/*

 * 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;

import sun.misc.FloatingDecimal;

import java.util.Arrays;

/**

 * A mutable sequence of characters.

 * <p>

 * Implements a modifiable string. At any point in time it contains some

 * particular sequence of characters, but the length and content of the

 * sequence can be changed through certain method calls.

 *

 * <p>Unless otherwise noted, passing a {@code null} argument to a constructor

 * or method in this class will cause a {@link NullPointerException} to be

 * thrown.

 *

 * @author      Michael McCloskey

 * @author      Martin Buchholz

 * @author      Ulf Zibis

 * @since       1.5

 */

abstract class AbstractStringBuilder implements Appendable, CharSequence {

    /**

     * The value is used for character storage.

     */

    char[] value;

    /**

     * The count is the number of characters used.

     */

    int count;

    /**

     * This no-arg constructor is necessary for serialization of subclasses.

     */

    AbstractStringBuilder() {

    }

    /**

     * Creates an AbstractStringBuilder of the specified capacity.

     */

    AbstractStringBuilder(int capacity) {

        value = new char[capacity];

    }

    /**

     * Returns the length (character count).

     *

     * @return  the length of the sequence of characters currently

     *          represented by this object

     */

    @Override

    public int length() {

        return count;

    }

    /**

     * Returns the current capacity. The capacity is the amount of storage

     * available for newly inserted characters, beyond which an allocation

     * will occur.

     *

     * @return  the current capacity

     */

    public int capacity() {

        return value.length;

    }

    /**

     * Ensures that the capacity is at least equal to the specified minimum.

     * If the current capacity is less than the argument, then a new internal

     * array is allocated with greater capacity. The new capacity is the

     * larger of:

     * <ul>

     * <li>The {@code minimumCapacity} argument.

     * <li>Twice the old capacity, plus {@code 2}.

     * </ul>

     * If the {@code minimumCapacity} argument is nonpositive, this

     * method takes no action and simply returns.

     * Note that subsequent operations on this object can reduce the

     * actual capacity below that requested here.

     *

     * @param   minimumCapacity   the minimum desired capacity.

     */

    public void ensureCapacity(int minimumCapacity) {

        if (minimumCapacity > 0)

            ensureCapacityInternal(minimumCapacity);

    }

    /**

     * This method has the same contract as ensureCapacity, but is

     * never synchronized.

     */

    private void ensureCapacityInternal(int minimumCapacity) {

        // overflow-conscious code

        if (minimumCapacity - value.length > 0)

            expandCapacity(minimumCapacity);

    }

    /**

     * This implements the expansion semantics of ensureCapacity with no

     * size check or synchronization.

     */

    void expandCapacity(int minimumCapacity) {

        int newCapacity = value.length * 2 + 2;

        if (newCapacity - minimumCapacity < 0)

            newCapacity = minimumCapacity;

        if (newCapacity < 0) {

            if (minimumCapacity < 0) // overflow

                throw new OutOfMemoryError();

            newCapacity = Integer.MAX_VALUE;

        }

        value = Arrays.copyOf(value, newCapacity);

    }

    /**

     * Attempts to reduce storage used for the character sequence.

     * If the buffer is larger than necessary to hold its current sequence of

     * characters, then it may be resized to become more space efficient.

     * Calling this method may, but is not required to, affect the value

     * returned by a subsequent call to the {@link #capacity()} method.

     */

    public void trimToSize() {

        if (count < value.length) {

            value = Arrays.copyOf(value, count);

        }

    }

    /**

     * Sets the length of the character sequence.

     * The sequence is changed to a new character sequence

     * whose length is specified by the argument. For every nonnegative

     * index <i>k</i> less than {@code newLength}, the character at

     * index <i>k</i> in the new character sequence is the same as the

     * character at index <i>k</i> in the old sequence if <i>k</i> is less

     * than the length of the old character sequence; otherwise, it is the

     * null character {@code '\u005Cu0000'}.

     *

     * In other words, if the {@code newLength} argument is less than

     * the current length, the length is changed to the specified length.

     * <p>

     * If the {@code newLength} argument is greater than or equal

     * to the current length, sufficient null characters

     * ({@code '\u005Cu0000'}) are appended so that

     * length becomes the {@code newLength} argument.

     * <p>

     * The {@code newLength} argument must be greater than or equal

     * to {@code 0}.

     *

     * @param      newLength   the new length

     * @throws     IndexOutOfBoundsException  if the

     *               {@code newLength} argument is negative.

     */

    public void setLength(int newLength) {

        if (newLength < 0)

            throw new StringIndexOutOfBoundsException(newLength);

        ensureCapacityInternal(newLength);

        if (count < newLength) {

            Arrays.fill(value, count, newLength, '\0');

        }

        count = newLength;

    }

    /**

     * Returns the {@code char} value in this sequence at the specified index.

     * The first {@code char} value is at index {@code 0}, the next at index

     * {@code 1}, and so on, as in array indexing.

     * <p>

     * The index argument must be greater than or equal to

     * {@code 0}, and less than the length of this sequence.

     *

     * <p>If the {@code char} value specified by the index is a

     * <a href="Character.html#unicode">surrogate</a>, the surrogate

     * value is returned.

     *

     * @param      index   the index of the desired {@code char} value.

     * @return     the {@code char} value at the specified index.

     * @throws     IndexOutOfBoundsException  if {@code index} is

     *             negative or greater than or equal to {@code length()}.

     */

    @Override

    public char charAt(int index) {

        if ((index < 0) || (index >= count))

            throw new StringIndexOutOfBoundsException(index);

        return value[index];

    }

    /**

     * Returns the character (Unicode code point) at the specified

     * index. The index refers to {@code char} values

     * (Unicode code units) and ranges from {@code 0} to

     * {@link #length()}{@code  - 1}.

     *

     * <p> If the {@code char} value specified at the given index

     * is in the high-surrogate range, the following index is less

     * than the length of this sequence, and the

     * {@code char} value at the following index is in the

     * low-surrogate range, then the supplementary code point

     * corresponding to this surrogate pair is returned. Otherwise,

     * the {@code char} value at the given index is returned.

     *

     * @param      index the index to the {@code char} values

     * @return     the code point value of the character at the

     *             {@code index}

     * @exception  IndexOutOfBoundsException  if the {@code index}

     *             argument is negative or not less than the length of this

     *             sequence.

     */

    public int codePointAt(int index) {

        if ((index < 0) || (index >= count)) {

            throw new StringIndexOutOfBoundsException(index);

        }

        return Character.codePointAtImpl(value, index, count);

    }

    /**

     * Returns the character (Unicode code point) before the specified

     * index. The index refers to {@code char} values

     * (Unicode code units) and ranges from {@code 1} to {@link

     * #length()}.

     *

     * <p> If the {@code char} value at {@code (index - 1)}

     * is in the low-surrogate range, {@code (index - 2)} is not

     * negative, and the {@code char} value at {@code (index -

     * 2)} is in the high-surrogate range, then the

     * supplementary code point value of the surrogate pair is

     * returned. If the {@code char} value at {@code index -

     * 1} is an unpaired low-surrogate or a high-surrogate, the

     * surrogate value is returned.

     *

     * @param     index the index following the code point that should be returned

     * @return    the Unicode code point value before the given index.

     * @exception IndexOutOfBoundsException if the {@code index}

     *            argument is less than 1 or greater than the length

     *            of this sequence.

     */

    public int codePointBefore(int index) {

        int i = index - 1;

        if ((i < 0) || (i >= count)) {

            throw new StringIndexOutOfBoundsException(index);

        }

        return Character.codePointBeforeImpl(value, index, 0);

    }

    /**

     * Returns the number of Unicode code points in the specified text

     * range of this sequence. The text range begins at the specified

     * {@code beginIndex} and extends to the {@code char} at

     * index {@code endIndex - 1}. Thus the length (in

     * {@code char}s) of the text range is

     * {@code endIndex-beginIndex}. Unpaired surrogates within

     * this sequence count as one code point each.

     *

     * @param beginIndex the index to the first {@code char} of

     * the text range.

     * @param endIndex the index after the last {@code char} of

     * the text range.

     * @return the number of Unicode code points in the specified text

     * range

     * @exception IndexOutOfBoundsException if the

     * {@code beginIndex} is negative, or {@code endIndex}

     * is larger than the length of this sequence, or

     * {@code beginIndex} is larger than {@code endIndex}.

     */

    public int codePointCount(int beginIndex, int endIndex) {

        if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {

            throw new IndexOutOfBoundsException();

        }

    }

    /**

     * Returns the index within this sequence that is offset from the

     * given {@code index} by {@code codePointOffset} code

     * points. Unpaired surrogates within the text range given by

     * {@code index} and {@code codePointOffset} count as

     * one code point each.

     *

     * @param index the index to be offset

     * @param codePointOffset the offset in code points

     * @return the index within this sequence

     * @exception IndexOutOfBoundsException if {@code index}

     *   is negative or larger then the length of this sequence,

     *   or if {@code codePointOffset} is positive and the subsequence

     *   starting with {@code index} has fewer than

     *   {@code codePointOffset} code points,

     *   or if {@code codePointOffset} is negative and the subsequence

     *   before {@code index} has fewer than the absolute value of

     *   {@code codePointOffset} code points.

     */

    public int offsetByCodePoints(int index, int codePointOffset) {

        if (index < 0 || index > count) {

            throw new IndexOutOfBoundsException();

        }

        return Character.offsetByCodePointsImpl(value, 0, count,

                                                index, codePointOffset);

    }

    /**

     * Characters are copied from this sequence into the

     * destination character array {@code dst}. The first character to

     * be copied is at index {@code srcBegin}; the last character to

     * be copied is at index {@code srcEnd-1}. The total number of

     * characters to be copied is {@code srcEnd-srcBegin}. The

     * characters are copied into the subarray of {@code dst} starting

     * at index {@code dstBegin} and ending at index:

     * <pre>{@code

     * dstbegin + (srcEnd-srcBegin) - 1

     * }</pre>

     *

     * @param      srcBegin   start copying at this offset.

     * @param      srcEnd     stop copying at this offset.

     * @param      dst        the array to copy the data into.

     * @param      dstBegin   offset into {@code dst}.

     * @throws     IndexOutOfBoundsException  if any of the following is true:

     *             <ul>

     *             <li>{@code srcBegin} is negative

     *             <li>{@code dstBegin} is negative

     *             <li>the {@code srcBegin} argument is greater than

     *             the {@code srcEnd} argument.

     *             <li>{@code srcEnd} is greater than

     *             {@code this.length()}.

     *             <li>{@code dstBegin+srcEnd-srcBegin} is greater than

     *             {@code dst.length}

     *             </ul>

     */

    public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)

    {

        if (srcBegin < 0)

            throw new StringIndexOutOfBoundsException(srcBegin);

        if ((srcEnd < 0) || (srcEnd > count))

            throw new StringIndexOutOfBoundsException(srcEnd);

        if (srcBegin > srcEnd)

            throw new StringIndexOutOfBoundsException("srcBegin > srcEnd");

        System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);

    }

    /**

     * The character at the specified index is set to {@code ch}. This

     * sequence is altered to represent a new character sequence that is

     * identical to the old character sequence, except that it contains the

     * character {@code ch} at position {@code index}.

     * <p>

     * The index argument must be greater than or equal to

     * {@code 0}, and less than the length of this sequence.

     *

     * @param      index   the index of the character to modify.

     * @param      ch      the new character.

     * @throws     IndexOutOfBoundsException  if {@code index} is

     *             negative or greater than or equal to {@code length()}.

     */

    public void setCharAt(int index, char ch) {

        if ((index < 0) || (index >= count))

            throw new StringIndexOutOfBoundsException(index);

        value[index] = ch;

    }

    /**

     * Appends the string representation of the {@code Object} argument.

     * <p>

     * The overall effect is exactly as if the argument were converted

     * to a string by the method {@link String#valueOf(Object)},

     * and the characters of that string were then

     * {@link #append(String) appended} to this character sequence.

     *

     * @param   obj   an {@code Object}.

     * @return  a reference to this object.

     */

    public AbstractStringBuilder append(Object obj) {

        return append(String.valueOf(obj));

    }

    /**

     * Appends the specified string to this character sequence.

     * <p>

     * The characters of the {@code String} argument are appended, in

     * order, increasing the length of this sequence by the length of the

     * argument. If {@code str} is {@code null}, then the four

     * characters {@code "null"} are appended.

     * <p>

     * Let <i>n</i> be the length of this character sequence just prior to

     * execution of the {@code append} method. Then the character at

     * index <i>k</i> in the new character sequence is equal to the character

     * at index <i>k</i> in the old character sequence, if <i>k</i> is less

     * than <i>n</i>; otherwise, it is equal to the character at index

     * <i>k-n</i> in the argument {@code str}.

     *

     * @param   str   a string.

     * @return  a reference to this object.

     */

    public AbstractStringBuilder append(String str) {

        if (str == null)

            return appendNull();

        int len = str.length();

        ensureCapacityInternal(count + len);

        str.getChars(0, len, value, count);

        count += len;

        return this;

    }

    // Documentation in subclasses because of synchro difference

    public AbstractStringBuilder append(StringBuffer sb) {

        if (sb == null)

            return appendNull();

        int len = sb.length();

        ensureCapacityInternal(count + len);

        sb.getChars(0, len, value, count);

        count += len;

        return this;

    }

    /**

     * @since 1.8

     */

    AbstractStringBuilder append(AbstractStringBuilder asb) {

        if (asb == null)

            return appendNull();

        int len = asb.length();

        ensureCapacityInternal(count + len);

        asb.getChars(0, len, value, count);

        count += len;

        return this;

    }

    // Documentation in subclasses because of synchro difference

    @Override

    public AbstractStringBuilder append(CharSequence s) {

        if (s == null)

            return appendNull();

        if (s instanceof String)

            return this.append((String)s);

        if (s instanceof AbstractStringBuilder)

            return this.append((AbstractStringBuilder)s);

        return this.append(s, 0, s.length());

    }

    private AbstractStringBuilder appendNull() {

        int c = count;

        ensureCapacityInternal(c + 4);

        final char[] value = this.value;

        value[c++] = 'n';

        value[c++] = 'u';

        value[c++] = 'l';

        value[c++] = 'l';

        count = c;

        return this;

    }

    /**

     * Appends a subsequence of the specified {@code CharSequence} to this

     * sequence.

     * <p>

     * Characters of the argument {@code s}, starting at

     * index {@code start}, are appended, in order, to the contents of

     * this sequence up to the (exclusive) index {@code end}. The length

     * of this sequence is increased by the value of {@code end - start}.

     * <p>

     * Let <i>n</i> be the length of this character sequence just prior to

     * execution of the {@code append} method. Then the character at

     * index <i>k</i> in this character sequence becomes equal to the

     * character at index <i>k</i> in this sequence, if <i>k</i> is less than

     * <i>n</i>; otherwise, it is equal to the character at index

     * <i>k+start-n</i> in the argument {@code s}.

     * <p>

     * If {@code s} is {@code null}, then this method appends

     * characters as if the s parameter was a sequence containing the four

     * characters {@code "null"}.

     *

     * @param   s the sequence to append.

     * @param   start   the starting index of the subsequence to be appended.

     * @param   end     the end index of the subsequence to be appended.

     * @return  a reference to this object.

     * @throws     IndexOutOfBoundsException if

     *             {@code start} is negative, or

     *             {@code start} is greater than {@code end} or