From 99e2e923d0c77b02f3fb4ff648ea916954868606 Mon Sep 17 00:00:00 2001
From: Yuqian Yang <crupest@crupest.life>
Date: Fri, 28 Feb 2025 23:13:39 +0800
Subject: chore(store): move everything to store.

---
 .../DeadLockDetectionDemo.cpp                      | 113 +++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 store/works/life/operating-system-experiment/DeadLockDetectionDemo.cpp

(limited to 'store/works/life/operating-system-experiment/DeadLockDetectionDemo.cpp')

diff --git a/store/works/life/operating-system-experiment/DeadLockDetectionDemo.cpp b/store/works/life/operating-system-experiment/DeadLockDetectionDemo.cpp
new file mode 100644
index 0000000..bea2b43
--- /dev/null
+++ b/store/works/life/operating-system-experiment/DeadLockDetectionDemo.cpp
@@ -0,0 +1,113 @@
+// Demo使用方法：
+// 本程序采用标准C++11代码写成，请使用支持C++11的编译器编译。
+//
+// 程序接受的输入为n个整数对，其中1-10000表示进程，10001及以上表示锁，顺序很重要：
+// 1 10001 -> process 1 is acquiring or waiting for lock 1
+// 10001 1 -> lock 1 is owned by process 1
+//
+// 建议采用重定向输入至文件的方式输入，提供4个典型情况的测试数据。
+//
+
+#include <iostream>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+const int LOCK_START_INDEX = 10000;
+
+struct Node {
+  int id;
+};
+
+bool operator==(const Node &left, const Node &right) {
+  return left.id == right.id;
+}
+
+template <> struct std::hash<Node> {
+  std::size_t operator()(const Node &node) const {
+    return std::hash<int>{}(node.id);
+  }
+};
+
+std::ostream &operator<<(std::ostream &left, const Node &right) {
+  left << (right.id > LOCK_START_INDEX ? "lock" : "process") << ' '
+       << (right.id > LOCK_START_INDEX ? right.id - LOCK_START_INDEX
+                                       : right.id);
+  return left;
+}
+
+bool dfs(
+    const Node *root,
+    std::unordered_map<const Node *, std::unordered_set<const Node *>> &edges,
+    std::unordered_map<const Node *, bool> &visited) {
+
+  if (visited[root]) {
+    std::cout << "Ohhhhhh, it is already visited!\n";
+    return true;
+  }
+
+  visited[root] = true;
+  auto r = edges.find(root);
+  if (r != edges.cend())
+    for (auto n : r->second) {
+      std::cout << "from " << *root << " go to " << *n << "\n";
+      if (dfs(n, edges, visited))
+        return true;
+      std::cout << "from " << *n << " back to " << *root << "\n";
+    }
+
+  edges.erase(root);
+  return false;
+}
+
+int main() {
+  std::vector<int> ns;
+
+  while (std::cin) {
+    int n;
+    std::cin >> n;
+    if (std::cin)
+      ns.push_back(n);
+  }
+
+  if (!std::cin.eof()) {
+    std::cerr << "Failed to parse input.\n";
+    return -1;
+  }
+
+  if (ns.size() % 2 != 0) {
+    std::cerr << "Input integer number must be even.\n";
+    return -1;
+  }
+
+  std::unordered_set<Node> nodes;
+  std::unordered_map<const Node *, std::unordered_set<const Node *>> edges;
+
+  for (int i = 0; i < ns.size(); i += 2) {
+    int p = ns[i];
+    int l = ns[i + 1];
+    auto r1 = nodes.insert({p});
+    auto r2 = nodes.insert({l});
+    edges[&(*r1.first)].insert(&(*r2.first));
+  }
+
+  bool h = false;
+
+  while (!edges.empty()) {
+    auto n = edges.cbegin()->first;
+    std::unordered_map<const Node *, bool> visited;
+    std::cout << "Begin to detect child graph containing '" << *n << "'.\n";
+    if (dfs(n, edges, visited)) {
+      h = true;
+      break;
+    }
+  }
+
+  if (h) {
+    std::cout << "Cycle, aka dead lock, detected.\n";
+  } else {
+    std::cout << "You are free of dead lock!!!\n";
+  }
+
+  return 0;
+}
-- 
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