Open-source multiplayer game server compatible with the RuneScape client
https://www.openrs2.org/
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158 lines
4.8 KiB
158 lines
4.8 KiB
package org.openrs2.deob.ast.transform
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import com.github.javaparser.ast.CompilationUnit
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import com.github.javaparser.ast.expr.BinaryExpr
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import com.github.javaparser.ast.expr.IntegerLiteralExpr
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import com.github.javaparser.ast.expr.LongLiteralExpr
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import org.openrs2.deob.ast.Library
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import org.openrs2.deob.ast.LibraryGroup
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import org.openrs2.deob.ast.util.checkedAsInt
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import org.openrs2.deob.ast.util.checkedAsLong
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import org.openrs2.deob.ast.util.toLongLiteralExpr
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import org.openrs2.deob.ast.util.walk
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import javax.inject.Singleton
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@Singleton
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public class BitMaskTransformer : Transformer() {
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override fun transformUnit(group: LibraryGroup, library: Library, unit: CompilationUnit) {
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/*
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* Transform:
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*
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* (x & y) >> z
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*
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* to:
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*
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* (x >> z) & (y >> z)
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*
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* For example:
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*
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* (x & 0xFF00) >> 8
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*
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* to:
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*
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* (x >> 8) & 0xFF
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*/
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unit.walk { expr: BinaryExpr ->
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val shiftOp = expr.operator
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val bitwiseExpr = expr.left
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val shamtExpr = expr.right
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if (shiftOp !in RIGHT_SHIFT_OPS || bitwiseExpr !is BinaryExpr || shamtExpr !is IntegerLiteralExpr) {
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return@walk
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}
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val bitwiseOp = bitwiseExpr.operator
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val argExpr = bitwiseExpr.left
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var maskExpr = bitwiseExpr.right
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if (bitwiseOp !in BITWISE_OPS) {
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return@walk
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}
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val shamt = shamtExpr.checkedAsInt()
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when (maskExpr) {
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is IntegerLiteralExpr -> {
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var mask = maskExpr.checkedAsInt()
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mask = when (shiftOp) {
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BinaryExpr.Operator.SIGNED_RIGHT_SHIFT -> mask shr shamt
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BinaryExpr.Operator.UNSIGNED_RIGHT_SHIFT -> mask ushr shamt
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else -> error("Invalid shiftOp")
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}
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maskExpr = IntegerLiteralExpr(mask.toString())
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}
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is LongLiteralExpr -> {
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var mask = maskExpr.checkedAsLong()
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mask = when (shiftOp) {
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BinaryExpr.Operator.SIGNED_RIGHT_SHIFT -> mask shr shamt
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BinaryExpr.Operator.UNSIGNED_RIGHT_SHIFT -> mask ushr shamt
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else -> error("Invalid shiftOp")
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}
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maskExpr = mask.toLongLiteralExpr()
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}
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else -> return@walk
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}
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expr.replace(BinaryExpr(BinaryExpr(argExpr.clone(), shamtExpr.clone(), shiftOp), maskExpr, bitwiseOp))
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}
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/*
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* Transform:
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*
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* (x << y) & z
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*
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* to:
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*
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* (x & (z >>> y)) << y
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*
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* For example:
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*
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* (x << 8) & 0xFF00
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*
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* to:
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*
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* (x & 0xFF) << 8
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*/
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unit.walk { expr: BinaryExpr ->
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val bitwiseOp = expr.operator
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val shiftExpr = expr.left
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val maskExpr = expr.right
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if (bitwiseOp !in BITWISE_OPS || shiftExpr !is BinaryExpr) {
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return@walk
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}
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val shiftOp = shiftExpr.operator
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val argExpr = shiftExpr.left
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val shamtExpr = shiftExpr.right
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if (shiftOp != BinaryExpr.Operator.LEFT_SHIFT || shamtExpr !is IntegerLiteralExpr) {
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return@walk
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}
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val shamt = shamtExpr.checkedAsInt()
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val newMaskExpr = when (maskExpr) {
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is IntegerLiteralExpr -> {
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var mask = maskExpr.checkedAsInt()
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if (shamt > Integer.numberOfTrailingZeros(mask)) {
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return@walk
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}
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mask = mask ushr shamt
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IntegerLiteralExpr(mask.toString())
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}
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is LongLiteralExpr -> {
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var mask = maskExpr.checkedAsLong()
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if (shamt > java.lang.Long.numberOfTrailingZeros(mask)) {
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return@walk
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}
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mask = mask ushr shamt
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mask.toLongLiteralExpr()
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}
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else -> return@walk
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}
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expr.replace(BinaryExpr(BinaryExpr(argExpr.clone(), newMaskExpr, bitwiseOp), shamtExpr.clone(), shiftOp))
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}
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}
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private companion object {
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private val RIGHT_SHIFT_OPS = setOf(
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BinaryExpr.Operator.SIGNED_RIGHT_SHIFT,
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BinaryExpr.Operator.UNSIGNED_RIGHT_SHIFT
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)
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private val BITWISE_OPS = setOf(
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BinaryExpr.Operator.BINARY_AND,
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BinaryExpr.Operator.BINARY_OR,
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BinaryExpr.Operator.XOR
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)
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}
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}
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