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/*
 * Copyright (c) 1997, 2023 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.eclipse.angus.mail.iap;

import org.eclipse.angus.mail.util.ASCIIUtility;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Inputstream that is used to read a Response.
 *
 * @author Arun Krishnan
 * @author Bill Shannon
 */

public class ResponseInputStream {

    private static final int minIncrement = 256;
    private static final int maxIncrement = 256 * 1024;
    private static final int incrementSlop = 16;

    // where we read from
    private BufferedInputStream bin;

    /**
     * Constructor.
     *
     * @param    in    the InputStream to wrap
     */
    public ResponseInputStream(InputStream in) {
        bin = new BufferedInputStream(in, 2 * 1024);
    }

    /**
     * Read a Response from the InputStream.
     *
     * @return ByteArray that contains the Response
     * @exception IOException    for I/O errors
     */
    public ByteArray readResponse() throws IOException {
        return readResponse(null);
    }

    /**
     * Read a Response from the InputStream.
     *
     * @param    ba    the ByteArray in which to store the response, or null
     * @return ByteArray that contains the Response
     * @exception IOException    for I/O errors
     */
    public ByteArray readResponse(ByteArray ba) throws IOException {
        if (ba == null)
            ba = new ByteArray(new byte[128], 0, 128);

        byte[] buffer = ba.getBytes();
        int idx = 0;
        for (; ; ) {    // read until CRLF with no preceeding literal
            // XXX - b needs to be an int, to handle bytes with value 0xff
            int b = 0;
            boolean gotCRLF = false;

            // Read a CRLF terminated line from the InputStream
            while (!gotCRLF &&
                    ((b = bin.read()) != -1)) {
                if (b == '\n') {
                    if ((idx > 0) && buffer[idx - 1] == '\r')
                        gotCRLF = true;
                }
                if (idx >= buffer.length) {
                    int incr = buffer.length;
                    if (incr > maxIncrement)
                        incr = maxIncrement;
                    ba.grow(incr);
                    buffer = ba.getBytes();
                }
                buffer[idx++] = (byte) b;
            }

            if (b == -1)
                throw new IOException("Connection dropped by server?");

            // Now lets check for literals : {}CRLF
            // Note: index needs to >= 5 for the above sequence to occur
            if (idx < 5 || buffer[idx - 3] != '}')
                break;

            int i;
            // look for left curly
            for (i = idx - 4; i >= 0; i--)
                if (buffer[i] == '{')
                    break;

            if (i < 0) // Nope, not a literal ?
                break;

            int count = 0;
            // OK, handle the literal ..
            try {
                count = ASCIIUtility.parseInt(buffer, i + 1, idx - 3);
            } catch (NumberFormatException e) {
                break;
            }

            // Now read 'count' bytes. (Note: count could be 0)
            if (count > 0) {
                int avail = buffer.length - idx; // available space in buffer
                if (count + incrementSlop > avail) {
                    // need count-avail more bytes
                    ba.grow(Math.max(minIncrement, count + incrementSlop - avail));
                    buffer = ba.getBytes();
                }

                /*
                 * read() might not return all the bytes in one shot,
                 * so call repeatedly till we are done
                 */
                int actual;
                while (count > 0) {
                    actual = bin.read(buffer, idx, count);
                    if (actual == -1)
                        throw new IOException("Connection dropped by server?");
                    count -= actual;
                    idx += actual;
                }
            }
            // back to top of loop to read until CRLF
        }
        ba.setCount(idx);
        return ba;
    }

    /**
     * How much buffered data do we have?
     *
     * @return number of bytes available
     * @exception IOException    if the stream has been closed
     * @since JavaMail 1.5.4
     */
    public int available() throws IOException {
        return bin.available();
    }
}