/* Jackson JSON-processor.
 *
 * Copyright (c) 2007- Tatu Saloranta, tatu.saloranta@iki.fi
 */

package com.fasterxml.jackson.core.util;

import java.io.OutputStream;
import java.util.*;

Helper class that is similar to ByteArrayOutputStream in usage, but more geared to Jackson use cases internally. Specific changes include segment storage (no need to have linear backing buffer, can avoid reallocations, copying), as well API not based on OutputStream. In short, a very much specialized builder object. 
 Also implements OutputStream to allow efficient aggregation of output content as a byte array, similar to how ByteArrayOutputStream works, but somewhat more efficiently for many use cases. 

NOTE: maximum size limited to Java Array maximum, 2 gigabytes: this
because usage pattern is to collect content for a `byte[]` and so although
theoretically this builder can aggregate more content it will not be usable
as things are. Behavior may be improved if we solve the access problem.
/**
 * Helper class that is similar to {@link java.io.ByteArrayOutputStream}
 * in usage, but more geared to Jackson use cases internally.
 * Specific changes include segment storage (no need to have linear
 * backing buffer, can avoid reallocations, copying), as well API
 * not based on {@link java.io.OutputStream}. In short, a very much
 * specialized builder object.
 *<p>
 * Also implements {@link OutputStream} to allow
 * efficient aggregation of output content as a byte array, similar
 * to how {@link java.io.ByteArrayOutputStream} works, but somewhat more
 * efficiently for many use cases.
 *<p>
 * NOTE: maximum size limited to Java Array maximum, 2 gigabytes: this
 * because usage pattern is to collect content for a `byte[]` and so although
 * theoretically this builder can aggregate more content it will not be usable
 * as things are. Behavior may be improved if we solve the access problem.
 */
public final class ByteArrayBuilder extends OutputStream
{
    public final static byte[] NO_BYTES = new byte[0];
    
    // Size of the first block we will allocate.
    private final static int INITIAL_BLOCK_SIZE = 500;
    
    // Maximum block size we will use for individual non-aggregated
    // blocks. Let's limit to using 256k chunks.
    private final static int MAX_BLOCK_SIZE = (1 << 18);
    
    final static int DEFAULT_BLOCK_ARRAY_SIZE = 40;

    // Optional buffer recycler instance that we can use for allocating the first block.
    private final BufferRecycler _bufferRecycler;
    private final LinkedList<byte[]> _pastBlocks = new LinkedList<byte[]>();
    
    // Number of bytes within byte arrays in {@link _pastBlocks}.
    private int _pastLen;
    private byte[] _currBlock;
    private int _currBlockPtr;

    public ByteArrayBuilder() { this(null); }
    public ByteArrayBuilder(BufferRecycler br) { this(br, INITIAL_BLOCK_SIZE); }
    public ByteArrayBuilder(int firstBlockSize) { this(null, firstBlockSize); }

    public ByteArrayBuilder(BufferRecycler br, int firstBlockSize) {
        _bufferRecycler = br;
        _currBlock = (br == null) ? new byte[firstBlockSize] : br.allocByteBuffer(BufferRecycler.BYTE_WRITE_CONCAT_BUFFER);
    }

    public void reset() {
        _pastLen = 0;
        _currBlockPtr = 0;

        if (!_pastBlocks.isEmpty()) {
            _pastBlocks.clear();
        }
    }

    
Since:
2.9/**
     * @since 2.9
     */
    public int size() {
        return _pastLen + _currBlockPtr;
    }

    
Clean up method to call to release all buffers this object may be
using. After calling the method, no other accessors can be used (and
attempt to do so may result in an exception)
/**
     * Clean up method to call to release all buffers this object may be
     * using. After calling the method, no other accessors can be used (and
     * attempt to do so may result in an exception)
     */
    public void release() {
        reset();
        if (_bufferRecycler != null && _currBlock != null) {
            _bufferRecycler.releaseByteBuffer(BufferRecycler.BYTE_WRITE_CONCAT_BUFFER, _currBlock);
            _currBlock = null;
        }
    }

    public void append(int i) {
        if (_currBlockPtr >= _currBlock.length) {
            _allocMore();
        }
        _currBlock[_currBlockPtr++] = (byte) i;
    }

    public void appendTwoBytes(int b16) {
        if ((_currBlockPtr + 1) < _currBlock.length) {
            _currBlock[_currBlockPtr++] = (byte) (b16 >> 8);
            _currBlock[_currBlockPtr++] = (byte) b16;
        } else {
            append(b16 >> 8);
            append(b16);
        }
    }

    public void appendThreeBytes(int b24) {
        if ((_currBlockPtr + 2) < _currBlock.length) {
            _currBlock[_currBlockPtr++] = (byte) (b24 >> 16);
            _currBlock[_currBlockPtr++] = (byte) (b24 >> 8);
            _currBlock[_currBlockPtr++] = (byte) b24;
        } else {
            append(b24 >> 16);
            append(b24 >> 8);
            append(b24);
        }
    }

    
Since:
2.9/**
     * @since 2.9
     */
    public void appendFourBytes(int b32) {
        if ((_currBlockPtr + 3) < _currBlock.length) {
            _currBlock[_currBlockPtr++] = (byte) (b32 >> 24);
            _currBlock[_currBlockPtr++] = (byte) (b32 >> 16);
            _currBlock[_currBlockPtr++] = (byte) (b32 >> 8);
            _currBlock[_currBlockPtr++] = (byte) b32;
        } else {
            append(b32 >> 24);
            append(b32 >> 16);
            append(b32 >> 8);
            append(b32);
        }
    }
    
    
Method called when results are finalized and we can get the
full aggregated result buffer to return to the caller
/**
     * Method called when results are finalized and we can get the
     * full aggregated result buffer to return to the caller
     */
    public byte[] toByteArray()
    {
        int totalLen = _pastLen + _currBlockPtr;
        
        if (totalLen == 0) { // quick check: nothing aggregated?
            return NO_BYTES;
        }
        byte[] result = new byte[totalLen];
        int offset = 0;

        for (byte[] block : _pastBlocks) {
            int len = block.length;
            System.arraycopy(block, 0, result, offset, len);
            offset += len;
        }
        System.arraycopy(_currBlock, 0, result, offset, _currBlockPtr);
        offset += _currBlockPtr;
        if (offset != totalLen) { // just a sanity check
            throw new RuntimeException("Internal error: total len assumed to be "+totalLen+", copied "+offset+" bytes");
        }
        // Let's only reset if there's sizable use, otherwise will get reset later on
        if (!_pastBlocks.isEmpty()) {
            reset();
        }
        return result;
    }

    /*
    /**********************************************************
    /* Non-stream API (similar to TextBuffer)
    /**********************************************************
     */

    
Method called when starting "manual" output: will clear out
current state and return the first segment buffer to fill
/**
     * Method called when starting "manual" output: will clear out
     * current state and return the first segment buffer to fill
     */
    public byte[] resetAndGetFirstSegment() {
        reset();
        return _currBlock;
    }

    
Method called when the current segment buffer is full; will
append to current contents, allocate a new segment buffer
and return it
/**
     * Method called when the current segment buffer is full; will
     * append to current contents, allocate a new segment buffer
     * and return it
     */
    public byte[] finishCurrentSegment() {
        _allocMore();
        return _currBlock;
    }

    
Method that will complete "manual" output process, coalesce
content (if necessary) and return results as a contiguous buffer.
Params:
lastBlockLength – Amount of content in the current segment
buffer.
Returns:
Coalesced contents/**
     * Method that will complete "manual" output process, coalesce
     * content (if necessary) and return results as a contiguous buffer.
     * 
     * @param lastBlockLength Amount of content in the current segment
     * buffer.
     * 
     * @return Coalesced contents
     */
    public byte[] completeAndCoalesce(int lastBlockLength) {
        _currBlockPtr = lastBlockLength;
        return toByteArray();
    }

    public byte[] getCurrentSegment() { return _currBlock; }
    public void setCurrentSegmentLength(int len) { _currBlockPtr = len; }
    public int getCurrentSegmentLength() { return _currBlockPtr; }

    /*
    /**********************************************************
    /* OutputStream implementation
    /**********************************************************
     */

    @Override
    public void write(byte[] b) {
        write(b, 0, b.length);
    }

    @Override
    public void write(byte[] b, int off, int len)
    {
        while (true) {
            int max = _currBlock.length - _currBlockPtr;
            int toCopy = Math.min(max, len);
            if (toCopy > 0) {
                System.arraycopy(b, off, _currBlock, _currBlockPtr, toCopy);
                off += toCopy;
                _currBlockPtr += toCopy;
                len -= toCopy;
            }
            if (len <= 0) break;
            _allocMore();
        }
    }

    @Override
    public void write(int b) {
        append(b);
    }

    @Override public void close() { /* NOP */ }
    @Override public void flush() { /* NOP */ }

    /*
    /**********************************************************
    /* Internal methods
    /**********************************************************
     */

    private void _allocMore()
    {
        final int newPastLen = _pastLen + _currBlock.length;

        // 13-Feb-2016, tatu: As per [core#351] let's try to catch problem earlier;
        //     for now we are strongly limited by 2GB limit of Java arrays        
        if (newPastLen < 0) {
            throw new IllegalStateException("Maximum Java array size (2GB) exceeded by `ByteArrayBuilder`");
        }

        _pastLen = newPastLen;

        /* Let's allocate block that's half the total size, except
         * never smaller than twice the initial block size.
         * The idea is just to grow with reasonable rate, to optimize
         * between minimal number of chunks and minimal amount of
         * wasted space.
         */
        int newSize = Math.max((_pastLen >> 1), (INITIAL_BLOCK_SIZE + INITIAL_BLOCK_SIZE));
        // plus not to exceed max we define...
        if (newSize > MAX_BLOCK_SIZE) {
            newSize = MAX_BLOCK_SIZE;
        }
        _pastBlocks.add(_currBlock);
        _currBlock = new byte[newSize];
        _currBlockPtr = 0;
    }
}