Module java.base

Package java.lang.classfile^PREVIEW

Interface BufWriter

public sealed interface BufWriter

BufWriter is a preview API of the Java platform.

Programs can only use BufWriter when preview features are enabled.

Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.

Supports writing portions of a classfile to a growable buffer. Methods are provided to write various standard entities (e.g., u2, u4) to the end of the buffer, as well as to create constant pool entries.

Since:

22

Method Summary

Modifier and Type	Method	Description
ByteBuffer	asByteBuffer()	Returns a ByteBuffer view of the bytes in the buffer.
boolean	canWriteDirect(ConstantPoolPREVIEW other)	Returns whether the provided constant pool is index-compatible with this one.
ConstantPoolBuilderPREVIEW	constantPool()	Returns the constant pool builder associated with this buffer.
void	copyTo(byte[] array, int bufferOffset)	Copy the contents of the buffer into a byte array.
void	patchInt(int offset, int size, int value)	Patch a previously written integer value.
void	reserveSpace(int freeBytes)	Ensure that the buffer has at least freeBytes bytes of unused space
int	size()	Returns the number of bytes that have been written to the buffer.
void	writeBytes(byte[] arr)	Write the contents of a byte array to the buffer
void	writeBytes(byte[] arr, int start, int length)	Write a range of a byte array to the buffer
void	writeBytes(BufWriterPREVIEW other)	Write the contents of another BufWriterPREVIEW to the buffer
void	writeDouble(double x)	Write a double value to the buffer
void	writeFloat(float x)	Write a float value to the buffer
void	writeIndex(PoolEntryPREVIEW entry)	Write the index of the specified constant pool entry, as a u2, to the buffer
void	writeIndexOrZero(PoolEntryPREVIEW entry)	Write the index of the specified constant pool entry, as a u2, to the buffer, or zero if the entry is null
void	writeInt(int x)	Write a signed int to the buffer
void	writeIntBytes(int intSize, long intValue)	Write a 1, 2, 4, or 8 byte integer value to the buffer.
<T extends WritableElementPREVIEW<?>> void	writeList(List<T> list)	Write a list of entities to the buffer.
void	writeListIndices(List<? extends PoolEntryPREVIEW> list)	Write a list of constant pool entry indexes to the buffer.
void	writeLong(long x)	Write a long value to the buffer
void	writeU1(int x)	Write an unsigned byte to the buffer
void	writeU2(int x)	Write an unsigned short to the buffer

Method Details

constantPool

ConstantPoolBuilderPREVIEW constantPool()

Returns the constant pool builder associated with this buffer.

Returns:

the constant pool builder associated with this buffer

canWriteDirect

boolean canWriteDirect(ConstantPoolPREVIEW other)

Returns whether the provided constant pool is index-compatible with this one. This may be because they are the same constant pool, or because this constant pool was copied from the other.

Parameters:

other - the other constant pool

Returns:

whether the provided constant pool is index-compatible with this one

reserveSpace

void reserveSpace(int freeBytes)

Ensure that the buffer has at least freeBytes bytes of unused space

Parameters:

freeBytes - the number of bytes to reserve

writeU1

void writeU1(int x)

Write an unsigned byte to the buffer

Parameters:

x - the byte value

writeU2

void writeU2(int x)

Write an unsigned short to the buffer

Parameters:

x - the short value

writeInt

void writeInt(int x)

Write a signed int to the buffer

Parameters:

x - the int value

writeFloat

void writeFloat(float x)

Write a float value to the buffer

Parameters:

x - the float value

writeLong

void writeLong(long x)

Write a long value to the buffer

Parameters:

x - the long value

writeDouble

void writeDouble(double x)

Write a double value to the buffer

Parameters:

x - the int value

writeBytes

void writeBytes(byte[] arr)

Write the contents of a byte array to the buffer

Parameters:

arr - the byte array

writeBytes

void writeBytes(BufWriterPREVIEW other)

Write the contents of another BufWriter^PREVIEW to the buffer

Parameters:

other - the other BufWriter^PREVIEW

writeBytes

void writeBytes(byte[] arr,
 int start,
 int length)

Write a range of a byte array to the buffer

Parameters:

arr - the byte array

start - the offset within the byte array of the range

length - the length of the range

patchInt

void patchInt(int offset,
 int size,
 int value)

Patch a previously written integer value. Depending on the specified size, the entire value, or the low 1 or 2 bytes, may be written.

Parameters:

offset - the offset at which to patch

size - the size of the integer value being written, in bytes

value - the integer value

writeIntBytes

void writeIntBytes(int intSize,
 long intValue)

Write a 1, 2, 4, or 8 byte integer value to the buffer. Depending on the specified size, the entire value, or the low 1, 2, or 4 bytes, may be written.

Parameters:

intSize - the size of the integer value being written, in bytes

intValue - the integer value

writeIndex

void writeIndex(PoolEntryPREVIEW entry)

Write the index of the specified constant pool entry, as a u2, to the buffer

Parameters:

entry - the constant pool entry

Throws:

NullPointerException - if the entry is null

writeIndexOrZero

void writeIndexOrZero(PoolEntryPREVIEW entry)

Write the index of the specified constant pool entry, as a u2, to the buffer, or zero if the entry is null

Parameters:

entry - the constant pool entry

writeList

<T extends WritableElementPREVIEW<?>> void writeList(List<T> list)

Write a list of entities to the buffer. The length of the list is written as a u2, followed by the bytes corresponding to each element in the list. Writing of the entities is delegated to the entry.

Type Parameters:

T - the type of entity

Parameters:

list - the entities

writeListIndices

void writeListIndices(List<? extends PoolEntryPREVIEW> list)

Write a list of constant pool entry indexes to the buffer. The length of the list is written as a u2, followed by a u2 for each entry in the list.

Parameters:

list - the list of entries

size

int size()

Returns the number of bytes that have been written to the buffer.

Returns:

the number of bytes that have been written to the buffer

asByteBuffer

ByteBuffer asByteBuffer()

Returns a ByteBuffer view of the bytes in the buffer.

Returns:

a ByteBuffer view of the bytes in the buffer

copyTo

void copyTo(byte[] array,
 int bufferOffset)

Copy the contents of the buffer into a byte array.

Parameters:

array - the byte array

bufferOffset - the offset into the array at which to write the contents of the buffer