Loading CJK fonts is very slow

[asolntsev]

Describe the bug
We use library FlyingSaucer which in turn uses OpenPDF 1.3.30.
We have a bunch of unit-tests that generate PDFs.
But every run of such a test takes 4+ seconds which is very slow and annoying.

Solution
I found that the problem is how class com.lowagie.text.pdf.BaseFont loads bytes from a jar.
Wrapping InputStream into BufferInputStream makes it much faster.
I am going to submit a pull request soon.

To Reproduce
To reproduce the issue, run the following code.

NB! Don't run it as a part of "OpenPDF" project.
Run it from a separate project. Then CJK fonts are loaded from JAR (openpdf-1.3.30.jar), and such loading is very slow.

import org.junit.jupiter.api.Test;

class CJKFontLoadingTest {

  /**
   * This method takes ~4 seconds (when using openpdf-1.3.30.jar as a JAR).
   * This is incredibly slow.
   */
  @Test
  void loadCJKFonts() throws Exception {
    for (String[] cjkFont : cjkFonts) {
      String fontName = cjkFont[0];
      String encoding = cjkFont[1];

      BaseFont.createFont(fontName + ",BoldItalic", encoding, false);
      BaseFont.createFont(fontName + ",Italic", encoding, false);
      BaseFont.createFont(fontName + ",Bold", encoding, false);
      BaseFont.createFont(fontName, encoding, false);
    }
  }

  // fontName, encoding
  private static final String[][] cjkFonts = {
    { "STSong-Light", "UniGB-UCS2-H" },
    { "STSong-Light", "UniGB-UCS2-V" },
    { "STSongStd-Light", "UniGB-UCS2-H" },
    { "STSongStd-Light", "UniGB-UCS2-V" },
    { "MHei-Medium", "UniCNS-UCS2-H" },
    { "MHei-Medium", "UniCNS-UCS2-V" },
    { "MSung-Light", "UniCNS-UCS2-H" },
    { "MSung-Light", "UniCNS-UCS2-V" },
    { "MSungStd-Light", "UniCNS-UCS2-H" },
    { "MSungStd-Light", "UniCNS-UCS2-V" },
    { "HeiseiMin-W3", "UniJIS-UCS2-H" },
    { "HeiseiMin-W3", "UniJIS-UCS2-V" },
    { "HeiseiKakuGo-W5", "UniJIS-UCS2-H" },
    { "HeiseiKakuGo-W5", "UniJIS-UCS2-V" },
    { "KozMinPro-Regular", "UniJIS-UCS2-HW-H" },
    { "KozMinPro-Regular", "UniJIS-UCS2-HW-V" },
    { "HYGoThic-Medium", "UniKS-UCS2-H" },
    { "HYGoThic-Medium", "UniKS-UCS2-V" },
    { "HYSMyeongJo-Medium", "UniKS-UCS2-H" },
    { "HYSMyeongJo-Medium", "UniKS-UCS2-V" },
    { "HYSMyeongJoStd-Medium", "UniKS-UCS2-H" },
    { "HYSMyeongJoStd-Medium", "UniKS-UCS2-V" }
  };
}

Expected behavior
We expect our unit-test to run very quickly (in a few milliseconds), not in 4+ seconds.