Question

我想将redis中的JPEG图像存储为单个键值对。从OpenCV，我从std::vector<unsigned char> jpeg

获得imencode()

现在我使用Hiredis将此向量转换为std::string和SET。问题是jpeg向量包含NUL个字符（ANSII == 0），Hiredis SET函数接收value.c_str()。 .c_str()在第一次出现NUL后截断字符串，因此只有这个子字符串存储在数据库中。

我的问题是：我如何使用Hiredis SET和GET std::vector<unsigned char>（包含NUL）？（最小化运行时间至关重要。）

这是我的代码：

// Create vector of uchars, = From CV [Disregard inefficiency here]

std::vector<unsigned char> jpeg;
jpeg.push_back( 'a' );
jpeg.push_back( 'b' );
jpeg.push_back( (unsigned char) 0 );
jpeg.push_back( 'c' );
jpeg.push_back( 'd' );

// Convert to string

std::string word = "";
for (int i=0; i<jpeg.size(); ++i)
{
    word.push_back(jpeg[i]);
}

std::cout << "word = " << word << std::endl;
std::cout << "word.c_str() = " << word.c_str() << std::endl;

// connect redis

std::string hostname = "127.0.0.1";
int port = 6379;
timeval timeout = { 1, 500000 }; // 1.5 seconds
redisContext* context = redisConnectWithTimeout(hostname.c_str(), port, timeout);

// set redis

std::string key = "jpeg";
redisReply* reply = (redisReply *)redisCommand(context, "SET %s %s", key.c_str(), word.c_str() );
freeReplyObject( (void*) reply);

// get redis

reply = (redisReply *)redisCommand(context, "GET %s", key.c_str() );
std::string value = reply->str;
freeReplyObject((void*) reply);
std::cout << "returned value = " << value << std::endl;

// Convert back to vector of uchars (this should be the same as the original jpeg)  [Disregard inefficiency here]

std::vector<unsigned char> jpeg_returned;
for (int i=0; i<value.size(); ++i)
{
    jpeg_returned.push_back(value[i]);
    // std::cout << "value[i] = " << value[i] << std::endl;
}

Answer 1

在显示代码之前，我想再次警告，在没有正确序列化的情况下存储二进制数据可能会有问题。至少要确保所有服务器具有相同的字节顺序并且具有相同的sizeof（int）。

std::vector<char> v{'A', 'B', '\0', 'C', 'D'};

std::string key = "jpeg";
redisReply* reply = static_cast<redisReply *>( redisCommand(context, "SET %s %b", key.c_str(), v.data(), v.size() ) );
freeReplyObject( reply );

从python阅读。

>>> import redis
>>> r = redis.StrictRedis(host='localhost', port=6379, db=0)
>>> r.get("jpeg")
'AB\x00CD'

在Redis中存储字符矢量 - 包含NUL

1 个答案: