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Berkeley DB Java Edition is a open source, transactional storage solution for Java applications. The Direct Persistence Layer (DPL) API is faster and easier to develop, deploy, and manage than serialized object files or ORM-based Java persistence solutions. The Collections API enhances the standard java.util.collections classes allowing them to be persisted to a local file system and accessed concurrently while protected by ACID transactions. Data is stored by serializing objects and managing class and instance data separately so as not to waste space. Berkeley DB Java Edition is the reliable drop-in solution for complex, fast, and scalable storage. Source for this release is in 'je-4.0.92-sources.jar', the Javadoc is located at 'http://download.oracle.com/berkeley-db/docs/je/4.0.92/'.

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/*-
 * Copyright (C) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
 *
 * This file was distributed by Oracle as part of a version of Oracle Berkeley
 * DB Java Edition made available at:
 *
 * http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/downloads/index.html
 *
 * Please see the LICENSE file included in the top-level directory of the
 * appropriate version of Oracle Berkeley DB Java Edition for a copy of the
 * license and additional information.
 */

package com.sleepycat.utilint;

import java.text.DecimalFormat;
import java.text.Format;
import java.util.Iterator;
import java.util.SortedSet;

/**
 * A home for misc formatting utilities.
 */
public class FormatUtil {

    private static final ThreadLocal DECIMAL_SCALE0 =
        new ThreadLocal() {
            @Override
            public DecimalFormat initialValue() {
                return new DecimalFormat("###,###,###,###,###,###,###");
            }
        };

    private static final ThreadLocal DECIMAL_SCALE2 =
        new ThreadLocal() {
            @Override
            public DecimalFormat initialValue() {
                return new DecimalFormat("###,###,###,###,###,###,###.##");
            }
        };

    /**
     * Returns a thread-local DecimalFormat with US formatting and scale zero:
     * ###,###,###,###,###,###,###
     *
     * A ThreadLocal value is returned because {@link Format} objects are
     * generally not synchronized. The returned value should only be used in
     * the current thread.
     */
    public static DecimalFormat decimalScale0() {
        return DECIMAL_SCALE0.get();
    }

    /**
     * Returns a thread-local DecimalFormat with US formatting and scale two:
     * ###,###,###,###,###,###,###.##
     *
     * A ThreadLocal value is returned because {@link Format} objects are
     * generally not synchronized. The returned value should only be used in
     * the current thread.
     */
    public static DecimalFormat decimalScale2() {
        return DECIMAL_SCALE2.get();
    }

    /**
     * Utility class to convert a sorted set of long values to a compact string
     * suitable for printing. The representation is made compact by identifying
     * ranges so that the sorted set can be represented as a sequence of hex
     * ranges and singletons.
     */
    public static String asHexString(final SortedSet set) {

        if (set.isEmpty()) {
            return "";
        }

        final StringBuilder sb = new StringBuilder();
        final Iterator i = set.iterator();
        long rstart = i.next();
        long rend = rstart;

        while (i.hasNext()) {
            final long f = i.next();
            if (f == (rend + 1)) {
                /* Continue the existing range. */
                rend++;
                continue;
            }

            /* flush and start new range */
            flushRange(sb, rstart, rend);
            rstart = rend = f;
        }

        flushRange(sb, rstart, rend);

        /* Discard initial space in return value. */
        sb.deleteCharAt(0);

        return sb.toString();
    }

    private static void flushRange(final StringBuilder sb,
                                   final long rstart,
                                   final long rend) {
        if (rstart == -1) {
            return;
        }

        if (rstart == rend) {
            sb.append(" 0x").append(Long.toHexString(rstart));
        } else {
            sb.append(" 0x").append(Long.toHexString(rstart)).
            append("-").
            append("0x").append(Long.toHexString(rend));
        }
    }
}