/*

 * Copyright (c) 2015, 2017, 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 java.lang;

/**

 * Helper for string concatenation. These methods are mostly looked up with private lookups

 * from {@link java.lang.invoke.StringConcatFactory}, and used in {@link java.lang.invoke.MethodHandle}

 * combinators there.

 */

final class StringConcatHelper {

    private StringConcatHelper() {

        // no instantiation

    }

    /**

     * Check for overflow, throw the exception on overflow.

     * @param len String length

     * @return length

     */

    private static int checkOverflow(int len) {

        if (len < 0) {

            throw new OutOfMemoryError("Overflow: String length out of range");

        }

        return len;

    }

    /**

     * Mix value length into current length

     * @param current current length

     * @param value   value to mix in

     * @return new length

     */

    static int mixLen(int current, boolean value) {

        return checkOverflow(current + (value ? 4 : 5));

    }

    /**

     * Mix value length into current length

     * @param current current length

     * @param value   value to mix in

     * @return new length

     */

    static int mixLen(int current, byte value) {

        return mixLen(current, (int)value);

    }

    /**

     * Mix value length into current length

     * @param current current length

     * @param value   value to mix in

     * @return new length

     */

    static int mixLen(int current, char value) {

        return checkOverflow(current + 1);

    }

    /**

     * Mix value length into current length

     * @param current current length

     * @param value   value to mix in

     * @return new length

     */

    static int mixLen(int current, short value) {

        return mixLen(current, (int)value);

    }

    /**

     * Mix value length into current length

     * @param current current length

     * @param value   value to mix in

     * @return new length

     */

    static int mixLen(int current, int value) {

        return checkOverflow(current + Integer.stringSize(value));

    }

    /**

     * Mix value length into current length

     * @param current current length

     * @param value   value to mix in

     * @return new length

     */

    static int mixLen(int current, long value) {

        return checkOverflow(current + Long.stringSize(value));

    }

    /**

     * Mix value length into current length

     * @param current current length

     * @param value   value to mix in

     * @return new length

     */

    static int mixLen(int current, String value) {

        return checkOverflow(current + value.length());

    }

    /**

     * Mix coder into current coder

     * @param current current coder

     * @param value   value to mix in

     * @return new coder

     */

    static byte mixCoder(byte current, char value) {

        return (byte)(current | (StringLatin1.canEncode(value) ? 0 : 1));

    }

    /**

     * Mix coder into current coder

     * @param current current coder

     * @param value   value to mix in

     * @return new coder

     */

    static byte mixCoder(byte current, String value) {

        return (byte)(current | value.coder());

    }

    /**

     * Mix coder into current coder

     * @param current current coder

     * @param value   value to mix in

     * @return new coder

     */

    static byte mixCoder(byte current, boolean value) {

        // Booleans are represented with Latin1

        return current;

    }

    /**

     * Mix coder into current coder

     * @param current current coder

     * @param value   value to mix in

     * @return new coder

     */

    static byte mixCoder(byte current, byte value) {

        // Bytes are represented with Latin1

        return current;

    }

    /**

     * Mix coder into current coder

     * @param current current coder

     * @param value   value to mix in

     * @return new coder

     */

    static byte mixCoder(byte current, short value) {

        // Shorts are represented with Latin1

        return current;

    }

    /**

     * Mix coder into current coder

     * @param current current coder

     * @param value   value to mix in

     * @return new coder

     */

    static byte mixCoder(byte current, int value) {

        // Ints are represented with Latin1

        return current;

    }

    /**

     * Mix coder into current coder

     * @param current current coder

     * @param value   value to mix in

     * @return new coder

     */

    static byte mixCoder(byte current, long value) {

        // Longs are represented with Latin1

        return current;

    }

    /**

     * Prepends the stringly representation of boolean value into buffer,

     * given the coder and final index. Index is measured in chars, not in bytes!

     *

     * @param index final char index in the buffer

     * @param buf   buffer to append to

     * @param coder coder to add with

     * @param value boolean value to encode

     * @return new index

     */

    static int prepend(int index, byte[] buf, byte coder, boolean value) {

        if (coder == String.LATIN1) {

            if (value) {

                buf[--index] = 'e';

                buf[--index] = 'u';

                buf[--index] = 'r';

                buf[--index] = 't';

            } else {

                buf[--index] = 'e';

                buf[--index] = 's';

                buf[--index] = 'l';

                buf[--index] = 'a';

                buf[--index] = 'f';

            }

        } else {

            if (value) {

                StringUTF16.putChar(buf, --index, 'e');

                StringUTF16.putChar(buf, --index, 'u');

                StringUTF16.putChar(buf, --index, 'r');

                StringUTF16.putChar(buf, --index, 't');

            } else {

                StringUTF16.putChar(buf, --index, 'e');

                StringUTF16.putChar(buf, --index, 's');

                StringUTF16.putChar(buf, --index, 'l');

                StringUTF16.putChar(buf, --index, 'a');

                StringUTF16.putChar(buf, --index, 'f');

            }

        }

        return index;

    }

    /**

     * Prepends the stringly representation of byte value into buffer,

     * given the coder and final index. Index is measured in chars, not in bytes!

     *

     * @param index final char index in the buffer

     * @param buf   buffer to append to

     * @param coder coder to add with

     * @param value byte value to encode

     * @return new index

     */

    static int prepend(int index, byte[] buf, byte coder, byte value) {

        return prepend(index, buf, coder, (int)value);

    }

    /**

     * Prepends the stringly representation of char value into buffer,

     * given the coder and final index. Index is measured in chars, not in bytes!

     *

     * @param index final char index in the buffer

     * @param buf   buffer to append to

     * @param coder coder to add with

     * @param value char value to encode

     * @return new index

     */

    static int prepend(int index, byte[] buf, byte coder, char value) {

        if (coder == String.LATIN1) {

            buf[--index] = (byte) (value & 0xFF);

        } else {

            StringUTF16.putChar(buf, --index, value);

        }

        return index;

    }

    /**

     * Prepends the stringly representation of short value into buffer,

     * given the coder and final index. Index is measured in chars, not in bytes!

     *

     * @param index final char index in the buffer

     * @param buf   buffer to append to

     * @param coder coder to add with

     * @param value short value to encode

     * @return new index

     */

    static int prepend(int index, byte[] buf, byte coder, short value) {

        return prepend(index, buf, coder, (int)value);

    }

    /**

     * Prepends the stringly representation of integer value into buffer,

     * given the coder and final index. Index is measured in chars, not in bytes!

     *

     * @param index final char index in the buffer

     * @param buf   buffer to append to

     * @param coder coder to add with

     * @param value integer value to encode

     * @return new index

     */

    static int prepend(int index, byte[] buf, byte coder, int value) {

        if (coder == String.LATIN1) {

            return Integer.getChars(value, index, buf);

        } else {

            return StringUTF16.getChars(value, index, buf);

        }

    }

    /**

     * Prepends the stringly representation of long value into buffer,

     * given the coder and final index. Index is measured in chars, not in bytes!

     *

     * @param index final char index in the buffer

     * @param buf   buffer to append to

     * @param coder coder to add with

     * @param value long value to encode

     * @return new index

     */

    static int prepend(int index, byte[] buf, byte coder, long value) {

        if (coder == String.LATIN1) {

            return Long.getChars(value, index, buf);

        } else {

            return StringUTF16.getChars(value, index, buf);

        }

    }

    /**

     * Prepends the stringly representation of String value into buffer,

     * given the coder and final index. Index is measured in chars, not in bytes!

     *

     * @param index final char index in the buffer

     * @param buf   buffer to append to

     * @param coder coder to add with

     * @param value String value to encode

     * @return new index

     */

    static int prepend(int index, byte[] buf, byte coder, String value) {

        index -= value.length();

        value.getBytes(buf, index, coder);

        return index;

    }

    /**

     * Instantiates the String with given buffer and coder

     * @param buf     buffer to use

     * @param index   remaining index

     * @param coder   coder to use

     * @return String resulting string

     */

    static String newString(byte[] buf, int index, byte coder) {

        // Use the private, non-copying constructor (unsafe!)

        if (index != 0) {

            throw new InternalError("Storage is not completely initialized, " + index + " bytes left");

        }

        return new String(buf, coder);

    }

    /**

     * Provides the initial coder for the String.

     * @return initial coder

     */

    static byte initialCoder() {

        return String.COMPACT_STRINGS ? String.LATIN1 : String.UTF16;

    }

}