/*
 * 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;
 }

}