From 95a981ed1224bd2a473a00996dd4cda8b51b1448 Mon Sep 17 00:00:00 2001
From: BasedDepartment1 <bayakl227@gmail.com>
Date: Mon, 19 Jan 2026 14:32:14 +0300
Subject: [PATCH] [hw6] Add lifo stack

---
 stack.cpp | 177 +++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 161 insertions(+), 16 deletions(-)

diff --git a/stack.cpp b/stack.cpp
index 954a5a5..e79eb97 100644
--- a/stack.cpp
+++ b/stack.cpp
@@ -1,48 +1,193 @@
 #include "stack.hpp"
 
 #include <cstddef>
-
-// TODO: remove me
-#define UNUSED(VAR) (void)(VAR)
+#include <cstdint>
+#include <limits>
+#include <memory>
+#include <stdexcept>
+#include <unordered_map>
+#include <utility>
+#include <vector>
 
 namespace stack
 {
 
+class Node
+{
+public:
+    explicit Node(const uint8_t* data, size_t size) : size_(size)
+    {
+        data_ = std::make_unique<uint8_t[]>(size);
+        std::copy(data, data + size, data_.get());
+    }
+
+    size_t Size() const
+    {
+        return size_;
+    }
+
+    uint8_t* begin()
+    {
+        return data_.get();
+    }
+
+    uint8_t* end()
+    {
+        return data_.get() + size_;
+    }
+
+private:
+    size_t size_;
+    std::unique_ptr<uint8_t[]> data_;
+};
+
+class LIFOStack
+{
+public:
+    explicit LIFOStack()
+    {
+    }
+
+    Handle Create()
+    {
+        auto next_handle = NextHandle();
+        mp_.insert({next_handle, std::vector<Node>()});
+
+        return next_handle;
+    }
+
+    void Destroy(const Handle handle)
+    {
+        mp_.erase(handle);
+        free_handles_.push_back(handle);
+    }
+
+    bool IsValid(const Handle handle) const
+    {
+        return mp_.find(handle) != mp_.end();
+    }
+
+    size_t Count(const Handle handle) const
+    {
+        if (!IsValid(handle))
+        {
+            return 0u;
+        }
+
+        const auto& stack = GetByHandle(handle);
+        return stack.size();
+    }
+
+    void Push(const Handle handle, const uint8_t* data, size_t size)
+    {
+        if (!IsValid(handle) || data == nullptr || size == 0)
+        {
+            return;
+        }
+
+        auto& stack = GetByHandle(handle);
+        stack.emplace_back(data, size);
+    }
+
+    size_t Pop(const Handle handle, uint8_t* data, size_t size)
+    {
+        if (!IsValid(handle) || data == nullptr || size == 0)
+        {
+            return 0u;
+        }
+
+        auto& stack = GetByHandle(handle);
+        if (stack.empty())
+        {
+            return 0u;
+        }
+
+        auto& last_node = stack.back();
+        if (last_node.Size() != size)
+        {
+            return 0u;
+        }
+
+        std::copy(last_node.begin(), last_node.end(), data);
+        stack.pop_back();
+
+        return size;
+    }
+
+private:
+    const std::vector<Node>& GetByHandle(const Handle handle) const
+    {
+        return mp_.at(handle);
+    }
+
+    std::vector<Node>& GetByHandle(const Handle handle)
+    {
+        return mp_.at(handle);
+    }
+
+    Handle NextHandle()
+    {
+        if (current_handle_ != std::numeric_limits<Handle>::max())
+        {
+            return current_handle_++;
+        }
+
+        if (free_handles_.empty())
+        {
+            throw std::runtime_error("all handle numbers have been used");
+        }
+
+        auto free_handle = free_handles_.back();
+        free_handles_.pop_back();
+
+        return free_handle;
+    }
+
+private:
+    std::unordered_map<Handle, std::vector<Node>> mp_{};
+    Handle current_handle_{};
+    std::vector<Handle> free_handles_{};
+};
+
+LIFOStack stack{};
+
 Handle create()
 {
-    return -1;
+    try
+    {
+        return stack.Create();
+    }
+    catch (...)
+    {
+        return -1;
+    }
 }
 
 void destroy(const Handle handle)
 {
-    UNUSED(handle);
+    stack.Destroy(handle);
 }
 
 bool valid(const Handle handle)
 {
-    UNUSED(handle);
-    return false;
+    return stack.IsValid(handle);
 }
 
 std::size_t count(const Handle handle)
 {
-    UNUSED(handle);
-    return 0u;
+    return stack.Count(handle);
 }
 
 void push(const Handle handle, const void* const data, const std::size_t size)
 {
-    UNUSED(handle);
-    UNUSED(data);
-    UNUSED(size);
+    auto data_to_insert = static_cast<const uint8_t*>(data);
+    stack.Push(handle, data_to_insert, size);
 }
 
 std::size_t pop(const Handle handle, void* const data, const std::size_t size)
 {
-    UNUSED(handle);
-    UNUSED(data);
-    UNUSED(size);
-    return 0u;
+    auto data_to_fill = static_cast<uint8_t*>(data);
+    return stack.Pop(handle, data_to_fill, size);
 }
 
 } // namespace stack