C++ BOOST:：CRC使用process.block（）方法创建校验和

我目前正在尝试创建自定义结构UMGR_s长度的校验和。我确实使用了BOOST:：crc方法process.block（）和我的结构的开始和结束地址

问题是，每次运行此方法时，即使结构中的数据保持一致，我也会得到不同的校验和。我不确定我在这里做错了什么

int checksum_manager::createCRC(UMGR_s *CRCdata)
{
    boost::crc_32_type result;

    result.process_block(CRCdata, CRCdata + 1);

    return result.checksum();
};

---

回顾你以前的问题：

#include <string>
#include <type_traits>

struct UMGR_s {
    std::string name;
    std::string description;
    std::string dlt_id;
    std::string log_mode;
    std::string log_level;
    std::string log_dir_path;
    uint ipc_port;
    uint reconnection_retry_offset;
    uint msg_buf_size;
    int checksum;
};

static_assert(std::is_standard_layout<UMGR_s>{});
static_assert(not std::is_trivial<UMGR_s>{});
static_assert(not std::is_pod<UMGR_s>{});

查看它

该示例始终返回

0xbf21e978

，并且没有警告或valgrind/ASAN警告

更好的是，让它更不容易出错：

struct CRC {
    boost::crc_32_type crc;
    void operator()(std::string_view s) {
        crc.process_bytes(s.data(), s.size());
    }
    template <typename T, typename = std::enable_if_t<std::is_integral_v<T>>>
    void operator()(T const& i) {
        static_assert(std::is_trivial_v<T>);
        static_assert(not std::is_class_v<T>);
        crc.process_bytes(&i, sizeof(i));
    }

    auto get() { return crc.checksum(); }
};

现场演示

#include <string>
#include <iostream>
#include <type_traits>
#include <boost/crc.hpp>

struct CRC {
    boost::crc_32_type crc;
    void operator()(std::string_view s) {
        crc.process_bytes(s.data(), s.size());
    }
    template <typename T, typename = std::enable_if_t<std::is_integral_v<T>>>
    void operator()(T const& i) {
        static_assert(std::is_trivial_v<T>);
        static_assert(not std::is_class_v<T>);
        crc.process_bytes(&i, sizeof(i));
    }

    auto get() { return crc.checksum(); }
};

struct UMGR_s {
    std::string name;
    std::string description;
    std::string dlt_id;
    std::string log_mode;
    std::string log_level;
    std::string log_dir_path;
    uint ipc_port;
    uint reconnection_retry_offset;
    uint msg_buf_size;
    int checksum;

    int calcCRC() {
        CRC crc;
        crc(name);
        crc(description);
        crc(dlt_id);
        crc(log_mode);
        crc(log_level);
        crc(log_dir_path);
        crc(ipc_port);
        crc(reconnection_retry_offset);
        crc(msg_buf_size);

        return crc.get();
    }
};

static_assert(std::is_standard_layout<UMGR_s>{});
static_assert(not std::is_trivial<UMGR_s>{});
//static_assert(not std::is_pod<UMGR_s>{});

int main() {
    UMGR_s data {
         "UMGR",
         "UpdateManager",
         "1234",
         "kConsole",
         "kVerbose",
         "",
         33,
         0,
         1000,
         0,
    };

    data.checksum = data.calcCRC();

    std::cout << "crc: " << std::hex << std::showbase << data.checksum << "\n";
}

---

我发现问题在于结构及其附带的填充。填充用于对齐，看起来是随机的。

int calcCRC() {
    CRC crc;
    crc(name);
    crc(description);
    crc(dlt_id);
    crc(log_mode);
    crc(log_level);
    crc(log_dir_path);
    crc(ipc_port);
    crc(reconnection_retry_offset);
    crc(msg_buf_size);

    return crc.get();
}

#include <string>
#include <iostream>
#include <type_traits>
#include <boost/crc.hpp>

struct CRC {
    boost::crc_32_type crc;
    void operator()(std::string_view s) {
        crc.process_bytes(s.data(), s.size());
    }
    template <typename T, typename = std::enable_if_t<std::is_integral_v<T>>>
    void operator()(T const& i) {
        static_assert(std::is_trivial_v<T>);
        static_assert(not std::is_class_v<T>);
        crc.process_bytes(&i, sizeof(i));
    }

    auto get() { return crc.checksum(); }
};

struct UMGR_s {
    std::string name;
    std::string description;
    std::string dlt_id;
    std::string log_mode;
    std::string log_level;
    std::string log_dir_path;
    uint ipc_port;
    uint reconnection_retry_offset;
    uint msg_buf_size;
    int checksum;

    int calcCRC() {
        CRC crc;
        crc(name);
        crc(description);
        crc(dlt_id);
        crc(log_mode);
        crc(log_level);
        crc(log_dir_path);
        crc(ipc_port);
        crc(reconnection_retry_offset);
        crc(msg_buf_size);

        return crc.get();
    }
};

static_assert(std::is_standard_layout<UMGR_s>{});
static_assert(not std::is_trivial<UMGR_s>{});
//static_assert(not std::is_pod<UMGR_s>{});

int main() {
    UMGR_s data {
         "UMGR",
         "UpdateManager",
         "1234",
         "kConsole",
         "kVerbose",
         "",
         33,
         0,
         1000,
         0,
    };

    data.checksum = data.calcCRC();

    std::cout << "crc: " << std::hex << std::showbase << data.checksum << "\n";
}

crc: 0xbf21e978