intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

7 files changed, 207 insertions, 0 deletions

diff --git a/library/cpp/containers/stack_array/range_ops.cpp b/library/cpp/containers/stack_array/range_ops.cpp
new file mode 100644
index 0000000000..f1b5e3af0d
--- /dev/null
+++ b/library/cpp/containers/stack_array/range_ops.cpp
@@ -0,0 +1 @@
+#include "range_ops.h"
diff --git a/library/cpp/containers/stack_array/range_ops.h b/library/cpp/containers/stack_array/range_ops.h
new file mode 100644
index 0000000000..1d40341aa1
--- /dev/null
+++ b/library/cpp/containers/stack_array/range_ops.h
@@ -0,0 +1,52 @@
+#pragma once
+
+#include <util/generic/typetraits.h>
+
+#include <new>
+
+namespace NRangeOps {
+    template <class T, bool isTrivial>
+    struct TRangeOpsBase {
+        static inline void DestroyRange(T* b, T* e) noexcept {
+            while (e > b) {
+                (--e)->~T();
+            }
+        }
+
+        static inline void InitializeRange(T* b, T* e) {
+            T* c = b;
+
+            try {
+                for (; c < e; ++c) {
+                    new (c) T();
+                }
+            } catch (...) {
+                DestroyRange(b, c);
+
+                throw;
+            }
+        }
+    };
+
+    template <class T>
+    struct TRangeOpsBase<T, true> {
+        static inline void DestroyRange(T*, T*) noexcept {
+        }
+
+        static inline void InitializeRange(T*, T*) noexcept {
+        }
+    };
+
+    template <class T>
+    using TRangeOps = TRangeOpsBase<T, TTypeTraits<T>::IsPod>;
+
+    template <class T>
+    static inline void DestroyRange(T* b, T* e) noexcept {
+        TRangeOps<T>::DestroyRange(b, e);
+    }
+
+    template <class T>
+    static inline void InitializeRange(T* b, T* e) {
+        TRangeOps<T>::InitializeRange(b, e);
+    }
+}
diff --git a/library/cpp/containers/stack_array/stack_array.cpp b/library/cpp/containers/stack_array/stack_array.cpp
new file mode 100644
index 0000000000..68e8b097ba
--- /dev/null
+++ b/library/cpp/containers/stack_array/stack_array.cpp
@@ -0,0 +1 @@
+#include "stack_array.h"
diff --git a/library/cpp/containers/stack_array/stack_array.h b/library/cpp/containers/stack_array/stack_array.h
new file mode 100644
index 0000000000..28e49bfc3c
--- /dev/null
+++ b/library/cpp/containers/stack_array/stack_array.h
@@ -0,0 +1,40 @@
+#pragma once
+
+#include "range_ops.h"
+
+#include <util/generic/array_ref.h>
+#include <util/system/defaults.h> /* For alloca. */
+
+namespace NStackArray {
+    /**
+     * A stack-allocated array. Should be used instead of � variable length
+     * arrays that are not part of C++ standard.
+     *
+     * Example usage:
+     * @code
+     * void f(int size) {
+     *    // T array[size]; // Wrong!
+     *    TStackArray<T> array(ALLOC_ON_STACK(T, size)); // Right!
+     *    // ...
+     * }
+     * @endcode
+     *
+     * Note that it is generally a *VERY BAD* idea to use this in inline methods
+     * as those might be called from a loop, and then stack overflow is in the cards.
+     */
+    template <class T>
+    class TStackArray: public TArrayRef<T> {
+    public:
+        inline TStackArray(void* data, size_t len)
+            : TArrayRef<T>((T*)data, len)
+        {
+            NRangeOps::InitializeRange(this->begin(), this->end());
+        }
+
+        inline ~TStackArray() {
+            NRangeOps::DestroyRange(this->begin(), this->end());
+        }
+    };
+}
+
+#define ALLOC_ON_STACK(type, n) alloca(sizeof(type) * (n)), (n)
diff --git a/library/cpp/containers/stack_array/ut/tests_ut.cpp b/library/cpp/containers/stack_array/ut/tests_ut.cpp
new file mode 100644
index 0000000000..3e96384f0e
--- /dev/null
+++ b/library/cpp/containers/stack_array/ut/tests_ut.cpp
@@ -0,0 +1,94 @@
+#include <library/cpp/containers/stack_array/stack_array.h>
+#include <library/cpp/testing/unittest/registar.h>
+
+Y_UNIT_TEST_SUITE(TestStackArray) {
+    using namespace NStackArray;
+
+    static inline void* FillWithTrash(void* d, size_t l) {
+        memset(d, 0xCC, l);
+
+        return d;
+    }
+
+#define ALLOC(type, len) FillWithTrash(alloca(sizeof(type) * len), sizeof(type) * len), len
+
+    Y_UNIT_TEST(Test1) {
+        TStackArray<ui32> s(ALLOC(ui32, 10));
+
+        UNIT_ASSERT_VALUES_EQUAL(s.size(), 10);
+
+        for (size_t i = 0; i < s.size(); ++i) {
+            UNIT_ASSERT_VALUES_EQUAL(s[i], 0xCCCCCCCC);
+        }
+
+        for (auto&& x : s) {
+            UNIT_ASSERT_VALUES_EQUAL(x, 0xCCCCCCCC);
+        }
+
+        for (size_t i = 0; i < s.size(); ++i) {
+            s[i] = i;
+        }
+
+        size_t ss = 0;
+
+        for (auto&& x : s) {
+            ss += x;
+        }
+
+        UNIT_ASSERT_VALUES_EQUAL(ss, 45);
+    }
+
+    static int N1 = 0;
+
+    struct TX1 {
+        inline TX1() {
+            ++N1;
+        }
+
+        inline ~TX1() {
+            --N1;
+        }
+    };
+
+    Y_UNIT_TEST(Test2) {
+        {
+            TStackArray<TX1> s(ALLOC(TX1, 10));
+
+            UNIT_ASSERT_VALUES_EQUAL(N1, 10);
+        }
+
+        UNIT_ASSERT_VALUES_EQUAL(N1, 0);
+    }
+
+    static int N2 = 0;
+    static int N3 = 0;
+
+    struct TX2 {
+        inline TX2() {
+            if (N2 >= 5) {
+                ythrow yexception() << "ups";
+            }
+
+            ++N3;
+            ++N2;
+        }
+
+        inline ~TX2() {
+            --N2;
+        }
+    };
+
+    Y_UNIT_TEST(Test3) {
+        bool haveException = false;
+
+        try {
+            TStackArray<TX2> s(ALLOC_ON_STACK(TX2, 10));
+        } catch (...) {
+            haveException = true;
+        }
+
+        UNIT_ASSERT(haveException);
+        UNIT_ASSERT_VALUES_EQUAL(N2, 0);
+        UNIT_ASSERT_VALUES_EQUAL(N3, 5);
+    }
+}
diff --git a/library/cpp/containers/stack_array/ut/ya.make b/library/cpp/containers/stack_array/ut/ya.make
new file mode 100644
index 0000000000..7db7340073
--- /dev/null
+++ b/library/cpp/containers/stack_array/ut/ya.make
@@ -0,0 +1,9 @@
+UNITTEST_FOR(library/cpp/containers/stack_array)
+
+OWNER(pg)
+
+SRCS(
+    tests_ut.cpp
+)
+
+END()
diff --git a/library/cpp/containers/stack_array/ya.make b/library/cpp/containers/stack_array/ya.make
new file mode 100644
index 0000000000..9bc0afc66c
--- /dev/null
+++ b/library/cpp/containers/stack_array/ya.make
@@ -0,0 +1,10 @@
+LIBRARY()
+
+OWNER(pg)
+
+SRCS(
+    range_ops.cpp
+    stack_array.cpp
+)
+
+END()