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