/* * This file is part of Mixin, licensed under the MIT License (MIT). * * Copyright (c) SpongePowered * Copyright (c) contributors * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ package org.spongepowered.asm.mixin.injection; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import org.spongepowered.asm.mixin.MixinEnvironment.Option; import org.spongepowered.asm.mixin.injection.selectors.ITargetSelector; import org.spongepowered.asm.mixin.injection.throwables.InjectionError; import org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException; import org.spongepowered.asm.util.ConstraintParser.Constraint; /** * Specifies that this mixin method should inject an argument modifier to itself * in the target method(s) identified by {@link #method}. This type of injection * provides a lightweight mechanism for changing a single argument of a selected * method invocation within the target method(s). To affect multiple arguments * of an invocation all at once, use {@link ModifyArgs} instead. * *

Use this injector when a (target) method contains an method invocation * (the subject) and you wish to change a single value being passed to * that subject method. If you need to alter an argument received by a * target method, use {@link ModifyVariable} instead.

* *

Consider the following method:

* * 
private void targetMethod() {
 *    Entity someEntity = this.obtainEntity();
 *    float x = 1.0F, y = 3.0F, z = 0.1F;
 *    someEntity.setLocation(x, y, z, true); // subject
 *}
*
* *

Let us assume that we wish to modify the y value when * calling the setLocation method. We know that the * arguments are floats and that the y value is the second * (index = 1) float argument. Thus our injector requires the * following signature: * *

@ModifyArg(method = "targetMethod", at = @At(value * = "INVOKE", target = "setLocation(FFFZ)V"), index = 1)
* private float adjustYCoord(float y) {
*     return y + 64.0F;
* }
* *

The callback consumes the original value of y and returns the * adjusted value.

* *

@ModifyArg can also consume all of the subject method's * arguments if required, to provide additional context for the callback. In * this case the arguments of the callback should match the target method:

* *
@ModifyArg(method = "targetMethod", at = @At(value * = "INVOKE", target = "setLocation(FFFZ)V"), index = 1)
* private float adjustYCoord(float x, float y, float z, boolean interpolate) { *
    return (x == 0 && y == 0) ? 0 : y;
* }
* *

Note that @ModifyArg cannot capture the arguments * of the target method like some other injectors can */ @Target({ ElementType.METHOD }) @Retention(RetentionPolicy.RUNTIME) public @interface ModifyArg { /** * String representation of one or more * {@link ITargetSelector target selectors} which identify the target * methods. * * @return target method(s) for this injector */ public String[] method() default {}; /** * Literal representation of one or more {@link Desc @Desc} annotations * which identify the target methods. * * @return target method(s) for this injector as descriptors */ public Desc[] target() default {}; /** * A {@link Slice} annotation which describes the method bisection used in * the {@link #at} query for this injector. * * @return slice */ public Slice slice() default @Slice; /** * An {@link At} annotation which describes the {@link InjectionPoint} in * the target method. The specified {@link InjectionPoint} must only * return {@link org.objectweb.asm.tree.MethodInsnNode} instances * and an exception will be thrown if this is not the case. * * @return {@link At} which identifies the target method invocation */ public At at(); /** *

Gets the argument index on the target to set. It is not necessary to * set this value if there is only one argument of the modifier type in the * hooked method's signature. For example if the target method accepts a * boolean, an integer and a String, and the modifier method accepts and * returns an integer, then the integer parameter will be automatically * selected.

* *

The index is zero-based.

* * @return argument index to modify or -1 for automatic */ public int index() default -1; /** * By default, the annotation processor will attempt to locate an * obfuscation mapping for all {@link ModifyArg} methods since it is * anticipated that in general the target of a {@link ModifyArg} annotation * will be an obfuscated method in the target class. However since it is * possible to also apply mixins to non-obfuscated targets (or non- * obfuscated methods in obfuscated targets, such as methods added by Forge) * it may be necessary to suppress the compiler error which would otherwise * be generated. Setting this value to false will cause the * annotation processor to skip this annotation when attempting to build the * obfuscation table for the mixin. * * @return True to instruct the annotation processor to search for * obfuscation mappings for this annotation */ public boolean remap() default true; /** * In general, injectors are intended to "fail soft" in that a failure to * locate the injection point in the target method is not considered an * error condition. Another transformer may have changed the method * structure or any number of reasons may cause an injection to fail. This * also makes it possible to define several injections to achieve the same * task given expected mutation of the target class and the * injectors which fail are simply ignored. * *

However, this behaviour is not always desirable. For example, if your * application depends on a particular injection succeeding you may wish to * detect the injection failure as an error condition. This argument is thus * provided to allow you to stipulate a minimum number of successful * injections for this callback handler. If the number of injections * specified is not achieved then an {@link InjectionError} is thrown at * application time. Use this option with care.

* * @return Minimum required number of injected callbacks, default specified * by the containing config */ public int require() default -1; /** * Like {@link #require()} but only enabled if the * {@link Option#DEBUG_INJECTORS mixin.debug.countInjections} option is set * to true and defaults to 1. Use this option during debugging to * perform simple checking of your injectors. Causes the injector to throw * a {@link InvalidInjectionException} if the expected number of injections * is not realised. * * @return Minimum number of expected callbacks, default 1 */ public int expect() default 1; /** * Injection points are in general expected to match every candidate * instruction in the target method or slice, except in cases where options * such as {@link At#ordinal} are specified which naturally limit the number * of results. * *

This option allows for sanity-checking to be performed on the results * of an injection point by specifying a maximum allowed number of matches, * similar to that afforded by {@link Group#max}. For example if your * injection is expected to match 4 invocations of a target method, but * instead matches 5, this can become a detectable tamper condition by * setting this value to 4. * *

Setting any value 1 or greater is allowed. Values less than 1 or less * than {@link #require} are ignored. {@link #require} supercedes this * argument such that if allow is less than require the * value of require is always used.

* *

Note that this option is not a limit on the query behaviour of * this injection point. It is only a sanity check used to ensure that the * number of matches is not too high * * @return Maximum allowed number of injections for this */ public int allow() default -1; /** * Returns constraints which must be validated for this injector to * succeed. See {@link Constraint} for details of constraint formats. * * @return Constraints for this annotation */ public String constraints() default ""; /** * By default almost all injectors for a target class apply their injections * at the same time. In other words, if multiple mixins target the same * class then injectors are applied in priority order (since the mixins * themselves are merged in priority order, and injectors run in the order * they were merged). The exception being redirect injectors, which apply in * a later pass. * *

The default order for injectors is 1000, and redirect * injectors use 10000.

* *

Specifying a value for order alters this default behaviour * and causes the injector to inject either earlier or later than it * normally would. For example specifying 900 will cause the * injector to apply before others, while 1100 will apply later. * Injectors with the same order will still apply in order of their * mixin's priority. * * @return the application order for this injector, uses DEFAULT (1000) if * not specified */ public int order() default 1000; }