我试图通过boost :: asio发送原始数据，因为boost :: serialization对我的需求来说太慢了。遵循各种示例和增强文档，我有一个客户端：
SimulationClient：
void SimulationClient::sendData(std::vector<WaveformDefinition>waveformPackets) {
socket.async_send_to(boost::asio::buffer(waveformPackets),
receiver_endpoint,
boost::bind(&ClientEnvironmentEngine::sendComplete, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
我尝试下面的坦纳桑斯伯里的解决方案，但无法让它工作。但是，我成功使用：
class WaveformReceiver {
WaveformDefinition *buffer;
WaveformReceiver(){
buffer = new WaveformDefinition[MAX_WAVEFORMS];
startReceive();
}
void startReceive() {
socket_.async_receive_from(boost::asio::null_buffers(), remote_endpoint_,
boost::bind(&WaveformReceiver::handleReceive, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
void handleReceive(const boost::system::error_code& error,
std::size_t size/*bytes_transferred*/)
{
if (!error)
{
int available = socket_.available();
int numWaveforms = available / sizeof(WaveformDefinition_c);
socket_.receive(boost::asio::buffer(buffer, available));
//copy buffer into another buffer so we can re-use the original buffer for the next read
WaveformDefinition_c* tempBuffer = new WaveformDefinition_c[numWaveforms];
std::memcpy ( tempBuffer, buffer, available );
//schedule a thread to handle the array of waveforms that we copied
threadPool.schedule( boost::bind( handleWaveforms, tempBuffer, numWaveforms));
//start listening for more waveforms
startReceive();
}
}
}
坦纳，或其他人，你能否告诉我，我在做什么也应该有用，或者我是否幸运，它目前正在运作？
答案 0 :(得分：3)
问题的基本部分是关于序列化和反序列化集合。
如果不控制服务器和客户端的编译器和体系结构，发送原始结构通常是不安全的，因为字节表示在系统之间可能不同。虽然在这种特定情况下编译器和体系结构是相同的，但#pragma pack(1)是无关紧要的，因为WAVEFORM_DATA_STRUCT没有被写为套接字的原始内存。相反，为收集write操作提供了多个内存缓冲区。
boost::array<boost::asio::mutable_buffer,2> buffer = {{
boost::asio::buffer(&waveformPacket->numWaveforms, ...), // &numWaveforms
boost::asio::buffer(waveformPacket->waveforms) // &waveforms[0]
}};
有许多工具可以帮助您序列化数据结构，例如Protocol Buffers。
下面的代码将演示序列化网络通信数据结构的基础知识。为了简化代码和解释，我选择专注于序列化和反序列化，而不是从套接字写入和读取。位于此部分下方的另一个示例将显示更多原始方法，它采用相同的编译器和体系结构。
从基本foo类型开始：
struct foo
{
char a;
char b;
boost::uint16_t c;
};
可以确定数据可以打包成4个总字节。下面是一个可能的线重新定位：
0 8 16 24 32
|--------+--------+--------+--------|
| a | b | c |
'--------+--------+--------+--------'
确定线表示后，可以使用两个函数将foo对象序列化（保存）到缓冲区，另一个函数可用于从缓冲区反序列化（加载）foo。由于foo.c大于一个字节，因此函数还需要考虑endianness。我选择在Boost.Asio详细命名空间中使用endian字节交换函数来实现某些平台中立性。
/// @brief Serialize foo into a network-byte-order buffer.
void serialize(const foo& foo, unsigned char* buffer)
{
buffer[0] = foo.a;
buffer[1] = foo.b;
// Handle endianness.
using ::boost::asio::detail::socket_ops::host_to_network_short;
boost::uint16_t c = host_to_network_short(foo.c);
std::memcpy(&buffer[2], &c, sizeof c);
}
/// @brief Deserialize foo from a network-byte-order buffer.
void deserialize(foo& foo, const unsigned char* buffer)
{
foo.a = buffer[0];
foo.b = buffer[1];
// Handle endianness.
using ::boost::asio::detail::socket_ops::network_to_host_short;
boost::uint16_t c;
std::memcpy(&c, &buffer[2], sizeof c);
foo.c = network_to_host_short(c);
}
对foo执行序列化和反序列化后，下一步是处理foo个对象的集合。在编写代码之前，需要确定线表示。在这种情况下，我决定使用32位计数字段为foo元素序列添加前缀。
0 8 16 24 32
|--------+--------+--------+--------|
| count of foo elements [n] |
|--------+--------+--------+--------|
| serialized foo [0] |
|--------+--------+--------+--------|
| serialized foo [1] |
|--------+--------+--------+--------|
| ... |
|--------+--------+--------+--------|
| serialized foo [n-1] |
'--------+--------+--------+--------'
再一次，可以引入两个辅助函数来序列化和反序列化foo个对象的集合，并且还需要考虑计数字段的字节顺序。
/// @brief Serialize a collection of foos into a network-byte-order buffer.
template <typename Foos>
std::vector<unsigned char> serialize(const Foos& foos)
{
boost::uint32_t count = foos.size();
// Allocate a buffer large enough to store:
// - Count of foo elements.
// - Each serialized foo object.
std::vector<unsigned char> buffer(
sizeof count + // count
foo_packed_size * count); // serialize foo objects
// Handle endianness for size.
using ::boost::asio::detail::socket_ops::host_to_network_long;
count = host_to_network_long(count);
// Pack size into buffer.
unsigned char* current = &buffer[0];
std::memcpy(current, &count, sizeof count);
current += sizeof count; // Adjust position.
// Pack each foo into the buffer.
BOOST_FOREACH(const foo& foo, foos)
{
serialize(foo, current);
current += foo_packed_size; // Adjust position.
}
return buffer;
};
/// @brief Deserialize a buffer into a collection of foo objects.
std::vector<foo> deserialize(const std::vector<unsigned char>& buffer)
{
const unsigned char* current = &buffer[0];
// Extract the count of elements from the buffer.
boost::uint32_t count;
std::memcpy(&count, current, sizeof count);
current += sizeof count;
// Handle endianness.
using ::boost::asio::detail::socket_ops::network_to_host_long;
count = network_to_host_long(count);
// With the count extracted, create the appropriate sized collection.
std::vector<foo> foos(count);
// Deserialize each foo from the buffer.
BOOST_FOREACH(foo& foo, foos)
{
deserialize(foo, current);
current += foo_packed_size;
}
return foos;
};
以下是完整的示例代码：
#include <iostream>
#include <vector>
#include <boost/asio.hpp>
#include <boost/asio/detail/socket_ops.hpp> // endian functions
#include <boost/cstdint.hpp>
#include <boost/foreach.hpp>
#include <boost/tuple/tuple.hpp> // boost::tie
#include <boost/tuple/tuple_comparison.hpp> // operator== for boost::tuple
/// @brief Mockup type.
struct foo
{
char a;
char b;
boost::uint16_t c;
};
/// @brief Equality check for foo objects.
bool operator==(const foo& lhs, const foo& rhs)
{
return boost::tie(lhs.a, lhs.b, lhs.c) ==
boost::tie(rhs.a, rhs.b, rhs.c);
}
/// @brief Calculated byte packed size for foo.
///
/// @note char + char + uint16 = 1 + 1 + 2 = 4
static const std::size_t foo_packed_size = 4;
/// @brief Serialize foo into a network-byte-order buffer.
///
/// @detail Data is packed as follows:
///
/// 0 8 16 24 32
/// |--------+--------+--------+--------|
/// | a | b | c |
/// '--------+--------+--------+--------'
void serialize(const foo& foo, unsigned char* buffer)
{
buffer[0] = foo.a;
buffer[1] = foo.b;
// Handle endianness.
using ::boost::asio::detail::socket_ops::host_to_network_short;
boost::uint16_t c = host_to_network_short(foo.c);
std::memcpy(&buffer[2], &c, sizeof c);
}
/// @brief Deserialize foo from a network-byte-order buffer.
void deserialize(foo& foo, const unsigned char* buffer)
{
foo.a = buffer[0];
foo.b = buffer[1];
// Handle endianness.
using ::boost::asio::detail::socket_ops::network_to_host_short;
boost::uint16_t c;
std::memcpy(&c, &buffer[2], sizeof c);
foo.c = network_to_host_short(c);
}
/// @brief Serialize a collection of foos into a network-byte-order buffer.
///
/// @detail Data is packed as follows:
///
/// 0 8 16 24 32
/// |--------+--------+--------+--------|
/// | count of foo elements [n] |
/// |--------+--------+--------+--------|
/// | serialized foo [0] |
/// |--------+--------+--------+--------|
/// | serialized foo [1] |
/// |--------+--------+--------+--------|
/// | ... |
/// |--------+--------+--------+--------|
/// | serialized foo [n-1] |
/// '--------+--------+--------+--------'
template <typename Foos>
std::vector<unsigned char> serialize(const Foos& foos)
{
boost::uint32_t count = foos.size();
// Allocate a buffer large enough to store:
// - Count of foo elements.
// - Each serialized foo object.
std::vector<unsigned char> buffer(
sizeof count + // count
foo_packed_size * count); // serialize foo objects
// Handle endianness for size.
using ::boost::asio::detail::socket_ops::host_to_network_long;
count = host_to_network_long(count);
// Pack size into buffer.
unsigned char* current = &buffer[0];
std::memcpy(current, &count, sizeof count);
current += sizeof count; // Adjust position.
// Pack each foo into the buffer.
BOOST_FOREACH(const foo& foo, foos)
{
serialize(foo, current);
current += foo_packed_size; // Adjust position.
}
return buffer;
};
/// @brief Deserialize a buffer into a collection of foo objects.
std::vector<foo> deserialize(const std::vector<unsigned char>& buffer)
{
const unsigned char* current = &buffer[0];
// Extract the count of elements from the buffer.
boost::uint32_t count;
std::memcpy(&count, current, sizeof count);
current += sizeof count;
// Handle endianness.
using ::boost::asio::detail::socket_ops::network_to_host_long;
count = network_to_host_long(count);
// With the count extracted, create the appropriate sized collection.
std::vector<foo> foos(count);
// Deserialize each foo from the buffer.
BOOST_FOREACH(foo& foo, foos)
{
deserialize(foo, current);
current += foo_packed_size;
}
return foos;
};
int main()
{
// Create a collection of foo objects with pre populated data.
std::vector<foo> foos_expected(5);
char a = 'a',
b = 'A';
boost::uint16_t c = 100;
// Populate each element.
BOOST_FOREACH(foo& foo, foos_expected)
{
foo.a = a++;
foo.b = b++;
foo.c = c++;
}
// Serialize the collection into a buffer.
std::vector<unsigned char> buffer = serialize(foos_expected);
// Deserialize the buffer back into a collection.
std::vector<foo> foos_actual = deserialize(buffer);
// Compare the two.
std::cout << (foos_expected == foos_actual) << std::endl; // expect 1
// Negative test.
foos_expected[0].c = 0;
std::cout << (foos_expected == foos_actual) << std::endl; // expect 0
}
这会产生1和0的预期结果。
如果使用相同的编译器和体系结构，则可以将原始缓冲区中的foo个对象的连续序列重新解释为foo个对象的数组，并填充std::vector<foo>与副本构造函数。例如：
// Create and populate a contiguous sequence of foo objects.
std::vector<foo> foo1;
populate(foo1);
// Get a handle to the contiguous memory block.
const char* buffer = reinterpret_cast<const char*>(&foo1[0]);
// Populate a new vector via iterator constructor.
const foo* begin = reinterpret_cast<const foo*>(buffer);
std::vector<foo> foos2(begin, begin + foos1.size());
最后，foo1应该等于foo2。 foo中的foo2个对象将由驻留在foo所拥有的内存中的重新解释的foo1对象进行复制构建。
#include <iostream>
#include <vector>
#include <boost/cstdint.hpp>
#include <boost/foreach.hpp>
#include <boost/tuple/tuple.hpp> // boost::tie
#include <boost/tuple/tuple_comparison.hpp> // operator== for boost::tuple
/// @brief Mockup type.
struct foo
{
char a;
char b;
boost::uint16_t c;
};
/// @brief Equality check for foo objects.
bool operator==(const foo& lhs, const foo& rhs)
{
return boost::tie(lhs.a, lhs.b, lhs.c) ==
boost::tie(rhs.a, rhs.b, rhs.c);
}
int main()
{
// Create a collection of foo objects with pre populated data.
std::vector<foo> foos_expected(5);
char a = 'a',
b = 'A';
boost::uint16_t c = 100;
// Populate each element.
BOOST_FOREACH(foo& foo, foos_expected)
{
foo.a = a++;
foo.b = b++;
foo.c = c++;
}
// Treat the collection as a raw buffer.
const char* buffer =
reinterpret_cast<const char*>(&foos_expected[0]);
// Populate a new vector.
const foo* begin = reinterpret_cast<const foo*>(buffer);
std::vector<foo> foos_actual(begin, begin + foos_expected.size());
// Compare the two.
std::cout << (foos_expected == foos_actual) << std::endl;
// Negative test.
foos_expected[0].c = 0;
std::cout << (foos_expected == foos_actual) << std::endl;
}
与其他方法一样，这会产生1和0的预期结果。
答案 1 :(得分：0)
首先，使用pragma pack(1)是不安全的。包装可能因不同的编译器/拱形而异。此外，您将在协议更改时遇到问题。我建议改用google protobuf。
二。您正在发送std::vector但此向量的实际数据不在结构WAVEFORM_DATA_STRUCT内（向量将其数据保存在堆中）。因此，您将向量及其指向堆的指针发送到另一台计算机，此指针在此处无效。你需要以某种方式序列化你的矢量。
P.S。与boost :: asio无关，这个问题与正确的序列化/反序列化有关。