More iterator support

include/fmt/core.h

@@ -200,7 +200,8 @@ class basic_buffer {
   std::size_t capacity_;
 
  protected:
-  basic_buffer() FMT_NOEXCEPT : ptr_(0), size_(0), capacity_(0) {}
+  basic_buffer(T *p = 0, 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 {
@@ -266,12 +267,12 @@ class basic_buffer {
   const T &operator[](std::size_t index) const { return ptr_[index]; }
 };
 
-using buffer = internal::basic_buffer<char>;
-using wbuffer = internal::basic_buffer<wchar_t>;
+using buffer = basic_buffer<char>;
+using wbuffer = basic_buffer<wchar_t>;
 
+// A container-backed buffer.
 template <typename Container>
-class container_buffer
-    : public internal::basic_buffer<typename Container::value_type> {
+class container_buffer : public basic_buffer<typename Container::value_type> {
  private:
   Container &container_;
 
@@ -282,7 +283,9 @@ class container_buffer
   }
 
  public:
-  explicit container_buffer(Container &c) : container_(c) {}
+  explicit container_buffer(Container &c)
+    : basic_buffer<typename Container::value_type>(&c[0], c.size(), c.size()),
+      container_(c) {}
 };
 
 // A helper function to suppress bogus "conditional expression is constant"
@@ -771,7 +774,6 @@ class context_base {
 
  private:
   basic_parse_context<typename Range::value_type> parse_context_;
-  Range range_;
   iterator out_;
   basic_format_args<Context> args_;
 
@@ -779,9 +781,9 @@ class context_base {
   using char_type = typename Range::value_type;
   using format_arg = basic_arg<Context>;
 
-  context_base(Range range, basic_string_view<char_type> format_str,
+  context_base(Range r, basic_string_view<char_type> format_str,
                basic_format_args<Context> args)
-  : parse_context_(format_str), range_(range), args_(args) {}
+  : parse_context_(format_str), out_(r.begin()), args_(args) {}
 
   basic_format_args<Context> args() const { return args_; }
 
@@ -811,23 +813,33 @@ class context_base {
 
   void on_error(const char *message) { parse_context_.on_error(message); }
 
-  Range range() { return range_; }
-
   // Returns an iterator to the beginning of the output range.
-  auto begin() { return std::back_inserter(range_.container()); }
+  auto begin() { return out_; }
 
   // Advances the begin iterator to ``it``.
   void advance_to(iterator it) { out_ = it; }
 };
 
-// A range that can grow dynamically.
+// Extracts a reference to the container from back_insert_iterator.
+template <typename Container>
+inline Container &get_container(std::back_insert_iterator<Container> it) {
+  using iterator = std::back_insert_iterator<Container>;
+  struct accessor: iterator {
+    accessor(iterator it) : iterator(it) {}
+    using iterator::container;
+  };
+  return *accessor(it).container;
+}
+}  // namespace internal
+
+// A range where begin() returns back_insert_iterator.
 template <typename Container>
-class dynamic_range {
+class back_insert_range {
  private:
   Container &container_;
 
  public:
-  using iterator = decltype(container_.begin());
+  using iterator = std::back_insert_iterator<Container>;
   using value_type = typename Container::value_type;
 
   struct sentinel {
@@ -835,20 +847,11 @@ class dynamic_range {
     friend bool operator!=(iterator, sentinel) { return false; }
   };
 
-  dynamic_range(Container &c) : container_(c) {}
+  back_insert_range(Container &c) : container_(c) {}
 
-  iterator begin() const { return container_.begin(); }
+  iterator begin() const { return std::back_inserter(container_); }
   sentinel end() const { return sentinel(); }
-
-  friend iterator grow(dynamic_range r, size_t n) {
-    auto size = r.container_.size();
-    r.container_.resize(size + n);
-    return r.container_.begin() + size;
-  }
-
-  Container &container() const { return container_; }
 };
-}  // namespace internal
 
 // Formatting context.
 template <typename Range>
@@ -895,8 +898,8 @@ class basic_context :
   format_arg get_arg(basic_string_view<char_type> name);
 };
 
-using context = basic_context<internal::dynamic_range<internal::buffer>>;
-using wcontext = basic_context<internal::dynamic_range<internal::wbuffer>>;
+using context = basic_context<back_insert_range<internal::buffer>>;
+using wcontext = basic_context<back_insert_range<internal::wbuffer>>;
 
 template <typename Context, typename ...Args>
 class arg_store {
@@ -1016,7 +1019,7 @@ struct named_arg_base {
   // Serialized value<context>.
   mutable char data[sizeof(basic_arg<context>)];
 
-  named_arg_base(basic_string_view<Char> name) : name(name) {}
+  named_arg_base(basic_string_view<Char> nm) : name(nm) {}
 
   template <typename Context>
   basic_arg<Context> deserialize() const {
@@ -1082,18 +1085,21 @@ void vformat_to(internal::buffer &buf, string_view format_str,
 void vformat_to(internal::wbuffer &buf, wstring_view format_str,
                 wformat_args args);
 
-/**
- Formats a string and writes the output to out.
- */
 template <typename Container>
-void vformat_to(std::back_insert_iterator<Container> out,
+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<fmt::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>::type
+    vformat_to(std::back_insert_iterator<Container> out,
                string_view format_str, format_args args) {
-  using iterator = std::back_insert_iterator<Container>;
-  struct container_accessor : iterator {
-    container_accessor(iterator it) : iterator(it) {}
-    using iterator::container;
-  } accessor(out);
-  internal::container_buffer<Container> buf(*accessor.container);
+  internal::container_buffer<Container> buf(internal::get_container(out));
   vformat_to(buf, format_str, args);
 }
 

include/fmt/format.cc

@@ -326,7 +326,7 @@ FMT_FUNC void windows_error::init(
 }
 
 FMT_FUNC void internal::format_windows_error(
-    buffer &out, int error_code, string_view message) FMT_NOEXCEPT {
+    internal::buffer &out, int error_code, string_view message) FMT_NOEXCEPT {
   FMT_TRY {
     wmemory_buffer buf;
     buf.resize(INLINE_BUFFER_SIZE);

include/fmt/printf.h

@@ -289,7 +289,7 @@ struct printf_formatter {
 
   template <typename FormatContext>
   auto format(const T &value, FormatContext &ctx) -> decltype(ctx.begin()) {
-    internal::format_value(ctx.range().container(), value);
+    internal::format_value(internal::get_container(ctx.begin()), value);
     return ctx.begin();
   }
 };
@@ -336,7 +336,6 @@ class basic_printf_context :
     : base(range, format_str, args) {}
 
   using base::parse_context;
-  using base::range;
   using base::begin;
   using base::advance_to;
 
@@ -419,7 +418,7 @@ unsigned basic_printf_context<Range, AF>::parse_header(
 
 template <typename Range, typename AF>
 void basic_printf_context<Range, AF>::format() {
-  auto &buffer = this->range().container();
+  auto &buffer = internal::get_container(this->begin());
   auto start = iterator(this->parse_context());
   auto it = start;
   using internal::pointer_from;
@@ -528,7 +527,7 @@ void printf(internal::basic_buffer<Char> &buf, basic_string_view<Char> format,
 }
 
 template <typename Buffer>
-using printf_context = basic_printf_context<internal::dynamic_range<Buffer>>;
+using printf_context = basic_printf_context<back_insert_range<Buffer>>;
 
 using printf_args = basic_format_args<printf_context<internal::buffer>>;
 

include/fmt/time.h

@@ -31,7 +31,7 @@ struct formatter<std::tm> {
   }
 
   auto format(const std::tm &tm, context &ctx) -> decltype(ctx.begin()) {
-    internal::buffer &buf = ctx.range().container();
+    internal::buffer &buf = internal::get_container(ctx.begin());
     std::size_t start = buf.size();
     for (;;) {
       std::size_t size = buf.capacity() - start;

test/custom-formatter-test.cc

@@ -15,15 +15,13 @@ using fmt::printf_arg_formatter;
 // A custom argument formatter that doesn't print `-` for floating-point values
 // rounded to 0.
 class CustomArgFormatter :
-    public fmt::arg_formatter<
-      fmt::internal::dynamic_range<fmt::internal::buffer>> {
+    public fmt::arg_formatter<fmt::back_insert_range<fmt::internal::buffer>> {
  public:
-  using range = fmt::internal::dynamic_range<fmt::internal::buffer>;
+  using range = fmt::back_insert_range<fmt::internal::buffer>;
   using base = fmt::arg_formatter<range>;
 
-  CustomArgFormatter(range r, fmt::basic_context<range> &ctx,
-                     fmt::format_specs &s)
-  : base(r, ctx, s) {}
+  CustomArgFormatter(fmt::basic_context<range> &ctx, fmt::format_specs &s)
+  : base(ctx, s) {}
 
   using base::operator();
 

test/format-test.cc

@@ -88,7 +88,7 @@ void std_format(long double value, std::wstring &result) {
 template <typename Char, typename T>
 ::testing::AssertionResult check_write(const T &value, const char *type) {
   fmt::basic_memory_buffer<Char> buffer;
-  using range = fmt::internal::dynamic_range<fmt::internal::basic_buffer<Char>>;
+  using range = fmt::back_insert_range<fmt::internal::basic_buffer<Char>>;
   fmt::basic_writer<range> writer(buffer);
   writer.write(value);
   std::basic_string<Char> actual = to_string(buffer);
@@ -1481,7 +1481,7 @@ TEST(FormatTest, Enum) {
   EXPECT_EQ("0", fmt::format("{}", A));
 }
 
-using buffer_range = fmt::internal::dynamic_range<fmt::internal::buffer>;
+using buffer_range = fmt::back_insert_range<fmt::internal::buffer>;
 
 class mock_arg_formatter :
     public fmt::internal::arg_formatter_base<buffer_range> {
@@ -1492,8 +1492,8 @@ class mock_arg_formatter :
   using base = fmt::internal::arg_formatter_base<buffer_range>;
   using range = buffer_range;
 
-  mock_arg_formatter(buffer_range r, fmt::context &, fmt::format_specs &s)
-    : base(r, s) {
+  mock_arg_formatter(fmt::context &ctx, fmt::format_specs &s)
+    : base(fmt::internal::get_container(ctx.begin()), s) {
     EXPECT_CALL(*this, call(42));
   }
 
@@ -1905,6 +1905,6 @@ TEST(FormatTest, FormatStringErrors) {
                int, int);
 }
 
-TEST(StringTest, ToString) {
+TEST(FormatTest, ToString) {
   EXPECT_EQ("42", fmt::to_string(42));
 }

test/ostream-test.cc

@@ -59,17 +59,15 @@ TEST(OStreamTest, Enum) {
 }
 
 struct test_arg_formatter : fmt::arg_formatter<fmt::context::range_type> {
-  using base = fmt::arg_formatter<fmt::context::range_type>;
-  test_arg_formatter(fmt::internal::buffer &buf, fmt::context &ctx,
-                     fmt::format_specs &s)
-    : base(buf, ctx, s) {}
+  test_arg_formatter(fmt::context &ctx, fmt::format_specs &s)
+    : fmt::arg_formatter<fmt::context::range_type>(ctx, s) {}
 };
 
 TEST(OStreamTest, CustomArg) {
   fmt::memory_buffer buffer;
   fmt::context ctx(buffer, "", fmt::format_args());
   fmt::format_specs spec;
-  test_arg_formatter af(buffer, ctx, spec);
+  test_arg_formatter af(ctx, spec);
   visit(af, fmt::internal::make_arg<fmt::context>(TestEnum()));
   EXPECT_EQ("TestEnum", std::string(buffer.data(), buffer.size()));
 }

test/util-test.cc

@@ -81,7 +81,7 @@ struct formatter<Test, Char> {
     return ctx.begin();
   }
 
-  using range = fmt::internal::dynamic_range<basic_buffer<Char>>;
+  using range = fmt::back_insert_range<basic_buffer<Char>>;
 
   auto format(Test, basic_context<range> &ctx) -> decltype(ctx.begin()) {
     const Char *test = "test";
@@ -521,7 +521,7 @@ VISIT_TYPE(float, double);
 #define CHECK_ARG_(Char, expected, value) { \
   testing::StrictMock<MockVisitor<decltype(expected)>> visitor; \
   EXPECT_CALL(visitor, visit(expected)); \
-  using range = fmt::internal::dynamic_range<basic_buffer<Char>>; \
+  using range = fmt::back_insert_range<basic_buffer<Char>>; \
   fmt::visit(visitor, make_arg<fmt::basic_context<range>>(value)); \
 }