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Date: Sun, 24 Mar 2013 22:49:15 +0000 (UTC)
From: "Mark (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Message-ID: <JIRA.12638762.1364165312827.46118.1364165355577@arcas>
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References: <JIRA.12638762.1364165312827@arcas>
Subject: [jira] [Commented] (IO-373) FileUtils.byteCountToDisplaySize
 improvement/rounding issues
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    [ https://issues.apache.org/jira/browse/IO-373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13612282#comment-13612282 ] 

Mark commented on IO-373:
-------------------------

Here is a variant that is able to let the user specify the maximum number of characters used to display the digits part of the displayed string. The rounding also makes a lot of sense to me.

{code}
public class FileUtils {

    private static final int DEFAULT_MAXCHARS = 3;
    private static final BigDecimal KILO_DIVISOR = new BigDecimal(1024L);

    enum SizeSuffix {

        B, KB, MB, GB, TB, PB, EB;
    }

    /**
     * Adopted and improved version of
     * {@link org.apache.commons.io.FileUtils#byteCountToDisplaySize(BigInteger)}.
     *
     * @see https://issues.apache.org/jira/browse/IO-226 - should the rounding be changed?
     * @param size
     * @param maxChars maximum length of digit part, ie. '1.2'
     * @return rounded byte size as {@link java.lang.String}
     */
    public static String byteCountToDisplaySize(BigInteger size, int maxChars) {
        String displaySize;
        BigDecimal bdSize = new BigDecimal(size);
        SizeSuffix selectedSuffix = SizeSuffix.B;
        for (SizeSuffix sizeSuffix : SizeSuffix.values()) {
            selectedSuffix = sizeSuffix;
            if (bdSize.setScale(0, RoundingMode.HALF_UP).toString().length() <= maxChars) {
                break;
            }
            bdSize = bdSize.divide(KILO_DIVISOR);
        }
        displaySize = bdSize.setScale(0, RoundingMode.HALF_UP).toString();
        if (displaySize.length() < maxChars - 1) {
            displaySize = bdSize.setScale(
                    maxChars - 1 - displaySize.length(), RoundingMode.HALF_UP).toString();
        }
        return displaySize + " " + selectedSuffix.toString();
    }

    public static String byteCountToDisplaySize(BigInteger size) {
        return byteCountToDisplaySize(size, DEFAULT_MAXCHARS);
    }

    public static String byteCountToDisplaySize(long size, int maxChars) {
        return byteCountToDisplaySize(BigInteger.valueOf(size), maxChars);
    }

    public static String byteCountToDisplaySize(long size) {
        return byteCountToDisplaySize(BigInteger.valueOf(size), DEFAULT_MAXCHARS);
    }
}
{code}

{code}
// CHECKSTYLE IGNORE MagicNumber FOR NEXT 1000 LINES
public class FileUtilsTest {

    /**
     * Test of byteCountToDisplaySize method, of class FileUtils.
     */
    @Test
    public void testByteCountToDisplaySize() {
        assertEquals("999 B", FileUtils.byteCountToDisplaySize(999L));
        assertEquals("1.0 KB", FileUtils.byteCountToDisplaySize(1000L));
        assertEquals("1.0 KB", FileUtils.byteCountToDisplaySize(1023L));
        assertEquals("1.1 KB", FileUtils.byteCountToDisplaySize(1124L));
        assertEquals("1.1 KB", FileUtils.byteCountToDisplaySize(1164L));
        assertEquals("999 KB", FileUtils.byteCountToDisplaySize(1024L * 999L + 511L));
        assertEquals("1.0 MB", FileUtils.byteCountToDisplaySize(1024L * 999L + 512L));
        assertEquals("1.0 MB", FileUtils.byteCountToDisplaySize(1024L * 1024L - 1L));
        assertEquals("1.0 GB", FileUtils.byteCountToDisplaySize(1024L * 1024L * 1024L - 1L));
        assertEquals("1.0 TB", FileUtils.byteCountToDisplaySize(1024L * 1024L * 1024L * 1024L - 1L));
        assertEquals("1.0 PB", FileUtils.byteCountToDisplaySize(1024L * 1024L * 1024L * 1024L * 1024L - 1L));
        assertEquals("1.0 EB", FileUtils.byteCountToDisplaySize(
                1024L * 1024L * 1024L * 1024L * 1024L * 1024L - 1L));

        assertEquals("0 KB", FileUtils.byteCountToDisplaySize(100L, 2));
        assertEquals("1 KB", FileUtils.byteCountToDisplaySize(1000L, 2));
        assertEquals("1 KB", FileUtils.byteCountToDisplaySize(1023L, 2));
        assertEquals("20 KB", FileUtils.byteCountToDisplaySize(19L * 1024L + 512L, 2));
        assertEquals("20 KB", FileUtils.byteCountToDisplaySize(19L * 1024L + 512L, 3));
        assertEquals("19.5 KB", FileUtils.byteCountToDisplaySize(19L * 1024L + 512L, 4));
        assertEquals("196 KB", FileUtils.byteCountToDisplaySize(195L * 1024L + 512L, 4));

        assertEquals("0 MB", FileUtils.byteCountToDisplaySize(19L * 1024L + 512L, 1));
    }
}
{code}
                
> FileUtils.byteCountToDisplaySize improvement/rounding issues
> ------------------------------------------------------------
>
>                 Key: IO-373
>                 URL: https://issues.apache.org/jira/browse/IO-373
>             Project: Commons IO
>          Issue Type: Improvement
>          Components: Utilities
>    Affects Versions: 2.4
>            Reporter: Mark
>            Priority: Minor
>
> Issue IO-226 is not fixed but closed.
> ?
> Here is my solution that also support a user-defined precision in terms of a maximum length of the digits part.

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