/*
 * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

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;
 }

}