1 // SPDX-License-Identifier: Apache-2.0
2 // SPDX-FileCopyrightText: Copyright OpenBMC Authors
3 #pragma once
4
5 #include <charconv>
6 #include <iterator>
7 #include <string_view>
8
9 namespace details
10 {
11
12 // This implementation avoids the complexity of using std::isdigit, which pulls
13 // in all of <locale>, and likely has other consequences.
simpleIsDigit(const char c)14 inline bool simpleIsDigit(const char c)
15 {
16 return c >= '0' && c <= '9';
17 }
18
19 enum class ModeType
20 {
21 STRING,
22 NUMBER
23 };
24
25 } // namespace details
26
alphanumComp(std::string_view left,std::string_view right)27 inline int alphanumComp(std::string_view left, std::string_view right)
28 {
29 std::string_view::const_iterator l = left.cbegin();
30 std::string_view::const_iterator r = right.cbegin();
31
32 details::ModeType mode = details::ModeType::STRING;
33
34 while (l != left.end() && r != right.end())
35 {
36 if (mode == details::ModeType::STRING)
37 {
38 // check if this are digit characters
39 const bool lDigit = details::simpleIsDigit(*l);
40 const bool rDigit = details::simpleIsDigit(*r);
41 // if both characters are digits, we continue in NUMBER mode
42 if (lDigit && rDigit)
43 {
44 mode = details::ModeType::NUMBER;
45 continue;
46 }
47 // if only the left character is a digit, we have a result
48 if (lDigit)
49 {
50 return -1;
51 } // if only the right character is a digit, we have a result
52 if (rDigit)
53 {
54 return +1;
55 }
56 // compute the difference of both characters
57 const int diff = *l - *r;
58 // if they differ we have a result
59 if (diff != 0)
60 {
61 return diff;
62 }
63 // otherwise process the next characters
64 std::advance(l, 1);
65 std::advance(r, 1);
66 }
67 else // mode==NUMBER
68 {
69 // get the left number
70 int lInt = 0;
71 auto fc = std::from_chars(&(*l), &(*left.end()), lInt);
72 std::advance(l, std::distance(l, fc.ptr));
73
74 // get the right number
75 int rInt = 0;
76 fc = std::from_chars(&(*r), &(*right.end()), rInt);
77 std::advance(r, std::distance(r, fc.ptr));
78
79 // if the difference is not equal to zero, we have a comparison
80 // result
81 const int diff = lInt - rInt;
82 if (diff != 0)
83 {
84 return diff;
85 }
86
87 // otherwise we process the next substring in STRING mode
88 mode = details::ModeType::STRING;
89 }
90 }
91 if (r == right.end() && l == left.end())
92 {
93 return 0;
94 }
95 if (r == right.end())
96 {
97 return 1;
98 }
99 return -1;
100 }
101
102 // A generic template type compatible with std::less that can be used on generic
103 // containers (set, map, etc)
104 template <class Type>
105 struct AlphanumLess
106 {
operator ()AlphanumLess107 bool operator()(const Type& left, const Type& right) const
108 {
109 return alphanumComp(left, right) < 0;
110 }
111 };
112