fix bugs

src/circ_queue.h

@@ -2,18 +2,21 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
 #include <atomic>
 #include <utility>
 #include <limits>
 #include <algorithm>
+#include <thread>
 
 namespace ipc {
 
 struct circ_queue_head {
     using u8_t = std::atomic<std::uint8_t>;
+    using ms_t = std::atomic<std::size_t>; // message head
 
-    u8_t cc_; // connection count
-    u8_t wt_; // write-index
+    u8_t cc_ { 0 }; // connection count
+    u8_t cr_ { 0 }; // write cursor
 };
 
 template <std::size_t Size>
@@ -24,14 +27,18 @@ public:
         head_size  = sizeof(circ_queue_head),
         block_size = Size - head_size,
         elem_max   = std::numeric_limits<std::uint8_t>::max(),
-        elem_size  = Size / (elem_max + 1)
+        elem_size  = (Size / (elem_max + 1)),
+        msg_size   = elem_size - sizeof(ms_t)
     };
 
-    static_assert(Size > head_size      , "Size must > head_size");
-    static_assert(elem_size >= head_size, "elem_size must >= head_size");
-    static_assert(Size % elem_size == 0 , "Size must be multiple of elem_size");
+    static_assert(Size > head_size        , "Size must > head_size");
+    static_assert(elem_size >= head_size  , "elem_size must >= head_size");
+    static_assert(elem_size > sizeof(ms_t), "elem_size must > sizeof(ms_t)");
+    static_assert(Size % elem_size == 0   , "Size must be multiple of elem_size");
 
-    circ_queue(void) = default;
+    circ_queue(void) {
+        ::memset(block_, 0, sizeof(block_));
+    }
     ~circ_queue(void) = delete;
 
     circ_queue(const circ_queue&) = delete;
@@ -47,30 +54,49 @@ public:
         return cc_.fetch_sub(1, std::memory_order_acq_rel);
     }
 
+    std::size_t conn_count(void) const {
+        return cc_.load(std::memory_order_acquire);
+    }
+
     void* acquire(void) {
-        return begin() + wt_.load(std::memory_order_relaxed);
+        auto st = begin() + id(cr_.load(std::memory_order_relaxed));
+        do {
+            // check remain count of consumers
+            if (st->head_.load(std::memory_order_acquire)) {
+                std::this_thread::yield();
+            }
+            else {
+                st->head_.store(conn_count());
+                break;
+            }
+        } while(1);
+        return st->msg_;
     }
 
     void commit(void) {
-        wt_.fetch_add(1, std::memory_order_release);
+        cr_.fetch_add(1, std::memory_order_release);
     }
 
     std::uint8_t cursor(void) const {
-        return wt_.load(std::memory_order_acquire);
+        return cr_.load(std::memory_order_acquire);
     }
 
-    void const * get(std::uint8_t index) const {
-        return begin() + index;
+    void* get(std::uint8_t index) {
+        auto st = begin() + id(index);
+        st->head_.fetch_sub(1, std::memory_order_release);
+        return st->msg_;
     }
 
 private:
-    using elem_t = std::uint8_t[elem_size];
-    elem_t const * begin(void) const {
-        return reinterpret_cast<elem_t const *>(
-               reinterpret_cast<std::uint8_t const *>(this) + elem_size);
+    struct elem_t {
+        ms_t head_;
+        std::uint8_t msg_[msg_size];
+    };
+    elem_t* begin(void) {
+        return reinterpret_cast<elem_t*>(this);
     }
-    elem_t * begin(void) {
-        return const_cast<elem_t *>(static_cast<circ_queue const *>(this)->begin());
+    static std::uint8_t id(std::uint8_t i) {
+        return (i += 1) ? i : 1;
     }
     std::uint8_t block_[block_size];
 };

test/test_circ_queue.cpp

@@ -1,15 +1,13 @@
-#include <thread>
 #include <iostream>
 #include <string>
 #include <type_traits>
+#include <memory>
 
 #include "circ_queue.h"
 #include "test.h"
 
 namespace {
 
-using namespace std::string_literals;
-
 class Unit : public TestSuite {
     Q_OBJECT
 
@@ -34,42 +32,46 @@ void Unit::test_inst(void) {
 }
 
 void Unit::test_producer(void) {
+    cq__ = new cq_t;
     std::thread consumers[3];
-    std::atomic_int flag(0);
 
     for (auto& c : consumers) {
-        c = std::thread{[&c, &flag] {
+        c = std::thread{[&c] {
             auto cur = cq__->cursor();
-            std::cout << &c << ": cur = " << (int)cur << std::endl;
-            flag.fetch_add(1, std::memory_order_release);
+            std::cout << "start consumer " << &c << ": cur = " << (int)cur << std::endl;
+
+            cq__->connect();
+            auto disconn = [](cq_t* cq) { cq->disconnect(); };
+            std::unique_ptr<cq_t, decltype(disconn)> guard(cq__, disconn);
+
+            int i = 0;
             do {
                 while (cur != cq__->cursor()) {
-                    auto data = static_cast<const char*>(cq__->get(cur));
-                    std::cout << &c << ": " << data << std::endl;
-                    if (data == "quit"s) {
+                    int d = *static_cast<const int*>(cq__->get(cur));
+//                    std::cout << &c << ": cur = " << (int)cur << ", " << d << std::endl;
+                    if (d < 0) {
                         return;
                     }
-                    else QCOMPARE(data, std::to_string(cur).c_str());
+                    else QCOMPARE(d, i);
                     ++cur;
+                    ++i;
                 }
-                std::this_thread::yield();
             } while(1);
         }};
     }
 
-    while (flag.load(std::memory_order_acquire) != std::extent<decltype(consumers)>::value) {
+    while (cq__->conn_count() != std::extent<decltype(consumers)>::value) {
         std::this_thread::yield();
     }
-
-    for (int i = 0; i < 10; ++i) {
-        auto str = static_cast<char*>(cq__->acquire());
-        strcpy(str, std::to_string(i).c_str());
-        std::cout << "put: " << str << std::endl;
+    std::cout << "start producer..." << std::endl;
+    for (int i = 0; i < 1000; ++i) {
+        auto d = static_cast<int*>(cq__->acquire());
+        *d = i;
         cq__->commit();
     }
-    auto str = static_cast<char*>(cq__->acquire());
-    strcpy(str, "quit");
-    std::cout << "put: " << str << std::endl;
+    auto d = static_cast<int*>(cq__->acquire());
+    *d = -1;
+    std::cout << "put: quit..." << std::endl;
     cq__->commit();
 
     for (auto& c : consumers) {