/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.connector;

import java.io.IOException;
import java.io.Reader;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;

import jakarta.servlet.ReadListener;

import org.apache.catalina.security.SecurityUtil;
import org.apache.coyote.ActionCode;
import org.apache.coyote.ContainerThreadMarker;
import org.apache.coyote.Request;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.buf.B2CConverter;
import org.apache.tomcat.util.buf.ByteChunk;
import org.apache.tomcat.util.collections.SynchronizedStack;
import org.apache.tomcat.util.net.ApplicationBufferHandler;
import org.apache.tomcat.util.res.StringManager;

The buffer used by Tomcat request. This is a derivative of the Tomcat 3.3
OutputBuffer, adapted to handle input instead of output. This allows
complete recycling of the facade objects (the ServletInputStream and the
BufferedReader).
Author:
Remy Maucherat/**
 * The buffer used by Tomcat request. This is a derivative of the Tomcat 3.3
 * OutputBuffer, adapted to handle input instead of output. This allows
 * complete recycling of the facade objects (the ServletInputStream and the
 * BufferedReader).
 *
 * @author Remy Maucherat
 */
public class InputBuffer extends Reader
    implements ByteChunk.ByteInputChannel, ApplicationBufferHandler {

    
The string manager for this package.
/**
     * The string manager for this package.
     */
    protected static final StringManager sm = StringManager.getManager(InputBuffer.class);

    private static final Log log = LogFactory.getLog(InputBuffer.class);

    public static final int DEFAULT_BUFFER_SIZE = 8 * 1024;

    // The buffer can be used for byte[] and char[] reading
    // ( this is needed to support ServletInputStream and BufferedReader )
    public final int INITIAL_STATE = 0;
    public final int CHAR_STATE = 1;
    public final int BYTE_STATE = 2;


    
Encoder cache.
/**
     * Encoder cache.
     */
    private static final Map<Charset, SynchronizedStack<B2CConverter>> encoders = new ConcurrentHashMap<>();

    // ----------------------------------------------------- Instance Variables

    
The byte buffer.
/**
     * The byte buffer.
     */
    private ByteBuffer bb;


    
The char buffer.
/**
     * The char buffer.
     */
    private CharBuffer cb;


    
State of the output buffer.
/**
     * State of the output buffer.
     */
    private int state = 0;


    
Flag which indicates if the input buffer is closed.
/**
     * Flag which indicates if the input buffer is closed.
     */
    private boolean closed = false;


    
Current byte to char converter.
/**
     * Current byte to char converter.
     */
    protected B2CConverter conv;


    
Associated Coyote request.
/**
     * Associated Coyote request.
     */
    private Request coyoteRequest;


    
Buffer position.
/**
     * Buffer position.
     */
    private int markPos = -1;


    
Char buffer limit.
/**
     * Char buffer limit.
     */
    private int readLimit;


    
Buffer size.
/**
     * Buffer size.
     */
    private final int size;


    // ----------------------------------------------------------- Constructors


    
Default constructor. Allocate the buffer with the default buffer size.
/**
     * Default constructor. Allocate the buffer with the default buffer size.
     */
    public InputBuffer() {

        this(DEFAULT_BUFFER_SIZE);

    }


    
Alternate constructor which allows specifying the initial buffer size.
Params:
size – Buffer size to use/**
     * Alternate constructor which allows specifying the initial buffer size.
     *
     * @param size Buffer size to use
     */
    public InputBuffer(int size) {

        this.size = size;
        bb = ByteBuffer.allocate(size);
        clear(bb);
        cb = CharBuffer.allocate(size);
        clear(cb);
        readLimit = size;

    }


    // ------------------------------------------------------------- Properties


    
Associated Coyote request.
Params:
coyoteRequest – Associated Coyote request/**
     * Associated Coyote request.
     *
     * @param coyoteRequest Associated Coyote request
     */
    public void setRequest(Request coyoteRequest) {
        this.coyoteRequest = coyoteRequest;
    }


    // --------------------------------------------------------- Public Methods

    
Recycle the output buffer.
/**
     * Recycle the output buffer.
     */
    public void recycle() {

        state = INITIAL_STATE;

        // If usage of mark made the buffer too big, reallocate it
        if (cb.capacity() > size) {
            cb = CharBuffer.allocate(size);
            clear(cb);
        } else {
            clear(cb);
        }
        readLimit = size;
        markPos = -1;
        clear(bb);
        closed = false;

        if (conv != null) {
            conv.recycle();
            encoders.get(conv.getCharset()).push(conv);
            conv = null;
        }
    }


    
Close the input buffer.
Throws:
IOException – An underlying IOException occurred/**
     * Close the input buffer.
     *
     * @throws IOException An underlying IOException occurred
     */
    @Override
    public void close() throws IOException {
        closed = true;
    }


    public int available() {
        int available = availableInThisBuffer();
        if (available == 0) {
            coyoteRequest.action(ActionCode.AVAILABLE,
                    Boolean.valueOf(coyoteRequest.getReadListener() != null));
            available = (coyoteRequest.getAvailable() > 0) ? 1 : 0;
        }
        return available;
    }


    private int availableInThisBuffer() {
        int available = 0;
        if (state == BYTE_STATE) {
            available = bb.remaining();
        } else if (state == CHAR_STATE) {
            available = cb.remaining();
        }
        return available;
    }


    public void setReadListener(ReadListener listener) {
        coyoteRequest.setReadListener(listener);

        // The container is responsible for the first call to
        // listener.onDataAvailable(). If isReady() returns true, the container
        // needs to call listener.onDataAvailable() from a new thread. If
        // isReady() returns false, the socket will be registered for read and
        // the container will call listener.onDataAvailable() once data arrives.
        // Must call isFinished() first as a call to isReady() if the request
        // has been finished will register the socket for read interest and that
        // is not required.
        if (!coyoteRequest.isFinished() && isReady()) {
            coyoteRequest.action(ActionCode.DISPATCH_READ, null);
            if (!ContainerThreadMarker.isContainerThread()) {
                // Not on a container thread so need to execute the dispatch
                coyoteRequest.action(ActionCode.DISPATCH_EXECUTE, null);
            }
        }
    }


    public boolean isFinished() {
        int available = 0;
        if (state == BYTE_STATE) {
            available = bb.remaining();
        } else if (state == CHAR_STATE) {
            available = cb.remaining();
        }
        if (available > 0) {
            return false;
        } else {
            return coyoteRequest.isFinished();
        }
    }


    public boolean isReady() {
        if (coyoteRequest.getReadListener() == null) {
            if (log.isDebugEnabled()) {
                log.debug(sm.getString("inputBuffer.requiresNonBlocking"));
            }
            return false;
        }
        if (isFinished()) {
            // If this is a non-container thread, need to trigger a read
            // which will eventually lead to a call to onAllDataRead() via a
            // container thread.
            if (!ContainerThreadMarker.isContainerThread()) {
                coyoteRequest.action(ActionCode.DISPATCH_READ, null);
                coyoteRequest.action(ActionCode.DISPATCH_EXECUTE, null);
            }
            return false;
        }
        // Checking for available data at the network level and registering for
        // read can be done sequentially for HTTP/1.x and AJP as there is only
        // ever a single thread processing the socket at any one time. However,
        // for HTTP/2 there is one thread processing the connection and separate
        // threads for each stream. For HTTP/2 the two operations have to be
        // performed atomically else it is possible for the connection thread to
        // read more data in to the buffer after the stream thread checks for
        // available network data but before it registers for read.
        if (availableInThisBuffer() > 0) {
            return true;
        }

        AtomicBoolean result = new AtomicBoolean();
        coyoteRequest.action(ActionCode.NB_READ_INTEREST, result);
        return result.get();
    }


    boolean isBlocking() {
        return coyoteRequest.getReadListener() == null;
    }


    // ------------------------------------------------- Bytes Handling Methods

    
Reads new bytes in the byte chunk.
Throws:
IOException – An underlying IOException occurred/**
     * Reads new bytes in the byte chunk.
     *
     * @throws IOException An underlying IOException occurred
     */
    @Override
    public int realReadBytes() throws IOException {
        if (closed) {
            return -1;
        }
        if (coyoteRequest == null) {
            return -1;
        }

        if (state == INITIAL_STATE) {
            state = BYTE_STATE;
        }

        try {
            return coyoteRequest.doRead(this);
        } catch (IOException ioe) {
            // An IOException on a read is almost always due to
            // the remote client aborting the request.
            throw new ClientAbortException(ioe);
        }
    }


    public int readByte() throws IOException {
        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (checkByteBufferEof()) {
            return -1;
        }
        return bb.get() & 0xFF;
    }


    public int read(byte[] b, int off, int len) throws IOException {
        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (checkByteBufferEof()) {
            return -1;
        }
        int n = Math.min(len, bb.remaining());
        bb.get(b, off, n);
        return n;
    }


    
Transfers bytes from the buffer to the specified ByteBuffer. After the
operation the position of the ByteBuffer will be returned to the one
before the operation, the limit will be the position incremented by
the number of the transferred bytes.
Params:
to – the ByteBuffer into which bytes are to be written.
Throws:
IOException – if an input or output exception has occurred
Returns:
an integer specifying the actual number of bytes read, or -1 if
        the end of the stream is reached/**
     * Transfers bytes from the buffer to the specified ByteBuffer. After the
     * operation the position of the ByteBuffer will be returned to the one
     * before the operation, the limit will be the position incremented by
     * the number of the transferred bytes.
     *
     * @param to the ByteBuffer into which bytes are to be written.
     * @return an integer specifying the actual number of bytes read, or -1 if
     *         the end of the stream is reached
     * @throws IOException if an input or output exception has occurred
     */
    public int read(ByteBuffer to) throws IOException {
        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (checkByteBufferEof()) {
            return -1;
        }
        int n = Math.min(to.remaining(), bb.remaining());
        int orgLimit = bb.limit();
        bb.limit(bb.position() + n);
        to.put(bb);
        bb.limit(orgLimit);
        to.limit(to.position()).position(to.position() - n);
        return n;
    }


    // ------------------------------------------------- Chars Handling Methods

    public int realReadChars() throws IOException {
        checkConverter();

        boolean eof = false;

        if (bb.remaining() <= 0) {
            int nRead = realReadBytes();
            if (nRead < 0) {
                eof = true;
            }
        }

        if (markPos == -1) {
            clear(cb);
        } else {
            // Make sure there's enough space in the worst case
            makeSpace(bb.remaining());
            if ((cb.capacity() - cb.limit()) == 0 && bb.remaining() != 0) {
                // We went over the limit
                clear(cb);
                markPos = -1;
            }
        }

        state = CHAR_STATE;
        conv.convert(bb, cb, this, eof);

        if (cb.remaining() == 0 && eof) {
            return -1;
        } else {
            return cb.remaining();
        }
    }


    @Override
    public int read() throws IOException {

        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (checkCharBufferEof()) {
            return -1;
        }
        return cb.get();
    }


    @Override
    public int read(char[] cbuf) throws IOException {

        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        return read(cbuf, 0, cbuf.length);
    }


    @Override
    public int read(char[] cbuf, int off, int len) throws IOException {

        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (checkCharBufferEof()) {
            return -1;
        }
        int n = Math.min(len, cb.remaining());
        cb.get(cbuf, off, n);
        return n;
    }


    @Override
    public long skip(long n) throws IOException {
        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (n < 0) {
            throw new IllegalArgumentException();
        }

        long nRead = 0;
        while (nRead < n) {
            if (cb.remaining() >= n) {
                cb.position(cb.position() + (int) n);
                nRead = n;
            } else {
                nRead += cb.remaining();
                cb.position(cb.limit());
                int nb = realReadChars();
                if (nb < 0) {
                    break;
                }
            }
        }
        return nRead;
    }


    @Override
    public boolean ready() throws IOException {
        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }
        if (state == INITIAL_STATE) {
            state = CHAR_STATE;
        }
        return (available() > 0);
    }


    @Override
    public boolean markSupported() {
        return true;
    }


    @Override
    public void mark(int readAheadLimit) throws IOException {

        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (cb.remaining() <= 0) {
            clear(cb);
        } else {
            if ((cb.capacity() > (2 * size)) && (cb.remaining()) < (cb.position())) {
                cb.compact();
                cb.flip();
            }
        }
        readLimit = cb.position() + readAheadLimit + size;
        markPos = cb.position();
    }


    @Override
    public void reset() throws IOException {

        if (closed) {
            throw new IOException(sm.getString("inputBuffer.streamClosed"));
        }

        if (state == CHAR_STATE) {
            if (markPos < 0) {
                clear(cb);
                markPos = -1;
                throw new IOException();
            } else {
                cb.position(markPos);
            }
        } else {
            clear(bb);
        }
    }


    public void checkConverter() throws IOException {
        if (conv != null) {
            return;
        }

        Charset charset = null;
        if (coyoteRequest != null) {
            charset = coyoteRequest.getCharset();
        }

        if (charset == null) {
            charset = org.apache.coyote.Constants.DEFAULT_BODY_CHARSET;
        }

        SynchronizedStack<B2CConverter> stack = encoders.get(charset);
        if (stack == null) {
            stack = new SynchronizedStack<>();
            encoders.putIfAbsent(charset, stack);
            stack = encoders.get(charset);
        }
        conv = stack.pop();

        if (conv == null) {
            conv = createConverter(charset);
        }
    }


    private static B2CConverter createConverter(Charset charset) throws IOException {
        if (SecurityUtil.isPackageProtectionEnabled()) {
            try {
                return AccessController.doPrivileged(new PrivilegedCreateConverter(charset));
            } catch (PrivilegedActionException ex) {
                Exception e = ex.getException();
                if (e instanceof IOException) {
                    throw (IOException) e;
                } else {
                    throw new IOException(e);
                }
            }
        } else {
            return new B2CConverter(charset);
        }

    }


    @Override
    public void setByteBuffer(ByteBuffer buffer) {
        bb = buffer;
    }


    @Override
    public ByteBuffer getByteBuffer() {
        return bb;
    }


    @Override
    public void expand(int size) {
        // no-op
    }


    private boolean checkByteBufferEof() throws IOException {
        if (bb.remaining() == 0) {
            int n = realReadBytes();
            if (n < 0) {
                return true;
            }
        }
        return false;
    }

    private boolean checkCharBufferEof() throws IOException {
        if (cb.remaining() == 0) {
            int n = realReadChars();
            if (n < 0) {
                return true;
            }
        }
        return false;
    }

    private void clear(Buffer buffer) {
        buffer.rewind().limit(0);
    }

    private void makeSpace(int count) {
        int desiredSize = cb.limit() + count;
        if(desiredSize > readLimit) {
            desiredSize = readLimit;
        }

        if(desiredSize <= cb.capacity()) {
            return;
        }

        int newSize = 2 * cb.capacity();
        if(desiredSize >= newSize) {
            newSize= 2 * cb.capacity() + count;
        }

        if (newSize > readLimit) {
            newSize = readLimit;
        }

        CharBuffer tmp = CharBuffer.allocate(newSize);
        int oldPosition = cb.position();
        cb.position(0);
        tmp.put(cb);
        tmp.flip();
        tmp.position(oldPosition);
        cb = tmp;
        tmp = null;
    }


    private static class PrivilegedCreateConverter
            implements PrivilegedExceptionAction<B2CConverter> {

        private final Charset charset;

        public PrivilegedCreateConverter(Charset charset) {
            this.charset = charset;
        }

        @Override
        public B2CConverter run() throws IOException {
            return new B2CConverter(charset);
        }
    }
}