clone_cache.h

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#ifndef TESSERACT_COMMON_OBJECT_CACHE_H
#define TESSERACT_COMMON_OBJECT_CACHE_H
 
#include <tesseract_common/macros.h>
TESSERACT_COMMON_IGNORE_WARNINGS_PUSH
#include <deque>
#include <memory>
#include <algorithm>
#include <mutex>
#include <console_bridge/console.h>
TESSERACT_COMMON_IGNORE_WARNINGS_POP
 
#include <tesseract_common/sfinae_utils.h>
 
namespace tesseract_common
{
template <typename CacheType>
class CloneCache
{
public:
  CREATE_MEMBER_FUNC_SIGNATURE_CHECK(update, bool, const std::shared_ptr<const CacheType>&)
  CREATE_MEMBER_FUNC_SIGNATURE_NOARGS_CHECK(getRevision, int)
  CREATE_MEMBER_FUNC_SIGNATURE_NOARGS_CHECK(clone, std::shared_ptr<CacheType>)
 
  CloneCache(std::shared_ptr<CacheType> original, const long& cache_size = 5)
    : supports_update(has_member_func_signature_update<CacheType>::value)
    , original_(std::move(original))
    , cache_size_(static_cast<std::size_t>(cache_size))
 
  {
    // These methods are required
    static_assert(has_member_func_signature_getRevision<CacheType>::value,
                  "Class 'getRevision' function has incorrect signature");
    static_assert(has_member_func_signature_clone<CacheType>::value, "Class 'clone' function has incorrect signature");
 
    for (long i = 0; i < cache_size; i++)
      createClone();
  }
 
  const std::shared_ptr<CacheType>& operator->() { return original_; }
 
  std::shared_ptr<CacheType> clone()
  {
    if (!original_)
      return nullptr;
 
    if (cache_.empty())
    {
      std::shared_ptr<CacheType> cache = getClone();
      if (cache == nullptr)
        return nullptr;
 
      return cache;
    }
 
    // If the cache needs updating, then update it
    std::unique_lock<std::mutex> lock(cache_mutex_);
    if (cache_.back()->getRevision() != original_->getRevision())
    {
      // Update if possible
      std::shared_ptr<CacheType> t;
      if constexpr (has_member_func_signature_update<CacheType>::value)
      {
        cache_.back()->update(original_);
      }
      else
      {
        std::shared_ptr<CacheType> cache = getClone();
        if (cache == nullptr)
          return nullptr;
 
        cache_.back() = cache;
      }
      t = cache_.back();
      cache_.pop_back();
      return t;
    }
 
    std::shared_ptr<CacheType> t;
    t = cache_.back();
    cache_.pop_back();
    return t;
  }
 
  void setCacheSize(long size)
  {
    {
      std::unique_lock<std::mutex> lock(cache_mutex_);
      cache_size_ = static_cast<std::size_t>(size);
    }
    updateCache();
  }
 
  long getCacheSize() const { return static_cast<long>(cache_size_); }
 
  long getCurrentCacheSize() const
  {
    std::unique_lock<std::mutex> lock(cache_mutex_);
    return static_cast<long>(cache_.size());
  }
 
  void updateCache()
  {
    std::unique_lock<std::mutex> lock(cache_mutex_);
    if (!original_)
      return;
 
    std::shared_ptr<CacheType> t;
 
    // Update all cached objects
    for (auto& cache : cache_)
    {
      if (cache->getRevision() != original_->getRevision())
      {
        // Update if possible
        if constexpr (has_member_func_signature_update<CacheType>::value)
        {
          cache->update(original_);
        }
        else
        {  // Update is not available to assign new clone
          cache = getClone();
        }
      }
    }
 
    // Prune nullptr
    cache_.erase(std::remove_if(cache_.begin(),
                                cache_.end(),
                                [](const std::shared_ptr<CacheType>& cache) { return (cache == nullptr); }),
                 cache_.end());
 
    while (cache_.size() < cache_size_)
    {
      CONSOLE_BRIDGE_logDebug("Adding clone to the cache. Current cache size: %i", cache_.size());
      std::shared_ptr<CacheType> clone = getClone();
      if (clone != nullptr)
        cache_.push_back(clone);
    }
  }
 
  const bool supports_update;
 
protected:
  void createClone()
  {
    if (original_ == nullptr)
      return;
 
    std::shared_ptr<CacheType> clone = getClone();
    if (clone == nullptr)
      return;
 
    // Lock cache
    std::unique_lock<std::mutex> lock(cache_mutex_);
    cache_.push_back(clone);
  }
 
  std::shared_ptr<CacheType> getClone() const
  {
    std::shared_ptr<CacheType> clone;
    try
    {
      clone = original_->clone();
    }
    catch (std::exception& e)
    {
      CONSOLE_BRIDGE_logError("Clone Cache failed to update cache with the following exception: %s", e.what());
      return nullptr;
    }
    return clone;
  }
 
  std::shared_ptr<CacheType> original_;
 
  std::size_t cache_size_{ 5 };
 
  std::deque<std::shared_ptr<CacheType>> cache_;
 
  mutable std::mutex cache_mutex_;
};
 
}  // namespace tesseract_common
#endif