/*
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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/*
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 * 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;
 }
}