hphp/util/compression-ctx-pool.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-present Facebook, Inc. (http://www.facebook.com)  |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16
  17 #pragma once
  18
  19 #include <memory>
  20 #include <string>
  21
  22 #include <folly/Memory.h>
  23 #include <folly/Synchronized.h>
  24
  25 namespace HPHP {
  26
  27 template <typename T, T* (*Creator)(), void (*Deleter)(T*)>
  28 class CompressionContextPool {
  29  private:
  30   using InternalRef =
  31       std::unique_ptr<T, folly::static_function_deleter<T, Deleter>>;
  32
  33   class ReturnToPoolDeleter {
  34    public:
  35     using Pool = CompressionContextPool<T, Creator, Deleter>;
  36
  37     // lets us default-construct non-attached deleters, so we can
  38     // default-construct empty Refs.
  39     ReturnToPoolDeleter() : pool_(nullptr) {}
  40
  41     explicit ReturnToPoolDeleter(Pool* pool) : pool_(pool) {}
  42
  43     void operator()(T* t) {
  44       InternalRef ptr(t);
  45       if (pool_ != nullptr) {
  46         pool_->add(std::move(ptr));
  47       }
  48     }
  49
  50    private:
  51     Pool* pool_;
  52   };
  53
  54  public:
  55   using Object = T;
  56   using Ref = std::unique_ptr<T, ReturnToPoolDeleter>;
  57
  58   explicit CompressionContextPool() {}
  59
  60   Ref get() {
  61     auto stack = stack_.wlock();
  62     if (stack->empty()) {
  63       T* t = Creator();
  64       if (t == nullptr) {
  65         throw std::runtime_error("Failed to allocate new pool object!");
  66       }
  67       return Ref(t, ReturnToPoolDeleter(this));
  68     }
  69     auto ptr = std::move(stack->back());
  70     stack->pop_back();
  71     return Ref(ptr.release(), ReturnToPoolDeleter(this));
  72   }
  73
  74  private:
  75   void add(InternalRef ptr) {
  76     DCHECK(ptr);
  77     stack_->push_back(std::move(ptr));
  78   }
  79
  80   folly::Synchronized<std::vector<InternalRef>> stack_;
  81 };
  82 } // namespace HPHP