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Interface BufWriter

public sealed interface BufWriter

Advanced class file writing support for AttributeMappers. Supports writing portions of a class file to a growable buffer, such as writing various numerical types (e.g., u2, u4), to the end of the buffer, as well as to create constant pool entries.

All numeric values in the class file format are big endian. Writing larger numeric values to smaller numeric values are always done with truncation, that the least significant bytes are kept and the other bytes are silently dropped. As a result, numeric value writing methods can write both signed and unsigned values, and users should validate their values before writing if silent dropping of most significant bytes is not the intended behavior.

Since:

See Also:

Method Summary

Modifier and Type	Method	Description
`boolean`	`canWriteDirect(ConstantPool other)`	Returns whether the provided constant pool is index-compatible with the constant pool of this buffer.
`ConstantPoolBuilder`	`constantPool()`	Returns the constant pool builder associated with this buffer.
`void`	`patchInt(int offset, int size, int value)`	Patches a previously written integer value.
`void`	`reserveSpace(int freeBytes)`	Ensures that the buffer has at least `freeBytes` bytes of free space in the end of the buffer.
`int`	`size()`	Returns the number of bytes that have been written to the buffer.
`void`	`writeBytes(byte[] arr)`	Writes the contents of a byte array to the buffer.
`void`	`writeBytes(byte[] arr, int start, int length)`	Writes a range of a byte array to the buffer.
`void`	`writeDouble(double x)`	Writes a double value, of 8 bytes, to the buffer.
`void`	`writeFloat(float x)`	Writes a float value, of 4 bytes, to the buffer.
`void`	`writeIndex(PoolEntry entry)`	Writes the index of the specified constant pool entry as a `u2`.
`void`	`writeIndexOrZero(PoolEntry entry)`	Writes the index of the specified constant pool entry, or the value `0` if the specified entry is `null`, as a `u2`.
`void`	`writeInt(int x)`	Writes 4 bytes, or an int, to the buffer.
`void`	`writeIntBytes(int intSize, long intValue)`	Writes a multibyte value to the buffer.
`void`	`writeLong(long x)`	Writes 8 bytes, or a long, to the buffer.
`void`	`writeU1(int x)`	Writes a byte to the buffer.
`void`	`writeU2(int x)`	Writes 2 bytes, or a short, to the buffer.

Method Details

constantPool

ConstantPoolBuilder constantPool()

Returns the constant pool builder associated with this buffer.

Returns:

the constant pool builder associated with this buffer

See Also:

canWriteDirect

boolean canWriteDirect(ConstantPool other)

Returns whether the provided constant pool is index-compatible with the constant pool of this buffer.

This is a shortcut for constantPool().canWriteDirect(other).

Parameters:

other - the other constant pool

Returns:

whether the provided constant pool is index-compatible with the constant pool of this buffer

See Also:

reserveSpace

void reserveSpace(int freeBytes)

Ensures that the buffer has at least freeBytes bytes of free space in the end of the buffer.

The writing result is the same without calls to this method, but the writing process may be slower.

API Note:: This is a hint that changes no visible state of the buffer; it helps to reduce reallocation of the underlying storage by allocating sufficient space at once.
Parameters:: freeBytes - the number of bytes to reserve

writeU1

void writeU1(int x)

Writes a byte to the buffer. x is truncated to a byte and written.

Parameters:: x - the value to truncate to a byte

writeU2

void writeU2(int x)

Writes 2 bytes, or a short, to the buffer. x is truncated to two bytes and written.

Parameters:: x - the value to truncate to a short

writeInt

void writeInt(int x)

Writes 4 bytes, or an int, to the buffer.

Parameters:: x - the int value

writeFloat

void writeFloat(float x)

Writes a float value, of 4 bytes, to the buffer.

In the conversions, all NaN values of the float may or may not be collapsed into a single "canonical" NaN value.

Parameters:: x - the float value

writeLong

void writeLong(long x)

Writes 8 bytes, or a long, to the buffer.

Parameters:: x - the long value

writeDouble

void writeDouble(double x)

Writes a double value, of 8 bytes, to the buffer.

In the conversions, all NaN values of the double may or may not be collapsed into a single "canonical" NaN value.

Parameters:: x - the double value

writeBytes

void writeBytes(byte[] arr)

Writes the contents of a byte array to the buffer.

Parameters:: arr - the byte array

writeBytes

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

Writes a range of a byte array to the buffer.

Parameters:: arr - the byte array; start - the start offset of the range within the byte array; length - the length of the range
Throws:: IndexOutOfBoundsException - if range is outside the array bounds

patchInt

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

Patches a previously written integer value. value is truncated to the given size number of bytes and written at the given


offset

. The end of this buffer stays unchanged.

API Note:

The offset can be obtained by calling size() before writing the previous integer value.

Parameters:

offset - the offset in this buffer at which to patch

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

value - the integer value to be truncated

Throws:

IndexOutOfBoundsException - if patched int is outside of bounds

See Also:

writeIntBytes

void writeIntBytes(int intSize, long intValue)

Writes a multibyte value to the buffer. intValue is truncated to the given intSize number of bytes and written.

Parameters:: intSize - the size of the integer value being written, in bytes; intValue - the value to be truncated

writeIndex

void writeIndex(PoolEntry entry)

Writes the index of the specified constant pool entry as a u2. If the entry does not belong to the constant pool of this buffer, it will be converted, and the index of the converted pool entry is written instead.

Parameters:: entry - the constant pool entry
Throws:: IllegalArgumentException - if the entry has invalid index

writeIndexOrZero

void writeIndexOrZero(PoolEntry entry)

Writes the index of the specified constant pool entry, or the value 0 if the specified entry is null, as a u2. If the entry does not belong to the constant pool of this buffer, it will be converted, and the index of the converted pool entry is written instead.

Parameters:: entry - the constant pool entry, may be null
Throws:: IllegalArgumentException - if the entry is not null and has invalid index

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

See Also:

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