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c++读取时同步共享内存

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我想同步一个 shared_memory_object 来读取 iff shared_memory_object 已经存在。这是我用于与 bool 变量同步的代码。

boost::interprocess::shared_memory_object my_shared_mat;
bool mat_ready = true;
while (mat_ready)
{
try {
my_shared_mat = boost::interprocess::shared_memory_object(
boost::interprocess::open_only, // only open
"shared_mat", // name
boost::interprocess::read_only); // read-only mode
mat_ready = false;
}
catch (boost::interprocess::interprocess_exception &ex) {
std::cout << ex.what() << std::endl;
mat_ready = true;
}
}

boost::interprocess::mapped_region region(my_shared_mat, boost::interprocess::read_only);

如果共享内存存在,我没有任何问题,数据在进程之间共享,但如果共享内存不存在,程序会在 mapped_region 调用时崩溃。

最佳答案

如果你想与另一个进程同步,使用同步原语:condition variablemutex :

#include <boost/interprocess/shared_memory_object.hpp>
#include <boost/interprocess/mapped_region.hpp>
#include <boost/interprocess/sync/named_mutex.hpp>
#include <boost/interprocess/sync/scoped_lock.hpp>
#include <boost/interprocess/sync/named_condition.hpp>
#include <iostream>

namespace bip = boost::interprocess;
using Mutex = bip::named_mutex;
using Condition = bip::named_condition;

int main(int argc, char**) {
Mutex mx(bip::open_or_create, "shared_mat_mx");
Condition cv(bip::open_or_create, "shared_mat_cv");

if (argc>1) { // server
auto mat = bip::shared_memory_object(bip::create_only, "shared_mat", bip::read_write);
mat.truncate(10 << 10); // 10kb

bip::mapped_region region(mat, bip::read_only);

{
bip::scoped_lock<Mutex> lk(mx);
cv.notify_all(); // notify all clients we're there
}
} else {
{
bip::scoped_lock<Mutex> lk(mx);
cv.wait(lk); // wait for server signal
}
auto mat = bip::shared_memory_object(bip::open_only, "shared_mat", bip::read_only);
bip::mapped_region region(mat, bip::read_only);

std::cout << "Mapped the region of size " << region.get_size() << "\n";
}
}

在后台运行多个客户端:

for a in {1..10}; do ./sotest& done

让他们都等待。启动服务器:

./sotest server

让他们都进步,他们表现出:

Mapped the region of size 10240

关于c++读取时同步共享内存,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49808659/

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