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An unofficial backport of the JDK Classfile API to Java 17
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/*
 * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package io.github.dmlloyd.classfile;

import io.github.dmlloyd.classfile.constantpool.ConstantPool;
import io.github.dmlloyd.classfile.constantpool.ConstantPoolBuilder;
import io.github.dmlloyd.classfile.constantpool.PoolEntry;

import io.github.dmlloyd.classfile.impl.BufWriterImpl;

/**
 * Supports writing portions of a classfile to a growable buffer.   Methods
 * are provided to write various standard entities (e.g., {@code u2}, {@code u4})
 * to the end of the buffer, as well as to create constant pool entries.
 *
 * @since 24
 */
public sealed interface BufWriter
        permits BufWriterImpl {

    /** {@return the constant pool builder associated with this buffer} */
    ConstantPoolBuilder constantPool();

    /**
     * {@return 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.
     *
     * @param other the other constant pool
     */
    boolean canWriteDirect(ConstantPool other);

    /**
     * Ensure that the buffer has at least {@code freeBytes} bytes of unused space
     * @param freeBytes the number of bytes to reserve
     */
    void reserveSpace(int freeBytes);

    /**
     * Write an unsigned byte to the buffer
     *
     * @param x the byte value
     */
    void writeU1(int x);

    /**
     * Write an unsigned short to the buffer
     *
     * @param x the short value
     */
    void writeU2(int x);

    /**
     * Write a signed int to the buffer
     *
     * @param x the int value
     */
    void writeInt(int x);

    /**
     * Write a float value to the buffer
     *
     * @param x the float value
     */
    void writeFloat(float x);

    /**
     * Write a long value to the buffer
     *
     * @param x the long value
     */
    void writeLong(long x);

    /**
     * Write a double value to the buffer
     *
     * @param x the int value
     */
    void writeDouble(double x);

    /**
     * Write the contents of a byte array to the buffer
     *
     * @param arr the byte array
     */
    void writeBytes(byte[] arr);

    /**
     * Write a range of a byte array to the buffer
     *
     * @param arr the byte array
     * @param start the offset within the byte array of the range
     * @param length the length of the range
     * @throws IndexOutOfBoundsException if range is outside of the array bounds
     */
    void writeBytes(byte[] arr, int start, int length);

    /**
     * Patch a previously written integer value.  Depending on the specified
     * size, the entire value, or the low 1 or 2 bytes, may be written.
     *
     * @param offset the offset at which to patch
     * @param size the size of the integer value being written, in bytes
     * @param value the integer value
     * @throws IndexOutOfBoundsException if patched int is outside of bounds
     */
    void patchInt(int offset, int size, int value);

    /**
     * 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.
     *
     * @param intSize the size of the integer value being written, in bytes
     * @param intValue the integer value
     */
    void writeIntBytes(int intSize, long intValue);

    /**
     * Write the index of the specified constant pool entry, as a {@code u2},
     * to the buffer
     *
     * @param entry the constant pool entry
     * @throws IllegalArgumentException if the entry has invalid index
     */
    void writeIndex(PoolEntry entry);

    /**
     * Write the index of the specified constant pool entry, as a {@code u2},
     * to the buffer, or zero if the entry is null
     *
     * @param entry the constant pool entry
     * @throws IllegalArgumentException if the entry has invalid index
     */
    void writeIndexOrZero(PoolEntry entry);

    /**
     * {@return the number of bytes that have been written to the buffer}
     */
    int size();
}