More escaping

include/fmt/format-inl.h

@@ -2525,8 +2525,8 @@ template <> struct formatter<detail::bigint> {
 };
 
 FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
-  for_each_codepoint(s, [this](uint32_t cp, int error) {
-    if (error != 0) FMT_THROW(std::runtime_error("invalid utf8"));
+  for_each_codepoint(s, [this](uint32_t cp, string_view) {
+    if (cp == invalid_code_point) FMT_THROW(std::runtime_error("invalid utf8"));
     if (cp <= 0xFFFF) {
       buffer_.push_back(static_cast<wchar_t>(cp));
     } else {
@@ -2534,6 +2534,7 @@ FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
       buffer_.push_back(static_cast<wchar_t>(0xD800 + (cp >> 10)));
       buffer_.push_back(static_cast<wchar_t>(0xDC00 + (cp & 0x3FF)));
     }
+    return true;
   });
   buffer_.push_back(0);
 }

include/fmt/format.h

@@ -483,27 +483,38 @@ FMT_CONSTEXPR inline auto utf8_decode(const char* s, uint32_t* c, int* e)
   return next;
 }
 
+enum { invalid_code_point = ~uint32_t() };
+
+// Invokes f(cp, sv) for every code point cp in s with sv being the string view
+// corresponding to the code point. cp is invalid_code_point on error.
 template <typename F>
 FMT_CONSTEXPR void for_each_codepoint(string_view s, F f) {
-  auto decode = [f](const char* p) {
+  auto decode = [f](const char* buf_ptr, const char* ptr) {
     auto cp = uint32_t();
     auto error = 0;
-    p = utf8_decode(p, &cp, &error);
-    f(cp, error);
-    return p;
+    auto end = utf8_decode(buf_ptr, &cp, &error);
+    bool result = f(error ? invalid_code_point : cp,
+                    string_view(ptr, to_unsigned(end - buf_ptr)));
+    return result ? end : nullptr;
   };
   auto p = s.data();
   const size_t block_size = 4;  // utf8_decode always reads blocks of 4 chars.
   if (s.size() >= block_size) {
-    for (auto end = p + s.size() - block_size + 1; p < end;) p = decode(p);
+    for (auto end = p + s.size() - block_size + 1; p < end;) {
+      p = decode(p, p);
+      if (!p) return;
+    }
   }
   if (auto num_chars_left = s.data() + s.size() - p) {
     char buf[2 * block_size - 1] = {};
     copy_str<char>(p, p + num_chars_left, buf);
-    p = buf;
+    const char* buf_ptr = buf;
     do {
-      p = decode(p);
-    } while (p - buf < num_chars_left);
+      auto end = decode(buf_ptr, p);
+      if (!end) return;
+      p += end - buf_ptr;
+      buf_ptr = end;
+    } while (buf_ptr - buf < num_chars_left);
   }
 }
 
@@ -518,10 +529,10 @@ FMT_CONSTEXPR inline size_t compute_width(string_view s) {
   // It is not a lambda for compatibility with C++14.
   struct count_code_points {
     size_t* count;
-    FMT_CONSTEXPR void operator()(uint32_t cp, int error) const {
+    FMT_CONSTEXPR auto operator()(uint32_t cp, string_view) const -> bool {
       *count += detail::to_unsigned(
           1 +
-          (error == 0 && cp >= 0x1100 &&
+          (cp >= 0x1100 &&
            (cp <= 0x115f ||  // Hangul Jamo init. consonants
             cp == 0x2329 ||  // LEFT-POINTING ANGLE BRACKET
             cp == 0x232a ||  // RIGHT-POINTING ANGLE BRACKET
@@ -539,6 +550,7 @@ FMT_CONSTEXPR inline size_t compute_width(string_view s) {
             (cp >= 0x1f300 && cp <= 0x1f64f) ||
             // Supplemental Symbols and Pictographs:
             (cp >= 0x1f900 && cp <= 0x1f9ff))));
+      return true;
     }
   };
   for_each_codepoint(s, count_code_points{&num_code_points});

include/fmt/ranges.h

@@ -227,17 +227,65 @@ template <typename OutputIt> OutputIt write_delimiter(OutputIt out) {
   return out;
 }
 
-template <typename Char> inline bool is_printable_ascii(Char c) {
-  return c >= 0x20 && c < 0x7e;
+inline auto is_printable(uint32_t cp) -> bool {
+  if (0x2a6de <= cp && cp < 0x2a700) return false;
+  if (0x2b735 <= cp && cp < 0x2b740) return false;
+  if (0x2b81e <= cp && cp < 0x2b820) return false;
+  if (0x2cea2 <= cp && cp < 0x2ceb0) return false;
+  if (0x2ebe1 <= cp && cp < 0x2f800) return false;
+  if (0x2fa1e <= cp && cp < 0x30000) return false;
+  if (0x3134b <= cp && cp < 0xe0100) return false;
+  if (0xe01f0 <= cp && cp < 0x110000) return false;
+  return true;
 }
 
-template <
-    typename Char, typename OutputIt, typename T,
-    FMT_ENABLE_IF(is_std_string_like<typename std::decay<T>::type>::value)>
-OutputIt write_range_entry(OutputIt out, const T& str) {
+inline auto needs_escape(uint32_t cp) -> bool {
+  return cp < 0x20 || cp == 0x7f || cp == '"' || cp == '\\' ||
+         !is_printable(cp);
+}
+
+template <typename Char> struct find_escape_result {
+  const Char* begin;
+  const Char* end;
+  uint32_t cp;
+};
+
+template <typename Char>
+auto find_escape(const Char* begin, const Char* end)
+    -> find_escape_result<Char> {
+  for (; begin != end; ++begin) {
+    auto cp = static_cast<typename std::make_unsigned<Char>::type>(*begin);
+    if (needs_escape(cp)) return {begin, begin + 1, cp};
+  }
+  return {begin, nullptr, 0};
+}
+
+auto find_escape(const char* begin, const char* end)
+    -> find_escape_result<char> {
+  if (!is_utf8()) return find_escape<char>(begin, end);
+  auto result = find_escape_result<char>{end, nullptr, 0};
+  for_each_codepoint(string_view(begin, to_unsigned(end - begin)),
+                     [&](uint32_t cp, string_view sv) {
+                       if (needs_escape(cp)) {
+                         result = {sv.begin(), sv.end(), cp};
+                         return false;
+                       }
+                       return true;
+                     });
+  return result;
+}
+
+template <typename Char, typename OutputIt>
+auto write_range_entry(OutputIt out, basic_string_view<Char> str) -> OutputIt {
   *out++ = '"';
-  for (Char c : basic_string_view<Char>(str)) {
-    switch (c) {
+  auto begin = str.begin(), end = str.end();
+  do {
+    auto escape = find_escape(begin, end);
+    out = copy_str<Char>(begin, escape.begin, out);
+    begin = escape.end;
+    if (!begin) break;
+    auto c = static_cast<Char>(escape.cp);
+    switch (escape.cp) {
     case '\n':
       *out++ = '\\';
       c = 'n';
@@ -256,13 +304,14 @@ OutputIt write_range_entry(OutputIt out, const T& str) {
       *out++ = '\\';
       break;
     default:
-      if (is_printable_ascii(c)) break;
-      if (sizeof(Char) != 1 && c >= 0x80) break;
-      out = format_to(out, "\\x{:02x}", c);
+      for (Char escape_char : basic_string_view<Char>(
+               escape.begin, to_unsigned(escape.end - escape.begin))) {
+        out = format_to(out, "\\x{:02x}", escape_char);
+      }
       continue;
     }
     *out++ = c;
-  }
+  } while (begin != end);
   *out++ = '"';
   return out;
 }

test/ranges-test.cc

@@ -264,7 +264,8 @@ TEST(ranges_test, join_range) {
 #endif  // FMT_RANGES_TEST_ENABLE_JOIN
 
 TEST(ranges_test, escape_string) {
-  EXPECT_EQ(fmt::format("{}", std::vector<std::string>{"\n\r\t\"\\"}),
-            "[\"\\n\\r\\t\\\"\\\\\"]");
-  EXPECT_EQ(fmt::format("{}", std::vector<std::string>{"\x7"}), "[\"\\x07\"]");
-}
+  using vec = std::vector<std::string>;
+  EXPECT_EQ(fmt::format("{}", vec{"\n\r\t\"\\"}), "[\"\\n\\r\\t\\\"\\\\\"]");
+  EXPECT_EQ(fmt::format("{}", vec{"\x07"}), "[\"\\x07\"]");
+  EXPECT_EQ(fmt::format("{}", vec{"\x7f"}), "[\"\\x7f\"]");
+}