From 5470b3168bb343b33098add052d26ccaac01f405 Mon Sep 17 00:00:00 2001
From: jvoisin <julien.voisin@dustri.org>
Date: Fri, 21 May 2021 12:56:46 +0200
Subject: [PATCH] Use a switch-case instead of a map, on elsid@' advice

elsid@ said:

> From my measurements static map + exceptions is slower than original code
when loading polish morrowind localization by 25% with GCC 10.2.0. Switch-based
solution is about 25x times faster than the original and static map with find
only is ~20x faster.
---
 components/fontloader/fontloader.cpp | 94 +++++++++++++---------------
 1 file changed, 43 insertions(+), 51 deletions(-)

diff --git a/components/fontloader/fontloader.cpp b/components/fontloader/fontloader.cpp
index 4c9cc11bd6..ef71d8edbb 100644
--- a/components/fontloader/fontloader.cpp
+++ b/components/fontloader/fontloader.cpp
@@ -75,63 +75,55 @@ namespace
         return unicode;
     }
 
+    /// This is a hack for Polish font
+    unsigned char mapUtf8Char(unsigned char c) {
+        switch(c){
+            case 0x80: return 0xc6;
+            case 0x81: return 0x9c;
+            case 0x82: return 0xe6;
+            case 0x83: return 0xb3;
+            case 0x84: return 0xf1;
+            case 0x85: return 0xb9;
+            case 0x86: return 0xbf;
+            case 0x87: return 0x9f;
+            case 0x88: return 0xea;
+            case 0x89: return 0xea;
+            case 0x8a: return 0x00; // not contained in win1250
+            case 0x8b: return 0x00; // not contained in win1250
+            case 0x8c: return 0x8f;
+            case 0x8d: return 0xaf;
+            case 0x8e: return 0xa5;
+            case 0x8f: return 0x8c;
+            case 0x90: return 0xca;
+            case 0x93: return 0xa3;
+            case 0x94: return 0xf6;
+            case 0x95: return 0xf3;
+            case 0x96: return 0xaf;
+            case 0x97: return 0x8f;
+            case 0x99: return 0xd3;
+            case 0x9a: return 0xd1;
+            case 0x9c: return 0x00; // not contained in win1250
+            case 0xa0: return 0xb9;
+            case 0xa1: return 0xaf;
+            case 0xa2: return 0xf3;
+            case 0xa3: return 0xbf;
+            case 0xa4: return 0x00; // not contained in win1250
+            case 0xe1: return 0x8c;
+            // case 0xe1: return 0x8c; // Can't remember if this was supposed to read 0xe2, or is it just an extraneous copypaste?
+            case 0xe3: return 0x00; // not contained in win1250
+            case 0xf5: return 0x00; // not contained in win1250
+            default: return c;
+        }
+    }
+
     // getUtf8, aka the worst function ever written.
     // This includes various hacks for dealing with Morrowind's .fnt files that are *mostly*
     // in the expected win12XX encoding, but also have randomly swapped characters sometimes.
     // Looks like the Morrowind developers found standard encodings too boring and threw in some twists for fun.
     std::string getUtf8 (unsigned char c, ToUTF8::Utf8Encoder& encoder, ToUTF8::FromType encoding)
     {
-        if (encoding == ToUTF8::WINDOWS_1250)
-        {
-            // Hacks for polish font
-            unsigned char win1250;
-            static const std::map<unsigned char, unsigned char> conv {
-                {0x80, 0xc6},
-                {0x81, 0x9c},
-                {0x82, 0xe6},
-                {0x83, 0xb3},
-                {0x84, 0xf1},
-                {0x85, 0xb9},
-                {0x86, 0xbf},
-                {0x87, 0x9f},
-                {0x88, 0xea},
-                {0x89, 0xea},
-                {0x8a, 0x00}, // not contained in win1250
-                {0x8b, 0x00}, // not contained in win1250
-                {0x8c, 0x8f},
-                {0x8d, 0xaf},
-                {0x8e, 0xa5},
-                {0x8f, 0x8c},
-                {0x90, 0xca},
-                {0x93, 0xa3},
-                {0x94, 0xf6},
-                {0x95, 0xf3},
-                {0x96, 0xaf},
-                {0x97, 0x8f},
-                {0x99, 0xd3},
-                {0x9a, 0xd1},
-                {0x9c, 0x00}, // not contained in win1250
-                {0xa0, 0xb9},
-                {0xa1, 0xaf},
-                {0xa2, 0xf3},
-                {0xa3, 0xbf},
-                {0xa4, 0x00}, // not contained in win1250
-                {0xe1, 0x8c},
-                // Can't remember if this was supposed to read 0xe2, or is it just an extraneous copypaste?
-                //{0xe1, 0x8c},
-                {0xe3, 0x0}, // not contained in win1250
-                {0xf5, 0x0} // not contained in win1250
-            };
-            try
-            {
-                win1250 = conv.at(c);
-            }
-            catch (std::out_of_range)
-            {
-                win1250 = c;
-            }
-            return encoder.getUtf8(std::string(1, win1250));
-        }
+        if (encoding == ToUTF8::WINDOWS_1250) // Hack for polish font
+            return encoder.getUtf8(std::string(1, mapUtf8Char(c)));
         else
             return encoder.getUtf8(std::string(1, c));
     }