About reassignment by activej-codegen

[zhangtianxiao]

    val cb2: ClassBuilder<Function<Any?, Any?>> =
        ClassBuilder.create(Function::class.java).self()
    cb2.withMethod(
        "apply",
        let(cast(arg(0), Array::class.java)) { arr ->
            let(value(0)) { v ->
                sequence(
                    iterateArray(arr) {
                        call(staticField(System::class.java, "out"), "println", it)
                    },
                    // == HELP ==
                    // How to accumulate and return 1 + 2 + 3
                    add(v, cast(arrayGet(arr, value(0)), Int::class.java))
                    , v
                )
            }
        }
    )
    val c2 = cb2.defineClass(classLoader)
    println(c2.getDeclaredConstructor().newInstance().apply(arrayOf(1, 2, 3)))

thanks!

[zhangtianxiao]

package org.feather

import io.activej.codegen.ClassBuilder
import io.activej.codegen.DefiningClassLoader
import io.activej.codegen.expression.Expressions
import io.activej.codegen.expression.Expressions.cast
import java.io.File
import java.lang.reflect.Method
import java.util.function.Function

private val classLoader = DefiningClassLoader.create()

private fun makeCall2(o: Any, method: Method): CCall {
    val cb = ClassBuilder.create(CCall::class.java)
    cb.withMethod("invoke",
        Expressions.let(cast(Expressions.arg(0), Array::class.java)) { arr ->
            Expressions.call(
                cast(Expressions.call(Expressions.self(), "getO"), method.declaringClass),
                method.name,
                *(method.parameterTypes.mapIndexed { index, it ->
                    Expressions.arrayGet(arr, Expressions.value(index))
                }.toTypedArray())
            )
        }
    )

    val bytecode = cb.toBytecode(classLoader)
    val f = File("target/classes", bytecode.className.replace(".", "/") + ".class")
    val p = f.parentFile
    if (!p.exists()) p.mkdirs()
    f.writeBytes(bytecode.bytecode)

    val c = bytecode.defineClass(classLoader) as Class<CCall>
    println(c.canonicalName)

    val cc = c.getDeclaredConstructor().newInstance()
    cc.o = o
    return cc
}

abstract class CCall : Function<Array<*>, Any?> {
    lateinit var o: Any
    abstract operator fun invoke(vararg args: Any?): Any?
}


fun main() {
    val fn = makeCall2("123", String::class.java.getDeclaredMethod("length"))
    println(fn(arrayOf(0)))

    val fn2 = makeCall2(listOf(1, 2, 3), List::class.java.getDeclaredMethod("size"))
    println(fn2(arrayOf(0)))
}

The generated bytecode will contain the new instruction, like:

public final class CCall_2 extends CCall {
  public static Void $GENERATED;

  public CCall_2() {
  }

  public final Object invoke(Object[] var1) {
    // ???
    return new Integer(((List)this.getO()).size());
  }
}

[zhangtianxiao]

@eduard-vasinskyi

[eduard-vasinskyi]

    val cb2: ClassBuilder<Function<Any?, Any?>> =
        ClassBuilder.create(Function::class.java).self()
    cb2.withMethod(
        "apply",
        let(cast(arg(0), Array::class.java)) { arr ->
            let(value(0)) { v ->
                sequence(
                    iterateArray(arr) {
                        call(staticField(System::class.java, "out"), "println", it)
                    },
                    // == HELP ==
                    // How to accumulate and return 1 + 2 + 3
                    add(v, cast(arrayGet(arr, value(0)), Int::class.java))
                    , v
                )
            }
        }
    )
    val c2 = cb2.defineClass(classLoader)
    println(c2.getDeclaredConstructor().newInstance().apply(arrayOf(1, 2, 3)))

thanks!

Hi, @zhangtianxiao
To add all array values you can use code like this (It is in Java, but should be easy to convert to Kotlin):

cb2.withMethod("apply", let(cast(arg(0), int[].class),
      array -> let(value(0), v -> sequence(
            iterateArray(array, it -> set(v, add(v, it))),
            v
      ))));

I didn't quite get the other code snippets. What is the problem there?

[zhangtianxiao]

@eduard-vasinskyi Maybe, I didn't understand correctly,
The generated code I expected does not contain new,
This may be the default behavior of bytecode when type cast,
I am not familiar with bytecode.