Get rid of null_terminating_iterator in format

include/fmt/printf.h

@@ -16,6 +16,130 @@
 FMT_BEGIN_NAMESPACE
 namespace internal {
 
+// An iterator that produces a null terminator on *end. This simplifies parsing
+// and allows comparing the performance of processing a null-terminated string
+// vs string_view.
+template <typename Char>
+class null_terminating_iterator {
+ public:
+  typedef std::ptrdiff_t difference_type;
+  typedef Char value_type;
+  typedef const Char* pointer;
+  typedef const Char& reference;
+  typedef std::random_access_iterator_tag iterator_category;
+
+  null_terminating_iterator() : ptr_(0), end_(0) {}
+
+  FMT_CONSTEXPR null_terminating_iterator(const Char *ptr, const Char *end)
+    : ptr_(ptr), end_(end) {}
+
+  template <typename Range>
+  FMT_CONSTEXPR explicit null_terminating_iterator(const Range &r)
+    : ptr_(r.begin()), end_(r.end()) {}
+
+  FMT_CONSTEXPR null_terminating_iterator &operator=(const Char *ptr) {
+    assert(ptr <= end_);
+    ptr_ = ptr;
+    return *this;
+  }
+
+  FMT_CONSTEXPR Char operator*() const {
+    return ptr_ != end_ ? *ptr_ : Char();
+  }
+
+  FMT_CONSTEXPR null_terminating_iterator operator++() {
+    ++ptr_;
+    return *this;
+  }
+
+  FMT_CONSTEXPR null_terminating_iterator operator++(int) {
+    null_terminating_iterator result(*this);
+    ++ptr_;
+    return result;
+  }
+
+  FMT_CONSTEXPR null_terminating_iterator operator--() {
+    --ptr_;
+    return *this;
+  }
+
+  FMT_CONSTEXPR null_terminating_iterator operator+(difference_type n) {
+    return null_terminating_iterator(ptr_ + n, end_);
+  }
+
+  FMT_CONSTEXPR null_terminating_iterator operator-(difference_type n) {
+    return null_terminating_iterator(ptr_ - n, end_);
+  }
+
+  FMT_CONSTEXPR null_terminating_iterator operator+=(difference_type n) {
+    ptr_ += n;
+    return *this;
+  }
+
+  FMT_CONSTEXPR difference_type operator-(
+      null_terminating_iterator other) const {
+    return ptr_ - other.ptr_;
+  }
+
+  FMT_CONSTEXPR bool operator!=(null_terminating_iterator other) const {
+    return ptr_ != other.ptr_;
+  }
+
+  bool operator>=(null_terminating_iterator other) const {
+    return ptr_ >= other.ptr_;
+  }
+
+  // This should be a friend specialization pointer_from<Char> but the latter
+  // doesn't compile by gcc 5.1 due to a compiler bug.
+  template <typename CharT>
+  friend FMT_CONSTEXPR_DECL const CharT *pointer_from(
+      null_terminating_iterator<CharT> it);
+
+ private:
+  const Char *ptr_;
+  const Char *end_;
+};
+
+template <typename T>
+FMT_CONSTEXPR const T *pointer_from(const T *p) { return p; }
+
+template <typename Char>
+FMT_CONSTEXPR const Char *pointer_from(null_terminating_iterator<Char> it) {
+  return it.ptr_;
+}
+
+// DEPRECATED: Parses the input as an unsigned integer. This function assumes
+// that the first character is a digit and presence of a non-digit character at
+// the end.
+// it: an iterator pointing to the beginning of the input range.
+template <typename Iterator, typename ErrorHandler>
+FMT_CONSTEXPR unsigned parse_nonnegative_int(Iterator &it, ErrorHandler &&eh) {
+  assert('0' <= *it && *it <= '9');
+  if (*it == '0') {
+    ++it;
+    return 0;
+  }
+  unsigned value = 0;
+  // Convert to unsigned to prevent a warning.
+  unsigned max_int = (std::numeric_limits<int>::max)();
+  unsigned big = max_int / 10;
+  do {
+    // Check for overflow.
+    if (value > big) {
+      value = max_int + 1;
+      break;
+    }
+    value = value * 10 + unsigned(*it - '0');
+    // Workaround for MSVC "setup_exception stack overflow" error:
+    auto next = it;
+    ++next;
+    it = next;
+  } while ('0' <= *it && *it <= '9');
+  if (value > max_int)
+    eh.on_error("number is too big");
+  return value;
+}
+
 // Checks if a value fits in int - used to avoid warnings about comparing
 // signed and unsigned integers.
 template <bool IsSigned>