package sun.misc;

/**
 * An internal extension of CharSequence that guarantees it's
 * {@link #length()} to be constant. The underlying characters can change
 * concurrently only as a result of improper use of objects this object
 * was derived from and were not intended for multi-thread use without
 * proper synchronization.
 */
public interface ConstantLengthCharSequence extends CharSequence {

    /**
     * Returns a {@link ConstantLengthCharSequence} for given {@code charSequence}.
     * If given {@code charSequence} is a {@link ConstantLengthCharSequence} then it
     * returns the given instance itself.
     *
     * @return a {@link ConstantLengthCharSequence} for given {@code charSequence}
     */
    static ConstantLengthCharSequence valueFor(CharSequence charSequence) {
        if (charSequence instanceof ConstantLengthCharSequence) {
            return (ConstantLengthCharSequence) charSequence;
        } else {
            return charSequence.toString();
        }
    }

    /**
     * Copies characters from this {@code ConstantLengthCharSequence} into the
     * destination character array.
     * <p>
     * The first character to be copied is at index {@code srcBegin};
     * the last character to be copied is at index {@code srcEnd-1}
     * (thus 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:
     * <blockquote><pre>
     *     dstBegin + (srcEnd-srcBegin) - 1
     * </pre></blockquote>
     *
     * @param srcBegin index of the first character in the sequence
     *                 to copy.
     * @param srcEnd   index after the last character in the sequence
     *                 to copy.
     * @param dst      the destination array.
     * @param dstBegin the start offset in the destination array.
     * @throws IndexOutOfBoundsException If any of the following
     *                                   is true:
     *                                   <ul><li>{@code srcBegin} is negative.
     *                                   <li>{@code srcBegin} is greater than
     *                                   {@code srcEnd}
     *                                   <li>{@code srcEnd} is greater than the
     *                                   length of this sequence
     *                                   <li>{@code dstBegin} is negative
     *                                   <li>{@code dstBegin+(srcEnd-srcBegin)}
     *                                   is larger than {@code dst.length}</ul>
     */
    void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin);
}