1 //===-- UserIDResolver.h ----------------------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLDB_UTILITY_USERIDRESOLVER_H
10 #define LLDB_UTILITY_USERIDRESOLVER_H
11 
12 #include "llvm/ADT/DenseMap.h"
13 #include "llvm/ADT/StringRef.h"
14 #include <mutex>
15 #include <optional>
16 
17 namespace lldb_private {
18 
19 /// An abstract interface for things that know how to map numeric user/group IDs
20 /// into names. It caches the resolved names to avoid repeating expensive
21 /// queries. The cache is internally protected by a mutex, so concurrent queries
22 /// are safe.
23 class UserIDResolver {
24 public:
25   typedef uint32_t id_t;
26   virtual ~UserIDResolver(); // anchor
27 
28   std::optional<llvm::StringRef> GetUserName(id_t uid) {
29     return Get(uid, m_uid_cache, &UserIDResolver::DoGetUserName);
30   }
31   std::optional<llvm::StringRef> GetGroupName(id_t gid) {
32     return Get(gid, m_gid_cache, &UserIDResolver::DoGetGroupName);
33   }
34 
35   /// Returns a resolver which returns a failure value for each query. Useful as
36   /// a fallback value for the case when we know all lookups will fail.
37   static UserIDResolver &GetNoopResolver();
38 
39 protected:
40   virtual std::optional<std::string> DoGetUserName(id_t uid) = 0;
41   virtual std::optional<std::string> DoGetGroupName(id_t gid) = 0;
42 
43 private:
44   using Map = llvm::DenseMap<id_t, std::optional<std::string>>;
45 
46   std::optional<llvm::StringRef>
47   Get(id_t id, Map &cache,
48       std::optional<std::string> (UserIDResolver::*do_get)(id_t));
49 
50   std::mutex m_mutex;
51   Map m_uid_cache;
52   Map m_gid_cache;
53 };
54 
55 } // namespace lldb_private
56 
57 #endif // LLDB_UTILITY_USERIDRESOLVER_H
58