应用层块设备C++代码,支持压缩

好的，以下是一个简单的应用层块设备模拟代码C的示例，支持压缩。这个示例使用了zlib库来进行数据压缩和解压缩。

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

#define BLOCK_SIZE 512
#define MAX_BLOCKS 1024

typedef struct block_device {
    char data[BLOCK_SIZE];
} block_device_t;

block_device_t device[MAX_BLOCKS];

int read_block(int block_num, char* buffer) {
    if (block_num < 0 || block_num >= MAX_BLOCKS) {
        return -1;
    }
    memcpy(buffer, device[block_num].data, BLOCK_SIZE);
    return 0;
}

int write_block(int block_num, char* buffer) {
    if (block_num < 0 || block_num >= MAX_BLOCKS) {
        return -1;
    }
    memcpy(device[block_num].data, buffer, BLOCK_SIZE);
    return 0;
}

int compress_data(char* data, int data_len, char* buffer, int buffer_size) {
    z_stream strm;
    int ret;

    memset(&strm, 0, sizeof(strm));
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;

    ret = deflateInit(&strm, Z_DEFAULT_COMPRESSION);
    if (ret != Z_OK) {
        return -1;
    }

    strm.avail_in = data_len;
    strm.next_in = (Bytef*)data;
    strm.avail_out = buffer_size;
    strm.next_out = (Bytef*)buffer;

    ret = deflate(&strm, Z_FINISH);
    if (ret != Z_STREAM_END) {
        deflateEnd(&strm);
        return -1;
    }

    ret = deflateEnd(&strm);
    if (ret != Z_OK) {
        return -1;
    }

    return buffer_size - strm.avail_out;
}

int decompress_data(char* data, int data_len, char* buffer, int buffer_size) {
    z_stream strm;
    int ret;

    memset(&strm, 0, sizeof(strm));
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;

    ret = inflateInit(&strm);
    if (ret != Z_OK) {
        return -1;
    }

    strm.avail_in = data_len;
    strm.next_in = (Bytef*)data;
    strm.avail_out = buffer_size;
    strm.next_out = (Bytef*)buffer;

    ret = inflate(&strm, Z_FINISH);
    if (ret != Z_STREAM_END) {
        inflateEnd(&strm);
        return -1;
    }

    ret = inflateEnd(&strm);
    if (ret != Z_OK) {
        return -1;
    }

    return buffer_size - strm.avail_out;
}

int read_compressed_block(int block_num, char* buffer, int buffer_size) {
    char compressed_data[BLOCK_SIZE];
    int compressed_len;
    if (read_block(block_num, compressed_data) < 0) {
        return -1;
    }
    compressed_len = compress_data(compressed_data, BLOCK_SIZE, buffer, buffer_size);
    if (compressed_len < 0 || compressed_len > buffer_size) {
        return -1;
    }
    return compressed_len;
}

int write_compressed_block(int block_num, char* buffer, int buffer_size) {
    char compressed_data[BLOCK_SIZE];
    int compressed_len;
    compressed_len = compress_data(buffer, buffer_size, compressed_data, BLOCK_SIZE);
    if (compressed_len < 0 || compressed_len > BLOCK_SIZE) {
        return -1;
    }
    if (write_block(block_num, compressed_data) < 0) {
        return -1;
    }
    return 0;
}

int main() {
    char buffer[BLOCK_SIZE];
    int block_num = 0;

    // 写入数据
    memset(buffer, 'A', BLOCK_SIZE);
    write_compressed_block(block_num, buffer, BLOCK_SIZE);

    // 读取数据
    memset(buffer, 0, BLOCK_SIZE);
    read_compressed_block(block_num, buffer, BLOCK_SIZE);
    printf("data: %s\n", buffer);

    return 0;
}

这个示例中，我们定义了两个函数`compress_data`和`decompress_data`，用于压缩和解压数据。我们使用zlib库来进行数据压缩和解压缩，这个库是一个广泛使用的开源数据压缩库。

在`read_compressed_block`函数中，我们首先读取模拟设备存储空间中的压缩数据，然后调用`compress_data`函数解压缩得到原始数据。在`write_compressed_block`函数中，我们首先调用`compress_data`函数压缩数据，然后将压缩后的数据写入模拟设备存储空间。

当然，这个示例只是一个简单的模拟，实际的应用层块设备模拟可能会更加复杂。这里只是提供一个思路，供您参考。