From 2207ea0b36c82ebf7ebba8568b035a86c2b6438a Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Sun, 22 Aug 2021 16:33:39 -0700
Subject: [PATCH] More escaping

---
 include/fmt/ranges.h | 17 ++++++++++++++---
 test/ranges-test.cc  |  7 +++++--
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index 8649bb81..a35c0664 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -431,6 +431,7 @@ 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 (sizeof(Char) == 1 && cp >= 0x80) continue;
     if (needs_escape(cp)) return {begin, begin + 1, cp};
   }
   return {begin, nullptr, 0};
@@ -480,9 +481,19 @@ auto write_range_entry(OutputIt out, basic_string_view<Char> str) -> OutputIt {
       *out++ = '\\';
       break;
     default:
-      if (is_utf8() && escape.cp > 0xffff) {
-        out = format_to(out, "\\U{:08x}", escape.cp);
-        continue;
+      if (is_utf8()) {
+        if (escape.cp < 0x100) {
+          out = format_to(out, "\\x{:02x}", escape.cp);
+          continue;
+        }
+        if (escape.cp < 0x10000) {
+          out = format_to(out, "\\u{:04x}", escape.cp);
+          continue;
+        }
+        if (escape.cp < 0x110000) {
+          out = format_to(out, "\\U{:08x}", escape.cp);
+          continue;
+        }
       }
       for (Char escape_char : basic_string_view<Char>(
                escape.begin, to_unsigned(escape.end - escape.begin))) {
diff --git a/test/ranges-test.cc b/test/ranges-test.cc
index fd1608f2..603d1976 100644
--- a/test/ranges-test.cc
+++ b/test/ranges-test.cc
@@ -275,10 +275,13 @@ TEST(ranges_test, escape_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\"]");
+  EXPECT_EQ(fmt::format("{}", vec{"n\xcc\x83"}), "[\"n\xcc\x83\"]");
 
-  // Unassigned Unicode code points.
   if (fmt::detail::is_utf8()) {
+    EXPECT_EQ(fmt::format("{}", vec{"\xcd\xb8"}), "[\"\\u0378\"]");
+    // Unassigned Unicode code points.
     EXPECT_EQ(fmt::format("{}", vec{"\xf0\xaa\x9b\x9e"}), "[\"\\U0002a6de\"]");
-    EXPECT_EQ(fmt::format("{}", vec{"\xf4\x8f\xbf\xbf"}), "[\"\\U0010ffff\"]");
+    EXPECT_EQ(fmt::format("{}", vec{"\xf4\x8f\xbf\xc0"}),
+              "[\"\\xf4\\x8f\\xbf\\xc0\"]");
   }
 }