Re: Font operation takes a long time with 3.0.1

[Tilman Hausherr]

Does the stack trace appear at every start? If yes then it's a bug. The 
intent of the current code is that bad fonts aren't retried. The font 
cache file should contain a line with "*skipexception*" for that font. 
Can you look at it for the two font files?

I could change SHA512 to CRC32. It has the advantage that it won't 
trigger people who heard about MD5 😂

I made a test and CRC32 is 20% faster.

Tilman

On 04.12.2023 18:48, Gili Tzabari wrote:
I think the commit contains a typo:


872 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l872> 
    private static String computeHash(byte[] ba)
873 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l873> 
    {
874 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l874> 
    MessageDigest md;
875 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l875> 
    try
876 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l876> 
    {
877 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l877> 
    md = MessageDigest.getInstance("SHA512");
878 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l878> 
    byte[] md5 = md.digest(ba);
879 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l879> 
    return Hex.getString(md5);
880 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l880> 
    }
881 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l881> 
    catch (NoSuchAlgorithmException ex)
882 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l882> 
    {
883 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l883> 
    // never happens
884 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l884> 
    return "";
885 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l885> 
    }
886 
<https://svn.apache.org/viewvc/pdfbox/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/font/FileSystemFontProvider.java?revision=1912514&view=markup&pathrev=1912514#l886> 
    }

You shouldn't need to use SHA512 to detect changes by a non-malicious 
actor. MD5 should be plenty, and even CRC32 would be enough. I suggest 
downgrading the hash complexity.

Gili

On 2023-12-04 10:21, Kjetil Ødegaard wrote:
Hi,

I tried to upgrade an app to PDFBox 3.0.1 and I see a performance issue.

It only affects the first PDF operation (after that it's quite fast), 
but
it's a bit annoying since it takes about 20 seconds (on my M1 Macboox).

Profiling reveals that this Kotlin code triggers the delay:

     val font = PDType1Font(Standard14Fonts.FontName.COURIER)

The thread dump shows that almost all time is spent in this method:

org.apache.pdfbox.pdmodel.font.FileSystemFontProvider#computeHash

I assume that this is related to PDFBOX-5684.

Is this possible to work around? Or is it possible to fix?

BR Kjetil



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