From bc1b89da26300c31c8653acc376fc2d9f6bc8189 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Fri, 22 May 2020 14:59:23 -0700
Subject: [PATCH] Temporarily revert parsing changes

---
 include/fmt/format.h | 77 ++++++++++++++------------------------------
 1 file changed, 24 insertions(+), 53 deletions(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 45bcef12..f73e8053 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2514,63 +2514,12 @@ template <typename Handler, typename Char> struct id_adapter {
   Handler& handler;
 };
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR_DECL FMT_INLINE const Char* parse_replacement_field(
-    const Char* begin, const Char* end, Handler&& handler) {
-  ++begin;
-  if (begin == end) return handler.on_error("invalid format string"), end;
-  if (static_cast<char>(*begin) == '}') {
-    handler.on_arg_id();
-    handler.on_replacement_field(begin);
-  } else if (*begin == '{') {
-    handler.on_text(begin, begin + 1);
-  } else {
-    begin = parse_arg_id(begin, end, id_adapter<Handler, Char>{handler});
-    Char c = begin != end ? *begin : Char();
-    if (c == '}') {
-      handler.on_replacement_field(begin);
-    } else if (c == ':') {
-      begin = handler.on_format_specs(begin + 1, end);
-      if (begin == end || *begin != '}')
-        return handler.on_error("unknown format specifier"), end;
-    } else {
-      return handler.on_error("missing '}' in format string"), end;
-    }
-  }
-  return begin + 1;
-}
-
 template <bool IS_CONSTEXPR, typename Char, typename Handler>
 FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
                                        Handler&& handler) {
-  auto begin = format_str.data();
-  auto end = begin + format_str.size();
-  if (end - begin < 32) {
-    // Use a simple loop instead of memchr for small strings.
-    const Char* p = begin;
-    while (p != end) {
-      auto c = *p++;
-      if (c == '{') {
-        handler.on_text(begin, p - 1);
-        begin = p = parse_replacement_field(p - 1, end, handler);
-      } else if (c == '}') {
-        if (p == end || *p != '}')
-          return handler.on_error("unmatched '}' in format string");
-        handler.on_text(begin, p);
-        begin = ++p;
-      }
-    }
-    handler.on_text(begin, end);
-    return;
-  }
   struct writer {
     FMT_CONSTEXPR void operator()(const Char* begin, const Char* end) {
-      if (begin + 1 >= end) {
-        if (begin == end) return;
-        if (*begin == '}')
-          return handler_.on_error("unmatched '}' in format string");
-        return handler_.on_text(begin, begin + 1);
-      }
+      if (begin == end) return;
       for (;;) {
         const Char* p = nullptr;
         if (!find<IS_CONSTEXPR>(begin, end, '}', p))
@@ -2584,6 +2533,8 @@ FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
     }
     Handler& handler_;
   } write{handler};
+  auto begin = format_str.data();
+  auto end = begin + format_str.size();
   while (begin != end) {
     // Doing two passes with memchr (one for '{' and another for '}') is up to
     // 2.5x faster than the naive one-pass implementation on big format strings.
@@ -2591,7 +2542,27 @@ FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
     if (*begin != '{' && !find<IS_CONSTEXPR>(begin + 1, end, '{', p))
       return write(begin, end);
     write(begin, p);
-    begin = parse_replacement_field(p, end, handler);
+    ++p;
+    if (p == end) return handler.on_error("invalid format string");
+    if (static_cast<char>(*p) == '}') {
+      handler.on_arg_id();
+      handler.on_replacement_field(p);
+    } else if (*p == '{') {
+      handler.on_text(p, p + 1);
+    } else {
+      p = parse_arg_id(p, end, id_adapter<Handler, Char>{handler});
+      Char c = p != end ? *p : Char();
+      if (c == '}') {
+        handler.on_replacement_field(p);
+      } else if (c == ':') {
+        p = handler.on_format_specs(p + 1, end);
+        if (p == end || *p != '}')
+          return handler.on_error("unknown format specifier");
+      } else {
+        return handler.on_error("missing '}' in format string");
+      }
+    }
+    begin = p + 1;
   }
 }