org.graalvm.compiler.bytecode

Class BytecodeStream

java.lang.Object

org.graalvm.compiler.bytecode.BytecodeStream

public final class BytecodeStream
extends Object

A utility class that makes iterating over bytecodes and reading operands simpler and less error prone. For example, it handles the Bytecodes.WIDE instruction and wide variants of instructions internally.

Constructor Summary

Constructors

Constructor and Description
BytecodeStream(byte[] code) Creates a new BytecodeStream for the specified bytecode.

Method Summary

Modifier and Type	Method and Description
int	currentBC() Gets the current opcode.
int	currentBCI() Gets the current bytecode index.
int	endBCI() Gets the bytecode index of the end of the code.
void	next() Advances to the next bytecode.
int	nextBCI() Gets the next bytecode index (no side-effects).
int	readBranchDest() Read the destination of a Bytecodes.GOTO or IF instructions.
byte	readByte() Reads a signed, 1-byte value for the current instruction (e.g.
char	readCPI() Reads a constant pool index for the current instruction.
int	readCPI4() Reads a constant pool index for an invokedynamic instruction.
int	readIncrement() Read the delta for an Bytecodes.IINC bytecode.
int	readInt(int bci) Read a signed 4-byte integer from the bytecode stream at the specified bytecode index.
int	readLocalIndex() Reads the index of a local variable for one of the load or store instructions.
short	readShort() Reads a signed, 2-byte short for the current instruction (e.g.
int	readUByte(int bci) Reads an unsigned, 1-byte value from the bytecode stream at the specified bytecode index.
void	setBCI(int bci) Sets the bytecode index to the specified value.

Methods inherited from class java.lang.Object

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

Constructor Detail

BytecodeStream

public BytecodeStream(byte[] code)

Creates a new BytecodeStream for the specified bytecode.

Parameters:

code - the array of bytes that contains the bytecode

Method Detail

next

public void next()

Advances to the next bytecode.

nextBCI

public int nextBCI()

Gets the next bytecode index (no side-effects).

Returns:

the next bytecode index

currentBCI

public int currentBCI()

Gets the current bytecode index.

Returns:

the current bytecode index

endBCI

public int endBCI()

Gets the bytecode index of the end of the code.

Returns:

the index of the end of the code

currentBC

public int currentBC()

Gets the current opcode. This method will never return the WIDE opcode, but will instead return the opcode that is modified by the WIDE opcode.

Returns:

the current opcode; Bytecodes.END if at or beyond the end of the code

readLocalIndex

public int readLocalIndex()

Reads the index of a local variable for one of the load or store instructions. The WIDE modifier is handled internally.

Returns:

the index of the local variable

readIncrement

public int readIncrement()

Read the delta for an Bytecodes.IINC bytecode.

Returns:

the delta for the IINC

readBranchDest

public int readBranchDest()

Read the destination of a Bytecodes.GOTO or IF instructions.

Returns:

the destination bytecode index

readInt

public int readInt(int bci)

Read a signed 4-byte integer from the bytecode stream at the specified bytecode index.

Parameters:

bci - the bytecode index

Returns:

the integer value

readUByte

public int readUByte(int bci)

Reads an unsigned, 1-byte value from the bytecode stream at the specified bytecode index.

Parameters:

bci - the bytecode index

Returns:

the byte

readCPI

public char readCPI()

Reads a constant pool index for the current instruction.

Returns:

the constant pool index

readCPI4

public int readCPI4()

Reads a constant pool index for an invokedynamic instruction.

Returns:

the constant pool index

readByte

public byte readByte()

Reads a signed, 1-byte value for the current instruction (e.g. BIPUSH).

Returns:

the byte

readShort

public short readShort()

Reads a signed, 2-byte short for the current instruction (e.g. SIPUSH).

Returns:

the short value

setBCI

public void setBCI(int bci)

Sets the bytecode index to the specified value. If bci is beyond the end of the array, BytecodeStream.currentBC() will return Bytecodes.END and other methods may throw ArrayIndexOutOfBoundsException.

Parameters:

bci - the new bytecode index