From ac99791d3a9d298fa75cf552c81737059512d3f6 Mon Sep 17 00:00:00 2001
From: embeddedt <42941056+embeddedt@users.noreply.github.com>
Date: Sat, 21 Jan 2023 12:39:27 -0500
Subject: [PATCH] Deduplicate empty byte arrays

---
 .../ModernFixCachingClassTransformer.java       | 17 +++++++++++++++++
 .../hashers/MixinTransformerHasher.java         |  3 ++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/main/java/cpw/mods/modlauncher/ModernFixCachingClassTransformer.java b/src/main/java/cpw/mods/modlauncher/ModernFixCachingClassTransformer.java
index ec7f42b2..6eee287e 100644
--- a/src/main/java/cpw/mods/modlauncher/ModernFixCachingClassTransformer.java
+++ b/src/main/java/cpw/mods/modlauncher/ModernFixCachingClassTransformer.java
@@ -41,6 +41,8 @@ public class ModernFixCachingClassTransformer extends ClassTransformer {
 
     private ConcurrentHashMap<String, Pair<List<byte[]>, byte[]>> transformationCache;
 
+    public static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
+
     private static File childFile(File file) {
         file.getParentFile().mkdirs();
         return file;
@@ -85,6 +87,19 @@ public class ModernFixCachingClassTransformer extends ClassTransformer {
         this.transformationCache = new ConcurrentHashMap<>();
         try(ObjectInputStream inStream = new ObjectInputStream(new FileInputStream(CLASS_CACHE_DAT))) {
             this.transformationCache = (ConcurrentHashMap<String, Pair<List<byte[]>,byte[]>>)inStream.readObject();
+            /* Deduplicate any empty byte arrays to minimize impact of empty classes */
+            List<String> keys = new ArrayList<>(this.transformationCache.keySet());
+            for(String key : keys) {
+                Pair<List<byte[]>,byte[]> pair = this.transformationCache.get(key);
+                for(int i = 0; i < pair.getLeft().size(); i++) {
+                    if(pair.getLeft().get(i).length == 0) {
+                        pair.getLeft().set(i, EMPTY_BYTE_ARRAY);
+                    }
+                }
+                if(pair.getRight().length == 0) {
+                    this.transformationCache.put(key, Pair.of(pair.getLeft(), EMPTY_BYTE_ARRAY));
+                }
+            }
             int size = 0;
             /* Approximate the size in bytes */
             for(Map.Entry<String, Pair<List<byte[]>,byte[]>> entry : this.transformationCache.entrySet()) {
@@ -172,6 +187,8 @@ public class ModernFixCachingClassTransformer extends ClassTransformer {
                    LOGGER.warn("Hashes have changed, discarding cached version of " + name);
                }
                byte[] transformed = super.transform(inputClass, name, reason);
+               if(transformed.length == 0)
+                   transformed = EMPTY_BYTE_ARRAY; /* deduplicate */
                return Pair.of(hashList, transformed);
             }
         }).getRight();
diff --git a/src/main/java/org/embeddedt/modernfix/classloading/hashers/MixinTransformerHasher.java b/src/main/java/org/embeddedt/modernfix/classloading/hashers/MixinTransformerHasher.java
index 63d31c7c..30e2919b 100644
--- a/src/main/java/org/embeddedt/modernfix/classloading/hashers/MixinTransformerHasher.java
+++ b/src/main/java/org/embeddedt/modernfix/classloading/hashers/MixinTransformerHasher.java
@@ -2,6 +2,7 @@ package org.embeddedt.modernfix.classloading.hashers;
 
 import com.google.common.collect.HashMultimap;
 import com.google.common.io.Resources;
+import cpw.mods.modlauncher.ModernFixCachingClassTransformer;
 import org.spongepowered.asm.launch.IClassProcessor;
 import org.spongepowered.asm.launch.MixinLaunchPluginLegacy;
 import org.spongepowered.asm.mixin.extensibility.IMixinInfo;
@@ -92,6 +93,6 @@ public class MixinTransformerHasher {
                 }
             }
         }
-        return hashesByClass.getOrDefault(className, new byte[0]);
+        return hashesByClass.getOrDefault(className, ModernFixCachingClassTransformer.EMPTY_BYTE_ARRAY);
     }
 }