CMake/Source/cmString.hxx

/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
   file Copyright.txt or https://cmake.org/licensing for details.  */
#ifndef cmString_hxx
#define cmString_hxx

#include "cmConfigure.h" // IWYU pragma: keep

#include "cm_string_view.hxx"

#include <algorithm>
#include <functional>
#include <initializer_list>
#include <memory>
#include <ostream>
#include <string>
#include <type_traits>

namespace cm {

class String;

/**
 * Trait to convert type T into a String.
 * Implementations must derive from 'std::true_type'
 * and define an 'into_string' member that accepts
 * type T (by value or reference) and returns one of:
 *
 * - 'std::string' to construct an owned instance.
 * - 'cm::string_view' to construct a borrowed or null instances.
 *   The buffer from which the view is borrowed must outlive
 *   all copies of the resulting String, e.g. static storage.
 * - 'cm::String' for already-constructed instances.
 */
template <typename T>
struct IntoString : std::false_type
{
};

template <typename T>
struct IntoString<T&> : IntoString<T>
{
};

template <typename T>
struct IntoString<T const> : IntoString<T>
{
};

template <typename T>
struct IntoString<T const*> : IntoString<T*>
{
};

template <typename T, std::string::size_type N>
struct IntoString<T const[N]> : IntoString<T[N]>
{
};

template <>
struct IntoString<char*> : std::true_type
{
  static String into_string(const char* s);
};

template <>
struct IntoString<std::nullptr_t> : std::true_type
{
  static string_view into_string(std::nullptr_t) { return string_view(); }
};

template <std::string::size_type N>
struct IntoString<char[N]> : std::true_type
{
  static std::string into_string(char const (&s)[N])
  {
    return std::string(s, N - 1);
  }
};

template <>
struct IntoString<std::string> : std::true_type
{
  static std::string into_string(std::string s) { return s; }
};

template <>
struct IntoString<string_view> : std::true_type
{
  static std::string into_string(string_view s) { return std::string(s); }
};

template <>
struct IntoString<char> : std::true_type
{
  static std::string into_string(char const& c) { return std::string(1, c); }
};

/**
 * Trait to convert type T into a 'cm::string_view'.
 * Implementations must derive from 'std::true_type' and
 * define a 'view' member that accepts type T (by reference)
 * and returns a 'cm::string_view'.
 */
template <typename T>
struct AsStringView : std::false_type
{
};

template <typename T>
struct AsStringView<T&> : AsStringView<T>
{
};

template <typename T>
struct AsStringView<T const> : AsStringView<T>
{
};

template <typename T>
struct AsStringView<T const*> : AsStringView<T*>
{
};

template <typename T, std::string::size_type N>
struct AsStringView<T const[N]> : AsStringView<T[N]>
{
};

template <>
struct AsStringView<char*> : std::true_type
{
  static string_view view(const char* s) { return s; }
};

template <std::string::size_type N>
struct AsStringView<char[N]> : std::true_type
{
  static string_view view(char const (&s)[N]) { return string_view(s, N - 1); }
};

template <>
struct AsStringView<std::string> : std::true_type
{
  static string_view view(std::string const& s) { return s; }
};

template <>
struct AsStringView<char> : std::true_type
{
  static string_view view(const char& s) { return string_view(&s, 1); }
};

template <>
struct AsStringView<string_view> : std::true_type
{
  static string_view view(string_view const& s) { return s; }
};

template <>
struct AsStringView<String> : std::true_type
{
  static string_view view(String const& s);
};

/**
 * \class String
 *
 * A custom string type that holds a view of a string buffer
 * and optionally shares ownership of the buffer.  Instances
 * may have one of the following states:
 *
 * - null: views and owns nothing.
 *   Conversion to 'bool' is 'false'.
 *   'data()' and 'c_str()' return nullptr.
 *   'size()' returns 0.
 *   'str()' returns an empty string.
 *
 * - borrowed: views a string but does not own it.  This is used
 *   to bind to static storage (e.g. string literals) or for
 *   temporary instances that do not outlive the borrowed buffer.
 *   Copies and substrings still borrow the original buffer.
 *   Mutation allocates a new internal string and converts to
 *   the 'owned' state.
 *   Conversion to 'bool' is 'true'.
 *   'c_str()' may internally mutate to the 'owned' state.
 *   'str()' internally mutates to the 'owned' state.
 *
 * - owned: views an immutable 'std::string' instance owned internally.
 *   Copies and substrings share ownership of the internal string.
 *   Mutation allocates a new internal string.
 *   Conversion to 'bool' is 'true'.
 */
class String
{
  enum class Private
  {
  };

public:
  using traits_type = std::string::traits_type;
  using value_type = string_view::value_type;
  using pointer = string_view::pointer;
  using const_pointer = string_view::const_pointer;
  using reference = string_view::reference;
  using const_reference = string_view::const_reference;
  using const_iterator = string_view::const_iterator;
  using iterator = string_view::const_iterator;
  using const_reverse_iterator = string_view::const_reverse_iterator;
  using reverse_iterator = string_view::const_reverse_iterator;
  using difference_type = string_view::difference_type;
  using size_type = string_view::size_type;

  static size_type const npos = string_view::npos;

  /** Construct a null string.  */
  String() = default;

  /** Construct from any type implementing the IntoString trait.  */
  template <typename T,
            typename = typename std::enable_if<IntoString<T>::value>::type>
  String(T&& s)
    : String(IntoString<T>::into_string(std::forward<T>(s)), Private())
  {
  }

  /** Construct via std::string initializer list constructor.  */
  String(std::initializer_list<char> il)
    : String(std::string(il))
  {
  }

  /** Construct by copying the specified buffer.  */
  String(const char* d, size_type s)
    : String(std::string(d, s))
  {
  }

  /** Construct by copying from input iterator range.  */
  template <typename InputIterator>
  String(InputIterator first, InputIterator last)
    : String(std::string(first, last))
  {
  }

  /** Construct a string with 'n' copies of character 'c'.  */
  String(size_type n, char c)
    : String(std::string(n, c))
  {
  }

  /** Construct from a substring of another String instance.
      This shares ownership of the other string's buffer
      but views only a substring.  */
  String(String const& s, size_type pos, size_type count = npos)
    : string_(s.string_)
    , view_(s.data() + pos, std::min(count, s.size() - pos))
  {
  }

  /** Construct by moving from another String instance.
      The other instance is left as a null string.  */
  String(String&& s) noexcept
    : string_(std::move(s.string_))
    , view_(s.view_)
  {
    s.view_ = string_view();
  }

  /** Construct by copying from another String instance.
      This shares ownership of the other string's buffer.  */
  String(String const&) noexcept = default;

  ~String() = default;

  /** Assign by moving from another String instance.
      The other instance is left as a null string.  */
  String& operator=(String&& s) noexcept
  {
    string_ = std::move(s.string_);
    view_ = s.view_;
    s.view_ = string_view();
    return *this;
  }

  /** Assign by copying from another String instance.
      This shares ownership of the other string's buffer.  */
  String& operator=(String const&) noexcept = default;

  /** Assign from any type implementing the IntoString trait.  */
  template <typename T>
  typename // NOLINT(*)
    std::enable_if<IntoString<T>::value, String&>::type
    operator=(T&& s)
  {
    *this = String(std::forward<T>(s));
    return *this;
  }

  /** Assign via std::string initializer list constructor.  */
  String& operator=(std::initializer_list<char> il)
  {
    *this = String(il);
    return *this;
  }

  /** Return true if the instance is not a null string.  */
  explicit operator bool() const noexcept { return data() != nullptr; }

  /** Return a view of the string.  */
  string_view view() const noexcept { return view_; }

  /** Return true if the instance is an empty stringn or null string.  */
  bool empty() const noexcept { return view_.empty(); }

  /** Return a pointer to the start of the string.  */
  const char* data() const noexcept { return view_.data(); }

  /** Return the length of the string in bytes.  */
  size_type size() const noexcept { return view_.size(); }
  size_type length() const noexcept { return view_.length(); }

  /** Return the character at the given position.
      No bounds checking is performed.  */
  char operator[](size_type pos) const noexcept { return view_[pos]; }

  /** Return the character at the given position.
      If the position is out of bounds, throws std::out_of_range.  */
  char at(size_type pos) const { return view_.at(pos); }

  char front() const noexcept { return view_.front(); }

  char back() const noexcept { return view_.back(); }

  /** Get a refernce to a normal std::string.  The reference
      is valid until this instance is mutated or destroyed.  */
  std::string const& str();

  /** Get a pointer to a C-style null-terminated string
      containing the same value as this instance.  The pointer
      is valid until this instance is mutated, destroyed,
      or str() is called.  */
  const char* c_str();

  const_iterator begin() const noexcept { return view_.begin(); }
  const_iterator end() const noexcept { return view_.end(); }
  const_iterator cbegin() const noexcept { return begin(); }
  const_iterator cend() const noexcept { return end(); }

  const_reverse_iterator rbegin() const noexcept { return view_.rbegin(); }
  const_reverse_iterator rend() const noexcept { return view_.rend(); }
  const_reverse_iterator crbegin() const noexcept { return rbegin(); }
  const_reverse_iterator crend() const noexcept { return rend(); }

  /** Append to the string using any type that implements the
      AsStringView trait.  */
  template <typename T>
  typename std::enable_if<AsStringView<T>::value, String&>::type operator+=(
    T&& s)
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    std::string r;
    r.reserve(size() + v.size());
    r.assign(data(), size());
    r.append(v.data(), v.size());
    return *this = std::move(r);
  }

  /** Assign to an empty string.  */
  void clear() { *this = String(string_view("", 0), Private()); }

  /** Insert 'count' copies of 'ch' at position 'index'.  */
  String& insert(size_type index, size_type count, char ch);

  /** Erase 'count' characters starting at position 'index'.  */
  String& erase(size_type index = 0, size_type count = npos);

  void push_back(char ch)
  {
    std::string s;
    s.reserve(size() + 1);
    s.assign(data(), size());
    s.push_back(ch);
    *this = std::move(s);
  }

  void pop_back() { *this = String(*this, 0, size() - 1); }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, String&>::type replace(
    size_type pos, size_type count, T&& s)
  {
    const_iterator first = begin() + pos;
    const_iterator last = first + count;
    return replace(first, last, std::forward<T>(s));
  }

  template <typename InputIterator>
  String& replace(const_iterator first, const_iterator last,
                  InputIterator first2, InputIterator last2)
  {
    std::string out;
    out.append(view_.begin(), first);
    out.append(first2, last2);
    out.append(last, view_.end());
    return *this = std::move(out);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, String&>::type replace(
    const_iterator first, const_iterator last, T&& s)
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    std::string out;
    out.reserve((first - view_.begin()) + v.size() + (view_.end() - last));
    out.append(view_.begin(), first);
    out.append(v.data(), v.size());
    out.append(last, view_.end());
    return *this = std::move(out);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, String&>::type replace(
    size_type pos, size_type count, T&& s, size_type pos2,
    size_type count2 = npos)
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    v = v.substr(pos2, count2);
    return replace(pos, count, v);
  }

  String& replace(size_type pos, size_type count, size_type count2, char ch)
  {
    const_iterator first = begin() + pos;
    const_iterator last = first + count;
    return replace(first, last, count2, ch);
  }

  String& replace(const_iterator first, const_iterator last, size_type count2,
                  char ch)
  {
    std::string out;
    out.reserve((first - view_.begin()) + count2 + (view_.end() - last));
    out.append(view_.begin(), first);
    out.append(count2, ch);
    out.append(last, view_.end());
    return *this = std::move(out);
  }

  size_type copy(char* dest, size_type count, size_type pos = 0) const;

  void resize(size_type count) { resize(count, char()); }

  void resize(size_type count, char ch)
  {
    std::string s;
    s.reserve(count);
    if (count <= size()) {
      s.assign(data(), count);
    } else {
      s.assign(data(), size());
      s.resize(count, ch);
    }
    *this = std::move(s);
  }

  void swap(String& other)
  {
    std::swap(string_, other.string_);
    std::swap(view_, other.view_);
  }

  /** Return a substring starting at position 'pos' and
      consisting of at most 'count' characters.  */
  String substr(size_type pos = 0, size_type count = npos) const;

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, int>::type compare(
    T&& s) const
  {
    return view_.compare(AsStringView<T>::view(std::forward<T>(s)));
  }

  int compare(size_type pos1, size_type count1, string_view v) const
  {
    return view_.compare(pos1, count1, v);
  }

  int compare(size_type pos1, size_type count1, string_view v, size_type pos2,
              size_type count2) const
  {
    return view_.compare(pos1, count1, v, pos2, count2);
  }

  int compare(size_type pos1, size_type count1, const char* s) const
  {
    return view_.compare(pos1, count1, s);
  }

  int compare(size_type pos1, size_type count1, const char* s,
              size_type count2) const
  {
    return view_.compare(pos1, count1, s, count2);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, size_type>::type find(
    T&& s, size_type pos = 0) const
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    return view_.find(v, pos);
  }

  size_type find(const char* s, size_type pos, size_type count) const
  {
    return view_.find(s, pos, count);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, size_type>::type rfind(
    T&& s, size_type pos = npos) const
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    return view_.rfind(v, pos);
  }

  size_type rfind(const char* s, size_type pos, size_type count) const
  {
    return view_.rfind(s, pos, count);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, size_type>::type
  find_first_of(T&& s, size_type pos = 0) const
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    return view_.find_first_of(v, pos);
  }

  size_type find_first_of(const char* s, size_type pos, size_type count) const
  {
    return view_.find_first_of(s, pos, count);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, size_type>::type
  find_first_not_of(T&& s, size_type pos = 0) const
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    return view_.find_first_not_of(v, pos);
  }

  size_type find_first_not_of(const char* s, size_type pos,
                              size_type count) const
  {
    return view_.find_first_not_of(s, pos, count);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, size_type>::type
  find_last_of(T&& s, size_type pos = npos) const
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    return view_.find_last_of(v, pos);
  }

  size_type find_last_of(const char* s, size_type pos, size_type count) const
  {
    return view_.find_last_of(s, pos, count);
  }

  template <typename T>
  typename std::enable_if<AsStringView<T>::value, size_type>::type
  find_last_not_of(T&& s, size_type pos = npos) const
  {
    string_view v = AsStringView<T>::view(std::forward<T>(s));
    return view_.find_last_not_of(v, pos);
  }

  size_type find_last_not_of(const char* s, size_type pos,
                             size_type count) const
  {
    return view_.find_last_not_of(s, pos, count);
  }

private:
  // Internal constructor to move from existing String.
  String(String&& s, Private) noexcept
    : String(std::move(s))
  {
  }

  // Internal constructor for dynamically allocated string.
  String(std::string&& s, Private);

  // Internal constructor for view of statically allocated string.
  String(string_view v, Private)
    : string_()
    , view_(v)
  {
  }

  void internally_mutate_to_stable_string();

  std::shared_ptr<std::string const> string_;
  string_view view_;
};

template <typename L, typename R>
typename std::enable_if<AsStringView<L>::value && AsStringView<R>::value,
                        bool>::type
operator==(L&& l, R&& r)
{
  return (AsStringView<L>::view(std::forward<L>(l)) ==
          AsStringView<R>::view(std::forward<R>(r)));
}

template <typename L, typename R>
typename std::enable_if<AsStringView<L>::value && AsStringView<R>::value,
                        bool>::type
operator!=(L&& l, R&& r)
{
  return (AsStringView<L>::view(std::forward<L>(l)) !=
          AsStringView<R>::view(std::forward<R>(r)));
}

template <typename L, typename R>
typename std::enable_if<AsStringView<L>::value && AsStringView<R>::value,
                        bool>::type
operator<(L&& l, R&& r)
{
  return (AsStringView<L>::view(std::forward<L>(l)) <
          AsStringView<R>::view(std::forward<R>(r)));
}

template <typename L, typename R>
typename std::enable_if<AsStringView<L>::value && AsStringView<R>::value,
                        bool>::type
operator<=(L&& l, R&& r)
{
  return (AsStringView<L>::view(std::forward<L>(l)) <=
          AsStringView<R>::view(std::forward<R>(r)));
}

template <typename L, typename R>
typename std::enable_if<AsStringView<L>::value && AsStringView<R>::value,
                        bool>::type
operator>(L&& l, R&& r)
{
  return (AsStringView<L>::view(std::forward<L>(l)) >
          AsStringView<R>::view(std::forward<R>(r)));
}

template <typename L, typename R>
typename std::enable_if<AsStringView<L>::value && AsStringView<R>::value,
                        bool>::type
operator>=(L&& l, R&& r)
{
  return (AsStringView<L>::view(std::forward<L>(l)) >=
          AsStringView<R>::view(std::forward<R>(r)));
}

std::ostream& operator<<(std::ostream& os, String const& s);
std::string& operator+=(std::string& self, String const& s);

template <typename L, typename R>
struct StringOpPlus
{
  L l;
  R r;
#if defined(__SUNPRO_CC)
  StringOpPlus(L in_l, R in_r)
    : l(in_l)
    , r(in_r)
  {
  }
#endif
  operator std::string() const;
  std::string::size_type size() const { return l.size() + r.size(); }
};

template <typename T>
struct StringAdd
{
  static const bool value = AsStringView<T>::value;
  typedef string_view temp_type;
  template <typename S>
  static temp_type temp(S&& s)
  {
    return AsStringView<T>::view(std::forward<S>(s));
  }
};

template <typename L, typename R>
struct StringAdd<StringOpPlus<L, R>> : std::true_type
{
  typedef StringOpPlus<L, R> const& temp_type;
  static temp_type temp(temp_type s) { return s; }
};

template <typename L, typename R>
StringOpPlus<L, R>::operator std::string() const
{
  std::string s;
  s.reserve(size());
  s += *this;
  return s;
}

template <typename L, typename R>
std::string& operator+=(std::string& s, StringOpPlus<L, R> const& a)
{
  s.reserve(s.size() + a.size());
  s += a.l;
  s += a.r;
  return s;
}

template <typename L, typename R>
String& operator+=(String& s, StringOpPlus<L, R> const& a)
{
  std::string r;
  r.reserve(s.size() + a.size());
  r.assign(s.data(), s.size());
  r += a.l;
  r += a.r;
  s = std::move(r);
  return s;
}

template <typename L, typename R>
std::ostream& operator<<(std::ostream& os, StringOpPlus<L, R> const& a)
{
  return os << a.l << a.r;
}

template <typename L, typename R>
struct IntoString<StringOpPlus<L, R>> : std::true_type
{
  static std::string into_string(StringOpPlus<L, R> const& a) { return a; }
};

template <typename L, typename R>
typename std::enable_if<StringAdd<L>::value && StringAdd<R>::value,
                        StringOpPlus<typename StringAdd<L>::temp_type,
                                     typename StringAdd<R>::temp_type>>::type
operator+(L&& l, R&& r)
{
  return { StringAdd<L>::temp(std::forward<L>(l)),
           StringAdd<R>::temp(std::forward<R>(r)) };
}

template <typename LL, typename LR, typename R>
typename std::enable_if<AsStringView<R>::value, bool>::type operator==(
  StringOpPlus<LL, LR> const& l, R&& r)
{
  return std::string(l) == AsStringView<R>::view(std::forward<R>(r));
}

template <typename L, typename RL, typename RR>
typename std::enable_if<AsStringView<L>::value, bool>::type operator==(
  L&& l, StringOpPlus<RL, RR> const& r)
{
  return AsStringView<L>::view(std::forward<L>(l)) == std::string(r);
}

} // namespace cm

namespace std {

template <>
struct hash<cm::String>
{
  typedef cm::String argument_type;
  typedef size_t result_type;

  result_type operator()(argument_type const& s) const noexcept
  {
    result_type const h(std::hash<cm::string_view>{}(s.view()));
    return h;
  }
};
}

#endif