From 28639969ef6ca5deaf32c550151a7cd604cbf0b1 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Thu, 28 May 2020 19:44:33 -0700
Subject: [PATCH] Use memcpy for copying digits

---
 include/fmt/format.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 123a9e26..f3ea2043 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2862,16 +2862,17 @@ class format_int {
       // "Three Optimization Tips for C++". See speed-test for a comparison.
       auto index = static_cast<unsigned>((value % 100) * 2);
       value /= 100;
-      *--ptr = detail::data::digits[index + 1];
-      *--ptr = detail::data::digits[index];
+      ptr -= 2;
+      // memcpy is faster than copying character by character.
+      memcpy(ptr, detail::data::digits + index, 2);
     }
     if (value < 10) {
       *--ptr = static_cast<char>('0' + value);
       return ptr;
     }
     auto index = static_cast<unsigned>(value * 2);
-    *--ptr = detail::data::digits[index + 1];
-    *--ptr = detail::data::digits[index];
+    ptr -= 2;
+    memcpy(ptr, detail::data::digits + index, 2);
     return ptr;
   }