CODEWITHSUNDEEP
c++stringserializationstructdeserialization
user3126089
user3126089

Reputation: 83

Serializing struct to file, and deserializing it again with string

I have a following struct :

struct ArchiveTableEntry
        {
            uint32_t id;
            char filename[MAX_FILENAME_LEN + 1];
            uint32_t filename_crc32;
            uint32_t real_data_size;
            uint32_t block_data_size;

            uint32_t data_crc32;
            char data_md5_checksum[16];

            uint64_t data_offset;
            uint8_t flag;
        };

And after serialization of it I have good output to file. Also loading from file work propertly too. I use memcpy to perform serialization/deserialization, and now my question is : How can I replace char filename[MAX_FILENAME_LEN + 1]; by std::string, and keep serialization/deserialization working with save unused bytes that char waste. Thanks!

Upvotes: 1

Views: 4247

Answers (1)

Brandon
Brandon

Reputation: 23510

Try to avoid using memcpy-ing to a pointer for serialization.. Instead, make use of streams.. You can even make a stream class that serializes any type of data. Next you'll just have to add << and >> operators to any class that needs to be serialized.

#include <iostream>
#include <fstream>
#include <string>
#include <cstring>

struct ArchiveTableEntry
{
    uint32_t id;
    std::string filename;
    uint32_t filename_crc32;
    uint32_t real_data_size;
    uint32_t block_data_size;

    uint32_t data_crc32;
    char data_md5_checksum[16];

    uint64_t data_offset;
    uint8_t flag;
};

std::ostream& operator << (std::ostream& os, const ArchiveTableEntry entry)
{
    return os << entry.id << entry.filename.size() << entry.filename
              << entry.filename_crc32 << entry.real_data_size << entry.block_data_size
              << entry.data_crc32 << entry.data_md5_checksum << entry.data_offset << entry.flag;
}

std::istream& operator >> (std::istream& os, ArchiveTableEntry& entry)
{
    std::size_t filesize = 0;
    os >> entry.id;
    os >> filesize;
    entry.filename.resize(filesize);
    os.read(&entry.filename[0], filesize);
    os >> entry.filename_crc32 >> entry.real_data_size >> entry.block_data_size >> entry.data_crc32;
    os >> entry.data_md5_checksum >> entry.data_offset >> entry.flag;
    return os;
}



int main()
{
    const char* md5_checksum = "some checksum";

    ArchiveTableEntry data;
    data.id = 1;
    data.filename = "file.txt";
    data.filename_crc32 = 10434235;
    data.real_data_size = 1024;
    data.block_data_size = 256;
    data.data_crc32 = 324225252;
    data.data_md5_checksum = 1;

    std::memset(data.data_md5_checksum, 0, sizeof(data.data_md5_checksum) / sizeof(char));
    strcpy(data.data_md5_checksum, md5_checksum);

    data.data_offset = 512;
    data.flag = 1;

    std::fstream out("C:/Users/School/Desktop/Test.bin", std::ios::out);
    if (out.is_open())
    {
        out << data;
        out.close();
    }

    std::fstream in("C:/Users/School/Desktop/Test.bin", std::ios::in);
    if (in.is_open())
    {
        in >> data;
        in.close();
    }

    std::cout<<data.id<<" "<<data.filename<<" "<<data.filename_crc32<<" "<<data.real_data_size<<" "<<data.block_data_size<<" ";
    std::cout<<data.data_crc32<<" "<<data.data_md5_checksum<<" ";
}

Upvotes: 3

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