我试了几个小时，这个问题几乎让我发疯。
我想在共享内存上创建spsc_queue，队列中的每个元素都是mq_item_t结构。
typedef struct _mq_item_t{
mq_item_type type;
union
{
struct{
log_level_t level;
char * text;
} log;
struct{
char * control;
size_t control_size;
char * payload;
size_t payload_size;
} error;
struct{
char * channel;
char * control;
size_t control_size;
char * payload;
size_t payload_size;
} data;
};
} mq_item_t;
然后我有以下代码来创建spsc_queue。
typedef boost::interprocess::managed_windows_shared_memory native_managed_shared_memory;
typedef boost::interprocess::allocator<mq_item_t, native_managed_shared_memory::segment_manager> shmem_allocator;
typedef boost::lockfree::spsc_queue< mq_item_t, boost::lockfree::allocator<shmem_allocator>> lockfree_queue;
m_segment = new native_managed_shared_memory(create_only, mem_name, SHARED_MEMORY_BYTES, NULL, perm);
shmem_allocator alloc(m_segment->get_segment_manager());
m_segment->find_or_construct<lockfree_queue>("name of the queue")(65535, alloc);
它会导致编译错误。请问我在这里做错了什么？
boost/lockfree/spsc_queue.hpp(609): error C2664: 'boost::lockfree::detail::ringbuffer_base<T>::pop' : cannot convert parameter 3 from 'boost::interprocess::offset_ptr<PointedType,DifferenceType,OffsetType,OffsetAlignment>' to 'mq_item_t *'
1> with
1> [
1> T=mq_item_t
1> ]
1> and
1> [
1> PointedType=mq_item_t,
1> DifferenceType=ptrdiff_t,
1> OffsetType=size_t,
1> OffsetAlignment=0x00
1> ]
1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1> boost/lockfree/spsc_queue.hpp(608) : while compiling class template member function 'boost::lockfree::detail::runtime_sized_ringbuffer<T,Alloc>::size_type boost::lockfree::detail::runtime_sized_ringbuffer<T,Alloc>::pop(T *,boost::lockfree::detail::runtime_sized_ringbuffer<T,Alloc>::size_type)'
1> with
1> [
1> T=mq_item_t,
1> Alloc=boost::interprocess::allocator<mq_item_t,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>
1> ]
1> boost/lockfree/spsc_queue.hpp(681) : see reference to class template instantiation 'boost::lockfree::detail::runtime_sized_ringbuffer<T,Alloc>' being compiled
1> with
1> [
1> T=mq_item_t,
1> Alloc=boost::interprocess::allocator<mq_item_t,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>>
1> ]
1> boost/interprocess/detail/named_proxy.hpp(213) : see reference to class template instantiation 'boost::lockfree::spsc_queue<T,A0>' being compiled
1> with
1> [
1> T=mq_item_t,
1> A0=boost::lockfree::allocator<shmem_allocator>
1> ]
1> boost/interprocess/detail/named_proxy.hpp(213) : while compiling class template member function 'void boost::interprocess::ipcdetail::CtorArg2<T,P0,P1>::construct_n(void *,size_t,size_t &)'
1> with
1> [
1> T=lockfree_queue,
1> P0=int,
1> P1=boost::interprocess::allocator<mq_item_t,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>> &
1> ]
1> boost/interprocess/detail/named_proxy.hpp(282) : see reference to class template instantiation 'boost::interprocess::ipcdetail::CtorArg2<T,P0,P1>' being compiled
1> with
1> [
1> T=lockfree_queue,
1> P0=int,
1> P1=boost::interprocess::allocator<mq_item_t,boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>> &
1> ]
1> ..\common\sink.cpp(26) : see reference to function template instantiation 'T *boost::interprocess::ipcdetail::named_proxy<SegmentManager,T,is_iterator>::operator ()<int,shmem_allocator&>(P0 &&,P1) const' being compiled
1> with
1> [
1> T=lockfree_queue,
1> SegmentManager=boost::interprocess::segment_manager<char,boost::interprocess::rbtree_best_fit<boost::interprocess::mutex_family>,boost::interprocess::iset_index>,
1> is_iterator=false,
1> P0=int,
1> P1=shmem_allocator &
1> ]
答案 0 :(得分：4)
我之前已经展示了如何执行此操作：Shared-memory IPC synchronization (lock-free)
目前我似乎无法使lockfree::allocator<>版本正常工作（因为spsc_queue似乎无法使用非原始指针（offset_ptr<>）参与）。
奇怪的是，我无法使用旧的升级版本，所以现在我想知道这是否有效。但这并不是真的相关：
然而，还有一些更大的问题需要解决：
因为共享内存区域是固定大小，所以静态限制spsc_queue容量似乎也是有意义的。为此，请使用boost::lockfree::capacity<65535>代替boost::lockfree::allocator<>。这 does compile ，但
你的mq_item_t充斥着原始指针。这将无法工作，因为指针在另一个进程空间中无效。我建议像：
typedef boost::interprocess::allocator<char, msm_t::segment_manager> char_alloc;
typedef boost::interprocess::basic_string<char, std::char_traits<char>, char_alloc> shmem_string;
typedef boost::interprocess::vector<char, char_alloc> shmem_blob;
struct log {
typedef char_alloc allocator_type;
log(char_alloc alloc);
log(log_level_t level, const char* txt, char_alloc alloc);
log_level_t level;
shmem_string text;
};
struct error {
typedef char_alloc allocator_type;
error(char_alloc alloc);
template <typename Ctl, typename Payload>
error(Ctl const& ctl, Payload const& pl, char_alloc alloc);
shmem_blob control, payload;
};
struct data {
typedef char_alloc allocator_type;
data(char_alloc alloc);
template <typename Ctl, typename Payload>
data(char const* channel, Ctl const& ctl, Payload const& pl, char_alloc alloc);
shmem_string channel;
shmem_blob control, payload;
};
typedef boost::variant<log, error, data> item_t;
现场观看完整演示：
<强> Live On Coliru
#include <boost/lockfree/spsc_queue.hpp>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/managed_mapped_file.hpp>
#include <boost/interprocess/containers/string.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <boost/variant.hpp>
#include <boost/range.hpp>
#include <string>
#include <iostream>
namespace bip = boost::interprocess;
using boost::lockfree::spsc_queue;
#ifdef COLIRU
typedef bip::managed_mapped_file msm_t;
#else
typedef bip::managed_shared_memory msm_t;
#endif
namespace mq {
enum log_level_t { default_level };
typedef boost::interprocess::allocator<char, msm_t::segment_manager> char_alloc;
typedef boost::interprocess::basic_string<char, std::char_traits<char>, char_alloc> shmem_string;
typedef boost::interprocess::vector<char, char_alloc> shmem_blob;
using boost::begin;
using boost::end;
struct log {
typedef char_alloc allocator_type;
log(char_alloc alloc) : text(alloc) {}
log(log_level_t level, const char* txt, char_alloc alloc) : level(level), text(txt, alloc) { };
log_level_t level;
shmem_string text;
};
struct error {
typedef char_alloc allocator_type;
error(char_alloc alloc) : control(alloc), payload(alloc) {}
template <typename Ctl, typename Payload>
error(Ctl const& ctl, Payload const& pl, char_alloc alloc)
: control(begin(ctl), end(ctl), alloc),
payload(begin(pl), end(pl), alloc)
{ }
shmem_blob control, payload;
};
struct data {
typedef char_alloc allocator_type;
data(char_alloc alloc) : channel(alloc), control(alloc), payload(alloc) {}
template <typename Ctl, typename Payload>
data(char const* channel, Ctl const& ctl, Payload const& pl, char_alloc alloc)
: channel(channel, alloc),
control(begin(ctl), end(ctl), alloc),
payload(begin(pl), end(pl), alloc)
{ }
shmem_string channel;
shmem_blob control, payload;
};
typedef boost::variant<log, error, data> item_t;
}
namespace {
static char const* mem_name = "21845989-f5e0-4c84-b170-cd34dc9f37fc";
static constexpr size_t SHARED_MEMORY_BYTES = 10ul << 10;
}
int main()
{
typedef boost::interprocess::allocator<mq::item_t, msm_t::segment_manager> shmem_allocator;
#ifdef COLIRU
typedef boost::lockfree::spsc_queue<mq::item_t, boost::lockfree::capacity<10> > lockfree_queue;
#else
typedef boost::lockfree::spsc_queue<mq::item_t, boost::lockfree::capacity<65535> > lockfree_queue;
#endif
msm_t m_segment(bip::create_only, mem_name, SHARED_MEMORY_BYTES);
shmem_allocator alloc(m_segment.get_segment_manager());
auto queue = m_segment.find_or_construct<lockfree_queue>("name of the queue")();
queue->push(mq::error("control", "payload", alloc));
queue->push(mq::data("channel", "control", "payload", alloc));
queue->push(mq::log(mq::default_level, "text", alloc));
}