写一段用huffman实现文件压缩和解压缩的代码

好的，下面是一个使用 Huffman 编码实现文件压缩和解压缩的示例代码：

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

#define MAX_TREE_HT 100
#define MAX_CHAR 256

// Huffman树节点结构体
struct MinHeapNode {
    char data;
    unsigned freq;
    struct MinHeapNode *left, *right;
};

// Huffman编码表结构体
struct HuffmanCode {
    char c;
    char *code;
};

// Huffman编码表
struct HuffmanCode huffmanCodes[MAX_CHAR];

// Huffman树节点最小堆结构体
struct MinHeap {
    unsigned size;
    unsigned capacity;
    struct MinHeapNode **array;
};

// 创建一个新的Huffman树节点
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;
}

// 创建一个空的最小堆
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;
}

// 交换两个Huffman树节点
void swapMinHeapNode(struct MinHeapNode **a, struct MinHeapNode **b) {
    struct MinHeapNode *t = *a;
    *a = *b;
    *b = t;
}

// 最小堆的堆化操作
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);
    }
}

// 判断最小堆是否只有一个节点
int isSizeOne(struct MinHeap *minHeap) {
    return (minHeap->size == 1);
}

// 从最小堆中取出频率最小的节点
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;
}

// 插入一个新的Huffman树节点到最小堆中
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;
}

// 构建Huffman树
struct MinHeapNode *buildHuffmanTree(char data[], int freq[], int size) {
    struct MinHeapNode *left, *right, *top;
    struct MinHeap *minHeap = createMinHeap(size);

    for (int i = 0; i < size; ++i) {
        insertMinHeap(minHeap, newNode(data[i], freq[i]));
    }

    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);
}

// 将Huffman编码表写入文件
void writeHuffmanCodesToFile(FILE *fp, struct MinHeapNode *root, char *code, int index) {
    if (root == NULL) {
        return;
    }

    if (root->data != '$') {
        huffmanCodes[root->data].c = root->data;
        huffmanCodes[root->data].code = (char *) malloc((index + 1) * sizeof(char));
        strcpy(huffmanCodes[root->data].code, code);
        fprintf(fp, "%c%s\n", root->data, code);
    }

    writeHuffmanCodesToFile(fp, root->left, strcat(code, "0"), index + 1);
    code[index] = '\0';
    writeHuffmanCodesToFile(fp, root->right, strcat(code, "1"), index + 1);
    code[index] = '\0';
}

// 从文件中读取Huffman编码表
void readHuffmanCodesFromFile(FILE *fp) {
    char line[MAX_TREE_HT];
    while (fgets(line, MAX_TREE_HT, fp)) {
        char c = line[0];
        char *code = strtok(line + 1, "\n");
        huffmanCodes[c].c = c;
        huffmanCodes[c].code = (char *) malloc((strlen(code) + 1) * sizeof(char));
        strcpy(huffmanCodes[c].code, code);
    }
}

// 压缩文件
void compressFile(char *sourceFile, char *destinationFile) {
    FILE *source = fopen(sourceFile, "rb");
    if (!source) {
        printf("Error: Failed to open source file.\n");
        return;
    }

    fseek(source, 0, SEEK_END);
    unsigned long sourceSize = ftell(source);
    fseek(source, 0, SEEK_SET);

    char *sourceData = (char *) malloc(sourceSize * sizeof(char));
    fread(sourceData, sizeof(char), sourceSize, source);

    int freq[MAX_CHAR] = {0};
    for (unsigned long i = 0; i < sourceSize; ++i) {
        ++freq[sourceData[i]];
    }

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

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

    FILE *dest = fopen(destinationFile, "wb");
    if (!dest) {
        printf("Error: Failed to create destination file.\n");
        return;
    }

    char code[MAX_TREE_HT] = "";
    writeHuffmanCodesToFile(dest, root, code, 0);

    int bitIndex = 0;
    unsigned char currentByte = 0;
    for (unsigned long i = 0; i < sourceSize; ++i) {
        char c = sourceData[i];
        char *huffmanCode = huffmanCodes[c].code;
        int len = strlen(huffmanCode);
        for (int j = 0; j < len; ++j) {
            if (huffmanCode[j] == '1') {
                currentByte |= (1 << (7 - bitIndex));
            }

            if (++bitIndex == 8) {
                fwrite(&currentByte, sizeof(unsigned char), 1, dest);
                bitIndex = 0;
                currentByte = 0;
            }
            else if (i == sourceSize - 1 && j == len - 1) {
                fwrite(&currentByte, sizeof(unsigned char), 1, dest);
            }
        }
    }

    fclose(source);
    fclose(dest);

    printf("File compressed successfully.\n");
}

// 解压文件
void decompressFile(char *sourceFile, char *destinationFile) {
    FILE *source = fopen(sourceFile, "rb");
    if (!source) {
        printf("Error: Failed to open source file.\n");
        return;
    }

    fseek(source, 0, SEEK_END);
    unsigned long sourceSize = ftell(source);
    fseek(source, 0, SEEK_SET);

    char *sourceData = (char *) malloc(sourceSize * sizeof(char));
    fread(sourceData, sizeof(char), sourceSize, source);

    int freq[MAX_CHAR] = {0};
    int pos = 0;
    while (sourceData[pos] != '\n') {
        char c = sourceData[pos++];
        char *code = strtok(sourceData + pos, "\n");
        huffmanCodes[c].c = c;
        huffmanCodes[c].code = (char *) malloc((strlen(code) + 1) * sizeof(char));
        strcpy(huffmanCodes[c].code, code);
        pos += strlen(code) + 1;
    }

    FILE *dest = fopen(destinationFile, "wb");
    if (!dest) {
        printf("Error: Failed to create destination file.\n");
        return;
    }

    struct MinHeapNode *root = buildHuffmanTree(NULL, freq, 0);

    int bitIndex = 0;
    unsigned char currentByte = 0;
    for (unsigned long i = pos; i < sourceSize; ++i) {
        unsigned char byte = sourceData[i];
        for (int j = 7; j >= 0; --j) {
            if (byte & (1 << j)) {
                root = root->right;
            }
            else {
                root = root->left;
            }

            if (root->left == NULL && root->right == NULL) {
                fwrite(&root->data, sizeof(char), 1, dest);
                root = buildHuffmanTree(NULL, freq, 0);
            }
        }
    }

    fclose(source);
    fclose(dest);

    printf("File decompressed successfully.\n");
}

int main() {
    compressFile("source.txt", "compressed.bin");
    decompressFile("compressed.bin", "decompressed.txt");
    return 0;
}

上述代码中，使用了一个最小堆来构建 Huffman 树，并生成 Huffman 编码表。压缩文件时，先将文件数据读入内存，统计每个字符出现的频率，然后构建 Huffman 树并生成 Huffman 编码表，最后将编码后的数据写入到压缩文件中。解压文件时，从压缩文件中读取 Huffman 编码表和编码后的数据，然后根据 Huffman 编码表进行解码，将解码后的数据写入到解压文件中。

需要注意的是，在压缩文件时，因为是按位写入数据，所以需要特别注意写入最后一个字节时的边界问题。

希望能够帮助到您！