Add Sig data class, SigScanner class and Patcher class

SigScanner and Patcher are WIP.
Patcher contains test/debug code.

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

@@ -1,4 +1,25 @@
 package net.revanced.patcher
 
+import net.revanced.patcher.sigscan.Sig
+import net.revanced.patcher.sigscan.SigScanner
+import org.jf.dexlib2.Opcode
+import java.io.File
+import java.lang.reflect.Modifier
+
 class Patcher {
-}
+    companion object {
+        /**
+         * Invokes the patcher on the given input file.
+         *
+         * @param input the input file
+         * @param output the output file
+         */
+        fun invoke(input: File, output: File) {
+            SigScanner(Sig(
+                arrayOf(Opcode.ADD_INT),
+                Modifier.PUBLIC or Modifier.STATIC,
+                String.Companion::class
+            )).scan(emptyArray())
+        }
+    }
+}

src/main/kotlin/net/revanced/patcher/sigscan/Sig.kt

@@ -0,0 +1,30 @@
+package net.revanced.patcher.sigscan
+
+import org.jf.dexlib2.Opcode
+import kotlin.reflect.KClass
+
+data class Sig(
+    val opcodes: Array<Opcode>,
+    val attributes: Int,
+    val returnType: KClass<*>
+) {
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (javaClass != other?.javaClass) return false
+
+        other as Sig
+
+        if (!opcodes.contentEquals(other.opcodes)) return false
+        if (attributes != other.attributes) return false
+        if (returnType != other.returnType) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = opcodes.contentHashCode()
+        result = 31 * result + attributes.hashCode()
+        result = 31 * result + returnType.hashCode()
+        return result
+    }
+}

src/main/kotlin/net/revanced/patcher/sigscan/SigScanner.kt

@@ -0,0 +1,9 @@
+package net.revanced.patcher.sigscan
+
+import org.jf.dexlib2.iface.ClassDef
+
+class SigScanner (sig: Sig) {
+    fun scan(classes: Array<ClassDef>) {
+
+    }
+}