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>

include/fmt/time.h

@@ -116,17 +116,16 @@ template <typename Char>
 struct formatter<std::tm, Char> {
   template <typename ParseContext>
   auto parse(ParseContext &ctx) -> decltype(ctx.begin()) {
-    auto it = internal::null_terminating_iterator<Char>(ctx);
-    if (*it == ':')
+    auto it = ctx.begin();
+    if (it != ctx.end() && *it == ':')
       ++it;
     auto end = it;
-    while (*end && *end != '}')
+    while (end != ctx.end() && *end != '}')
       ++end;
     tm_format.reserve(end - it + 1);
-    using internal::pointer_from;
-    tm_format.append(pointer_from(it), pointer_from(end));
+    tm_format.append(it, end);
     tm_format.push_back('\0');
-    return pointer_from(end);
+    return end;
   }
 
   template <typename FormatContext>

test/format-test.cc

@@ -193,13 +193,16 @@ TEST(UtilTest, ParseNonnegativeInt) {
     fmt::print("Skipping parse_nonnegative_int test\n");
     return;
   }
-  const char *s = "10000000000";
+  fmt::string_view s = "10000000000";
+  auto begin = s.begin(), end = s.end();
   EXPECT_THROW_MSG(
-        parse_nonnegative_int(s, fmt::internal::error_handler()),
+        parse_nonnegative_int(begin, end, fmt::internal::error_handler()),
         fmt::format_error, "number is too big");
   s = "2147483649";
+  begin = s.begin();
+  end = s.end();
   EXPECT_THROW_MSG(
-        parse_nonnegative_int(s, fmt::internal::error_handler()),
+        parse_nonnegative_int(begin, end, fmt::internal::error_handler()),
         fmt::format_error, "number is too big");
 }
 
@@ -941,6 +944,7 @@ TEST(FormatterTest, Fill) {
   EXPECT_EQ("abc**", format("{0:*<5}", "abc"));
   EXPECT_EQ("**0xface", format("{0:*>8}", reinterpret_cast<void*>(0xface)));
   EXPECT_EQ("foo=", format("{:}=", "foo"));
+  EXPECT_EQ(std::string("\0\0\0*", 4), format(string_view("{:\0>4}", 6), '*'));
 }
 
 TEST(FormatterTest, PlusSign) {
@@ -2087,9 +2091,10 @@ struct test_arg_id_handler {
   FMT_CONSTEXPR void on_error(const char *) { res = ERROR; }
 };
 
-FMT_CONSTEXPR test_arg_id_handler parse_arg_id(const char* s) {
+template <size_t N>
+FMT_CONSTEXPR test_arg_id_handler parse_arg_id(const char (&s)[N]) {
   test_arg_id_handler h;
-  fmt::internal::parse_arg_id(s, h);
+  fmt::internal::parse_arg_id(s, s + N, h);
   return h;
 }
 
@@ -2149,9 +2154,10 @@ struct test_format_specs_handler {
   FMT_CONSTEXPR void on_error(const char *) { res = ERROR; }
 };
 
-FMT_CONSTEXPR test_format_specs_handler parse_test_specs(const char *s) {
+template <size_t N>
+FMT_CONSTEXPR test_format_specs_handler parse_test_specs(const char (&s)[N]) {
   test_format_specs_handler h;
-  fmt::internal::parse_format_specs(s, h);
+  fmt::internal::parse_format_specs(s, s + N, h);
   return h;
 }
 
@@ -2195,11 +2201,12 @@ struct test_context {
   FMT_CONSTEXPR test_context error_handler() { return *this; }
 };
 
-FMT_CONSTEXPR fmt::format_specs parse_specs(const char *s) {
+template <size_t N>
+FMT_CONSTEXPR fmt::format_specs parse_specs(const char (&s)[N]) {
   fmt::format_specs specs;
   test_context ctx{};
   fmt::internal::specs_handler<test_context> h(specs, ctx);
-  parse_format_specs(s, h);
+  parse_format_specs(s, s + N, h);
   return specs;
 }
 
@@ -2220,12 +2227,13 @@ TEST(FormatTest, ConstexprSpecsHandler) {
   static_assert(parse_specs("d").type == 'd', "");
 }
 
+template <size_t N>
 FMT_CONSTEXPR fmt::internal::dynamic_format_specs<char>
-    parse_dynamic_specs(const char *s) {
+    parse_dynamic_specs(const char (&s)[N]) {
   fmt::internal::dynamic_format_specs<char> specs;
   test_context ctx{};
   fmt::internal::dynamic_specs_handler<test_context> h(specs, ctx);
-  parse_format_specs(s, h);
+  parse_format_specs(s, s + N, h);
   return specs;
 }
 
@@ -2246,10 +2254,11 @@ TEST(FormatTest, ConstexprDynamicSpecsHandler) {
   static_assert(parse_dynamic_specs("d").type == 'd', "");
 }
 
-FMT_CONSTEXPR test_format_specs_handler check_specs(const char *s) {
+template <size_t N>
+FMT_CONSTEXPR test_format_specs_handler check_specs(const char (&s)[N]) {
   fmt::internal::specs_checker<test_format_specs_handler>
       checker(test_format_specs_handler(), fmt::internal::double_type);
-  parse_format_specs(s, checker);
+  parse_format_specs(s, s + N, checker);
   return checker;
 }
 
@@ -2278,11 +2287,11 @@ struct test_format_string_handler {
   template <typename T>
   FMT_CONSTEXPR void on_arg_id(T) {}
 
-  template <typename Iterator>
-  FMT_CONSTEXPR void on_replacement_field(Iterator) {}
+  FMT_CONSTEXPR void on_replacement_field(const char *) {}
 
-  template <typename Iterator>
-  FMT_CONSTEXPR Iterator on_format_specs(Iterator it) { return it; }
+  FMT_CONSTEXPR const char *on_format_specs(const char *begin, const char*) {
+    return begin;
+  }
 
   FMT_CONSTEXPR void on_error(const char *) { error = true; }