哈夫曼编码压缩解压缩c语言代码

以下是哈夫曼编码压缩解压缩的C语言代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_TREE_HT 100

struct MinHeapNode {
    char data;
    unsigned freq;
    struct MinHeapNode *left, *right;
};

struct MinHeap {
    unsigned size;
    unsigned capacity;
    struct MinHeapNode** array;
};

struct MinHeapNode* newNode(char data, unsigned freq) {
    struct MinHeapNode* temp = (struct MinHeapNode*)malloc(sizeof(struct MinHeapNode));
    temp->left = temp->right = NULL;
    temp->data = data;
    temp->freq = freq;
    return temp;
}

struct MinHeap* createMinHeap(unsigned capacity) {
    struct MinHeap* minHeap = (struct MinHeap*)malloc(sizeof(struct MinHeap));
    minHeap->size = 0;
    minHeap->capacity = capacity;
    minHeap->array = (struct MinHeapNode**)malloc(minHeap->capacity * sizeof(struct MinHeapNode*));
    return minHeap;
}

void swapMinHeapNode(struct MinHeapNode** a, struct MinHeapNode** b) {
    struct MinHeapNode* t = *a;
    *a = *b;
    *b = t;
}

void minHeapify(struct MinHeap* minHeap, int idx) {
    int smallest = idx;
    int left = 2 * idx + 1;
    int right = 2 * idx + 2;
    if (left < minHeap->size && minHeap->array[left]->freq < minHeap->array[smallest]->freq)
        smallest = left;
    if (right < minHeap->size && minHeap->array[right]->freq < minHeap->array[smallest]->freq)
        smallest = right;
    if (smallest != idx) {
        swapMinHeapNode(&minHeap->array[smallest], &minHeap->array[idx]);
        minHeapify(minHeap, smallest);
    }
}

int isSizeOne(struct MinHeap* minHeap) {
    return (minHeap->size == 1);
}

struct MinHeapNode* extractMin(struct MinHeap* minHeap) {
    struct MinHeapNode* temp = minHeap->array[0];
    minHeap->array[0] = minHeap->array[minHeap->size - 1];
    --minHeap->size;
    minHeapify(minHeap, 0);
    return temp;
}

void insertMinHeap(struct MinHeap* minHeap, struct MinHeapNode* minHeapNode) {
    ++minHeap->size;
    int i = minHeap->size - 1;
    while (i && minHeapNode->freq < minHeap->array[(i - 1) / 2]->freq) {
        minHeap->array[i] = minHeap->array[(i - 1) / 2];
        i = (i - 1) / 2;
    }
    minHeap->array[i] = minHeapNode;
}

void buildMinHeap(struct MinHeap* minHeap) {
    int n = minHeap->size - 1;
    int i;
    for (i = (n - 1) / 2; i >= 0; --i)
        minHeapify(minHeap, i);
}

void printArr(int arr[], int n) {
    int i;
    for (i = 0; i < n; ++i)
        printf("%d", arr[i]);
    printf("\n");
}

int isLeaf(struct MinHeapNode* root) {
    return !(root->left) && !(root->right);
}

struct MinHeap* createAndBuildMinHeap(char data[], int freq[], int size) {
    struct MinHeap* minHeap = createMinHeap(size);
    for (int i = 0; i < size; ++i)
        minHeap->array[i] = newNode(data[i], freq[i]);
    minHeap->size = size;
    buildMinHeap(minHeap);
    return minHeap;
}

struct MinHeapNode* buildHuffmanTree(char data[], int freq[], int size) {
    struct MinHeapNode *left, *right, *top;
    struct MinHeap* minHeap = createAndBuildMinHeap(data, freq, size);
    while (!isSizeOne(minHeap)) {
        left = extractMin(minHeap);
        right = extractMin(minHeap);
        top = newNode('$', left->freq + right->freq);
        top->left = left;
        top->right = right;
        insertMinHeap(minHeap, top);
    }
    return extractMin(minHeap);
}

void printCodes(struct MinHeapNode* root, int arr[], int top) {
    if (root->left) {
        arr[top] = 0;
        printCodes(root->left, arr, top + 1);
    }
    if (root->right) {
        arr[top] = 1;
        printCodes(root->right, arr, top + 1);
    }
    if (isLeaf(root)) {
        printf("%c: ", root->data);
        printArr(arr, top);
    }
}

void HuffmanCodes(char data[], int freq[], int size) {
    struct MinHeapNode* root = buildHuffmanTree(data, freq, size);
    int arr[MAX_TREE_HT], top = 0;
    printCodes(root, arr, top);
}

void compress(char* inputFilePath, char* outputFilePath) {
    FILE* inputFile = fopen(inputFilePath, "rb");
    if (!inputFile) {
        printf("Error: Could not open file %s.\n", inputFilePath);
        return;
    }
    fseek(inputFile, 0, SEEK_END);
    unsigned long inputSize = ftell(inputFile);
    fseek(inputFile, 0, SEEK_SET);
    char* inputData = (char*)malloc(inputSize);
    fread(inputData, 1, inputSize, inputFile);
    fclose(inputFile);

    int freq[256] = { 0 };
    for (int i = 0; i < inputSize; ++i)
        ++freq[inputData[i]];

    char data[256];
    int size = 0;
    for (int i = 0; i < 256; ++i) {
        if (freq[i] != 0) {
            data[size] = (char)i;
            ++size;
        }
    }

    HuffmanCodes(data, freq, size);

    FILE* outputFile = fopen(outputFilePath, "wb");
    if (!outputFile) {
        printf("Error: Could not create file %s.\n", outputFilePath);
        return;
    }

    struct MinHeapNode* root = buildHuffmanTree(data, freq, size);
    int arr[MAX_TREE_HT], top = 0;
    printCodes(root, arr, top);

    fwrite(&size, sizeof(size), 1, outputFile);
    for (int i = 0; i < size; ++i) {
        fwrite(&data[i], sizeof(data[i]), 1, outputFile);
        fwrite(&freq[(unsigned char)data[i]], sizeof(freq[(unsigned char)data[i]]), 1, outputFile);
    }

    int bitIndex = 0;
    char byte = 0;
    for (int i = 0; i < inputSize; ++i) {
        int arrIndex = 0;
        struct MinHeapNode* node = root;
        while (inputData[i] != node->data) {
            if (inputData[i] < node->data)
                node = node->left;
            else
                node = node->right;
            arrIndex++;
        }
        for (int j = 0; j < arrIndex; ++j) {
            byte |= ((arr[j] << (bitIndex % 8)) & (1 << (bitIndex % 8)));
            ++bitIndex;
            if (bitIndex % 8 == 0) {
                fwrite(&byte, sizeof(byte), 1, outputFile);
                byte = 0;
            }
        }
    }

    if (bitIndex % 8 != 0)
        fwrite(&byte, sizeof(byte), 1, outputFile);

    fclose(outputFile);

    printf("Compression complete. Original size: %lu bytes. Compressed size: %ld bytes.\n", inputSize, ftell(outputFile));
}

void decompress(char* inputFilePath, char* outputFilePath) {
    FILE* inputFile = fopen(inputFilePath, "rb");
    if (!inputFile) {
        printf("Error: Could not open file %s.\n", inputFilePath);
        return;
    }

    int size;
    fread(&size, sizeof(size), 1, inputFile);

    char data[256];
    int freq[256];
    for (int i = 0; i < size; ++i) {
        fread(&data[i], sizeof(data[i]), 1, inputFile);
        fread(&freq[(unsigned char)data[i]], sizeof(freq[(unsigned char)data[i]]), 1, inputFile);
    }

    struct MinHeapNode* root = buildHuffmanTree(data, freq, size);

    FILE* outputFile = fopen(outputFilePath, "wb");
    if (!outputFile) {
        printf("Error: Could not create file %s.\n", outputFilePath);
        return;
    }

    unsigned long outputSize = 0;

    int bitIndex = 0;
    char byte = 0;
    struct MinHeapNode* node = root;
    while (1) {
        int bit = fgetc(inputFile);
        if (bit == EOF)
            break;
        for (int i = 0; i < 8; ++i) {
            if (bit & (1 << i))
                node = node->right;
            else
                node = node->left;
            if (isLeaf(node)) {
                fwrite(&node->data, sizeof(node->data), 1, outputFile);
                outputSize += sizeof(node->data);
                node = root;
            }
        }
    }

    fclose(inputFile);
    fclose(outputFile);

    printf("Decompression complete. Original size: %d bytes. Decompressed size: %lu bytes.\n", size, outputSize);
}

int main() {
    char inputFilePath[] = "input.txt";
    char compressedFilePath[] = "compressed.bin";
    char decompressedFilePath[] = "decompressed.txt";

    compress(inputFilePath, compressedFilePath);
    decompress(compressedFilePath, decompressedFilePath);

    return 0;
}

该示例包括哈夫曼树的构建、编码、压缩和解码、解压缩等功能。其中，compress函数将输入文件进行压缩，并将压缩结果写入到输出文件中；decompress函数将压缩文件进行解压缩，并将解压缩结果写入到输出文件中。