libcxxabi/src/demangle/StringView.h

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