intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 100 insertions, 0 deletions

diff --git a/library/cpp/codecs/tls_cache.h b/library/cpp/codecs/tls_cache.h
new file mode 100644
index 0000000000..0184e4bb6c
--- /dev/null
+++ b/library/cpp/codecs/tls_cache.h
@@ -0,0 +1,100 @@
+#pragma once
+
+#include <util/generic/buffer.h>
+#include <util/generic/deque.h>
+#include <util/generic/noncopyable.h>
+#include <util/generic/strbuf.h>
+#include <util/system/tls.h>
+#include <util/thread/singleton.h>
+
+namespace NCodecs {
+    template <class TItem>
+    struct TClear {
+        void operator()(TItem& item) const {
+            item.Clear();
+        }
+    };
+
+    template <class TItem, class TCleaner = TClear<TItem>>
+    class TTlsCache {
+        using TSelf = TTlsCache<TItem, TCleaner>;
+
+        struct TItemHolder: public TIntrusiveListItem<TItemHolder> {
+            TItemHolder(TSelf& factory)
+                : Factory(factory)
+            {
+            }
+
+            void Release() {
+                Factory.Release(*this);
+            }
+
+            TSelf& Factory;
+            TItem Item;
+        };
+
+        class TItemGuard {
+        public:
+            explicit TItemGuard(TSelf& fact)
+                : Holder(fact.Acquire())
+            {
+            }
+
+            TItemGuard(TItemGuard&& other) noexcept {
+                *this = std::move(other);
+            }
+
+            TItemGuard& operator=(TItemGuard&& other) noexcept {
+                if (&other != this) {
+                    std::swap(Holder, other.Holder);
+                }
+                return *this;
+            }
+
+            ~TItemGuard() {
+                if (Holder) {
+                    Holder->Release();
+                }
+            }
+
+            TItem& Get() & {
+                Y_ASSERT(Holder);
+                return Holder->Item;
+            }
+
+            TItem& Get() && = delete;
+
+        private:
+            TItemHolder* Holder = nullptr;
+        };
+
+    public:
+        TItemGuard Item() {
+            return TItemGuard(*this);
+        }
+
+        static TSelf& TlsInstance() {
+            return *FastTlsSingleton<TSelf>();
+        }
+
+    private:
+        TItemHolder* Acquire() {
+            if (Free.Empty()) {
+                return new TItemHolder(*this);
+            } else {
+                return Free.PopBack();
+            }
+        }
+
+        void Release(TItemHolder& item) {
+            Cleaner(item.Item);
+            Free.PushBack(&item);
+        }
+
+    private:
+        TIntrusiveListWithAutoDelete<TItemHolder, TDelete> Free;
+        TCleaner Cleaner;
+    };
+
+    using TBufferTlsCache = TTlsCache<TBuffer>;
+}