Package org.spongepowered.asm.mixin.injection.points

Class BeforeFieldAccess

java.lang.Object

org.spongepowered.asm.mixin.injection.InjectionPoint

org.spongepowered.asm.mixin.injection.points.BeforeInvoke

org.spongepowered.asm.mixin.injection.points.BeforeFieldAccess

public class BeforeFieldAccess
extends BeforeInvoke

This injection point searches for GETFIELD and PUTFIELD (and static equivalent) opcodes matching its arguments and returns a list of insns immediately prior to matching instructions. It accepts the following parameters from At:

target

A Target Selector which identifies the target field.

opcode

The opcode of the field access, must be one of GETSTATIC, PUTSTATIC, GETFIELD or PUTFIELD.

ordinal

The ordinal position of the field access to match. For example if the field is referenced 3 times and you want to match the 3rd then you can specify an ordinal of 2 (ordinals are zero-indexed). The default value is -1 which supresses ordinal matching

named argument: array

For matching accesses to an array field element following a GETFIELD or GETSTATIC. Specify get, set or length to match the desired operation.

named argument: fuzz

When matching array operations using array the injection point will by default search up to 8 instructions after the matched field insn. However in some cases the array operation may be further from the matched GETFIELD or GETSTATIC and the amount to search (the "fuzz factor" can be specified using this argument. Likewise to optimise the search against false positives, this value can be specified as a lower value if desired. Has no effect if array is not specified.

Example:

@At(value = "FIELD", target="field_59_z:I", opcode = Opcodes.GETFIELD)

Matching array access:

For array fields, it is possible to match field accesses followed by a corresponding array element get, set or length operation. To enable this behaviour specify the array named-argument with the desired operation:

@At(value = "FIELD", target="myIntArray:[I", opcode = Opcodes.GETFIELD, args = "array=get")

See Redirect for information on array element redirection.

Note that like all standard injection points, this class matches the insn itself, putting the injection point immediately before the access in question. Use At.shift() specifier to adjust the matched opcode as necessary.

Nested Class Summary

Nested classes/interfaces inherited from class org.spongepowered.asm.mixin.injection.points.BeforeInvoke

BeforeInvoke.SearchType

Nested classes/interfaces inherited from class org.spongepowered.asm.mixin.injection.InjectionPoint

InjectionPoint.AtCode, InjectionPoint.Flags, InjectionPoint.RestrictTargetLevel, InjectionPoint.Specifier

Field Summary

Fields

Modifier and Type	Field	Description
static final int	ARRAY_SEARCH_FUZZ_DEFAULT	Default fuzz factor for searching for array access opcodes

Fields inherited from class org.spongepowered.asm.mixin.injection.points.BeforeInvoke

allowPermissive, className, context, logger, mixin, ordinal, target

Fields inherited from class org.spongepowered.asm.mixin.injection.InjectionPoint

DEFAULT_ALLOWED_SHIFT_BY, MAX_ALLOWED_SHIFT_BY

Constructor Summary

Constructors

Constructor	Description
BeforeFieldAccess(InjectionPointData data)

Method Summary

Modifier and Type	Method	Description
protected boolean	addInsn(org.objectweb.asm.tree.InsnList insns, Collection<org.objectweb.asm.tree.AbstractInsnNode> nodes, org.objectweb.asm.tree.AbstractInsnNode insn)
static org.objectweb.asm.tree.AbstractInsnNode	findArrayNode(org.objectweb.asm.tree.InsnList insns, org.objectweb.asm.tree.FieldInsnNode fieldNode, int opcode, int searchRange)	Searches for an array access instruction in the supplied instruction list which is within searchRange instructions of the supplied field instruction.
int	getArrayOpcode()
int	getFuzzFactor()
protected boolean	matchesInsn(org.objectweb.asm.tree.AbstractInsnNode insn)

Methods inherited from class org.spongepowered.asm.mixin.injection.points.BeforeInvoke

find, find, inspectInsn, log, matchesOrdinal, setLogging

Methods inherited from class org.spongepowered.asm.mixin.injection.InjectionPoint

addMessage, after, and, before, checkPriority, getAtCode, getId, getSlice, getSpecifier, getTargetRestriction, nextNode, or, parse, parse, parse, parse, parse, parse, parse, parse, register, register, setTargetRestriction, shift, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

ARRAY_SEARCH_FUZZ_DEFAULT

public static final int ARRAY_SEARCH_FUZZ_DEFAULT

Default fuzz factor for searching for array access opcodes

See Also:

• Constant Field Values

Constructor Details

BeforeFieldAccess

public BeforeFieldAccess(InjectionPointData data)

Method Details

getFuzzFactor

public int getFuzzFactor()

getArrayOpcode

public int getArrayOpcode()

matchesInsn

protected boolean matchesInsn(org.objectweb.asm.tree.AbstractInsnNode insn)

Overrides:

matchesInsn in class BeforeInvoke

addInsn

protected boolean addInsn(org.objectweb.asm.tree.InsnList insns,
 Collection<org.objectweb.asm.tree.AbstractInsnNode> nodes,
 org.objectweb.asm.tree.AbstractInsnNode insn)

Overrides:

addInsn in class BeforeInvoke

findArrayNode

public static org.objectweb.asm.tree.AbstractInsnNode findArrayNode(org.objectweb.asm.tree.InsnList insns,
 org.objectweb.asm.tree.FieldInsnNode fieldNode,
 int opcode,
 int searchRange)

Searches for an array access instruction in the supplied instruction list which is within searchRange instructions of the supplied field instruction. Searching halts if the search range is exhausted, if an Opcodes.ARRAYLENGTH opcode is encountered immediately after the specified access, if a matching field access is found, or if the end of the method is reached.

Parameters:

insns - Instruction list to search

fieldNode - Field instruction to search from

opcode - array access opcode to search for

searchRange - search range

Returns:

matching opcode or null if not matched