From 7a56dca004cd793121a59ea854c77f4c1a01bd6f Mon Sep 17 00:00:00 2001
From: Lucaskyy <contact@sculas.xyz>
Date: Wed, 13 Apr 2022 20:17:31 +0200
Subject: [PATCH] feat: add fuzzy resolver

fixed docs for MethodSignature & added tests for fuzzy resolver
---
 .../patcher/signature/MethodSignature.kt      | 13 +++--
 .../signature/resolver/SignatureResolver.kt   | 56 ++++++++++++-------
 .../app/revanced/patcher/PatcherTest.kt       |  4 +-
 3 files changed, 47 insertions(+), 26 deletions(-)

diff --git a/src/main/kotlin/app/revanced/patcher/signature/MethodSignature.kt b/src/main/kotlin/app/revanced/patcher/signature/MethodSignature.kt
index 5704285..f52aae1 100644
--- a/src/main/kotlin/app/revanced/patcher/signature/MethodSignature.kt
+++ b/src/main/kotlin/app/revanced/patcher/signature/MethodSignature.kt
@@ -46,20 +46,23 @@ data class MethodMetadata(
 
 /**
  * Metadata for the Patcher, this contains things like how the Patcher should interpret this signature.
- * @param method The method the Patcher should use to resolve the signature.
+ * @param method The method the resolver should use to resolve the signature.
  */
 data class PatcherMetadata(
-    val method: PatcherMethod
+    val method: ResolverMethod
 )
 
-interface PatcherMethod {
+/**
+ * The method the resolver should use to resolve the signature.
+ */
+interface ResolverMethod {
     /**
      * When comparing the signature, if one or more of the opcodes do not match, skip.
      */
-    class Direct : PatcherMethod
+    class Direct : ResolverMethod
 
     /**
      * When comparing the signature, if [threshold] or more of the opcodes do not match, skip.
      */
-    class Fuzzy(val threshold: Int) : PatcherMethod
+    class Fuzzy(val threshold: Int) : ResolverMethod
 }
\ No newline at end of file
diff --git a/src/main/kotlin/app/revanced/patcher/signature/resolver/SignatureResolver.kt b/src/main/kotlin/app/revanced/patcher/signature/resolver/SignatureResolver.kt
index bdeeda5..700353f 100644
--- a/src/main/kotlin/app/revanced/patcher/signature/resolver/SignatureResolver.kt
+++ b/src/main/kotlin/app/revanced/patcher/signature/resolver/SignatureResolver.kt
@@ -3,9 +3,9 @@ package app.revanced.patcher.signature.resolver
 import app.revanced.patcher.cache.MethodMap
 import app.revanced.patcher.proxy.ClassProxy
 import app.revanced.patcher.signature.MethodSignature
+import app.revanced.patcher.signature.ResolverMethod
 import app.revanced.patcher.signature.PatternScanResult
 import app.revanced.patcher.signature.SignatureResolverResult
-import org.jf.dexlib2.Opcode
 import org.jf.dexlib2.iface.ClassDef
 import org.jf.dexlib2.iface.Method
 import org.jf.dexlib2.iface.instruction.Instruction
@@ -75,10 +75,44 @@ internal class SignatureResolver(
             return if (signature.opcodes == null) {
                 PatternScanResult(0, 0)
             } else {
-                method.implementation?.instructions?.scanFor(signature.opcodes)
+                method.implementation?.instructions?.let {
+                    compareOpcodes(signature, it)
+                }
             }
         }
 
+        private fun compareOpcodes(
+            signature: MethodSignature,
+            instructions: Iterable<Instruction>
+        ): PatternScanResult? {
+            val count = instructions.count()
+            val pattern = signature.opcodes!!
+            val size = pattern.count()
+            var threshold = 0
+            if (signature.metadata.patcher.method is ResolverMethod.Fuzzy) {
+                threshold = signature.metadata.patcher.method.threshold
+            }
+
+            for (instructionIndex in 0 until count) {
+                var patternIndex = 0
+                var currentThreshold = threshold
+                while (instructionIndex + patternIndex < count) {
+                    println("currentThreshold = $currentThreshold")
+                    if (
+                        instructions.elementAt(
+                            instructionIndex + patternIndex
+                        ).opcode != pattern.elementAt(patternIndex)
+                        && currentThreshold-- == 0
+                    ) break
+                    if (++patternIndex < size) continue
+
+                    return PatternScanResult(instructionIndex, instructionIndex + patternIndex)
+                }
+            }
+
+            return null
+        }
+
         private fun compareParameterTypes(
             signature: Iterable<String>,
             original: MutableList<out CharSequence>
@@ -89,20 +123,4 @@ internal class SignatureResolver(
 }
 
 private operator fun ClassDef.component1() = this
-private operator fun ClassDef.component2() = this.methods
-
-private fun MutableIterable<Instruction>.scanFor(pattern: Iterable<Opcode>): PatternScanResult? {
-    val count = this.count()
-    val size = pattern.count()
-    for (instructionIndex in 0 until count) {
-        var patternIndex = 0
-        while (instructionIndex + patternIndex < count) {
-            if (this.elementAt(instructionIndex + patternIndex).opcode != pattern.elementAt(patternIndex)) break
-            if (++patternIndex < size) continue
-
-            return PatternScanResult(instructionIndex, instructionIndex + patternIndex)
-        }
-    }
-
-    return null
-}
\ No newline at end of file
+private operator fun ClassDef.component2() = this.methods
\ No newline at end of file
diff --git a/src/test/kotlin/app/revanced/patcher/PatcherTest.kt b/src/test/kotlin/app/revanced/patcher/PatcherTest.kt
index a4d613d..de3fb03 100644
--- a/src/test/kotlin/app/revanced/patcher/PatcherTest.kt
+++ b/src/test/kotlin/app/revanced/patcher/PatcherTest.kt
@@ -38,7 +38,7 @@ internal class PatcherTest {
                         comment = "Main method of TestClass. Version 1.0.0"
                     ),
                     patcher = PatcherMetadata(
-                        method = PatcherMethod.Fuzzy(2)
+                        method = ResolverMethod.Fuzzy(2)
                     )
                 ),
                 "V",
@@ -46,7 +46,7 @@ internal class PatcherTest {
                 listOf("[L"),
                 listOf(
                     Opcode.CONST_STRING,
-                    Opcode.INVOKE_VIRTUAL,
+                    Opcode.INVOKE_STATIC, // This is intentionally wrong to test the Fuzzy resolver.
                     Opcode.RETURN_VOID
                 )
             )