1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CRDTP_FIND_BY_FIRST_H_
#define CRDTP_FIND_BY_FIRST_H_
#include <algorithm>
#include <cstdint>
#include <memory>
#include <vector>
#include "export.h"
#include "span.h"
namespace crdtp {
// =============================================================================
// FindByFirst - Retrieval from a sorted vector that's keyed by span<uint8_t>.
// =============================================================================
// Given a vector of pairs sorted by the first element of each pair, find
// the corresponding value given a key to be compared to the first element.
// Together with std::inplace_merge and pre-sorting or std::sort, this can
// be used to implement a minimalistic equivalent of Chromium's flat_map.
// In this variant, the template parameter |T| is a value type and a
// |default_value| is provided.
template <typename T>
T FindByFirst(const std::vector<std::pair<span<uint8_t>, T>>& sorted_by_first,
span<uint8_t> key,
T default_value) {
auto it = std::lower_bound(
sorted_by_first.begin(), sorted_by_first.end(), key,
[](const std::pair<span<uint8_t>, T>& left, span<uint8_t> right) {
return SpanLessThan(left.first, right);
});
return (it != sorted_by_first.end() && SpanEquals(it->first, key))
? it->second
: default_value;
}
// In this variant, the template parameter |T| is a class or struct that's
// instantiated in std::unique_ptr, and we return either a T* or a nullptr.
template <typename T>
T* FindByFirst(const std::vector<std::pair<span<uint8_t>, std::unique_ptr<T>>>&
sorted_by_first,
span<uint8_t> key) {
auto it = std::lower_bound(
sorted_by_first.begin(), sorted_by_first.end(), key,
[](const std::pair<span<uint8_t>, std::unique_ptr<T>>& left,
span<uint8_t> right) { return SpanLessThan(left.first, right); });
return (it != sorted_by_first.end() && SpanEquals(it->first, key))
? it->second.get()
: nullptr;
}
} // namespace crdtp
#endif // CRDTP_FIND_BY_FIRST_H_
|
