Class CodeWriter
- java.lang.Object
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- org.gjt.sp.jedit.bsh.org.objectweb.asm.CodeWriter
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- All Implemented Interfaces:
CodeVisitor
public class CodeWriter extends java.lang.Object implements CodeVisitor
ACodeVisitor
that generates Java bytecode instructions. Each visit method of this class appends the bytecode corresponding to the visited instruction to a byte vector, in the order these methods are called.
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Constructor Summary
Constructors Modifier Constructor Description protected
CodeWriter(ClassWriter cw, boolean computeMaxs)
Constructs a CodeWriter.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected byte[]
getCode()
Returns the current bytecode of this method.protected int
getCodeSize()
Returns the current size of the bytecode of this method.protected void
init(int access, java.lang.String name, java.lang.String desc, java.lang.String[] exceptions)
Initializes this CodeWriter to define the bytecode of the specified method.protected int[]
resizeInstructions(int[] indexes, int[] sizes, int len)
Resizes the designated instructions, while keeping jump offsets and instruction addresses consistent.void
visitFieldInsn(int opcode, java.lang.String owner, java.lang.String name, java.lang.String desc)
Visits a field instruction.void
visitIincInsn(int var, int increment)
Visits an IINC instruction.void
visitInsn(int opcode)
Visits a zero operand instruction.void
visitIntInsn(int opcode, int operand)
Visits an instruction with a single int operand.void
visitJumpInsn(int opcode, Label label)
Visits a jump instruction.void
visitLabel(Label label)
Visits a label.void
visitLdcInsn(java.lang.Object cst)
Visits a LDC instruction.void
visitLineNumber(int line, Label start)
Visits a line number declaration.void
visitLocalVariable(java.lang.String name, java.lang.String desc, Label start, Label end, int index)
Visits a local variable declaration.void
visitLookupSwitchInsn(Label dflt, int[] keys, Label[] labels)
Visits a LOOKUPSWITCH instruction.void
visitMaxs(int maxStack, int maxLocals)
Visits the maximum stack size and the maximum number of local variables of the method.void
visitMethodInsn(int opcode, java.lang.String owner, java.lang.String name, java.lang.String desc)
Visits a method instruction.void
visitMultiANewArrayInsn(java.lang.String desc, int dims)
Visits a MULTIANEWARRAY instruction.void
visitTableSwitchInsn(int min, int max, Label dflt, Label[] labels)
Visits a TABLESWITCH instruction.void
visitTryCatchBlock(Label start, Label end, Label handler, java.lang.String type)
Visits a try catch block.void
visitTypeInsn(int opcode, java.lang.String desc)
Visits a type instruction.void
visitVarInsn(int opcode, int var)
Visits a local variable instruction.
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Constructor Detail
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CodeWriter
protected CodeWriter(ClassWriter cw, boolean computeMaxs)
Constructs a CodeWriter.- Parameters:
cw
- the class writer in which the method must be added.computeMaxs
-true
if the maximum stack size and number of local variables must be automatically computed.
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Method Detail
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init
protected void init(int access, java.lang.String name, java.lang.String desc, java.lang.String[] exceptions)
Initializes this CodeWriter to define the bytecode of the specified method.
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visitInsn
public void visitInsn(int opcode)
Description copied from interface:CodeVisitor
Visits a zero operand instruction.- Specified by:
visitInsn
in interfaceCodeVisitor
- Parameters:
opcode
- the opcode of the instruction to be visited. This opcode is either NOP, ACONST_NULL, ICONST_M1, ICONST_0, ICONST_1, ICONST_2, ICONST_3, ICONST_4, ICONST_5, LCONST_0, LCONST_1, FCONST_0, FCONST_1, FCONST_2, DCONST_0, DCONST_1, IALOAD, LALOAD, FALOAD, DALOAD, AALOAD, BALOAD, CALOAD, SALOAD, IASTORE, LASTORE, FASTORE, DASTORE, AASTORE, BASTORE, CASTORE, SASTORE, POP, POP2, DUP, DUP_X1, DUP_X2, DUP2, DUP2_X1, DUP2_X2, SWAP, IADD, LADD, FADD, DADD, ISUB, LSUB, FSUB, DSUB, IMUL, LMUL, FMUL, DMUL, IDIV, LDIV, FDIV, DDIV, IREM, LREM, FREM, DREM, INEG, LNEG, FNEG, DNEG, ISHL, LSHL, ISHR, LSHR, IUSHR, LUSHR, IAND, LAND, IOR, LOR, IXOR, LXOR, I2L, I2F, I2D, L2I, L2F, L2D, F2I, F2L, F2D, D2I, D2L, D2F, I2B, I2C, I2S, LCMP, FCMPL, FCMPG, DCMPL, DCMPG, IRETURN, LRETURN, FRETURN, DRETURN, ARETURN, RETURN, ARRAYLENGTH, ATHROW, MONITORENTER, or MONITOREXIT.
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visitIntInsn
public void visitIntInsn(int opcode, int operand)
Description copied from interface:CodeVisitor
Visits an instruction with a single int operand.- Specified by:
visitIntInsn
in interfaceCodeVisitor
- Parameters:
opcode
- the opcode of the instruction to be visited. This opcode is either BIPUSH, SIPUSH or NEWARRAY.operand
- the operand of the instruction to be visited.
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visitVarInsn
public void visitVarInsn(int opcode, int var)
Description copied from interface:CodeVisitor
Visits a local variable instruction. A local variable instruction is an instruction that loads or stores the value of a local variable.- Specified by:
visitVarInsn
in interfaceCodeVisitor
- Parameters:
opcode
- the opcode of the local variable instruction to be visited. This opcode is either ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE or RET.var
- the operand of the instruction to be visited. This operand is the index of a local variable.
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visitTypeInsn
public void visitTypeInsn(int opcode, java.lang.String desc)
Description copied from interface:CodeVisitor
Visits a type instruction. A type instruction is an instruction that takes a type descriptor as parameter.- Specified by:
visitTypeInsn
in interfaceCodeVisitor
- Parameters:
opcode
- the opcode of the type instruction to be visited. This opcode is either NEW, ANEWARRAY, CHECKCAST or INSTANCEOF.desc
- the operand of the instruction to be visited. This operand is must be a fully qualified class name in internal form, or the type descriptor of an array type (seeType
).
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visitFieldInsn
public void visitFieldInsn(int opcode, java.lang.String owner, java.lang.String name, java.lang.String desc)
Description copied from interface:CodeVisitor
Visits a field instruction. A field instruction is an instruction that loads or stores the value of a field of an object.- Specified by:
visitFieldInsn
in interfaceCodeVisitor
- Parameters:
opcode
- the opcode of the type instruction to be visited. This opcode is either GETSTATIC, PUTSTATIC, GETFIELD or PUTFIELD.owner
- the internal name of the field's owner class (seegetInternalName
).name
- the field's name.desc
- the field's descriptor (seeType
).
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visitMethodInsn
public void visitMethodInsn(int opcode, java.lang.String owner, java.lang.String name, java.lang.String desc)
Description copied from interface:CodeVisitor
Visits a method instruction. A method instruction is an instruction that invokes a method.- Specified by:
visitMethodInsn
in interfaceCodeVisitor
- Parameters:
opcode
- the opcode of the type instruction to be visited. This opcode is either INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC or INVOKEINTERFACE.owner
- the internal name of the method's owner class (seegetInternalName
).name
- the method's name.desc
- the method's descriptor (seeType
).
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visitJumpInsn
public void visitJumpInsn(int opcode, Label label)
Description copied from interface:CodeVisitor
Visits a jump instruction. A jump instruction is an instruction that may jump to another instruction.- Specified by:
visitJumpInsn
in interfaceCodeVisitor
- Parameters:
opcode
- the opcode of the type instruction to be visited. This opcode is either IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE, IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE, GOTO, JSR, IFNULL or IFNONNULL.label
- the operand of the instruction to be visited. This operand is a label that designates the instruction to which the jump instruction may jump.
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visitLabel
public void visitLabel(Label label)
Description copied from interface:CodeVisitor
Visits a label. A label designates the instruction that will be visited just after it.- Specified by:
visitLabel
in interfaceCodeVisitor
- Parameters:
label
- aLabel
object.
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visitLdcInsn
public void visitLdcInsn(java.lang.Object cst)
Description copied from interface:CodeVisitor
Visits a LDC instruction.- Specified by:
visitLdcInsn
in interfaceCodeVisitor
- Parameters:
cst
- the constant to be loaded on the stack. This parameter must be a non nullInteger
, aFloat
, aLong
, aDouble
or aString
.
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visitIincInsn
public void visitIincInsn(int var, int increment)
Description copied from interface:CodeVisitor
Visits an IINC instruction.- Specified by:
visitIincInsn
in interfaceCodeVisitor
- Parameters:
var
- index of the local variable to be incremented.increment
- amount to increment the local variable by.
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visitTableSwitchInsn
public void visitTableSwitchInsn(int min, int max, Label dflt, Label[] labels)
Description copied from interface:CodeVisitor
Visits a TABLESWITCH instruction.- Specified by:
visitTableSwitchInsn
in interfaceCodeVisitor
- Parameters:
min
- the minimum key value.max
- the maximum key value.dflt
- beginning of the default handler block.labels
- beginnings of the handler blocks.labels[i]
is the beginning of the handler block for themin + i
key.
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visitLookupSwitchInsn
public void visitLookupSwitchInsn(Label dflt, int[] keys, Label[] labels)
Description copied from interface:CodeVisitor
Visits a LOOKUPSWITCH instruction.- Specified by:
visitLookupSwitchInsn
in interfaceCodeVisitor
- Parameters:
dflt
- beginning of the default handler block.keys
- the values of the keys.labels
- beginnings of the handler blocks.labels[i]
is the beginning of the handler block for thekeys[i]
key.
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visitMultiANewArrayInsn
public void visitMultiANewArrayInsn(java.lang.String desc, int dims)
Description copied from interface:CodeVisitor
Visits a MULTIANEWARRAY instruction.- Specified by:
visitMultiANewArrayInsn
in interfaceCodeVisitor
- Parameters:
desc
- an array type descriptor (seeType
).dims
- number of dimensions of the array to allocate.
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visitTryCatchBlock
public void visitTryCatchBlock(Label start, Label end, Label handler, java.lang.String type)
Description copied from interface:CodeVisitor
Visits a try catch block.- Specified by:
visitTryCatchBlock
in interfaceCodeVisitor
- Parameters:
start
- beginning of the exception handler's scope (inclusive).end
- end of the exception handler's scope (exclusive).handler
- beginning of the exception handler's code.type
- internal name of the type of exceptions handled by the handler, ornull
to catch any exceptions (for "finally" blocks).
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visitMaxs
public void visitMaxs(int maxStack, int maxLocals)
Description copied from interface:CodeVisitor
Visits the maximum stack size and the maximum number of local variables of the method.- Specified by:
visitMaxs
in interfaceCodeVisitor
- Parameters:
maxStack
- maximum stack size of the method.maxLocals
- maximum number of local variables for the method.
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visitLocalVariable
public void visitLocalVariable(java.lang.String name, java.lang.String desc, Label start, Label end, int index)
Description copied from interface:CodeVisitor
Visits a local variable declaration.- Specified by:
visitLocalVariable
in interfaceCodeVisitor
- Parameters:
name
- the name of a local variable.desc
- the type descriptor of this local variable.start
- the first instruction corresponding to the scope of this local variable (inclusive).end
- the last instruction corresponding to the scope of this local variable (exclusive).index
- the local variable's index.
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visitLineNumber
public void visitLineNumber(int line, Label start)
Description copied from interface:CodeVisitor
Visits a line number declaration.- Specified by:
visitLineNumber
in interfaceCodeVisitor
- Parameters:
line
- a line number. This number refers to the source file from which the class was compiled.start
- the first instruction corresponding to this line number.
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resizeInstructions
protected int[] resizeInstructions(int[] indexes, int[] sizes, int len)
Resizes the designated instructions, while keeping jump offsets and instruction addresses consistent. This may require to resize other existing instructions, or even to introduce new instructions: for example, increasing the size of an instruction by 2 at the middle of a method can increases the offset of an IFEQ instruction from 32766 to 32768, in which case IFEQ 32766 must be replaced with IFNEQ 8 GOTO_W 32765. This, in turn, may require to increase the size of another jump instruction, and so on... All these operations are handled automatically by this method.This method must be called after all the method that is being built has been visited. In particular, the
Label
objects used to construct the method are no longer valid after this method has been called.- Parameters:
indexes
- current positions of the instructions to be resized. Each instruction must be designated by the index of its last byte, plus one (or, in other words, by the index of the first byte of the next instruction).sizes
- the number of bytes to be added to the above instructions. More precisely, for each i <len
,sizes
[i] bytes will be added at the end of the instruction designated byindexes[i]
or, ifsizes[i]
is negative, the last |sizes[i]
| bytes of the instruction will be removed (the instruction size must not become negative or null). The gaps introduced by this method must be filled in "manually" in the array returned by thegetCode
method.len
- the number of instruction to be resized. Must be smaller than or equal toindexes.length
andsizes.length
.- Returns:
- the
indexes
array, which now contains the new positions of the resized instructions (designated as above).
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getCodeSize
protected int getCodeSize()
Returns the current size of the bytecode of this method. This size just includes the size of the bytecode instructions: it does not include the size of the Exceptions, LocalVariableTable, LineNumberTable, Synthetic and Deprecated attributes, if present.- Returns:
- the current size of the bytecode of this method.
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getCode
protected byte[] getCode()
Returns the current bytecode of this method. This bytecode only contains the instructions: it does not include the Exceptions, LocalVariableTable, LineNumberTable, Synthetic and Deprecated attributes, if present.- Returns:
- the current bytecode of this method. The bytecode is contained
between the index 0 (inclusive) and the index
getCodeSize
(exclusive).
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