feat: migrate to dexlib

BREAKING CHANGE: Removed usage of ASM library

build.gradle.kts

@@ -12,10 +12,7 @@ repositories {
 
 dependencies {
     implementation(kotlin("stdlib"))
-    implementation("org.ow2.asm:asm:9.2")
-    implementation("org.ow2.asm:asm-util:9.2")
-    implementation("org.ow2.asm:asm-tree:9.2")
-    implementation("org.ow2.asm:asm-commons:9.2")
+    implementation("com.github.lanchon.dexpatcher:multidexlib2:2.3.4")
     implementation("io.github.microutils:kotlin-logging:2.1.21")
     testImplementation("ch.qos.logback:logback-classic:1.2.11") // use your own logger!
     testImplementation(kotlin("test"))

src/main/kotlin/app/revanced/patcher/Patcher.kt

@@ -3,49 +3,51 @@ package app.revanced.patcher
 import app.revanced.patcher.cache.Cache
 import app.revanced.patcher.patch.Patch
 import app.revanced.patcher.resolver.MethodResolver
-import app.revanced.patcher.signature.Signature
-import app.revanced.patcher.util.Io
-import org.objectweb.asm.tree.ClassNode
-import java.io.IOException
-import java.io.InputStream
-import java.io.OutputStream
+import app.revanced.patcher.signature.MethodSignature
+import lanchon.multidexlib2.BasicDexFileNamer
+import lanchon.multidexlib2.MultiDexIO
+import org.jf.dexlib2.Opcodes
+import org.jf.dexlib2.iface.ClassDef
+import org.jf.dexlib2.iface.DexFile
+import java.io.File
 
-/**
- * The Patcher class.
- * ***It is of utmost importance that the input and output streams are NEVER closed.***
- *
- * @param input the input stream to read from, must be a JAR
- * @param output the output stream to write to
- * @param signatures the signatures
- * @sample app.revanced.patcher.PatcherTest
- * @throws IOException if one of the streams are closed
- */
 class Patcher(
-    private val input: InputStream,
-    private val output: OutputStream,
-    signatures: Array<Signature>,
-) {
-    var cache: Cache
+    input: File,
+    private val output: File,
+    signatures: Array<MethodSignature>,
 
-    private var io: Io
-    private val patches = mutableListOf<Patch>()
+    ) {
+    private val cache: Cache
+    private val patches = mutableSetOf<Patch>()
 
     init {
-        val classes = mutableListOf<ClassNode>()
-        io = Io(input, output, classes)
-        io.readFromJar()
-        cache = Cache(classes, MethodResolver(classes, signatures).resolve())
+        // TODO: find a way to load all dex classes, the code below only loads the first .dex file
+        val dexFile = MultiDexIO.readDexFile(true, input, BasicDexFileNamer(), Opcodes.getDefault(), null)
+        cache = Cache(dexFile.classes, MethodResolver(dexFile.classes, signatures).resolve())
     }
 
-    /**
-     * Saves the output to the output stream.
-     * Calling this method will close the input and output streams,
-     * meaning this method should NEVER be called after.
-     *
-     * @throws IOException if one of the streams are closed
-     */
     fun save() {
-        io.saveAsJar()
+        val newDexFile = object : DexFile {
+            override fun getClasses(): MutableSet<out ClassDef> {
+                // TODO: find a way to return a set with a custom iterator
+                // TODO: the iterator would return the proxied class matching the current index of the list
+                // TODO: instead of the original class
+                for (classProxy in cache.classProxy) {
+                    if (!classProxy.proxyused) continue
+                    // TODO: merge this class with cache.classes somehow in an iterator
+                    classProxy.mutatedClass
+                }
+                return cache.classes.toMutableSet()
+            }
+
+            override fun getOpcodes(): Opcodes {
+                // TODO find a way to get the opcodes format
+                return Opcodes.getDefault()
+            }
+        }
+
+        // TODO: not sure about maxDexPoolSize & we should use the multithreading overload for writeDexFile
+        MultiDexIO.writeDexFile(true, output, BasicDexFileNamer(), newDexFile, 10, null)
     }
 
     fun addPatches(vararg patches: Patch) {

src/main/kotlin/app/revanced/patcher/cache/Cache.kt

@@ -1,14 +1,30 @@
 package app.revanced.patcher.cache
 
-import org.objectweb.asm.tree.ClassNode
+import app.revanced.patcher.cache.proxy.ClassProxy
+import app.revanced.patcher.signature.MethodSignatureScanResult
+import org.jf.dexlib2.iface.ClassDef
 
 class Cache(
-    val classes: List<ClassNode>,
-    val methods: MethodMap
-)
+    internal val classes: Set<ClassDef>,
+    val resolvedMethods: MethodMap
+) {
+    internal val classProxy = mutableListOf<ClassProxy>()
 
-class MethodMap : LinkedHashMap<String, PatchData>() {
-    override fun get(key: String): PatchData {
+    fun findClass(predicate: (ClassDef) -> Boolean): ClassProxy? {
+        // if a class has been found with the given predicate,
+        val foundClass = classes.singleOrNull(predicate) ?: return null
+        // create a class proxy with the index of the class in the classes list
+        // TODO: There might be a more elegant way to the comment above
+        val classProxy = ClassProxy(foundClass, classes.indexOf(foundClass))
+        // add it to the cache and
+        this.classProxy.add(classProxy)
+        // return the proxy class
+        return classProxy
+    }
+}
+
+class MethodMap : LinkedHashMap<String, MethodSignatureScanResult>() {
+    override fun get(key: String): MethodSignatureScanResult {
         return super.get(key) ?: throw MethodNotFoundException("Method $key was not found in the method cache")
     }
 }

src/main/kotlin/app/revanced/patcher/cache/PatchData.kt

@@ -1,22 +0,0 @@
-package app.revanced.patcher.cache
-
-import app.revanced.patcher.resolver.MethodResolver
-import app.revanced.patcher.signature.Signature
-import org.objectweb.asm.tree.ClassNode
-import org.objectweb.asm.tree.MethodNode
-
-data class PatchData(
-    val declaringClass: ClassNode,
-    val method: MethodNode,
-    val scanData: PatternScanData
-) {
-    @Suppress("Unused") // TODO(Sculas): remove this when we have coverage for this method.
-    fun findParentMethod(signature: Signature): PatchData? {
-        return MethodResolver.resolveMethod(declaringClass, signature)
-    }
-}
-
-data class PatternScanData(
-    val startIndex: Int,
-    val endIndex: Int
-)

src/main/kotlin/app/revanced/patcher/cache/proxy/ClassProxy.kt

@@ -0,0 +1,21 @@
+package app.revanced.patcher.cache.proxy
+
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableClass
+import org.jf.dexlib2.iface.ClassDef
+
+
+class ClassProxy(
+    val immutableClass: ClassDef,
+    val originalClassIndex: Int,
+) {
+    internal var proxyused = false
+    internal lateinit var mutatedClass: MutableClass
+
+    fun resolve(): MutableClass {
+        if (!proxyused) {
+            proxyused = true
+            mutatedClass = MutableClass(immutableClass)
+        }
+        return mutatedClass
+    }
+}

src/main/kotlin/app/revanced/patcher/cache/proxy/mutableTypes/MutableAnnotation.kt

@@ -0,0 +1,29 @@
+package app.revanced.patcher.cache.proxy.mutableTypes
+
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableAnnotationElement.Companion.toMutable
+import org.jf.dexlib2.base.BaseAnnotation
+import org.jf.dexlib2.iface.Annotation
+
+class MutableAnnotation(annotation: Annotation) : BaseAnnotation() {
+    private val visibility = annotation.visibility
+    private val type = annotation.type
+    private val elements = annotation.elements.map { element -> element.toMutable() }.toMutableSet()
+
+    override fun getType(): String {
+        return type
+    }
+
+    override fun getElements(): MutableSet<MutableAnnotationElement> {
+        return elements
+    }
+
+    override fun getVisibility(): Int {
+        return visibility
+    }
+
+    companion object {
+        fun Annotation.toMutable(): MutableAnnotation {
+            return MutableAnnotation(this)
+        }
+    }
+}

src/main/kotlin/app/revanced/patcher/cache/proxy/mutableTypes/MutableAnnotationElement.kt

@@ -0,0 +1,33 @@
+package app.revanced.patcher.cache.proxy.mutableTypes
+
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableEncodedValue.Companion.toMutable
+import org.jf.dexlib2.base.BaseAnnotationElement
+import org.jf.dexlib2.iface.AnnotationElement
+import org.jf.dexlib2.iface.value.EncodedValue
+
+class MutableAnnotationElement(annotationElement: AnnotationElement) : BaseAnnotationElement() {
+    private var name = annotationElement.name
+    private var value = annotationElement.value.toMutable()
+
+    fun setName(name: String) {
+        this.name = name
+    }
+
+    fun setValue(value: MutableEncodedValue) {
+        this.value = value
+    }
+
+    override fun getName(): String {
+        return name
+    }
+
+    override fun getValue(): EncodedValue {
+        return value
+    }
+
+    companion object {
+        fun AnnotationElement.toMutable(): MutableAnnotationElement {
+            return MutableAnnotationElement(this)
+        }
+    }
+}

src/main/kotlin/app/revanced/patcher/cache/proxy/mutableTypes/MutableClass.kt

@@ -0,0 +1,94 @@
+package app.revanced.patcher.cache.proxy.mutableTypes
+
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableAnnotation.Companion.toMutable
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableField.Companion.toMutable
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableMethod.Companion.toMutable
+import org.jf.dexlib2.base.reference.BaseTypeReference
+import org.jf.dexlib2.iface.ClassDef
+
+class MutableClass(classDef: ClassDef) : ClassDef, BaseTypeReference() {
+    // Class
+    private var type = classDef.type
+    private var sourceFile = classDef.sourceFile
+    private var accessFlags = classDef.accessFlags
+    private var superclass = classDef.superclass
+
+    private val interfaces = classDef.interfaces.toMutableList()
+    private val annotations = classDef.annotations.map { annotation -> annotation.toMutable() }.toMutableSet()
+
+    // Methods
+    private val methods = classDef.methods.map { method -> method.toMutable() }.toMutableSet()
+    private val directMethods = classDef.directMethods.map { directMethod -> directMethod.toMutable() }.toMutableSet()
+    private val virtualMethods =
+        classDef.virtualMethods.map { virtualMethod -> virtualMethod.toMutable() }.toMutableSet()
+
+    // Fields
+    private val fields = classDef.fields.map { field -> field.toMutable() }.toMutableSet()
+    private val staticFields = classDef.staticFields.map { staticField -> staticField.toMutable() }.toMutableSet()
+    private val instanceFields =
+        classDef.instanceFields.map { instanceFields -> instanceFields.toMutable() }.toMutableSet()
+
+    fun setType(type: String) {
+        this.type = type
+    }
+
+    fun setSourceFile(sourceFile: String?) {
+        this.sourceFile = sourceFile
+    }
+
+    fun setAccessFlags(accessFlags: Int) {
+        this.accessFlags = accessFlags
+    }
+
+    fun setSuperClass(superclass: String?) {
+        this.superclass = superclass
+    }
+
+    override fun getType(): String {
+        return type
+    }
+
+    override fun getAccessFlags(): Int {
+        return accessFlags
+    }
+
+    override fun getSourceFile(): String? {
+        return sourceFile
+    }
+
+    override fun getSuperclass(): String? {
+        return superclass
+    }
+
+    override fun getInterfaces(): MutableList<String> {
+        return interfaces
+    }
+
+    override fun getAnnotations(): MutableSet<MutableAnnotation> {
+        return annotations
+    }
+
+    override fun getStaticFields(): MutableSet<MutableField> {
+        return staticFields
+    }
+
+    override fun getInstanceFields(): MutableSet<MutableField> {
+        return instanceFields
+    }
+
+    override fun getFields(): MutableSet<MutableField> {
+        return fields
+    }
+
+    override fun getDirectMethods(): MutableSet<MutableMethod> {
+        return directMethods
+    }
+
+    override fun getVirtualMethods(): MutableSet<MutableMethod> {
+        return virtualMethods
+    }
+
+    override fun getMethods(): MutableSet<MutableMethod> {
+        return methods
+    }
+}

src/main/kotlin/app/revanced/patcher/cache/proxy/mutableTypes/MutableEncodedValue.kt

@@ -0,0 +1,26 @@
+package app.revanced.patcher.cache.proxy.mutableTypes
+
+import org.jf.dexlib2.iface.value.EncodedValue
+
+class MutableEncodedValue(encodedValue: EncodedValue) : EncodedValue {
+    private var valueType = encodedValue.valueType
+
+    fun setValueType(valueType: Int) {
+        this.valueType = valueType
+    }
+
+    override fun compareTo(other: EncodedValue): Int {
+        return valueType - other.valueType
+
+    }
+
+    override fun getValueType(): Int {
+        return valueType
+    }
+
+    companion object {
+        fun EncodedValue.toMutable(): MutableEncodedValue {
+            return MutableEncodedValue(this)
+        }
+    }
+}

src/main/kotlin/app/revanced/patcher/cache/proxy/mutableTypes/MutableField.kt

@@ -0,0 +1,65 @@
+package app.revanced.patcher.cache.proxy.mutableTypes
+
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableAnnotation.Companion.toMutable
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableEncodedValue.Companion.toMutable
+import org.jf.dexlib2.base.reference.BaseFieldReference
+import org.jf.dexlib2.iface.Field
+
+class MutableField(field: Field) : Field, BaseFieldReference() {
+    private var definingClass = field.definingClass
+    private var name = field.name
+    private var type = field.type
+    private var accessFlags = field.accessFlags
+    private var initialValue = field.initialValue?.toMutable()
+    private val annotations = field.annotations.map { annotation -> annotation.toMutable() }.toMutableSet()
+
+    fun setDefiningClass(definingClass: String) {
+        this.definingClass
+    }
+
+    fun setName(name: String) {
+        this.name = name
+    }
+
+    fun setType(type: String) {
+        this.type = type
+    }
+
+    fun setAccessFlags(accessFlags: Int) {
+        this.accessFlags = accessFlags
+    }
+
+    fun setInitialValue(initialValue: MutableEncodedValue?) {
+        this.initialValue = initialValue
+    }
+
+    override fun getDefiningClass(): String {
+        return this.definingClass
+    }
+
+    override fun getName(): String {
+        return this.name
+    }
+
+    override fun getType(): String {
+        return this.type
+    }
+
+    override fun getAnnotations(): MutableSet<MutableAnnotation> {
+        return this.annotations
+    }
+
+    override fun getAccessFlags(): Int {
+        return this.accessFlags
+    }
+
+    override fun getInitialValue(): MutableEncodedValue? {
+        return this.initialValue
+    }
+
+    companion object {
+        fun Field.toMutable(): MutableField {
+            return MutableField(this)
+        }
+    }
+}

src/main/kotlin/app/revanced/patcher/cache/proxy/mutableTypes/MutableMethod.kt

@@ -0,0 +1,58 @@
+package app.revanced.patcher.cache.proxy.mutableTypes
+
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableAnnotation.Companion.toMutable
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableMethodParameter.Companion.toMutable
+import org.jf.dexlib2.base.reference.BaseMethodReference
+import org.jf.dexlib2.builder.MutableMethodImplementation
+import org.jf.dexlib2.iface.Method
+
+class MutableMethod(method: Method) : Method, BaseMethodReference() {
+    private var definingClass = method.definingClass
+    private var name = method.name
+    private var accessFlags = method.accessFlags
+    private var returnType = method.returnType
+
+    // Create own mutable MethodImplementation (due to not being able to change members like register count)
+    private var implementation = method.implementation?.let { MutableMethodImplementation(it) }
+    private val annotations = method.annotations.map { annotation -> annotation.toMutable() }.toMutableSet()
+    private val parameters = method.parameters.map { parameter -> parameter.toMutable() }.toMutableList()
+    private val parameterTypes = method.parameterTypes.toMutableList()
+
+    override fun getDefiningClass(): String {
+        return this.definingClass
+    }
+
+    override fun getName(): String {
+        return name
+    }
+
+    override fun getParameterTypes(): MutableList<CharSequence> {
+        return parameterTypes
+    }
+
+    override fun getReturnType(): String {
+        return returnType
+    }
+
+    override fun getAnnotations(): MutableSet<MutableAnnotation> {
+        return annotations
+    }
+
+    override fun getAccessFlags(): Int {
+        return accessFlags
+    }
+
+    override fun getParameters(): MutableList<MutableMethodParameter> {
+        return parameters
+    }
+
+    override fun getImplementation(): MutableMethodImplementation? {
+        return implementation
+    }
+
+    companion object {
+        fun Method.toMutable(): MutableMethod {
+            return MutableMethod(this)
+        }
+    }
+}

src/main/kotlin/app/revanced/patcher/cache/proxy/mutableTypes/MutableMethodParameter.kt

@@ -0,0 +1,35 @@
+package app.revanced.patcher.cache.proxy.mutableTypes
+
+import app.revanced.patcher.cache.proxy.mutableTypes.MutableAnnotation.Companion.toMutable
+import org.jf.dexlib2.base.BaseMethodParameter
+import org.jf.dexlib2.iface.MethodParameter
+
+// TODO: finish overriding all members if necessary
+class MutableMethodParameter(parameter: MethodParameter) : MethodParameter, BaseMethodParameter() {
+    private var type = parameter.type
+    private var name = parameter.name
+    private var signature = parameter.signature
+    private val annotations = parameter.annotations.map { annotation -> annotation.toMutable() }.toMutableSet()
+
+    override fun getType(): String {
+        return type
+    }
+
+    override fun getName(): String? {
+        return name
+    }
+
+    override fun getSignature(): String? {
+        return signature
+    }
+
+    override fun getAnnotations(): MutableSet<MutableAnnotation> {
+        return annotations
+    }
+
+    companion object {
+        fun MethodParameter.toMutable(): MutableMethodParameter {
+            return MutableMethodParameter(this)
+        }
+    }
+}

src/main/kotlin/app/revanced/patcher/resolver/MethodResolver.kt

@@ -1,36 +1,31 @@
 package app.revanced.patcher.resolver
 
 import app.revanced.patcher.cache.MethodMap
-import app.revanced.patcher.cache.PatchData
-import app.revanced.patcher.cache.PatternScanData
-import app.revanced.patcher.signature.Signature
-import app.revanced.patcher.util.ExtraTypes
-import mu.KotlinLogging
-import org.objectweb.asm.Type
-import org.objectweb.asm.tree.*
+import app.revanced.patcher.signature.MethodSignatureScanResult
+import app.revanced.patcher.signature.PatternScanData
+import app.revanced.patcher.signature.MethodSignature
+import org.jf.dexlib2.Opcode
+import org.jf.dexlib2.iface.ClassDef
+import org.jf.dexlib2.iface.Method
 
-private val logger = KotlinLogging.logger("MethodResolver")
-
-internal class MethodResolver(private val classList: List<ClassNode>, private val signatures: Array<Signature>) {
+// TODO: add logger
+internal class MethodResolver(private val classes: Set<ClassDef>, private val signatures: Array<MethodSignature>) {
     fun resolve(): MethodMap {
         val methodMap = MethodMap()
 
-        for ((classNode, methods) in classList) {
-            for (method in methods) {
-                for (signature in signatures) {
-                    if (methodMap.containsKey(signature.name)) { // method already found for this sig
-                        logger.trace { "Sig ${signature.name} already found, skipping." }
+        for (classDef in classes) {
+            for (method in classDef.methods) {
+                for (methodSignature in signatures) {
+                    if (methodMap.containsKey(methodSignature.name)) { // method already found for this sig
                         continue
                     }
-                    logger.trace { "Resolving sig ${signature.name}: ${classNode.name} / ${method.name}" }
-                    val (r, sr) = cmp(method, signature)
+
+                    val (r, sr) = cmp(method, methodSignature)
                     if (!r || sr == null) {
-                        logger.trace { "Compare result for sig ${signature.name} has failed!" }
                         continue
                     }
-                    logger.trace { "Method for sig ${signature.name} found!" }
-                    methodMap[signature.name] = PatchData(
-                        classNode,
+
+                    methodMap[methodSignature.name] = MethodSignatureScanResult(
                         method,
                         PatternScanData(
                             // sadly we cannot create contracts for a data class, so we must assert
@@ -44,7 +39,6 @@ internal class MethodResolver(private val classList: List<ClassNode>, private va
 
         for (signature in signatures) {
             if (methodMap.containsKey(signature.name)) continue
-            logger.error { "Could not find method for sig ${signature.name}!" }
         }
 
         return methodMap
@@ -52,12 +46,11 @@ internal class MethodResolver(private val classList: List<ClassNode>, private va
 
     // These functions do not require the constructor values, so they can be static.
     companion object {
-        fun resolveMethod(classNode: ClassNode, signature: Signature): PatchData? {
+        fun resolveMethod(classNode: ClassDef, signature: MethodSignature): MethodSignatureScanResult? {
             for (method in classNode.methods) {
                 val (r, sr) = cmp(method, signature)
                 if (!r || sr == null) continue
-                return PatchData(
-                    classNode,
+                return MethodSignatureScanResult(
                     method,
                     PatternScanData(0, 0) // opcode list is always ignored.
                 )
@@ -65,92 +58,72 @@ internal class MethodResolver(private val classList: List<ClassNode>, private va
             return null
         }
 
-        private fun cmp(method: MethodNode, signature: Signature): Pair<Boolean, ScanResult?> {
-            signature.returns?.let { _ ->
-                val methodReturns = Type.getReturnType(method.desc).convertObject()
-                if (signature.returns != methodReturns) {
-                    logger.trace {
-                        """
-                            Comparing sig ${signature.name}: invalid return type:
-                            expected ${signature.returns},
-                            got $methodReturns
-                        """.trimIndent()
-                    }
+        private fun cmp(method: Method, signature: MethodSignature): Pair<Boolean, MethodResolverScanResult?> {
+            // TODO: compare as generic object if not primitive
+            signature.returnType?.let { _ ->
+                if (signature.returnType != method.returnType) {
                     return@cmp false to null
                 }
             }
 
-            signature.accessors?.let { _ ->
-                if (signature.accessors != method.access) {
-                    logger.trace {
-                        """
-                            Comparing sig ${signature.name}: invalid accessors:
-                            expected ${signature.accessors},
-                            got ${method.access}
-                        """.trimIndent()
-                    }
+            signature.accessFlags?.let { _ ->
+                if (signature.accessFlags != method.accessFlags) {
                     return@cmp false to null
                 }
             }
 
-            signature.parameters?.let { _ ->
-                val parameters = Type.getArgumentTypes(method.desc).convertObjects()
-                if (!signature.parameters.contentEquals(parameters)) {
-                    logger.trace {
-                        """
-                            Comparing sig ${signature.name}: invalid parameter types:
-                            expected ${signature.parameters.joinToString()}},
-                            got ${parameters.joinToString()}
-                        """.trimIndent()
-                    }
+            // TODO: compare as generic object if the parameter is not primitive
+            signature.methodParameters?.let { _ ->
+                if (signature.methodParameters != method.parameters) {
                     return@cmp false to null
                 }
             }
 
             signature.opcodes?.let { _ ->
-                val result = method.instructions.scanFor(signature.opcodes)
-                if (!result.found) {
-                    logger.trace { "Comparing sig ${signature.name}: invalid opcode pattern" }
-                    return@cmp false to null
-                }
-                return@cmp true to result
+                val result = method.implementation?.instructions?.scanFor(signature.opcodes)
+                return@cmp if (result != null && result.found) true to result else false to null
             }
 
-            return true to ScanResult(true)
+            return true to MethodResolverScanResult(true)
         }
     }
 }
 
-private operator fun ClassNode.component1() = this
-private operator fun ClassNode.component2() = this.methods
+private operator fun ClassDef.component1() = this
+private operator fun ClassDef.component2() = this.methods
 
-private fun InsnList.scanFor(pattern: IntArray): ScanResult {
-    for (i in 0 until this.size()) {
+private fun <T> MutableIterable<T>.scanFor(pattern: Array<Opcode>): MethodResolverScanResult {
+    // TODO: create var for count?
+    for (i in 0 until this.count()) {
         var occurrence = 0
-        while (i + occurrence < this.size()) {
-            val n = this[i + occurrence]
-            if (!n.shouldSkip() && n.opcode != pattern[occurrence]) break
+        while (i + occurrence < this.count()) {
+            val n = this.elementAt(i + occurrence)
+            if (!n.shouldSkip() && n != pattern[occurrence]) break
             if (++occurrence >= pattern.size) {
                 val current = i + occurrence
-                return ScanResult(true, current - pattern.size, current)
+                return MethodResolverScanResult(true, current - pattern.size, current)
             }
         }
     }
 
-    return ScanResult(false)
+    return MethodResolverScanResult(false)
 }
 
-private fun Type.convertObject(): Type {
-    return when (this.sort) {
-        Type.OBJECT -> ExtraTypes.Any
-        Type.ARRAY -> ExtraTypes.ArrayAny
-        else -> this
-    }
+// TODO: extend Opcode type, not T (requires a cast to Opcode)
+private fun <T> T.shouldSkip(): Boolean {
+    return this == Opcode.GOTO // TODO: and: this == AbstractInsnNode.LINE
 }
 
-private fun Array<Type>.convertObjects(): Array<Type> {
-    return this.map { it.convertObject() }.toTypedArray()
-}
+// TODO: use this somehow to compare types as generic objects if not primitive
+// private fun Type.convertObject(): Type {
+//     return when (this.sort) {
+//         Type.OBJECT -> ExtraTypes.Any
+//         Type.ARRAY -> ExtraTypes.ArrayAny
+//         else -> this
+//     }
+// }
+//
+// private fun Array<Type>.convertObjects(): Array<Type> {
+//     return this.map { it.convertObject() }.toTypedArray()
+// }
 
-private fun AbstractInsnNode.shouldSkip() =
-    type == AbstractInsnNode.LABEL || type == AbstractInsnNode.LINE

src/main/kotlin/app/revanced/patcher/resolver/MethodResolverScanResult.kt

@@ -1,6 +1,6 @@
 package app.revanced.patcher.resolver
 
-internal data class ScanResult(
+internal data class MethodResolverScanResult(
     val found: Boolean,
     val startIndex: Int? = 0,
     val endIndex: Int? = 0

src/main/kotlin/app/revanced/patcher/signature/MethodSignature.kt

@@ -0,0 +1,12 @@
+package app.revanced.patcher.signature
+
+import org.jf.dexlib2.Opcode
+
+@Suppress("ArrayInDataClass")
+data class MethodSignature(
+    val name: String,
+    val returnType: String?,
+    val accessFlags: Int?,
+    val methodParameters: Iterable<CharSequence>?,
+    val opcodes: Array<Opcode>?
+)

src/main/kotlin/app/revanced/patcher/signature/MethodSignatureScanResult.kt

@@ -0,0 +1,23 @@
+package app.revanced.patcher.signature
+
+import app.revanced.patcher.resolver.MethodResolver
+import org.jf.dexlib2.iface.ClassDef
+import org.jf.dexlib2.iface.Method
+import org.jf.dexlib2.immutable.reference.ImmutableTypeReference
+
+// TODO: IMPORTANT: we might have to use a class proxy as well here
+data class MethodSignatureScanResult(
+    val method: Method,
+    val scanData: PatternScanData
+) {
+    @Suppress("Unused") // TODO(Sculas): remove this when we have coverage for this method.
+    fun findParentMethod(signature: MethodSignature): MethodSignatureScanResult? {
+        // TODO: find a way to get the classNode out of method.definingClass
+        return MethodResolver.resolveMethod(ImmutableTypeReference(method.definingClass) as ClassDef, signature)
+    }
+}
+
+data class PatternScanData(
+    val startIndex: Int,
+    val endIndex: Int
+)

src/main/kotlin/app/revanced/patcher/signature/Signature.kt

@@ -1,27 +0,0 @@
-package app.revanced.patcher.signature
-
-import org.objectweb.asm.Type
-
-/**
- * An ASM signature list for the Patcher.
- *
- * @param name The name of the method.
- * Do not use the actual method name, instead try to guess what the method name originally was.
- * If you are unable to guess a method name, doing something like "patch-name-1" is fine too.
- * For example: "override-codec-1".
- * This method name will be mapped to the method matching the signature.
- * Even though this is technically not needed for the `findParentMethod` method,
- * it is still recommended giving the method a name, so it can be identified easily.
- * @param returns The return type/signature of the method.
- * @param accessors The accessors of the method.
- * @param parameters The parameter types of the method.
- * @param opcodes The opcode pattern of the method, used to find the method by pattern scanning.
- */
-@Suppress("ArrayInDataClass")
-data class Signature(
-    val name: String,
-    val returns: Type?,
-    val accessors: Int?,
-    val parameters: Array<Type>?,
-    val opcodes: IntArray?
-)

src/main/kotlin/app/revanced/patcher/util/ExtraTypes.kt

@@ -1,12 +0,0 @@
-package app.revanced.patcher.util
-
-import org.objectweb.asm.Type
-
-object ExtraTypes {
-    /**
-     * Any object type.
-     * Should be used instead of types such as: "Ljava/lang/String;"
-     */
-    val Any: Type = Type.getType(Object::class.java)
-    val ArrayAny: Type = Type.getType(Array<Any>::class.java)
-}

src/main/kotlin/app/revanced/patcher/util/Io.kt

@@ -1,94 +0,0 @@
-package app.revanced.patcher.util
-
-import org.objectweb.asm.ClassReader
-import org.objectweb.asm.ClassWriter
-import org.objectweb.asm.tree.ClassNode
-import java.io.BufferedInputStream
-import java.io.InputStream
-import java.io.OutputStream
-import java.util.jar.JarEntry
-import java.util.jar.JarInputStream
-import java.util.zip.ZipEntry
-import java.util.zip.ZipInputStream
-import java.util.zip.ZipOutputStream
-
-internal class Io(
-    private val input: InputStream,
-    private val output: OutputStream,
-    private val classes: MutableList<ClassNode>
-) {
-    private val bufferedInputStream = BufferedInputStream(input)
-
-    fun readFromJar() {
-        bufferedInputStream.mark(Integer.MAX_VALUE)
-        // create a BufferedInputStream in order to read the input stream again when calling saveAsJar(..)
-        val jis = JarInputStream(bufferedInputStream)
-
-        // read all entries from the input stream
-        // we use JarEntry because we only read .class files
-        lateinit var jarEntry: JarEntry
-        while (jis.nextJarEntry.also { if (it != null) jarEntry = it } != null) {
-            // if the current entry ends with .class (indicating a java class file), add it to our list of classes to return
-            if (jarEntry.name.endsWith(".class")) {
-                // create a new ClassNode
-                val classNode = ClassNode()
-                // read the bytes with a ClassReader into the ClassNode
-                ClassReader(jis.readBytes()).accept(classNode, ClassReader.EXPAND_FRAMES)
-                // add it to our list
-                classes.add(classNode)
-            }
-
-            // finally, close the entry
-            jis.closeEntry()
-        }
-
-        // at last reset the buffered input stream
-        bufferedInputStream.reset()
-    }
-
-    fun saveAsJar() {
-        val jis = ZipInputStream(bufferedInputStream)
-        val jos = ZipOutputStream(output)
-        val classReaders = mutableMapOf<String, ClassReader>()
-
-        // first write all non .class zip entries from the original input stream to the output stream
-        // we read it first to close the input stream as fast as possible
-        // TODO(oSumAtrIX): There is currently no way to remove non .class files.
-        lateinit var zipEntry: ZipEntry
-        while (jis.nextEntry.also { if (it != null) zipEntry = it } != null) {
-            if (zipEntry.name.endsWith(".class")) {
-                classReaders[zipEntry.name] = ClassReader(jis.readBytes())
-                continue
-            }
-
-            // create a new zipEntry and write the contents of the zipEntry to the output stream and close it
-            jos.putNextEntry(ZipEntry(zipEntry))
-            jos.write(jis.readBytes())
-            jos.closeEntry()
-        }
-
-        // finally, close the input stream
-        jis.close()
-        bufferedInputStream.close()
-        input.close()
-
-        // now write all the patched classes to the output stream
-        for (patchedClass in classes) {
-            // create a new entry of the patched class
-            val name = patchedClass.name + ".class"
-            jos.putNextEntry(JarEntry(name))
-
-            // parse the patched class to a byte array and write it to the output stream
-            val cw = ClassWriter(classReaders[name]!!, ClassWriter.COMPUTE_MAXS)
-            patchedClass.accept(cw)
-            jos.write(cw.toByteArray())
-
-            // close the newly created jar entry
-            jos.closeEntry()
-        }
-
-        // finally, close the rest of the streams
-        jos.close()
-        output.close()
-    }
-}

src/main/kotlin/app/revanced/patcher/writer/ASMWriter.kt

@@ -1,21 +0,0 @@
-package app.revanced.patcher.writer
-
-import org.objectweb.asm.tree.AbstractInsnNode
-import org.objectweb.asm.tree.InsnList
-
-object ASMWriter {
-    fun InsnList.setAt(index: Int, node: AbstractInsnNode) {
-        this[this.get(index)] = node
-    }
-
-    fun InsnList.insertAt(index: Int = 0, vararg nodes: AbstractInsnNode) {
-        this.insert(this.get(index), nodes.toInsnList())
-    }
-
-    // TODO(Sculas): Should this be public?
-    private fun Array<out AbstractInsnNode>.toInsnList(): InsnList {
-        val list = InsnList()
-        this.forEach { list.add(it) }
-        return list
-    }
-}

src/test/kotlin/app/revanced/patcher/PatcherTest.kt

@@ -1,177 +0,0 @@
-package app.revanced.patcher
-
-import app.revanced.patcher.cache.Cache
-import app.revanced.patcher.patch.Patch
-import app.revanced.patcher.patch.PatchResult
-import app.revanced.patcher.patch.PatchResultSuccess
-import app.revanced.patcher.signature.Signature
-import app.revanced.patcher.util.ExtraTypes
-import app.revanced.patcher.util.TestUtil
-import app.revanced.patcher.writer.ASMWriter.insertAt
-import app.revanced.patcher.writer.ASMWriter.setAt
-import org.junit.jupiter.api.assertDoesNotThrow
-import org.objectweb.asm.Opcodes.*
-import org.objectweb.asm.Type
-import org.objectweb.asm.tree.FieldInsnNode
-import org.objectweb.asm.tree.LdcInsnNode
-import org.objectweb.asm.tree.MethodInsnNode
-import java.io.ByteArrayOutputStream
-import java.io.PrintStream
-import kotlin.test.Test
-
-internal class PatcherTest {
-    companion object {
-        val testSignatures: Array<Signature> = arrayOf(
-            // Java:
-            // public static void main(String[] args) {
-            //     System.out.println("Hello, world!");
-            // }
-            // Bytecode:
-            // public static main(java.lang.String[] arg0) { // Method signature: ([Ljava/lang/String;)V
-            //     getstatic java/lang/System.out:java.io.PrintStream
-            //     ldc "Hello, world!" (java.lang.String)
-            //     invokevirtual java/io/PrintStream.println(Ljava/lang/String;)V
-            //     return
-            // }
-            Signature(
-                "mainMethod",
-                Type.VOID_TYPE,
-                ACC_PUBLIC or ACC_STATIC,
-                arrayOf(ExtraTypes.ArrayAny),
-                intArrayOf(
-                    GETSTATIC,
-                    LDC,
-                    INVOKEVIRTUAL,
-                    RETURN
-                )
-            )
-        )
-    }
-
-    @Test
-    fun testPatcher() {
-        val patcher = Patcher(
-            PatcherTest::class.java.getResourceAsStream("/test1.jar")!!,
-            ByteArrayOutputStream(),
-            testSignatures
-        )
-
-        patcher.addPatches(
-            object : Patch("TestPatch") {
-                override fun execute(cache: Cache): PatchResult {
-                    // Get the method from the resolver cache
-                    val mainMethod = patcher.cache.methods["mainMethod"]
-                    // Get the instruction list
-                    val instructions = mainMethod.method.instructions!!
-
-                    // Let's modify it, so it prints "Hello, ReVanced! Editing bytecode."
-                    // Get the start index of our opcode pattern.
-                    // This will be the index of the LDC instruction.
-                    val startIndex = mainMethod.scanData.startIndex
-
-                    // Ignore this, just testing if the method resolver works :)
-                    TestUtil.assertNodeEqual(
-                        FieldInsnNode(
-                            GETSTATIC,
-                            Type.getInternalName(System::class.java),
-                            "out",
-                            // for whatever reason, it adds an "L" and ";" to the node string
-                            "L${Type.getInternalName(PrintStream::class.java)};"
-                        ),
-                        instructions[startIndex]!!
-                    )
-
-                    // Create a new LDC node and replace the LDC instruction.
-                    val stringNode = LdcInsnNode("Hello, ReVanced! Editing bytecode.")
-                    instructions.setAt(startIndex, stringNode)
-
-                    // Now lets print our string twice!
-                    // Insert our instructions after the second instruction by our pattern.
-                    // This will place our instructions after the original INVOKEVIRTUAL call.
-                    // You could also copy the instructions from the list and then modify the LDC instruction again,
-                    // but this is to show a more advanced example of writing bytecode using the patcher and ASM.
-                    instructions.insertAt(
-                        startIndex + 1,
-                        FieldInsnNode(
-                            GETSTATIC,
-                            Type.getInternalName(System::class.java), // "java/lang/System"
-                            "out",
-                            Type.getInternalName(PrintStream::class.java) // "java/io/PrintStream"
-                        ),
-                        LdcInsnNode("Hello, ReVanced! Adding bytecode."),
-                        MethodInsnNode(
-                            INVOKEVIRTUAL,
-                            Type.getInternalName(PrintStream::class.java), // "java/io/PrintStream"
-                            "println",
-                            Type.getMethodDescriptor(
-                                Type.VOID_TYPE,
-                                Type.getType(String::class.java)
-                            ) // "(Ljava/lang/String;)V"
-                        )
-                    )
-
-                    // Our code now looks like this:
-                    // public static main(java.lang.String[] arg0) { // Method signature: ([Ljava/lang/String;)V
-                    //     getstatic java/lang/System.out:java.io.PrintStream
-                    //     ldc "Hello, ReVanced! Editing bytecode." (java.lang.String) // We overwrote this instruction.
-                    //     invokevirtual java/io/PrintStream.println(Ljava/lang/String;)V
-                    //     getstatic java/lang/System.out:java.io.PrintStream // This instruction and the 2 instructions below are written manually.
-                    //     ldc "Hello, ReVanced! Adding bytecode." (java.lang.String)
-                    //     invokevirtual java/io/PrintStream.println(Ljava/lang/String;)V
-                    //     return
-                    // }
-
-                    // Finally, tell the patcher that this patch was a success.
-                    // You can also return PatchResultError with a message.
-                    // If an exception is thrown inside this function,
-                    // a PatchResultError will be returned with the error message.
-                    return PatchResultSuccess()
-                }
-            }
-        )
-
-        // Apply all patches loaded in the patcher
-        val patchResult = patcher.applyPatches()
-        // You can check if an error occurred
-        for ((patchName, result) in patchResult) {
-            if (result.isFailure) {
-                throw Exception("Patch $patchName failed", result.exceptionOrNull()!!)
-            }
-        }
-
-        patcher.save()
-    }
-
-    @Test
-    fun `test patcher with no changes`() {
-        val testData = PatcherTest::class.java.getResourceAsStream("/test1.jar")!!
-        // val available = testData.available()
-        val out = ByteArrayOutputStream()
-        Patcher(testData, out, testSignatures).save()
-        // FIXME(Sculas): There seems to be a 1-byte difference, not sure what it is.
-        // assertEquals(available, out.size())
-        out.close()
-    }
-
-    @Test()
-    fun `should not raise an exception if any signature member except the name is missing`() {
-        val sigName = "testMethod"
-
-        assertDoesNotThrow(
-            "Should not raise an exception if any signature member except the name is missing"
-        ) {
-            Patcher(
-                PatcherTest::class.java.getResourceAsStream("/test1.jar")!!,
-                ByteArrayOutputStream(),
-                arrayOf(
-                    Signature(
-                        sigName,
-                        null,
-                        null,
-                        null,
-                        null
-                    ))
-            )
-        }
-    }
-}

src/test/kotlin/app/revanced/patcher/ReaderTest.kt

@@ -1,12 +0,0 @@
-package app.revanced.patcher
-
-import java.io.ByteArrayOutputStream
-import kotlin.test.Test
-
-internal class ReaderTest {
-    @Test
-    fun `read jar containing multiple classes`() {
-        val testData = PatcherTest::class.java.getResourceAsStream("/test2.jar")!!
-        Patcher(testData, ByteArrayOutputStream(), PatcherTest.testSignatures).save() // reusing test sigs from PatcherTest
-    }
-}

src/test/kotlin/app/revanced/patcher/util/TestUtil.kt

@@ -1,45 +0,0 @@
-package app.revanced.patcher.util
-
-import org.objectweb.asm.tree.AbstractInsnNode
-import org.objectweb.asm.tree.FieldInsnNode
-import org.objectweb.asm.tree.LdcInsnNode
-import kotlin.test.fail
-
-object TestUtil {
-    fun <T: AbstractInsnNode> assertNodeEqual(expected: T, actual: T) {
-        val a = expected.nodeString()
-        val b = actual.nodeString()
-        if (a != b) {
-            fail("expected: $a,\nactual: $b\n")
-        }
-    }
-
-    private fun AbstractInsnNode.nodeString(): String {
-        val sb = NodeStringBuilder()
-        when (this) {
-            // TODO(Sculas): Add more types
-            is LdcInsnNode -> sb
-                .addType("cst", cst)
-            is FieldInsnNode -> sb
-                .addType("owner", owner)
-                .addType("name", name)
-                .addType("desc", desc)
-        }
-        return "(${this::class.simpleName}): (type = $type, opcode = $opcode, $sb)"
-    }
-}
-
-private class NodeStringBuilder {
-    private val sb = StringBuilder()
-
-    fun addType(name: String, value: Any): NodeStringBuilder {
-        sb.append("$name = \"$value\", ")
-        return this
-    }
-
-    override fun toString(): String {
-        if (sb.isEmpty()) return ""
-        val s = sb.toString()
-        return s.substring(0 .. (s.length - 2).coerceAtLeast(0)) // remove the last ", "
-    }
-}

src/test/kotlin/patcher/PatcherTest.kt

@@ -0,0 +1,75 @@
+package app.revanced.patcher
+
+import app.revanced.patcher.cache.Cache
+import app.revanced.patcher.patch.Patch
+import app.revanced.patcher.patch.PatchResult
+import app.revanced.patcher.patch.PatchResultError
+import app.revanced.patcher.patch.PatchResultSuccess
+import app.revanced.patcher.signature.MethodSignature
+import org.jf.dexlib2.AccessFlags
+import org.jf.dexlib2.Opcode
+import org.jf.dexlib2.builder.instruction.BuilderInstruction21c
+import org.jf.dexlib2.iface.instruction.formats.Instruction21c
+import org.jf.dexlib2.iface.reference.FieldReference
+import org.jf.dexlib2.immutable.reference.ImmutableMethodReference
+import java.io.File
+
+
+fun main() {
+    val signatures = arrayOf(
+        MethodSignature(
+            "main-method",
+            "V",
+            AccessFlags.STATIC.value or AccessFlags.PUBLIC.value,
+            listOf("[O"),
+            arrayOf(
+                Opcode.SGET_OBJECT,
+                Opcode.CONST_STRING,
+                Opcode.INVOKE_VIRTUAL,
+                Opcode.RETURN_VOID
+            )
+        )
+    )
+
+    val patcher = Patcher(
+        File("black.apk"),
+        File("folder/"),
+        signatures
+    )
+
+    val mainMethodPatchViaClassProxy = object : Patch("main-method-patch-via-proxy") {
+        override fun execute(cache: Cache): PatchResult {
+            val proxy = cache.findClass { classDef ->
+                classDef.methods.any { method ->
+                    method.name == "main"
+                }
+            } ?: return PatchResultError("Class with method 'mainMethod' could not be found")
+
+            val mainMethodClass = proxy.resolve()
+            val mainMethod = mainMethodClass.methods.single { method -> method.name == "main" }
+
+            val hideReelMethodRef = ImmutableMethodReference(
+                "Lfi/razerman/youtube/XAdRemover;",
+                "HideReel",
+                listOf("Landroid/view/View;"),
+                "V"
+            )
+
+            val mainMethodInstructions = mainMethod.implementation!!.instructions
+            val printStreamFieldRef = (mainMethodInstructions.first() as Instruction21c).reference as FieldReference
+            // TODO: not sure how to use the registers yet, find a way
+            mainMethodInstructions.add(BuilderInstruction21c(Opcode.SGET_OBJECT, 0, printStreamFieldRef))
+            return PatchResultSuccess()
+        }
+    }
+
+    val mainMethodPatchViaSignature = object : Patch("main-method-patch-via-signature") {
+        override fun execute(cache: Cache): PatchResult {
+            cache.resolvedMethods["main-method"].method
+            return  PatchResultSuccess()
+        }
+    }
+    patcher.addPatches(mainMethodPatchViaClassProxy, mainMethodPatchViaSignature)
+    patcher.applyPatches()
+    patcher.save()
+}