/*

 * 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.

 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Written by Martin Buchholz with assistance from members of JCP

 * JSR-166 Expert Group and released to the public domain, as

 * explained at http://creativecommons.org/publicdomain/zero/1.0/

 */

package java.util.concurrent;

import java.util.Collection;

/** Shared implementation code for java.util.concurrent. */

class Helpers {

    private Helpers() {}                // non-instantiable

    /**

     * An implementation of Collection.toString() suitable for classes

     * with locks.  Instead of holding a lock for the entire duration of

     * toString(), or acquiring a lock for each call to Iterator.next(),

     * we hold the lock only during the call to toArray() (less

     * disruptive to other threads accessing the collection) and follows

     * the maxim "Never call foreign code while holding a lock".

     */

    static String collectionToString(Collection<?> c) {

        final Object[] a = c.toArray();

        final int size = a.length;

        if (size == 0)

            return "[]";

        int charLength = 0;

        // Replace every array element with its string representation

        for (int i = 0; i < size; i++) {

            Object e = a[i];

            // Extreme compatibility with AbstractCollection.toString()

            String s = (e == c) ? "(this Collection)" : objectToString(e);

            a[i] = s;

            charLength += s.length();

        }

        return toString(a, size, charLength);

    }

    /**

     * Like Arrays.toString(), but caller guarantees that size > 0,

     * each element with index 0 <= i < size is a non-null String,

     * and charLength is the sum of the lengths of the input Strings.

     */

    static String toString(Object[] a, int size, int charLength) {

        // assert a != null;

        // assert size > 0;

        // Copy each string into a perfectly sized char[]

        // Length of [ , , , ] == 2 * size

        final char[] chars = new char[charLength + 2 * size];

        chars[0] = '[';

        int j = 1;

        for (int i = 0; i < size; i++) {

            if (i > 0) {

                chars[j++] = ',';

                chars[j++] = ' ';

            }

            String s = (String) a[i];

            int len = s.length();

            s.getChars(0, len, chars, j);

            j += len;

        }

        chars[j] = ']';

        // assert j == chars.length - 1;

        return new String(chars);

    }

    /** Optimized form of: key + "=" + val */

    static String mapEntryToString(Object key, Object val) {

        final String k, v;

        final int klen, vlen;

        final char[] chars =

            new char[(klen = (k = objectToString(key)).length()) +

                     (vlen = (v = objectToString(val)).length()) + 1];

        k.getChars(0, klen, chars, 0);

        chars[klen] = '=';

        v.getChars(0, vlen, chars, klen + 1);

        return new String(chars);

    }

    private static String objectToString(Object x) {

        // Extreme compatibility with StringBuilder.append(null)

        String s;

        return (x == null || (s = x.toString()) == null) ? "null" : s;

    }

}