From 8f011387a05587aa1578fbe132cc585122221b30 Mon Sep 17 00:00:00 2001
From: Alex Barney <thealexbarney@gmail.com>
Date: Sun, 11 Oct 2020 01:26:43 -0700
Subject: [PATCH] Improve key parser performance a bit

---
 src/LibHac/Common/Keys/ExternalKeyReader.cs | 26 ++++++++++++++++-----
 src/LibHac/Util/StringUtils.cs              |  3 +--
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/LibHac/Common/Keys/ExternalKeyReader.cs b/src/LibHac/Common/Keys/ExternalKeyReader.cs
index de44f7a8..8c530728 100644
--- a/src/LibHac/Common/Keys/ExternalKeyReader.cs
+++ b/src/LibHac/Common/Keys/ExternalKeyReader.cs
@@ -177,6 +177,8 @@ namespace LibHac.Common.Keys
             Span<char> buffer = stackalloc char[1024];
             var ctx = new KvPairReaderContext(streamReader, buffer);
 
+            // Estimate the number of keys by assuming each line is about 69 bytes.
+            // Subtract 2 from that so we estimate slightly high. 
             keySet.ExternalKeySet.EnsureCapacity((int)reader.Length / 67);
 
             while (true)
@@ -310,11 +312,18 @@ namespace LibHac.Common.Keys
                         continue;
                     case ReaderState.Initial when IsValidNameChar(c):
                         state = ReaderState.Key;
-                        ToLower(ref buffer[i]);
                         keyOffset = i;
-                        continue;
-                    case ReaderState.Key when IsValidNameChar(c):
-                        ToLower(ref buffer[i]);
+
+                        // Skip the next few rounds through the state machine since we know we should be 
+                        // encountering a string of name characters
+                        do
+                        {
+                            ToLower(ref buffer[i]);
+                            i++;
+                        } while (i < buffer.Length && IsValidNameChar(buffer[i]));
+
+                        // Decrement so we can process this character the next round through the state machine
+                        i--;
                         continue;
                     case ReaderState.Key when IsWhiteSpace(c):
                         state = ReaderState.WhiteSpace1;
@@ -334,6 +343,13 @@ namespace LibHac.Common.Keys
                     case ReaderState.Delimiter when StringUtils.IsHexDigit((byte)c):
                         state = ReaderState.Value;
                         valueOffset = i;
+
+                        do
+                        {
+                            i++;
+                        } while (i < buffer.Length && !IsEndOfLine(buffer[i]) && !IsWhiteSpace(buffer[i]));
+
+                        i--;
                         continue;
                     case ReaderState.Value when IsEndOfLine(c):
                         state = ReaderState.End;
@@ -343,8 +359,6 @@ namespace LibHac.Common.Keys
                         state = ReaderState.WhiteSpace2;
                         valueLength = i - valueOffset;
                         continue;
-                    case ReaderState.Value when StringUtils.IsHexDigit((byte)c):
-                        continue;
                     case ReaderState.WhiteSpace2 when IsWhiteSpace(c):
                         continue;
                     case ReaderState.WhiteSpace2 when IsEndOfLine(c):
diff --git a/src/LibHac/Util/StringUtils.cs b/src/LibHac/Util/StringUtils.cs
index b20e2b62..aea3333d 100644
--- a/src/LibHac/Util/StringUtils.cs
+++ b/src/LibHac/Util/StringUtils.cs
@@ -194,8 +194,7 @@ namespace LibHac.Util
 
         public static bool IsHexDigit(byte c)
         {
-            return (uint)(c - (byte)'0') <= 9 ||
-                   (c | 0x20u) - (byte)'a' <= 'f' - 'a';
+            return HexConverter.CharToHexLookup[c] != 0xFF;
         }
 
         public static bool TryFromHexString(ReadOnlySpan<char> chars, Span<byte> outputBytes)