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  1. JDK
  2. JDK-8212731

JS ArrayBuffer constructor argument of type j.n.ByteBuffer is ignored

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      Description

      ADDITIONAL SYSTEM INFORMATION :
      Any OS, on JDK 8

      A DESCRIPTION OF THE PROBLEM :
      JS ArrayBuffer allows the usage of j.n.ByteBuffer as a constructor argument, in this case this buffer will become the underlying buffer to be used by the typed arrays in nashorn. This only works for JDK >=9 as for 8 the argument is silently ignored.

      The issue here is that if there is no way to specify the underlying buffer the performance boost of typed arrays in a script is totally ignored as in the end, the end user must perform a non optimized and slow copy byte by byte of the buffer to a JS array and then cast it to a Java Array to finally convert it back to a buffer...

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      In a nashorn shell or embedded script:

      // create a j.n.ByteBuffer
      var bb = java.nio.ByteBuffer.allocateDirect(10)
      // here is the issue, nashorn allows specifying a bb as underlying buffer for ArrayBuffer
      var ab = new ArrayBuffer(bb)
      // if we now wrap this as a typed array
      var ia = new Int8Array(ab)
      // the test
      print(ia.length)
      print(ab.byteLength)


      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      // we expect that the length and content of the buffer are visible, but...
      print(ia.length) // expected 10
      print(ab.byteLength) // expected 10

      ACTUAL -
      // we expect that the length and content of the buffer are visible, but...
      print(ia.length) // prints 0, expected 10
      print(ab.byteLength) // prints 0, expected 10


      CUSTOMER SUBMITTED WORKAROUND :
      backport the fix from the current JDK:

      https://hg.openjdk.java.net/jdk/jdk11/file/1ddf9a99e4ad/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/objects/NativeArrayBuffer.java#l99

      to

      https://hg.openjdk.java.net/jdk8/jdk8/nashorn/file/096dc407d310/src/jdk/nashorn/internal/objects/NativeArrayBuffer.java#l51

      FREQUENCY : always


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              • Assignee:
                pmangal Priyanka Mangal (Inactive)
                Reporter:
                webbuggrp Webbug Group
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                Dates

                • Created:
                  Updated:
                  Resolved: