From 5e987f1f61122af6b77370715d6b8a48f54debe3 Mon Sep 17 00:00:00 2001
From: Graham <gpe@openrs2.dev>
Date: Fri, 1 May 2020 20:20:41 +0100
Subject: [PATCH] Remove memory allocation delay during client startup

Signed-off-by: Graham <gpe@openrs2.dev>
---
 .../java/dev/openrs2/bundler/BundlerModule.kt |  2 +
 .../transform/MemoryAllocationTransformer.kt  | 64 +++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 bundler/src/main/java/dev/openrs2/bundler/transform/MemoryAllocationTransformer.kt

diff --git a/bundler/src/main/java/dev/openrs2/bundler/BundlerModule.kt b/bundler/src/main/java/dev/openrs2/bundler/BundlerModule.kt
index c5e7704d6a..299975cc52 100644
--- a/bundler/src/main/java/dev/openrs2/bundler/BundlerModule.kt
+++ b/bundler/src/main/java/dev/openrs2/bundler/BundlerModule.kt
@@ -9,6 +9,7 @@ import dev.openrs2.bundler.transform.DomainTransformer
 import dev.openrs2.bundler.transform.HostCheckTransformer
 import dev.openrs2.bundler.transform.LoadLibraryTransformer
 import dev.openrs2.bundler.transform.MacResizeTransformer
+import dev.openrs2.bundler.transform.MemoryAllocationTransformer
 import dev.openrs2.bundler.transform.NameTransformer
 import dev.openrs2.bundler.transform.PlatformDetectionTransformer
 import dev.openrs2.bundler.transform.PublicKeyTransformer
@@ -29,6 +30,7 @@ object BundlerModule : AbstractModule() {
         binder.addBinding().to(DomainTransformer::class.java)
         binder.addBinding().to(LoadLibraryTransformer::class.java)
         binder.addBinding().to(MacResizeTransformer::class.java)
+        binder.addBinding().to(MemoryAllocationTransformer::class.java)
         binder.addBinding().to(NameTransformer::class.java)
         binder.addBinding().to(PlatformDetectionTransformer::class.java)
         binder.addBinding().to(PublicKeyTransformer::class.java)
diff --git a/bundler/src/main/java/dev/openrs2/bundler/transform/MemoryAllocationTransformer.kt b/bundler/src/main/java/dev/openrs2/bundler/transform/MemoryAllocationTransformer.kt
new file mode 100644
index 0000000000..50116b0825
--- /dev/null
+++ b/bundler/src/main/java/dev/openrs2/bundler/transform/MemoryAllocationTransformer.kt
@@ -0,0 +1,64 @@
+package dev.openrs2.bundler.transform
+
+import com.github.michaelbull.logging.InlineLogger
+import dev.openrs2.asm.InsnMatcher
+import dev.openrs2.asm.classpath.ClassPath
+import dev.openrs2.asm.classpath.Library
+import dev.openrs2.asm.replaceExpression
+import dev.openrs2.asm.transform.Transformer
+import org.objectweb.asm.Opcodes
+import org.objectweb.asm.tree.ClassNode
+import org.objectweb.asm.tree.InsnNode
+import org.objectweb.asm.tree.MethodInsnNode
+import org.objectweb.asm.tree.MethodNode
+import org.objectweb.asm.tree.VarInsnNode
+import javax.inject.Singleton
+
+@Singleton
+class MemoryAllocationTransformer : Transformer() {
+    private var usedMemoryExprsZeroed = 0
+
+    override fun preTransform(classPath: ClassPath) {
+        usedMemoryExprsZeroed = 0
+    }
+
+    override fun transformCode(classPath: ClassPath, library: Library, clazz: ClassNode, method: MethodNode): Boolean {
+        if ((method.access and Opcodes.ACC_STATIC) != 0) {
+            return false
+        }
+
+        for (match in USED_MEMORY_MATCHER.match(method)) {
+            val load1 = match[0] as VarInsnNode
+            val load2 = match[2] as VarInsnNode
+            if (load1.`var` != load2.`var`) {
+                continue
+            }
+
+            val invoke1 = match[1] as MethodInsnNode
+            if (invoke1.owner != "java/lang/Runtime" || invoke1.name != "totalMemory" || invoke1.desc != "()J") {
+                continue
+            }
+
+            val invoke2 = match[3] as MethodInsnNode
+            if (invoke2.owner != "java/lang/Runtime" || invoke2.name != "freeMemory" || invoke2.desc != "()J") {
+                continue
+            }
+
+            if (method.instructions.replaceExpression(match[4], InsnNode(Opcodes.LCONST_0))) {
+                usedMemoryExprsZeroed++
+            }
+        }
+
+        return false
+    }
+
+    override fun postTransform(classPath: ClassPath) {
+        logger.info { "Zeroed $usedMemoryExprsZeroed used memory expressions" }
+    }
+
+    companion object {
+        private val logger = InlineLogger()
+
+        private val USED_MEMORY_MATCHER = InsnMatcher.compile("ALOAD INVOKEVIRTUAL ALOAD INVOKEVIRTUAL LSUB")
+    }
+}