fmt/include/fmt/core.h

// Formatting library for C++ - the core API
//
// Copyright (c) 2012 - present, Victor Zverovich
// All rights reserved.
//
// For the license information refer to format.h.

#ifndef FMT_CORE_H_
#define FMT_CORE_H_

#include <cassert>
#include <cstdio>
#include <cstring>
#include <iterator>
#include <string>
#include <type_traits>

// The fmt library version in the form major * 10000 + minor * 100 + patch.
#define FMT_VERSION 50000

#ifdef __has_feature
# define FMT_HAS_FEATURE(x) __has_feature(x)
#else
# define FMT_HAS_FEATURE(x) 0
#endif

#ifdef __has_include
# define FMT_HAS_INCLUDE(x) __has_include(x)
#else
# define FMT_HAS_INCLUDE(x) 0
#endif

#if defined(__GNUC__) && !defined(__clang__)
# define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
#else
# define FMT_GCC_VERSION 0
#endif

#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
# define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
#else
# define FMT_HAS_GXX_CXX11 0
#endif

#ifdef _MSC_VER
# define FMT_MSC_VER _MSC_VER
#else
# define FMT_MSC_VER 0
#endif

// Check if relaxed c++14 constexpr is supported.
// GCC doesn't allow throw in constexpr until version 6 (bug 67371).
#ifndef FMT_USE_CONSTEXPR
# define FMT_USE_CONSTEXPR \
  (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
   (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L))
#endif
#if FMT_USE_CONSTEXPR
# define FMT_CONSTEXPR constexpr
# define FMT_CONSTEXPR_DECL constexpr
#else
# define FMT_CONSTEXPR inline
# define FMT_CONSTEXPR_DECL
#endif

#ifndef FMT_OVERRIDE
# if FMT_HAS_FEATURE(cxx_override) || \
     (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || \
     FMT_MSC_VER >= 1900
#  define FMT_OVERRIDE override
# else
#  define FMT_OVERRIDE
# endif
#endif

#if FMT_HAS_FEATURE(cxx_explicit_conversions) || \
    FMT_MSC_VER >= 1800
# define FMT_EXPLICIT explicit
#else
# define FMT_EXPLICIT
#endif

#ifndef FMT_NULL
# if FMT_HAS_FEATURE(cxx_nullptr) || \
   (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || \
   FMT_MSC_VER >= 1600
#  define FMT_NULL nullptr
#  define FMT_USE_NULLPTR 1
# else
#  define FMT_NULL NULL
# endif
#endif

#ifndef FMT_USE_NULLPTR
# define FMT_USE_NULLPTR 0
#endif

// Check if exceptions are disabled.
#if defined(__GNUC__) && !defined(__EXCEPTIONS)
# define FMT_EXCEPTIONS 0
#elif FMT_MSC_VER && !_HAS_EXCEPTIONS
# define FMT_EXCEPTIONS 0
#endif
#ifndef FMT_EXCEPTIONS
# define FMT_EXCEPTIONS 1
#endif

// Define FMT_USE_NOEXCEPT to make fmt use noexcept (C++11 feature).
#ifndef FMT_USE_NOEXCEPT
# define FMT_USE_NOEXCEPT 0
#endif

#if FMT_USE_NOEXCEPT || FMT_HAS_FEATURE(cxx_noexcept) || \
    (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || \
    FMT_MSC_VER >= 1900
# define FMT_DETECTED_NOEXCEPT noexcept
#else
# define FMT_DETECTED_NOEXCEPT throw()
#endif

#ifndef FMT_NOEXCEPT
# if FMT_EXCEPTIONS
#  define FMT_NOEXCEPT FMT_DETECTED_NOEXCEPT
# else
#  define FMT_NOEXCEPT
# endif
#endif

// This is needed because GCC still uses throw() in its headers when exceptions
// are disabled.
#if FMT_GCC_VERSION
# define FMT_DTOR_NOEXCEPT FMT_DETECTED_NOEXCEPT
#else
# define FMT_DTOR_NOEXCEPT FMT_NOEXCEPT
#endif

#ifndef FMT_BEGIN_NAMESPACE
# if FMT_HAS_FEATURE(cxx_inline_namespaces) || FMT_GCC_VERSION >= 404 || \
     FMT_MSC_VER >= 1900
#  define FMT_INLINE_NAMESPACE inline namespace
#  define FMT_END_NAMESPACE }}
# else
#  define FMT_INLINE_NAMESPACE namespace
#  define FMT_END_NAMESPACE } using namespace v5; }
# endif
# define FMT_BEGIN_NAMESPACE namespace fmt { FMT_INLINE_NAMESPACE v5 {
#endif

#if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
# ifdef FMT_EXPORT
#  define FMT_API __declspec(dllexport)
# elif defined(FMT_SHARED)
#  define FMT_API __declspec(dllimport)
# endif
#endif
#ifndef FMT_API
# define FMT_API
#endif

#ifndef FMT_ASSERT
# define FMT_ASSERT(condition, message) assert((condition) && message)
#endif

#define FMT_DELETED = delete

// A macro to disallow the copy construction and assignment.
#define FMT_DISALLOW_COPY_AND_ASSIGN(Type) \
    Type(const Type &) FMT_DELETED; \
    void operator=(const Type &) FMT_DELETED

// libc++ supports string_view in pre-c++17.
#if (FMT_HAS_INCLUDE(<string_view>) && \
      (__cplusplus > 201402L || defined(_LIBCPP_VERSION))) || \
    (defined(_MSVC_LANG) && _MSVC_LANG > 201402L && _MSC_VER >= 1910)
# include <string_view>
# define FMT_USE_STD_STRING_VIEW
#elif (FMT_HAS_INCLUDE(<experimental/string_view>) && \
       __cplusplus >= 201402L)
# include <experimental/string_view>
# define FMT_USE_EXPERIMENTAL_STRING_VIEW
#endif

// std::result_of is defined in <functional> in gcc 4.4.
#if FMT_GCC_VERSION && FMT_GCC_VERSION <= 404
# include <functional>
#endif

FMT_BEGIN_NAMESPACE

// An implementation of declval for pre-C++11 compilers such as gcc 4.
namespace internal {
template <typename T>
typename std::add_rvalue_reference<T>::type declval() FMT_NOEXCEPT;
}

/**
  An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
  subset of the API. ``fmt::basic_string_view`` is used for format strings even
  if ``std::string_view`` is available to prevent issues when a library is
  compiled with a different ``-std`` option than the client code (which is not
  recommended).
 */
template <typename Char>
class basic_string_view {
 private:
  const Char *data_;
  size_t size_;

 public:
  typedef Char char_type;
  typedef const Char *iterator;

  // Standard basic_string_view type.
#if defined(FMT_USE_STD_STRING_VIEW)
  typedef std::basic_string_view<Char> type;
#elif defined(FMT_USE_EXPERIMENTAL_STRING_VIEW)
  typedef std::experimental::basic_string_view<Char> type;
#else
  struct type {
    const char *data() const { return FMT_NULL; }
    size_t size() const { return 0; };
  };
#endif

  FMT_CONSTEXPR basic_string_view() FMT_NOEXCEPT : data_(FMT_NULL), size_(0) {}

  /** Constructs a string reference object from a C string and a size. */
  FMT_CONSTEXPR basic_string_view(const Char *s, size_t size) FMT_NOEXCEPT
    : data_(s), size_(size) {}

  /**
    \rst
    Constructs a string reference object from a C string computing
    the size with ``std::char_traits<Char>::length``.
    \endrst
   */
  basic_string_view(const Char *s)
    : data_(s), size_(std::char_traits<Char>::length(s)) {}

  /** Constructs a string reference from a ``std::basic_string`` object. */
  template <typename Alloc>
  FMT_CONSTEXPR basic_string_view(
      const std::basic_string<Char, Alloc> &s) FMT_NOEXCEPT
  : data_(s.c_str()), size_(s.size()) {}

  FMT_CONSTEXPR basic_string_view(type s) FMT_NOEXCEPT
  : data_(s.data()), size_(s.size()) {}

  /** Returns a pointer to the string data. */
  const Char *data() const { return data_; }

  /** Returns the string size. */
  FMT_CONSTEXPR size_t size() const { return size_; }

  FMT_CONSTEXPR iterator begin() const { return data_; }
  FMT_CONSTEXPR iterator end() const { return data_ + size_; }

  FMT_CONSTEXPR void remove_prefix(size_t n) {
    data_ += n;
    size_ -= n;
  }

  // Lexicographically compare this string reference to other.
  int compare(basic_string_view other) const {
    size_t size = size_ < other.size_ ? size_ : other.size_;
    int result = std::char_traits<Char>::compare(data_, other.data_, size);
    if (result == 0)
      result = size_ == other.size_ ? 0 : (size_ < other.size_ ? -1 : 1);
    return result;
  }

  friend bool operator==(basic_string_view lhs, basic_string_view rhs) {
    return lhs.compare(rhs) == 0;
  }
  friend bool operator!=(basic_string_view lhs, basic_string_view rhs) {
    return lhs.compare(rhs) != 0;
  }
  friend bool operator<(basic_string_view lhs, basic_string_view rhs) {
    return lhs.compare(rhs) < 0;
  }
  friend bool operator<=(basic_string_view lhs, basic_string_view rhs) {
    return lhs.compare(rhs) <= 0;
  }
  friend bool operator>(basic_string_view lhs, basic_string_view rhs) {
    return lhs.compare(rhs) > 0;
  }
  friend bool operator>=(basic_string_view lhs, basic_string_view rhs) {
    return lhs.compare(rhs) >= 0;
  }
};

typedef basic_string_view<char> string_view;
typedef basic_string_view<wchar_t> wstring_view;

template <typename Context>
class basic_format_arg;

template <typename Context>
class basic_format_args;

// A formatter for objects of type T.
template <typename T, typename Char = char, typename Enable = void>
struct formatter;

namespace internal {

/** A contiguous memory buffer with an optional growing ability. */
template <typename T>
class basic_buffer {
 private:
  FMT_DISALLOW_COPY_AND_ASSIGN(basic_buffer);

  T *ptr_;
  std::size_t size_;
  std::size_t capacity_;

 protected:
  basic_buffer(T *p = FMT_NULL, std::size_t size = 0, std::size_t capacity = 0)
    FMT_NOEXCEPT: ptr_(p), size_(size), capacity_(capacity) {}

  /** Sets the buffer data and capacity. */
  void set(T *data, std::size_t capacity) FMT_NOEXCEPT {
    ptr_ = data;
    capacity_ = capacity;
  }

  /** Increases the buffer capacity to hold at least *capacity* elements. */
  virtual void grow(std::size_t capacity) = 0;

 public:
  typedef T value_type;
  typedef const T &const_reference;

  virtual ~basic_buffer() {}

  T *begin() FMT_NOEXCEPT { return ptr_; }
  T *end() FMT_NOEXCEPT { return ptr_ + size_; }

  /** Returns the size of this buffer. */
  std::size_t size() const FMT_NOEXCEPT { return size_; }

  /** Returns the capacity of this buffer. */
  std::size_t capacity() const FMT_NOEXCEPT { return capacity_; }

  /** Returns a pointer to the buffer data. */
  T *data() FMT_NOEXCEPT { return ptr_; }

  /** Returns a pointer to the buffer data. */
  const T *data() const FMT_NOEXCEPT { return ptr_; }

  /**
    Resizes the buffer. If T is a POD type new elements may not be initialized.
   */
  void resize(std::size_t new_size) {
    reserve(new_size);
    size_ = new_size;
  }

  /** Reserves space to store at least *capacity* elements. */
  void reserve(std::size_t capacity) {
    if (capacity > capacity_)
      grow(capacity);
  }

  void push_back(const T &value) {
    reserve(size_ + 1);
    ptr_[size_++] = value;
  }

  /** Appends data to the end of the buffer. */
  template <typename U>
  void append(const U *begin, const U *end);

  T &operator[](std::size_t index) { return ptr_[index]; }
  const T &operator[](std::size_t index) const { return ptr_[index]; }
};

typedef basic_buffer<char> buffer;
typedef basic_buffer<wchar_t> wbuffer;

// A container-backed buffer.
template <typename Container>
class container_buffer : public basic_buffer<typename Container::value_type> {
 private:
  Container &container_;

 protected:
  void grow(std::size_t capacity) FMT_OVERRIDE {
    container_.resize(capacity);
    this->set(&container_[0], capacity);
  }

 public:
  explicit container_buffer(Container &c)
    : basic_buffer<typename Container::value_type>(&c[0], c.size(), c.size()),
      container_(c) {}
};

struct error_handler {
  FMT_CONSTEXPR error_handler() {}
  FMT_CONSTEXPR error_handler(const error_handler &) {}

  // This function is intentionally not constexpr to give a compile-time error.
  FMT_API void on_error(const char *message);
};

// Formatting of wide characters and strings into a narrow output is disallowed:
//   fmt::format("{}", L"test"); // error
// To fix this, use a wide format string:
//   fmt::format(L"{}", L"test");
template <typename Char>
inline void require_wchar() {
  static_assert(
      std::is_same<wchar_t, Char>::value,
      "formatting of wide characters into a narrow output is disallowed");
}

template <typename Char>
struct named_arg_base;

template <typename T, typename Char>
struct named_arg;

template <typename T>
struct is_named_arg : std::false_type {};

template <typename T, typename Char>
struct is_named_arg<named_arg<T, Char>> : std::true_type {};

enum type {
  none_type, name_arg_type,
  // Integer types should go first,
  int_type, uint_type, long_long_type, ulong_long_type, bool_type, char_type,
  last_integer_type = char_type,
  // followed by floating-point types.
  double_type, long_double_type, last_numeric_type = long_double_type,
  cstring_type, string_type, pointer_type, custom_type
};

FMT_CONSTEXPR bool is_integral(type t) {
  FMT_ASSERT(t != internal::name_arg_type, "invalid argument type");
  return t > internal::none_type && t <= internal::last_integer_type;
}

FMT_CONSTEXPR bool is_arithmetic(type t) {
  FMT_ASSERT(t != internal::name_arg_type, "invalid argument type");
  return t > internal::none_type && t <= internal::last_numeric_type;
}

template <typename T, typename Char, bool ENABLE = true>
struct convert_to_int {
  enum {
    value = !std::is_arithmetic<T>::value && std::is_convertible<T, int>::value
  };
};

template <typename Char>
struct string_value {
  const Char *value;
  std::size_t size;
};

template <typename Context>
struct custom_value {
  const void *value;
  void (*format)(const void *arg, Context &ctx);
};

// A formatting argument value.
template <typename Context>
class value {
 public:
  typedef typename Context::char_type char_type;

  union {
    int int_value;
    unsigned uint_value;
    long long long_long_value;
    unsigned long long ulong_long_value;
    double double_value;
    long double long_double_value;
    const void *pointer;
    string_value<char_type> string;
    string_value<signed char> sstring;
    string_value<unsigned char> ustring;
    custom_value<Context> custom;
  };

  FMT_CONSTEXPR value(int val = 0) : int_value(val) {}
  value(unsigned val) { uint_value = val; }
  value(long long val) { long_long_value = val; }
  value(unsigned long long val) { ulong_long_value = val; }
  value(double val) { double_value = val; }
  value(long double val) { long_double_value = val; }
  value(const char_type *val) { string.value = val; }
  value(const signed char *val) {
    static_assert(std::is_same<char, char_type>::value,
                  "incompatible string types");
    sstring.value = val;
  }
  value(const unsigned char *val) {
    static_assert(std::is_same<char, char_type>::value,
                  "incompatible string types");
    ustring.value = val;
  }
  value(basic_string_view<char_type> val) {
    string.value = val.data();
    string.size = val.size();
  }
  value(const void *val) { pointer = val; }

  template <typename T>
  explicit value(const T &val) {
    custom.value = &val;
    custom.format = &format_custom_arg<T>;
  }

  const named_arg_base<char_type> &as_named_arg() {
    return *static_cast<const named_arg_base<char_type>*>(pointer);
  }

 private:
  // Formats an argument of a custom type, such as a user-defined class.
  template <typename T>
  static void format_custom_arg(const void *arg, Context &ctx) {
    // Get the formatter type through the context to allow different contexts
    // have different extension points, e.g. `formatter<T>` for `format` and
    // `printf_formatter<T>` for `printf`.
    typename Context::template formatter_type<T>::type f;
    auto &&parse_ctx = ctx.parse_context();
    parse_ctx.advance_to(f.parse(parse_ctx));
    ctx.advance_to(f.format(*static_cast<const T*>(arg), ctx));
  }
};

template <typename Context, type TYPE>
struct typed_value : value<Context> {
  static const type type_tag = TYPE;

  template <typename T>
  FMT_CONSTEXPR typed_value(const T &val) : value<Context>(val) {}
};

template <typename Context, typename T>
FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T &value);

#define FMT_MAKE_VALUE(TAG, ArgType, ValueType) \
  template <typename C> \
  FMT_CONSTEXPR typed_value<C, TAG> make_value(ArgType val) { \
    return static_cast<ValueType>(val); \
  }

FMT_MAKE_VALUE(bool_type, bool, int)
FMT_MAKE_VALUE(int_type, short, int)
FMT_MAKE_VALUE(uint_type, unsigned short, unsigned)
FMT_MAKE_VALUE(int_type, int, int)
FMT_MAKE_VALUE(uint_type, unsigned, unsigned)

// To minimize the number of types we need to deal with, long is translated
// either to int or to long long depending on its size.
typedef std::conditional<sizeof(long) == sizeof(int), int, long long>::type
        long_type;
FMT_MAKE_VALUE(
    (sizeof(long) == sizeof(int) ? int_type : long_long_type), long, long_type)
typedef std::conditional<sizeof(unsigned long) == sizeof(unsigned),
                         unsigned, unsigned long long>::type ulong_type;
FMT_MAKE_VALUE(
    (sizeof(unsigned long) == sizeof(unsigned) ? uint_type : ulong_long_type),
    unsigned long, ulong_type)

FMT_MAKE_VALUE(long_long_type, long long, long long)
FMT_MAKE_VALUE(ulong_long_type, unsigned long long, unsigned long long)
FMT_MAKE_VALUE(int_type, signed char, int)
FMT_MAKE_VALUE(uint_type, unsigned char, unsigned)
FMT_MAKE_VALUE(char_type, char, int)

#if !defined(_MSC_VER) || defined(_NATIVE_WCHAR_T_DEFINED)
template <typename C>
inline typed_value<C, char_type> make_value(wchar_t val) {
  require_wchar<typename C::char_type>();
  return static_cast<int>(val);
}
#endif

FMT_MAKE_VALUE(double_type, float, double)
FMT_MAKE_VALUE(double_type, double, double)
FMT_MAKE_VALUE(long_double_type, long double, long double)

// Formatting of wide strings into a narrow buffer and multibyte strings
// into a wide buffer is disallowed (https://github.com/fmtlib/fmt/pull/606).
FMT_MAKE_VALUE(cstring_type, typename C::char_type*,
               const typename C::char_type*)
FMT_MAKE_VALUE(cstring_type, const typename C::char_type*,
               const typename C::char_type*)

FMT_MAKE_VALUE(cstring_type, signed char*, const signed char*)
FMT_MAKE_VALUE(cstring_type, const signed char*, const signed char*)
FMT_MAKE_VALUE(cstring_type, unsigned char*, const unsigned char*)
FMT_MAKE_VALUE(cstring_type, const unsigned char*, const unsigned char*)
FMT_MAKE_VALUE(string_type, basic_string_view<typename C::char_type>,
               basic_string_view<typename C::char_type>)
FMT_MAKE_VALUE(string_type,
               typename basic_string_view<typename C::char_type>::type,
               basic_string_view<typename C::char_type>)
FMT_MAKE_VALUE(string_type, const std::basic_string<typename C::char_type>&,
               basic_string_view<typename C::char_type>)
FMT_MAKE_VALUE(pointer_type, void*, const void*)
FMT_MAKE_VALUE(pointer_type, const void*, const void*)

#if FMT_USE_NULLPTR
FMT_MAKE_VALUE(pointer_type, std::nullptr_t, const void*)
#endif

// Formatting of arbitrary pointers is disallowed. If you want to output a
// pointer cast it to "void *" or "const void *". In particular, this forbids
// formatting of "[const] volatile char *" which is printed as bool by
// iostreams.
template <typename C, typename T>
typed_value<C, pointer_type> make_value(const T *) {
  static_assert(!sizeof(T), "formatting of non-void pointers is disallowed");
}

template <typename C, typename T>
inline typename std::enable_if<
    std::is_enum<T>::value && convert_to_int<T, typename C::char_type>::value,
    typed_value<C, int_type>>::type
  make_value(const T &val) { return static_cast<int>(val); }

template <typename C, typename T, typename Char = typename C::char_type>
inline typename std::enable_if<
    !convert_to_int<T, Char>::value &&
    !std::is_convertible<T, basic_string_view<Char>>::value &&
    !std::is_convertible<T, std::basic_string<Char>>::value,
    typed_value<C, custom_type>>::type
  make_value(const T &val) { return val; }

template <typename C, typename T>
typed_value<C, name_arg_type>
    make_value(const named_arg<T, typename C::char_type> &val) {
  basic_format_arg<C> arg = make_arg<C>(val.value);
  std::memcpy(val.data, &arg, sizeof(arg));
  return static_cast<const void*>(&val);
}

// Maximum number of arguments with packed types.
enum { max_packed_args = 15 };

template <typename Context>
class arg_map;

template <typename>
struct result_of;

template <typename F, typename... Args>
struct result_of<F(Args...)> {
  // A workaround for gcc 4.4 that doesn't allow F to be a reference.
  typedef typename std::result_of<
    typename std::remove_reference<F>::type(Args...)>::type type;
};
}

// A formatting argument. It is a trivially copyable/constructible type to
// allow storage in basic_memory_buffer.
template <typename Context>
class basic_format_arg {
 private:
  internal::value<Context> value_;
  internal::type type_;

  template <typename ContextType, typename T>
  friend FMT_CONSTEXPR basic_format_arg<ContextType>
    internal::make_arg(const T &value);

  template <typename Visitor, typename Ctx>
  friend FMT_CONSTEXPR typename internal::result_of<Visitor(int)>::type
    visit(Visitor &&vis, basic_format_arg<Ctx> arg);

  friend class basic_format_args<Context>;
  friend class internal::arg_map<Context>;

  typedef typename Context::char_type char_type;

 public:
  class handle {
   public:
    explicit handle(internal::custom_value<Context> custom): custom_(custom) {}

    void format(Context &ctx) const { custom_.format(custom_.value, ctx); }

   private:
    internal::custom_value<Context> custom_;
  };

  FMT_CONSTEXPR basic_format_arg() : type_(internal::none_type) {}

  FMT_EXPLICIT operator bool() const FMT_NOEXCEPT {
    return type_ != internal::none_type;
  }

  internal::type type() const { return type_; }

  bool is_integral() const { return internal::is_integral(type_); }
  bool is_arithmetic() const { return internal::is_arithmetic(type_); }
};

// Parsing context consisting of a format string range being parsed and an
// argument counter for automatic indexing.
template <typename Char, typename ErrorHandler = internal::error_handler>
class basic_parse_context : private ErrorHandler {
 private:
  basic_string_view<Char> format_str_;
  int next_arg_id_;

 public:
  typedef Char char_type;
  typedef typename basic_string_view<Char>::iterator iterator;

  explicit FMT_CONSTEXPR basic_parse_context(
      basic_string_view<Char> format_str, ErrorHandler eh = ErrorHandler())
    : ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}

  // Returns an iterator to the beginning of the format string range being
  // parsed.
  FMT_CONSTEXPR iterator begin() const FMT_NOEXCEPT {
    return format_str_.begin();
  }

  // Returns an iterator past the end of the format string range being parsed.
  FMT_CONSTEXPR iterator end() const FMT_NOEXCEPT { return format_str_.end(); }

  // Advances the begin iterator to ``it``.
  FMT_CONSTEXPR void advance_to(iterator it) {
    format_str_.remove_prefix(it - begin());
  }

  // Returns the next argument index.
  FMT_CONSTEXPR unsigned next_arg_id();

  FMT_CONSTEXPR bool check_arg_id(unsigned) {
    if (next_arg_id_ > 0) {
      on_error("cannot switch from automatic to manual argument indexing");
      return false;
    }
    next_arg_id_ = -1;
    return true;
  }
  void check_arg_id(basic_string_view<Char>) {}

  FMT_CONSTEXPR void on_error(const char *message) {
    ErrorHandler::on_error(message);
  }

  FMT_CONSTEXPR ErrorHandler error_handler() const { return *this; }
};

typedef basic_parse_context<char> parse_context;
typedef basic_parse_context<wchar_t> wparse_context;

namespace internal {
// A map from argument names to their values for named arguments.
template <typename Context>
class arg_map {
 private:
  FMT_DISALLOW_COPY_AND_ASSIGN(arg_map);

  typedef typename Context::char_type char_type;

  struct entry {
    basic_string_view<char_type> name;
    basic_format_arg<Context> arg;
  };

  entry *map_;
  unsigned size_;

  void push_back(value<Context> val) {
    const internal::named_arg_base<char_type> &named = val.as_named_arg();
    map_[size_] = entry{named.name, named.template deserialize<Context>()};
    ++size_;
  }

 public:
  arg_map() : map_(FMT_NULL), size_(0) {}
  void init(const basic_format_args<Context> &args);
  ~arg_map() { delete [] map_; }

  basic_format_arg<Context> find(basic_string_view<char_type> name) const {
    // The list is unsorted, so just return the first matching name.
    for (auto it = map_, end = map_ + size_; it != end; ++it) {
      if (it->name == name)
        return it->arg;
    }
    return basic_format_arg<Context>();
  }
};

template <typename OutputIt, typename Context, typename Char>
class context_base {
 public:
  typedef OutputIt iterator;

 private:
  basic_parse_context<Char> parse_context_;
  iterator out_;
  basic_format_args<Context> args_;

 protected:
  typedef Char char_type;
  typedef basic_format_arg<Context> format_arg;

  context_base(OutputIt out, basic_string_view<char_type> format_str,
               basic_format_args<Context> args)
  : parse_context_(format_str), out_(out), args_(args) {}

  // Returns the argument with specified index.
  format_arg do_get_arg(unsigned arg_id) {
    format_arg arg = args_.get(arg_id);
    if (!arg)
      parse_context_.on_error("argument index out of range");
    return arg;
  }

  // Checks if manual indexing is used and returns the argument with
  // specified index.
  format_arg get_arg(unsigned arg_id) {
    return this->parse_context().check_arg_id(arg_id) ?
      this->do_get_arg(arg_id) : format_arg();
  }

 public:
  basic_parse_context<char_type> &parse_context() {
    return parse_context_;
  }

  internal::error_handler error_handler() {
    return parse_context_.error_handler();
  }

  void on_error(const char *message) { parse_context_.on_error(message); }

  // Returns an iterator to the beginning of the output range.
  iterator out() { return out_; }
  iterator begin() { return out_; }  // deprecated

  // Advances the begin iterator to ``it``.
  void advance_to(iterator it) { out_ = it; }

  basic_format_args<Context> args() const { return args_; }
};

// Extracts a reference to the container from back_insert_iterator.
template <typename Container>
inline Container &get_container(std::back_insert_iterator<Container> it) {
  typedef std::back_insert_iterator<Container> bi_iterator;
  struct accessor: bi_iterator {
    accessor(bi_iterator iter) : bi_iterator(iter) {}
    using bi_iterator::container;
  };
  return *accessor(it).container;
}
}  // namespace internal

// Formatting context.
template <typename OutputIt, typename Char>
class basic_format_context :
  public internal::context_base<
    OutputIt, basic_format_context<OutputIt, Char>, Char> {
 public:
  /** The character type for the output. */
  typedef Char char_type;

  // using formatter_type = formatter<T, char_type>;
  template <typename T>
  struct formatter_type { typedef formatter<T, char_type> type; };

 private:
  internal::arg_map<basic_format_context> map_;

  FMT_DISALLOW_COPY_AND_ASSIGN(basic_format_context);

  typedef internal::context_base<OutputIt, basic_format_context, Char> base;
  typedef typename base::format_arg format_arg;
  using base::get_arg;

 public:
  using typename base::iterator;

  /**
   Constructs a ``basic_format_context`` object. References to the arguments are
   stored in the object so make sure they have appropriate lifetimes.
   */
  basic_format_context(OutputIt out, basic_string_view<char_type> format_str,
                basic_format_args<basic_format_context> args)
    : base(out, format_str, args) {}

  format_arg next_arg() {
    return this->do_get_arg(this->parse_context().next_arg_id());
  }
  format_arg get_arg(unsigned arg_id) { return this->do_get_arg(arg_id); }

  // Checks if manual indexing is used and returns the argument with the
  // specified name.
  format_arg get_arg(basic_string_view<char_type> name);
};

template <typename Char>
struct buffer_context {
  typedef basic_format_context<
    std::back_insert_iterator<internal::basic_buffer<Char>>, Char> type;
};
typedef buffer_context<char>::type format_context;
typedef buffer_context<wchar_t>::type wformat_context;

namespace internal {
template <typename Context, typename T>
struct get_type {
  typedef decltype(make_value<Context>(
        declval<typename std::decay<T>::type&>())) value_type;
  static const type value = value_type::type_tag;
};

template <typename Context>
FMT_CONSTEXPR uint64_t get_types() { return 0; }

template <typename Context, typename Arg, typename... Args>
FMT_CONSTEXPR uint64_t get_types() {
  return get_type<Context, Arg>::value | (get_types<Context, Args...>() << 4);
}

template <typename Context, typename T>
FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T &value) {
  basic_format_arg<Context> arg;
  arg.type_ = get_type<Context, T>::value;
  arg.value_ = make_value<Context>(value);
  return arg;
}

template <bool IS_PACKED, typename Context, typename T>
inline typename std::enable_if<IS_PACKED, value<Context>>::type
    make_arg(const T &value) {
  return make_value<Context>(value);
}

template <bool IS_PACKED, typename Context, typename T>
inline typename std::enable_if<!IS_PACKED, basic_format_arg<Context>>::type
    make_arg(const T &value) {
  return make_arg<Context>(value);
}
}

/**
  \rst
  An array of references to arguments. It can be implicitly converted into
  `~fmt::basic_format_args` for passing into type-erased formatting functions
  such as `~fmt::vformat`.
  \endrst
 */
template <typename Context, typename ...Args>
class format_arg_store {
 private:
  static const size_t NUM_ARGS = sizeof...(Args);

  // Packed is a macro on MinGW so use IS_PACKED instead.
  static const bool IS_PACKED = NUM_ARGS < internal::max_packed_args;

  typedef typename std::conditional<IS_PACKED,
    internal::value<Context>, basic_format_arg<Context>>::type value_type;

  // If the arguments are not packed, add one more element to mark the end.
  value_type data_[NUM_ARGS + (IS_PACKED && NUM_ARGS != 0 ? 0 : 1)];

  friend class basic_format_args<Context>;

  static FMT_CONSTEXPR uint64_t get_types() {
    return IS_PACKED ? internal::get_types<Context, Args...>()
                : -static_cast<int64_t>(NUM_ARGS);
  }

 public:
#if FMT_USE_CONSTEXPR
  static constexpr uint64_t TYPES = get_types();
#else
  static const uint64_t TYPES;
#endif

#if FMT_GCC_VERSION && FMT_GCC_VERSION <= 405
  // Workaround an array initialization bug in gcc 4.5 and earlier.
  format_arg_store(const Args &... args) {
    data_ = {internal::make_arg<IS_PACKED, Context>(args)...};
  }
#else
  format_arg_store(const Args &... args)
    : data_{internal::make_arg<IS_PACKED, Context>(args)...} {}
#endif
};

#if !FMT_USE_CONSTEXPR
template <typename Context, typename ...Args>
const uint64_t format_arg_store<Context, Args...>::TYPES = get_types();
#endif

/**
  \rst
  Constructs an `~fmt::format_arg_store` object that contains references to
  arguments and can be implicitly converted to `~fmt::format_args`. `Context` can
  be omitted in which case it defaults to `~fmt::context`.
  \endrst
 */
template <typename Context, typename ...Args>
inline format_arg_store<Context, Args...>
    make_format_args(const Args & ... args) {
  return format_arg_store<Context, Args...>(args...);
}

template <typename ...Args>
inline format_arg_store<format_context, Args...>
    make_format_args(const Args & ... args) {
  return format_arg_store<format_context, Args...>(args...);
}

/** Formatting arguments. */
template <typename Context>
class basic_format_args {
 public:
  typedef unsigned size_type;
  typedef basic_format_arg<Context>  format_arg;

 private:
  // To reduce compiled code size per formatting function call, types of first
  // max_packed_args arguments are passed in the types_ field.
  uint64_t types_;
  union {
    // If the number of arguments is less than max_packed_args, the argument
    // values are stored in values_, otherwise they are stored in args_.
    // This is done to reduce compiled code size as storing larger objects
    // may require more code (at least on x86-64) even if the same amount of
    // data is actually copied to stack. It saves ~10% on the bloat test.
    const internal::value<Context> *values_;
    const format_arg *args_;
  };

  typename internal::type type(unsigned index) const {
    unsigned shift = index * 4;
    uint64_t mask = 0xf;
    return static_cast<typename internal::type>(
      (types_ & (mask << shift)) >> shift);
  }

  friend class internal::arg_map<Context>;

  void set_data(const internal::value<Context> *values) { values_ = values; }
  void set_data(const format_arg *args) { args_ = args; }

  format_arg do_get(size_type index) const {
    int64_t signed_types = static_cast<int64_t>(types_);
    if (signed_types < 0) {
      uint64_t num_args = -signed_types;
      return index < num_args ? args_[index] : format_arg();
    }
    format_arg arg;
    if (index > internal::max_packed_args)
      return arg;
    arg.type_ = type(index);
    if (arg.type_ == internal::none_type)
      return arg;
    internal::value<Context> &val = arg.value_;
    val = values_[index];
    return arg;
  }

 public:
  basic_format_args() : types_(0) {}

  /**
   \rst
   Constructs a `basic_format_args` object from `~fmt::format_arg_store`.
   \endrst
   */
  template <typename... Args>
  basic_format_args(const format_arg_store<Context, Args...> &store)
  : types_(store.TYPES) {
    set_data(store.data_);
  }

  /** Returns the argument at specified index. */
  format_arg get(size_type index) const {
    format_arg arg = do_get(index);
    return arg.type_ == internal::name_arg_type ?
          arg.value_.as_named_arg().template deserialize<Context>() : arg;
  }

  unsigned max_size() const {
    int64_t signed_types = static_cast<int64_t>(types_);
    return static_cast<unsigned>(
        signed_types < 0 ?
        -signed_types : static_cast<int64_t>(internal::max_packed_args));
  }
};

/** An alias to ``basic_format_args<context>``. */
// It is a separate type rather than a typedef to make symbols readable.
struct format_args: basic_format_args<format_context> {
  template <typename ...Args>
  format_args(Args && ... arg)
  : basic_format_args<format_context>(std::forward<Args>(arg)...) {}
};
struct wformat_args : basic_format_args<wformat_context> {
  template <typename ...Args>
  wformat_args(Args && ... arg)
  : basic_format_args<wformat_context>(std::forward<Args>(arg)...) {}
};

namespace internal {
template <typename Char>
struct named_arg_base {
  basic_string_view<Char> name;

  // Serialized value<context>.
  mutable char data[sizeof(basic_format_arg<format_context>)];

  named_arg_base(basic_string_view<Char> nm) : name(nm) {}

  template <typename Context>
  basic_format_arg<Context> deserialize() const {
    basic_format_arg<Context> arg;
    std::memcpy(&arg, data, sizeof(basic_format_arg<Context>));
    return arg;
  }
};

template <typename T, typename Char>
struct named_arg : named_arg_base<Char> {
  const T &value;

  named_arg(basic_string_view<Char> name, const T &val)
    : named_arg_base<Char>(name), value(val) {}
};
}

/**
  \rst
  Returns a named argument to be used in a formatting function.

  **Example**::

    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
  \endrst
 */
template <typename T>
inline internal::named_arg<T, char> arg(string_view name, const T &arg) {
  return internal::named_arg<T, char>(name, arg);
}

template <typename T>
inline internal::named_arg<T, wchar_t> arg(wstring_view name, const T &arg) {
  return internal::named_arg<T, wchar_t>(name, arg);
}

// This function template is deleted intentionally to disable nested named
// arguments as in ``format("{}", arg("a", arg("b", 42)))``.
template <typename S, typename T, typename Char>
void arg(S, internal::named_arg<T, Char>) FMT_DELETED;

enum color { black, red, green, yellow, blue, magenta, cyan, white };

FMT_API void vprint_colored(color c, string_view format, format_args args);
FMT_API void vprint_colored(color c, wstring_view format, wformat_args args);

/**
  Formats a string and prints it to stdout using ANSI escape sequences to
  specify color (experimental).
  Example:
    fmt::print_colored(fmt::RED, "Elapsed time: {0:.2f} seconds", 1.23);
 */
template <typename... Args>
inline void print_colored(color c, string_view format_str,
                          const Args & ... args) {
  vprint_colored(c, format_str, make_format_args(args...));
}

template <typename... Args>
inline void print_colored(color c, wstring_view format_str,
                          const Args & ... args) {
  vprint_colored(c, format_str, make_format_args<wformat_context>(args...));
}

format_context::iterator vformat_to(
    internal::buffer &buf, string_view format_str, format_args args);
wformat_context::iterator vformat_to(
    internal::wbuffer &buf, wstring_view format_str, wformat_args args);

template <typename Container>
struct is_contiguous : std::false_type {};

template <typename Char>
struct is_contiguous<std::basic_string<Char>> : std::true_type {};

template <typename Char>
struct is_contiguous<internal::basic_buffer<Char>> : std::true_type {};

/** Formats a string and writes the output to ``out``. */
template <typename Container>
typename std::enable_if<
  is_contiguous<Container>::value, std::back_insert_iterator<Container>>::type
    vformat_to(std::back_insert_iterator<Container> out,
               string_view format_str, format_args args) {
  auto& container = internal::get_container(out);
  internal::container_buffer<Container> buf(container);
  vformat_to(buf, format_str, args);
  return std::back_inserter(container);
}

template <typename Container>
typename std::enable_if<
  is_contiguous<Container>::value, std::back_insert_iterator<Container>>::type
  vformat_to(std::back_insert_iterator<Container> out,
             wstring_view format_str, wformat_args args) {
  auto& container = internal::get_container(out);
  internal::container_buffer<Container> buf(container);
  vformat_to(buf, format_str, args);
  return std::back_inserter(container);
}

std::string vformat(string_view format_str, format_args args);
std::wstring vformat(wstring_view format_str, wformat_args args);

/**
  \rst
  Formats arguments and returns the result as a string.

  **Example**::

    #include <fmt/core.h>
    std::string message = fmt::format("The answer is {}", 42);
  \endrst
*/
template <typename... Args>
inline std::string format(string_view format_str, const Args & ... args) {
  // This should be just
  // return vformat(format_str, make_format_args(args...));
  // but gcc has trouble optimizing the latter, so break it down.
  format_arg_store<format_context, Args...> as(args...);
  return vformat(format_str, as);
}
template <typename... Args>
inline std::wstring format(wstring_view format_str, const Args & ... args) {
  format_arg_store<wformat_context, Args...> as(args...);
  return vformat(format_str, as);
}

FMT_API void vprint(std::FILE *f, string_view format_str, format_args args);
FMT_API void vprint(std::FILE *f, wstring_view format_str, wformat_args args);

/**
  \rst
  Prints formatted data to the file *f*.

  **Example**::

    fmt::print(stderr, "Don't {}!", "panic");
  \endrst
 */
template <typename... Args>
inline void print(std::FILE *f, string_view format_str, const Args & ... args) {
  format_arg_store<format_context, Args...> as(args...);
  vprint(f, format_str, as);
}
template <typename... Args>
inline void print(std::FILE *f, wstring_view format_str, const Args & ... args) {
  format_arg_store<wformat_context, Args...> as(args...);
  vprint(f, format_str, as);
}

FMT_API void vprint(string_view format_str, format_args args);
FMT_API void vprint(wstring_view format_str, wformat_args args);

/**
  \rst
  Prints formatted data to ``stdout``.

  **Example**::

    fmt::print("Elapsed time: {0:.2f} seconds", 1.23);
  \endrst
 */
template <typename... Args>
inline void print(string_view format_str, const Args & ... args) {
  format_arg_store<format_context, Args...> as(args...);
  vprint(format_str, as);
}

template <typename... Args>
inline void print(wstring_view format_str, const Args & ... args) {
  format_arg_store<wformat_context, Args...> as(args...);
  vprint(format_str, as);
}
FMT_END_NAMESPACE

#endif  // FMT_CORE_H_