From 6355dd4f4d54e7a7c3a25ebef81e9d543e183d09 Mon Sep 17 00:00:00 2001
From: Marko Budiselic <mbudiselicbuda@gmail.com>
Date: Wed, 30 Nov 2016 17:20:48 +0100
Subject: [PATCH] PtrInt data structure (Pointer Integer pair inside one
 pointer location). Part of T150

Summary: PtrInt data structure (Pointer Integer pair inside one pointer location). Part of T150

Test Plan: manual

Reviewers: sale

Subscribers: buda, sale

Differential Revision: https://memgraph.phacility.com/D11
---
 include/data_structures/ptr_int.hpp | 54 +++++++++++++++++++++++++++++
 include/utils/numerics/log2.hpp     | 10 ++++++
 tests/unit/ptr_int.cpp              | 20 +++++++++++
 3 files changed, 84 insertions(+)
 create mode 100644 include/data_structures/ptr_int.hpp
 create mode 100644 include/utils/numerics/log2.hpp
 create mode 100644 tests/unit/ptr_int.cpp

diff --git a/include/data_structures/ptr_int.hpp b/include/data_structures/ptr_int.hpp
new file mode 100644
index 000000000..9cf0ba709
--- /dev/null
+++ b/include/data_structures/ptr_int.hpp
@@ -0,0 +1,54 @@
+#pragma once
+
+#include <cinttypes>
+
+#include "utils/numerics/log2.hpp"
+
+template <typename PtrT>
+struct PointerPackTraits
+{
+    // here is a place to embed something like platform specific things
+    // TODO: cover more cases
+    constexpr static int free_bits = utils::log2(alignof(PtrT));
+
+    static auto get_ptr(uintptr_t value) { return (PtrT)(value); }
+};
+
+template <typename PtrT, int IntBits, typename IntT = unsigned,
+          typename PtrTraits = PointerPackTraits<PtrT>>
+class PtrInt
+{
+private:
+    constexpr static int int_shift = PtrTraits::free_bits - IntBits;
+    constexpr static uintptr_t ptr_mask =
+        ~(uintptr_t)(((intptr_t)1 << PtrTraits::free_bits) - 1);
+    constexpr static uintptr_t int_mask =
+        (uintptr_t)(((intptr_t)1 << IntBits) - 1);
+
+    uintptr_t value {0};
+
+public:
+    PtrInt(PtrT pointer, IntT integer)
+    {
+        set_ptr(pointer);
+        set_int(integer);
+    }
+
+    auto set_ptr(PtrT pointer)
+    {
+        auto integer = static_cast<uintptr_t>(get_int());
+        auto ptr = reinterpret_cast<uintptr_t>(pointer);
+        value = (ptr_mask & ptr) | (integer << int_shift);
+    }
+
+    auto set_int(IntT integer)
+    {
+        auto ptr = reinterpret_cast<uintptr_t>(get_ptr());
+        auto int_shifted = static_cast<uintptr_t>(integer << int_shift);
+        value = (int_mask & int_shifted) | ptr;
+    }
+
+    auto get_ptr() const { return PtrTraits::get_ptr(value & ptr_mask); }
+
+    auto get_int() const { return (IntT)((value >> int_shift) & int_mask); }
+};
diff --git a/include/utils/numerics/log2.hpp b/include/utils/numerics/log2.hpp
new file mode 100644
index 000000000..90e0a087e
--- /dev/null
+++ b/include/utils/numerics/log2.hpp
@@ -0,0 +1,10 @@
+#pragma once
+
+#include <cstddef>
+
+namespace utils
+{
+
+constexpr size_t log2(size_t n) { return ((n < 2) ? 0 : 1 + log2(n >> 1)); }
+
+}
diff --git a/tests/unit/ptr_int.cpp b/tests/unit/ptr_int.cpp
new file mode 100644
index 000000000..a3589ae34
--- /dev/null
+++ b/tests/unit/ptr_int.cpp
@@ -0,0 +1,20 @@
+#define CATCH_CONFIG_MAIN
+#include "catch.hpp"
+
+#include "data_structures/ptr_int.hpp"
+
+TEST_CASE("Construct and read pointer integer pair type")
+{
+    auto ptr1 = std::make_unique<int>(2);
+    PtrInt<int *, 2, int> pack1(ptr1.get(), 1);
+
+    REQUIRE(pack1.get_int() == 1);
+    REQUIRE(pack1.get_ptr() == ptr1.get());
+
+
+    auto ptr2 = std::make_unique<int>(2);
+    PtrInt<int *, 3, int> pack2(ptr2.get(), 2);
+
+    REQUIRE(pack2.get_int() == 2);
+    REQUIRE(pack2.get_ptr() == ptr2.get());
+}