/* * 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.modify.AfterStoreLocal; import org.spongepowered.asm.mixin.injection.modify.BeforeLoadLocal; 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 a variable modifier callback * to itself in the target method(s) identified by {@link #method}. The variable * modifier can modify a single local variable in the target method frame. * *

If the variable being modified is a method argument, specifying the * {@link #argsOnly argsOnly=true} reduces the overhead of calculating * the local variable table for the method.

* *

ModifyVariable callbacks should always take one argument of the * type to capture and return the same type. For example a ModifyVariable * for a local of type {@link String} should have the * signature:

* *
private String myHandlerMethod(String * variable) {
    ...
* *

The callback receives the current value of the local variable, and should * return the new value.

* *

The injector has two operating modes, explicit and implicit * , and can operate either on the entire LVT or on the {@link #argsOnly * method arguments only}.

* *

Explicit mode

* *

In explicit mode, the variable to capture can be specified by * specifying values for the discriminator arguments {@link #ordinal}, * {@link #index} and {@link #name}. The injector uses the discriminators in * order to attempt to locate the variable to capture. If no local variable * matches any discriminators, the capture fails.

* *

Implicit mode

* *

If no values for the capture discrimiators are specified, the injector * operates in implicit mode. If exactly one variable of the capture * type exists in the target LVT, then capture will succeed. However, if more * than one variable of the required type is encountered in the LVT then an * {@link InvalidInjectionException} is thrown.

* *

Context-sensitive injection points

* *

Normally the {@link InjectionPoint injection points} specified by {@link * #at} are independent of the injector being used. With ModifyVariable * there are two special injection points which consume the discriminator from * the annotation:

* * * *

See the javadoc for each injection point for details.

* *

Notes

* *

Like other injectors, the callback signature can optionally include the * target method arguments by simply appending them to the handler method * signature.

*/ @Target({ ElementType.METHOD }) @Retention(RetentionPolicy.RUNTIME) public @interface ModifyVariable { /** * 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. * * @return {@link At} which identifies the location to inject inside the * target method. */ public At at(); /** * When creating a {@link ModifyVariable} callback, you may wish to first * inspect the local variable table in the target method at the injection * point. Set this value to true to print the local variable table * and perform no injection. * * @return true to print the LVT to the console */ public boolean print() default false; /** * Gets the local variable ordinal by type. For example, if there are 3 * {@link String} arguments in the local variable table, ordinal 0 specifies * the first, 1 specifies the second, etc. Use ordinal when the * index within the LVT is known. Takes precedence over {@link #index}. * * @return variable ordinal */ public int ordinal() default -1; /** * Gets the absolute index of the local variable within the local variable * table to capture. The local variable at the specified index must be of * the same type as the capture. Takes precedence over {@link #name}. * * @return argument index to modify or -1 for automatic */ public int index() default -1; /** * Gets the name of the variable to capture. Only used if the variable * cannot be located via {@link #ordinal} or {@link #index}. * * @return possible names to capture, only useful when the LVT in the target * method is known to be complete. */ public String[] name() default {}; /** * Under normal circumstances the injector will consider all local variables * including method arguments and all other local variables. This involves * reading (and possibly generating) the local variable table for the method * which can have mixed results. Set this value to true to only * consider method arguments. * * @return true if this injector should only consider method arguments and * not all locals. */ public boolean argsOnly() default false; /** * By default, the annotation processor will attempt to locate an * obfuscation mapping for all {@link ModifyVariable} methods since it is * anticipated that in general the target of a {@link ModifyVariable} * 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; }