure to represent a tree node
-typedef struct HuffmanNode {
-    unsigned char data;
-    unsigned frequency;
-    struct HuffmanNode* left;
-    struct HuffmanNode* right;
-} HuffmanNode;
+// Макрос для обмена двух узлов
+#define SWAP_NODES(a, b) { Node* temp = a; a = b; b = temp; }
 
-// A structure to represent the Min Heap (Priority Queue)
-typedef struct MinHeap {
-    unsigned size;
-    unsigned capacity;
-    HuffmanNode** array;
-} MinHeap;
+// Определение структуры узла дерева
+typedef struct Node {
+    int symbol;                
+    unsigned int frequency;     
+    struct Node *left, *right;  
+} Node;
 
-// Function to create a new node
-HuffmanNode* newNode(unsigned char data, unsigned frequency) {
-    HuffmanNode* node = (HuffmanNode*)malloc(sizeof(HuffmanNode));
-    if (!node) {
-        perror("Failed to allocate memory for new node");
-        exit(EXIT_FAILURE);
-    }
-    node->data = data;
+// Функция для создания нового узла
+Node* create_node(int symbol, unsigned int frequency) {
+    Node* node = (Node*)malloc(sizeof(Node));
+    node->symbol = symbol;
     node->frequency = frequency;
     node->left = node->right = NULL;
     return node;
 }
 
-// Function to create a MinHeap
-MinHeap* createMinHeap(unsigned capacity) {
-    MinHeap* minHeap = (MinHeap*)malloc(sizeof(MinHeap));
-    if (!minHeap) {
-        perror("Failed to allocate memory for MinHeap");
-        exit(EXIT_FAILURE);
-    }
-    minHeap->size = 0;
-    minHeap->capacity = capacity;
-    minHeap->array = (HuffmanNode**)malloc(capacity * sizeof(HuffmanNode*));
-    if (!minHeap->array) {
-        perror("Failed to allocate memory for MinHeap array");
-        exit(EXIT_FAILURE);
-    }
-    return minHeap;
-}
+// Функция для построения дерева Хаффмана
+Node* build_huffman_tree(const unsigned int* frequencies) {
+    Node* nodes[MAX_SYMBOLS];
+    int node_count = 0;
 
-// Function to swap two min heap nodes
-void swapMinHeapNode(HuffmanNode** a, HuffmanNode** b) {
-    HuffmanNode* temp = *a;
-    *a = *b;
-    *b = temp;
-}
-
-// Function to min heapify
-void minHeapify(MinHeap* minHeap, int idx) {
-    int smallest = idx;
-    int left = 2 * idx + 1;
-    int right = 2 * idx + 2;
-
-    if (left < (int)minHeap->size && minHeap->array[left]->frequency < minHeap->array[smallest]->frequency)
-        smallest = left;
-
-    if (right < (int)minHeap->size && minHeap->array[right]->frequency < minHeap->array[smallest]->frequency)
-        smallest = right;
-
-    if (smallest != idx) {
-        swapMinHeapNode(&minHeap->array[smallest], &minHeap->array[idx]);
-        minHeapify(minHeap, smallest);
-    }
-}
-
-// Check if the size of heap is one
-int isSizeOne(MinHeap* minHeap) {
-    return (minHeap->size == 1);
-}
-
-// Extract the minimum node from heap
-HuffmanNode* extractMin(MinHeap* minHeap) {
-    HuffmanNode* temp = minHeap->array[0];
-    minHeap->array[0] = minHeap->array[minHeap->size - 1];
-    --minHeap->size;
-    minHeapify(minHeap, 0);
-    return temp;
-}
-
-// Insert a new node to MinHeap
-void insertMinHeap(MinHeap* minHeap, HuffmanNode* node) {
-    ++minHeap->size;
-    int i = minHeap->size - 1;
-    while (i && node->frequency < minHeap->array[(i - 1) / 2]->frequency) {
-        minHeap->array[i] = minHeap->array[(i - 1) / 2];
-        i = (i - 1) / 2;
-    }
-    minHeap->array[i] = node;
-}
-
-// Build a min heap of given capacity
-void buildMinHeap(MinHeap* minHeap) {
-    int n = minHeap->size - 1;
-    for (int i = (n - 1) / 2; i >= 0; --i)
-        minHeapify(minHeap, i);
-}
-
-// Function to build the Huffman tree
-HuffmanNode* buildHuffmanTree(unsigned char* data, unsigned* freq, int size) {
-    HuffmanNode *left, *right, *top;
-
-    MinHeap* minHeap = createMinHeap(size);
-
-    for (int i = 0; i < size; ++i)
-        insertMinHeap(minHeap, newNode(data[i], freq[data[i]]));
-
-    buildMinHeap(minHeap);
-
-    while (!isSizeOne(minHeap)) {
-        left = extractMin(minHeap);
-        right = extractMin(minHeap);
-
-        top = newNode('$', left->frequency + right->frequency);
-        top->left = left;
-        top->right = right;
-
-        insertMinHeap(minHeap, top);
+    // Создаем узлы для всех символов с ненулевой частотой
+    for (int i = 0; i < MAX_SYMBOLS; i++) {
+        if (frequencies[i] > 0) {
+            nodes[node_count++] = create_node(i, frequencies[i]);
+        }
     }
 
-    return extractMin(minHeap);
+    // Объединяем узлы в дерево
+    while (node_count > 1) {
+        // Сортируем узлы по частоте
+        for (int i = 0; i < node_count - 1; i++) {
+            for (int j = i + 1; j < node_count; j++) {
+                if (nodes[i]->frequency > nodes[j]->frequency) {
+                    SWAP_NODES(nodes[i], nodes[j]);
+                }
+            }
+        }
+
+        // Объединяем два узла с наименьшей частотой
+        Node* left = nodes[0];
+        Node* right = nodes[1];
+        Node* parent = create_node(-1, left->frequency + right->frequency);
+        parent->left = left;
+        parent->right = right;
+
+        // Заменяем объединенные узлы новым родительским узлом
+        nodes[0] = parent;
+        nodes[1] = nodes[--node_count];
+    }
+
+    return nodes[0];
 }
 
-// Function to generate the Huffman codes for each character
-void generateCodes(HuffmanNode* root, char* arr, int top, char** codes) {
-    if (root->left) {
-        arr[top] = '0';
-        generateCodes(root->left, arr, top + 1, codes);
-    }
-
-    if (root->right) {
-        arr[top] = '1';
-        generateCodes(root->right, arr, top + 1, codes);
-    }
-
+// Рекурсивная функция для генерации кодов Хаффмана
+void generate_huffman_codes(Node* root, char* code, int depth, char codes[MAX_SYMBOLS][MAX_SYMBOLS]) {
     if (!root->left && !root->right) {
-        arr[top] = '\0';  // Null terminate the string
-        codes[root->data] = strdup(arr);
+        code[depth] = '\0'; // Завершаем код символа
+        strcpy(codes[root->symbol], code);
+        return;
+    }
+    if (root->left) {
+        code[depth] = '0'; // Добавляем бит '0' для левого поддерева
+        generate_huffman_codes(root->left, code, depth + 1, codes);
+    }
+    if (root->right) {
+        code[depth] = '1'; // Добавляем бит '1' для правого поддерева
+        generate_huffman_codes(root->right, code, depth + 1, codes);
     }
 }
-void free_huffman_tree(HuffmanNode* root) {
+
+// Функция для освобождения памяти, выделенной под дерево Хаффмана
+void free_huffman_tree(Node* root) {
     if (!root) return;
     free_huffman_tree(root->left);
     free_huffman_tree(root->right);
     free(root);
 }
 
-// Function to compress a file
+// Функция сжатия данных с использованием алгоритма Хаффмана
 int compress_1(const char* input_file, const char* output_file) {
     FILE* input = fopen(input_file, "rb");
     FILE* output = fopen(output_file, "wb");
-    if (!input || !output) {
-        perror("Error opening file");
-        return -1;
-    }
+    if (!input || !output) return -1;
 
-    unsigned freq[256] = {0};
-    unsigned char data;
-    while (fread(&data, sizeof(data), 1, input) == 1)
-        freq[data]++;
+    unsigned int frequencies[MAX_SYMBOLS] = {0};
+    unsigned char buffer[BUFFER_SIZE];
+    size_t bytes_read;
 
-    unsigned char unique_data[256];
-    int unique_count = 0;
-    for (int i = 0; i < 256; i++) {
-        if (freq[i] > 0) {
-            unique_data[unique_count++] = i;
+    // Подсчет частот символов
+    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, input)) > 0) {
+        for (size_t i = 0; i < bytes_read; i++) {
+            frequencies[buffer[i]]++;
         }
     }
+    frequencies[256] = 1; // Добавляем маркер EOF
 
-    HuffmanNode* root = buildHuffmanTree(unique_data, freq, unique_count);
+    Node* root = build_huffman_tree(frequencies);
+    if (!root) return -1;
 
-    char* codes[256] = {0};
-    char arr[256];
-    generateCodes(root, arr, 0, codes);
+    // Генерация кодов Хаффмана
+    char codes[MAX_SYMBOLS][MAX_SYMBOLS] = {{0}};
+    char code[MAX_SYMBOLS] = {0};
+    generate_huffman_codes(root, code, 0, codes);
 
-    fwrite(&unique_count, sizeof(int), 1, output);
-    for (int i = 0; i < unique_count; i++) {
-        unsigned char symbol = unique_data[i];
-        fwrite(&symbol, sizeof(unsigned char), 1, output);
-        fwrite(&freq[symbol], sizeof(unsigned), 1, output);
-    }
+    // Записываем частоты в выходной файл
+    fwrite(frequencies, sizeof(frequencies[0]), MAX_SYMBOLS, output);
 
-    fseek(input, 0, SEEK_SET);
-
-    unsigned char buffer = 0;
+    // Сжимаем данные
+    rewind(input);
+    unsigned char current_byte = 0;
     int bit_count = 0;
-    size_t total_bits = 0;
 
-    while (fread(&data, sizeof(data), 1, input) == 1) {
-        char* code = codes[data];
-        for (int i = 0; code[i] != '\0'; i++) {
-            unsigned char bit = code[i] - '0';
-            buffer = (buffer << 1) | bit;
-            bit_count++;
-            total_bits++;
-
-            if (bit_count == 8) {
-                fwrite(&buffer, sizeof(unsigned char), 1, output);
-                bit_count = 0;
-                buffer = 0;
+    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, input)) > 0) {
+        for (size_t i = 0; i < bytes_read; i++) {
+            char* symbol_code = codes[buffer[i]];
+            for (size_t j = 0; symbol_code[j] != '\0'; j++) {
+                current_byte = (current_byte << 1) | (symbol_code[j] - '0');
+                bit_count++;
+                if (bit_count == 8) {
+                    fwrite(&current_byte, 1, 1, output);
+                    current_byte = 0;
+                    bit_count = 0;
+                }
             }
         }
     }
 
-    if (bit_count > 0) {
-        buffer <<= (8 - bit_count);
-        fwrite(&buffer, sizeof(unsigned char), 1, output);
+    // Записываем маркер EOF
+    char* eof_code = codes[256];
+    for (size_t j = 0; eof_code[j] != '\0'; j++) {
+        current_byte = (current_byte << 1) | (eof_code[j] - '0');
+        bit_count++;
+        if (bit_count == 8) {
+            fwrite(&current_byte, 1, 1, output);
+            current_byte = 0;
+            bit_count = 0;
+        }
+    }
+    if (bit_count > 0) {
+        current_byte <<= (8 - bit_count);
+        fwrite(&current_byte, 1, 1, output);
     }
-
-    fwrite(&total_bits, sizeof(size_t), 1, output); // Write total bits used
 
     fclose(input);
     fclose(output);
@@ -226,62 +159,34 @@ int compress_1(const char* input_file, const char* output_file) {
     return 0;
 }
 
-// Function to decompress the compressed file
-int decompress_1(const char* input_file_name, const char* output_file_name) {
-    FILE* input = fopen(input_file_name, "rb");
-    if (!input) {
-        perror("Error opening input file");
-        return -1;
-    }
-    FILE* output = fopen(output_file_name, "wb");
-    if (!output) {
-        perror("Error opening output file");
-        fclose(input);
-        return -1;
-    }
+// Функция декомпрессии данных с использованием алгоритма Хаффмана
+int decompress_1(const char* input_file, const char* output_file) {
+    FILE* input = fopen(input_file, "rb");
+    FILE* output = fopen(output_file, "wb");
+    if (!input || !output) return -1;
 
-    int unique_count;
-    if (fread(&unique_count, sizeof(int), 1, input) != 1) {
-        perror("Error reading from input file");
-        fclose(input);
-        fclose(output);
-        return -1;
-    }
+    unsigned int frequencies[MAX_SYMBOLS] = {0};
+    fread(frequencies, sizeof(frequencies[0]), MAX_SYMBOLS, input);
+    Node* root = build_huffman_tree(frequencies);
+    if (!root) return -1;
 
-    unsigned char unique_data[256];
-    unsigned freq[256] = {0};
-    for (int i = 0; i < unique_count; i++) {
-        if (fread(&unique_data[i], sizeof(unsigned char), 1, input) != 1 ||
-            fread(&freq[unique_data[i]], sizeof(unsigned), 1, input) != 1) {
-            perror("Error reading from input file");
-            fclose(input);
-            fclose(output);
-            return -1;
-        }
-    }
-
-    HuffmanNode* root = buildHuffmanTree(unique_data, freq, unique_count);
-
-    size_t total_bits;
-    fseek(input, -(long long)sizeof(size_t), SEEK_END);
-    fread(&total_bits, sizeof(size_t), 1, input);
-
-    fseek(input, sizeof(int) + unique_count * (sizeof(unsigned char) + sizeof(unsigned)), SEEK_SET);
-
-    HuffmanNode* current = root;
+    Node* current = root;
     unsigned char byte;
-    size_t bits_read = 0;
+    int bit;
 
-    while (bits_read < total_bits && fread(&byte, sizeof(byte), 1, input) == 1) {
-        for (int i = 7; i >= 0 && bits_read < total_bits; i--, bits_read++) {
-            if (byte & (1 << i)) {
-                current = current->right;
-            } else {
-                current = current->left;
-            }
+    // Читаем и декодируем символы
+    while (fread(&byte, 1, 1, input) == 1) {
+        for (bit = 7; bit >= 0; bit--) {
+            current = (byte & (1 << bit)) ? current->right : current->left;
 
             if (!current->left && !current->right) {
-                fwrite(&current->data, sizeof(current->data), 1, output);
+                if (current->symbol == 256) { // Маркер EOF
+                    fclose(input);
+                    fclose(output);
+                    free_huffman_tree(root);
+                    return 0;
+                }
+                fwrite(&current->symbol, 1, 1, output);
                 current = root;
             }
         }
@@ -291,4 +196,12 @@ int decompress_1(const char* input_file_name, const char* output_file_name) {
     fclose(output);
     free_huffman_tree(root);
     return 0;
-}
\ No newline at end of file
+}
+
+int compress_2(const char* input_file_name, const char* output_file_name){
+    return 0;
+}
+
+int decompress_2(const char* input_file_name, const char* output_file_name){
+    return 0;
+}