1//===--- StringView.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// FIXME: Use std::string_view instead when we support C++17.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef DEMANGLE_STRINGVIEW_H
14#define DEMANGLE_STRINGVIEW_H
15
16#include "DemangleConfig.h"
17#include <algorithm>
18#include <cassert>
19#include <cstring>
20
21DEMANGLE_NAMESPACE_BEGIN
22
23class StringView {
24 const char *First;
25 const char *Last;
26
27public:
28 static const size_t npos = ~size_t(0);
29
30 template <size_t N>
31 StringView(const char (&Str)[N]) : First(Str), Last(Str + N - 1) {}
32 StringView(const char *First_, const char *Last_)
33 : First(First_), Last(Last_) {}
34 StringView(const char *First_, size_t Len)
35 : First(First_), Last(First_ + Len) {}
36 StringView(const char *Str) : First(Str), Last(Str + std::strlen(Str)) {}
37 StringView() : First(nullptr), Last(nullptr) {}
38
39 StringView substr(size_t From) const {
40 return StringView(begin() + From, size() - From);
41 }
42
43 size_t find(char C, size_t From = 0) const {
44 size_t FindBegin = std::min(From, size());
45 // Avoid calling memchr with nullptr.
46 if (FindBegin < size()) {
47 // Just forward to memchr, which is faster than a hand-rolled loop.
48 if (const void *P = ::memchr(First + FindBegin, C, size() - FindBegin))
49 return size_t(static_cast<const char *>(P) - First);
50 }
51 return npos;
52 }
53
54 StringView substr(size_t From, size_t To) const {
55 if (To >= size())
56 To = size() - 1;
57 if (From >= size())
58 From = size() - 1;
59 return StringView(First + From, First + To);
60 }
61
62 StringView dropFront(size_t N = 1) const {
63 if (N >= size())
64 N = size();
65 return StringView(First + N, Last);
66 }
67
68 StringView dropBack(size_t N = 1) const {
69 if (N >= size())
70 N = size();
71 return StringView(First, Last - N);
72 }
73
74 char front() const {
75 assert(!empty());
76 return *begin();
77 }
78
79 char back() const {
80 assert(!empty());
81 return *(end() - 1);
82 }
83
84 char popFront() {
85 assert(!empty());
86 return *First++;
87 }
88
89 bool consumeFront(char C) {
90 if (!startsWith(C))
91 return false;
92 *this = dropFront(1);
93 return true;
94 }
95
96 bool consumeFront(StringView S) {
97 if (!startsWith(S))
98 return false;
99 *this = dropFront(S.size());
100 return true;
101 }
102
103 bool startsWith(char C) const { return !empty() && *begin() == C; }
104
105 bool startsWith(StringView Str) const {
106 if (Str.size() > size())
107 return false;
108 return std::equal(Str.begin(), Str.end(), begin());
109 }
110
111 const char &operator[](size_t Idx) const { return *(begin() + Idx); }
112
113 const char *begin() const { return First; }
114 const char *end() const { return Last; }
115 size_t size() const { return static_cast<size_t>(Last - First); }
116 bool empty() const { return First == Last; }
117};
118
119inline bool operator==(const StringView &LHS, const StringView &RHS) {
120 return LHS.size() == RHS.size() &&
121 std::equal(LHS.begin(), LHS.end(), RHS.begin());
122}
123
124DEMANGLE_NAMESPACE_END
125
126#endif
127