1 // Copyright 2018 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 //
15 // Provides the internal API for hashtable_debug.h.
16
17 #ifndef ABSL_CONTAINER_INTERNAL_HASHTABLE_DEBUG_HOOKS_H_
18 #define ABSL_CONTAINER_INTERNAL_HASHTABLE_DEBUG_HOOKS_H_
19
20 #include <cstddef>
21
22 #include <algorithm>
23 #include <type_traits>
24 #include <vector>
25
26 #include "absl/base/config.h"
27
28 namespace absl {
29 ABSL_NAMESPACE_BEGIN
30 namespace container_internal {
31 namespace hashtable_debug_internal {
32
33 // If it is a map, call get<0>().
34 using std::get;
35 template <typename T, typename = typename T::mapped_type>
36 auto GetKey(const typename T::value_type& pair, int) -> decltype(get<0>(pair)) {
37 return get<0>(pair);
38 }
39
40 // If it is not a map, return the value directly.
41 template <typename T>
GetKey(const typename T::key_type & key,char)42 const typename T::key_type& GetKey(const typename T::key_type& key, char) {
43 return key;
44 }
45
46 // Containers should specialize this to provide debug information for that
47 // container.
48 template <class Container, typename Enabler = void>
49 struct HashtableDebugAccess {
50 // Returns the number of probes required to find `key` in `c`. The "number of
51 // probes" is a concept that can vary by container. Implementations should
52 // return 0 when `key` was found in the minimum number of operations and
53 // should increment the result for each non-trivial operation required to find
54 // `key`.
55 //
56 // The default implementation uses the bucket api from the standard and thus
57 // works for `std::unordered_*` containers.
GetNumProbesHashtableDebugAccess58 static size_t GetNumProbes(const Container& c,
59 const typename Container::key_type& key) {
60 if (!c.bucket_count()) return {};
61 size_t num_probes = 0;
62 size_t bucket = c.bucket(key);
63 for (auto it = c.begin(bucket), e = c.end(bucket);; ++it, ++num_probes) {
64 if (it == e) return num_probes;
65 if (c.key_eq()(key, GetKey<Container>(*it, 0))) return num_probes;
66 }
67 }
68
69 // Returns the number of bytes requested from the allocator by the container
70 // and not freed.
71 //
72 // static size_t AllocatedByteSize(const Container& c);
73
74 // Returns a tight lower bound for AllocatedByteSize(c) where `c` is of type
75 // `Container` and `c.size()` is equal to `num_elements`.
76 //
77 // static size_t LowerBoundAllocatedByteSize(size_t num_elements);
78 };
79
80 } // namespace hashtable_debug_internal
81 } // namespace container_internal
82 ABSL_NAMESPACE_END
83 } // namespace absl
84
85 #endif // ABSL_CONTAINER_INTERNAL_HASHTABLE_DEBUG_HOOKS_H_
86