Add comments and refine the implementation.

Author: mutouyun

include/libpmr/new.h

@@ -14,75 +14,75 @@
 #include "libimp/uninitialized.h"
 #include "libimp/byte.h"
 #include "libimp/detect_plat.h"
+#include "libimp/export.h"
 
 #include "libpmr/def.h"
 #include "libpmr/block_pool.h"
 #include "libpmr/memory_resource.h"
 
 LIBPMR_NAMESPACE_BEG_
 
+/// \brief Select the incremental level based on the size.
 constexpr inline std::size_t regular_level(std::size_t s) noexcept {
   return (s <= 128  ) ? 0 :
          (s <= 1024 ) ? 1 :
          (s <= 8192 ) ? 2 :
          (s <= 65536) ? 3 : 4;
 }
 
+/// \brief Calculates the appropriate memory block size based on the increment level and size.
 constexpr inline std::size_t regular_sizeof_impl(std::size_t l, std::size_t s) noexcept {
   return (l == 0) ? std::max<std::size_t>(::LIBIMP::round_up<std::size_t>(s, 8), regular_head_size) :
          (l == 1) ? ::LIBIMP::round_up<std::size_t>(s, 128 ) :
          (l == 2) ? ::LIBIMP::round_up<std::size_t>(s, 1024) :
          (l == 3) ? ::LIBIMP::round_up<std::size_t>(s, 8192) : (std::numeric_limits<std::size_t>::max)();
 }
 
+/// \brief Calculates the appropriate memory block size based on the size.
 constexpr inline std::size_t regular_sizeof(std::size_t s) noexcept {
   return regular_sizeof_impl(regular_level(s), s);
 }
 
+/// \brief Calculates the appropriate memory block size based on the specific type.
 template <typename T>
 constexpr inline std::size_t regular_sizeof() noexcept {
   return regular_sizeof(regular_head_size + sizeof(T));
 }
 
-class block_pool_like {
+/// \brief Defines the memory block collector interface.
+class LIBIMP_EXPORT block_collector {
  public:
-  virtual ~block_pool_like() noexcept = default;
-  virtual void *allocate() noexcept = 0;
+  virtual ~block_collector() noexcept = default;
   virtual void deallocate(void *p) noexcept = 0;
 };
 
-inline std::unordered_map<std::size_t, block_pool_like *> &get_block_pool_map() noexcept {
-  thread_local std::unordered_map<std::size_t, block_pool_like *> instances;
-  return instances;
-}
+/// \brief Gets all block pools of the thread cache.
+LIBIMP_EXPORT auto get_thread_block_pool_map() noexcept
+  -> std::unordered_map<std::size_t, block_collector *> &;
 
+/// \brief Defines block pool memory resource based on block pool.
 template <std::size_t BlockSize, std::size_t BlockPoolExpansion>
 class block_pool_resource;
 
+/// \brief Memory block collector of unknown size.
+/// \note This memory resource is only used to temporarily collect memory blocks 
+///       that cannot find a suitable block pool memory resource.
 template <>
 class block_pool_resource<0, 0> : public block_pool<0, 0>
-                                , public block_pool_like {
-
-  void *allocate() noexcept override {
-    return nullptr;
-  }
-
+                                , public block_collector {
 public:
   void deallocate(void *p) noexcept override {
     block_pool<0, 0>::deallocate(p);
   }
 };
 
+/// \brief A block pool memory resource for a block of memory of a specific size.
 template <std::size_t BlockSize, std::size_t BlockPoolExpansion>
 class block_pool_resource : public block_pool<BlockSize, BlockPoolExpansion>
-                          , public block_pool_like {
+                          , public block_collector {
 
   using base_t = block_pool<BlockSize, BlockPoolExpansion>;
 
-  void *allocate() noexcept override {
-    return base_t::allocate();
-  }
-
   void deallocate(void *p) noexcept override {
     base_t::deallocate(p);
   }
@@ -105,7 +105,9 @@ class block_pool_resource : public block_pool<BlockSize, BlockPoolExpansion>
       base_t::deallocate(p);
       return;
     }
-    auto &map = get_block_pool_map();
+    // When the actual size exceeds the current memory block size, 
+    // try to find a suitable pool among all memory block pools for this thread.
+    auto &map = get_thread_block_pool_map();
     auto it = map.find(r_size);
     if ((it == map.end()) || (it->second == nullptr)) {
       block_pool_resource<0, 0> *bp = nullptr;
@@ -128,62 +130,70 @@ class block_pool_resource : public block_pool<BlockSize, BlockPoolExpansion>
 template <std::size_t BlockSize, std::size_t BlockPoolExpansion>
 auto block_pool_resource<BlockSize, BlockPoolExpansion>::get() noexcept
   -> block_pool_resource<BlockSize, BlockPoolExpansion> * {
-  auto &map = get_block_pool_map();
   thread_local block_pool_resource *pi = nullptr;
   if (pi != nullptr) {
     return pi;
   }
+  // Create a new block pool resource for this thread.
+  auto &map = get_thread_block_pool_map();
   auto it = map.find(BlockSize);
   if ((it != map.end()) && (it->second != nullptr)) {
+    // If there are existing block pool resources in the thread cache, 
+    // a new block pool resource is constructed based on it and the cache is updated.
     auto *bp = static_cast <block_pool<0, 0> *>(
                dynamic_cast<block_pool_resource<0, 0> *>(it->second));
     if (bp == nullptr) {
       return nullptr;
     }
     thread_local block_pool_resource instance(std::move(*bp));
     delete static_cast<block_pool_resource<0, 0> *>(bp);
-    pi = &instance;
+    it->second = pi = &instance;
+    return pi;
   } else {
+    // If there are no existing block pool resources in the thread cache, 
+    // the thread local storage instance is constructed and the pointer is cached.
     thread_local block_pool_resource instance;
-    pi = &instance;
-  }
-  LIBIMP_TRY {
-    map.emplace(BlockSize, pi);
-  } LIBIMP_CATCH(...) {
-    return nullptr;
+    LIBIMP_TRY {
+      map.emplace(BlockSize, pi = &instance);
+      return pi;
+    } LIBIMP_CATCH(...) {
+      return nullptr;
+    }
   }
-  return pi;
 }
 
+/// \brief Match the appropriate memory block resources 
+///        according to the size of the specification.
 template <std::size_t N, std::size_t L = regular_level(N)>
 class regular_resource : public new_delete_resource {};
 
-template <std::size_t N>
-class regular_resource<N, 0> : public block_pool_resource<N, 512> {};
-
-template <std::size_t N>
-class regular_resource<N, 1> : public block_pool_resource<N, 256> {};
-
-template <std::size_t N>
-class regular_resource<N, 2> : public block_pool_resource<N, 128> {};
-
-template <std::size_t N>
-class regular_resource<N, 3> : public block_pool_resource<N, 64> {};
+/// \brief Different increment levels match different chunk sizes.
+///        512 means that 512 consecutive memory blocks are allocated at a time, and the block size is N.
+template <std::size_t N> class regular_resource<N, 0> : public block_pool_resource<N, 512> {};
+template <std::size_t N> class regular_resource<N, 1> : public block_pool_resource<N, 256> {};
+template <std::size_t N> class regular_resource<N, 2> : public block_pool_resource<N, 128> {};
+template <std::size_t N> class regular_resource<N, 3> : public block_pool_resource<N, 64 > {};
 
+/// \brief Creates an object based on the specified type and parameters with block pool resource.
+/// \note This function is thread-safe.
 template <typename T, typename... A>
 T *new$(A &&... args) noexcept {
   auto *mem_res = regular_resource<regular_sizeof<T>()>::get();
   if (mem_res == nullptr) return nullptr;
   return ::LIBIMP::construct<T>(mem_res->allocate(sizeof(T), alignof(T)), std::forward<A>(args)...);
 }
 
+/// \brief Destroys object previously allocated by the `new$` and releases obtained memory area.
+/// \note This function is thread-safe. If the pointer type passed in is different from `new$`, 
+///       additional performance penalties may be incurred.
 template <typename T>
 void delete$(T *p) noexcept {
   if (p == nullptr) return;
   ::LIBIMP::destroy(p);
   auto *mem_res = regular_resource<regular_sizeof<T>()>::get();
   if (mem_res == nullptr) return;
 #if defined(LIBIMP_CC_MSVC_2015)
+  // `alignof` of vs2015 requires that type must be able to be instantiated.
   mem_res->deallocate(p, sizeof(T));
 #else
   mem_res->deallocate(p, sizeof(T), alignof(T));

src/libpmr/new.cpp

@@ -0,0 +1,12 @@
+
+#include "libpmr/new.h"
+
+LIBPMR_NAMESPACE_BEG_
+
+auto get_thread_block_pool_map() noexcept 
+  -> std::unordered_map<std::size_t, block_collector *> & {
+  thread_local std::unordered_map<std::size_t, block_collector *> instances;
+  return instances;
+}
+
+LIBPMR_NAMESPACE_END_