ceph/src/common/split.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab ft=cpp
   3
   4 /*
   5  * Ceph - scalable distributed file system
   6  *
   7  * Copyright (C) 2019 Red Hat, Inc.
   8  *
   9  * This is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License version 2.1, as published by the Free Software
  12  * Foundation. See file COPYING.
  13  *
  14  */
  15
  16 #pragma once
  17
  18 #include <string_view>
  19
  20 namespace ceph {
  21
  22 // a forward iterator over the parts of a split string
  23 class spliterator {
  24   std::string_view str; // full string
  25   std::string_view delims; // delimiters
  26
  27   using size_type = std::string_view::size_type;
  28   size_type pos = 0; // start position of current part
  29   std::string_view part; // view of current part
  30
  31   // return the next part after the given position
  32   std::string_view next(size_type end) {
  33     pos = str.find_first_not_of(delims, end);
  34     if (pos == str.npos) {
  35       return {};
  36     }
  37     return str.substr(pos, str.find_first_of(delims, pos) - pos);
  38   }
  39  public:
  40   // types required by std::iterator_traits
  41   using difference_type = int;
  42   using value_type = std::string_view;
  43   using pointer = const value_type*;
  44   using reference = const value_type&;
  45   using iterator_category = std::forward_iterator_tag;
  46
  47   spliterator() = default;
  48
  49   spliterator(std::string_view str, std::string_view delims)
  50     : str(str), delims(delims), pos(0), part(next(0))
  51   {}
  52
  53   spliterator& operator++() {
  54     part = next(pos + part.size());
  55     return *this;
  56   }
  57   spliterator operator++(int) {
  58     spliterator tmp = *this;
  59     part = next(pos + part.size());
  60     return tmp;
  61   }
  62
  63   reference operator*() const { return part; }
  64   pointer operator->() const { return &part; }
  65
  66   friend bool operator==(const spliterator& lhs, const spliterator& rhs) {
  67     return lhs.part.data() == rhs.part.data()
  68         && lhs.part.size() == rhs.part.size();
  69   }
  70   friend bool operator!=(const spliterator& lhs, const spliterator& rhs) {
  71     return lhs.part.data() != rhs.part.data()
  72         || lhs.part.size() != rhs.part.size();
  73   }
  74 };
  75
  76 // represents an immutable range of split string parts
  77 //
  78 // ranged-for loop example:
  79 //
  80 //   for (std::string_view s : split(input)) {
  81 //     ...
  82 //
  83 // container initialization example:
  84 //
  85 //   auto parts = split(input);
  86 //
  87 //   std::vector<std::string> strings;
  88 //   strings.assign(parts.begin(), parts.end());
  89 //
  90 class split {
  91   std::string_view str; // full string
  92   std::string_view delims; // delimiters
  93  public:
  94   split(std::string_view str, std::string_view delims = ";,= \t\n")
  95     : str(str), delims(delims) {}
  96
  97   using iterator = spliterator;
  98   using const_iterator = spliterator;
  99
 100   iterator begin() const { return {str, delims}; }
 101   const_iterator cbegin() const { return {str, delims}; }
 102
 103   iterator end() const { return {}; }
 104   const_iterator cend() const { return {}; }
 105 };
 106
 107 } // namespace ceph