/*

 * 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 exception on overflow.

     * @param lengthCoder String length and coder

     * @return lengthCoder

     */

    private static long checkOverflow(long lengthCoder) {

        if ((int)lengthCoder >= 0) {

            return lengthCoder;

        }

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

    }

    /**

     * Mix value length and coder into current length and coder.

     * @param current current length

     * @param value   value to mix in

     * @return new length and coder

     */

    static long mix(long current, boolean value) {

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

    }

    /**

     * Mix value length and coder into current length and coder.

     * @param current current length

     * @param value   value to mix in

     * @return new length and coder

     */

    static long mix(long current, byte value) {

        return mix(current, (int)value);

    }

    /**

     * Mix value length and coder into current length and coder.

     * @param current current length

     * @param value   value to mix in

     * @return new length and coder

     */

    static long mix(long current, char value) {

        return checkOverflow(current + 1) | (StringLatin1.canEncode(value) ? 0 : UTF16);

    }

    /**

     * Mix value length and coder into current length and coder.

     * @param current current length

     * @param value   value to mix in

     * @return new length and coder

     */

    static long mix(long current, short value) {

        return mix(current, (int)value);

    }

    /**

     * Mix value length and coder into current length and coder.

     * @param current current length

     * @param value   value to mix in

     * @return new length and coder

     */

    static long mix(long current, int value) {

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

    }

    /**

     * Mix value length and coder into current length and coder.

     * @param current current length

     * @param value   value to mix in

     * @return new length and coder

     */

    static long mix(long current, long value) {

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

    }

    /**

     * Mix value length and coder into current length and coder.

     * @param current current length

     * @param value   value to mix in

     * @return new length and coder

     */

    static long mix(long current, String value) {

        current += value.length();

        if (value.coder() == String.UTF16) {

            current |= UTF16;

        }

        return checkOverflow(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 indexCoder final char index in the buffer, along with coder packed

     *                   into higher bits.

     * @param buf        buffer to append to

     * @param value      boolean value to encode

     * @return           updated index (coder value retained)

     */

    static long prepend(long indexCoder, byte[] buf, boolean value) {

        int index = (int)indexCoder;

        if (indexCoder < UTF16) {

            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';

            }

            return index;

        } 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 | UTF16;

        }

    }

    /**

     * Prepends the stringly representation of byte value into buffer,

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

     *

     * @param indexCoder final char index in the buffer, along with coder packed

     *                   into higher bits.

     * @param buf        buffer to append to

     * @param value      byte value to encode

     * @return           updated index (coder value retained)

     */

    static long prepend(long indexCoder, byte[] buf, byte value) {

        return prepend(indexCoder, buf, (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 indexCoder final char index in the buffer, along with coder packed

     *                   into higher bits.

     * @param buf        buffer to append to

     * @param value      char value to encode

     * @return           updated index (coder value retained)

     */

    static long prepend(long indexCoder, byte[] buf, char value) {

        if (indexCoder < UTF16) {

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

        } else {

            StringUTF16.putChar(buf, (int)(--indexCoder), value);

        }

        return indexCoder;

    }

    /**

     * Prepends the stringly representation of short value into buffer,

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

     *

     * @param indexCoder final char index in the buffer, along with coder packed

     *                   into higher bits.

     * @param buf        buffer to append to

     * @param value      short value to encode

     * @return           updated index (coder value retained)

     */

    static long prepend(long indexCoder, byte[] buf, short value) {

        return prepend(indexCoder, buf, (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 indexCoder final char index in the buffer, along with coder packed

     *                   into higher bits.

     * @param buf        buffer to append to

     * @param value      integer value to encode

     * @return           updated index (coder value retained)

     */

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

        if (indexCoder < UTF16) {

            return Integer.getChars(value, (int)indexCoder, buf);

        } else {

            return StringUTF16.getChars(value, (int)indexCoder, buf) | UTF16;

        }

    }

    /**

     * Prepends the stringly representation of long value into buffer,

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

     *

     * @param indexCoder final char index in the buffer, along with coder packed

     *                   into higher bits.

     * @param buf        buffer to append to

     * @param value      long value to encode

     * @return           updated index (coder value retained)

     */

    static long prepend(long indexCoder, byte[] buf, long value) {

        if (indexCoder < UTF16) {

            return Long.getChars(value, (int)indexCoder, buf);

        } else {

            return StringUTF16.getChars(value, (int)indexCoder, buf) | UTF16;

        }

    }

    /**

     * Prepends the stringly representation of String value into buffer,

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

     *

     * @param indexCoder final char index in the buffer, along with coder packed

     *                   into higher bits.

     * @param buf        buffer to append to

     * @param value      String value to encode

     * @return           updated index (coder value retained)

     */

    static long prepend(long indexCoder, byte[] buf, String value) {

        indexCoder -= value.length();

        if (indexCoder < UTF16) {

            value.getBytes(buf, (int)indexCoder, String.LATIN1);

        } else {

            value.getBytes(buf, (int)indexCoder, String.UTF16);

        }

        return indexCoder;

    }

    /**

     * Instantiates the String with given buffer and coder

     * @param buf           buffer to use

     * @param indexCoder    remaining index (should be zero) and coder

     * @return String       resulting string

     */

    static String newString(byte[] buf, long indexCoder) {

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

        if (indexCoder == LATIN1) {

            return new String(buf, String.LATIN1);

        } else if (indexCoder == UTF16) {

            return new String(buf, String.UTF16);

        } else {

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

        }

    }

    private static final long LATIN1 = (long)String.LATIN1 << 32;

    private static final long UTF16 = (long)String.UTF16 << 32;

    /**

     * Provides the initial coder for the String.

     * @return initial coder, adjusted into the upper half

     */

    static long initialCoder() {

        return String.COMPACT_STRINGS ? LATIN1 : UTF16;

    }

}