[jira] [Commented] (ARROW-2252) [Python] Create buffer from address, size and base

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-2252?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16385205#comment-16385205 ] 

ASF GitHub Bot commented on ARROW-2252:
---------------------------------------

xhochy opened a new pull request #1693: ARROW-2252: [Python] Create buffer from address, size and base
URL: https://github.com/apache/arrow/pull/1693
 
 
   Usage with Arrow Java vectors:
   
   ```
   import jpype
   import numpy as np
   import pyarrow as pa
   import sys
   
   # Start JVM with Arrow and all of its dependencies.
   jpype.startJVM(getDefaultJVMPath(), "-Djava.class.path=arrow-tools-0.9.0-SNAPSHOT-jar-with-dependencies.jar")
   
   # Create vector
   ra = jpype.JPackage("org").apache.arrow.memory.RootAllocator(sys.maxsize)
   uint1 = jpype.JPackage("org").apache.arrow.vector.UInt1Vector("int", ra)
   uint1.allocateNew(128)
   for i in range(128):
       uint1.setSafe(i, i)
   uint1.setValueCount(128)
   
   # Access it in Python
   addr = uint1.getDataBuffer().unwrap().memoryAddress()
   size = uint1.getDataBuffer().unwrap().capacity()
   fb = pa.ForeignBuffer(addr, size, n)
   np.asarray(fb)
   ```

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> [Python] Create buffer from address, size and base
> --------------------------------------------------
>
>                 Key: ARROW-2252
>                 URL: https://issues.apache.org/jira/browse/ARROW-2252
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: Python
>            Reporter: Uwe L. Korn
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 0.9.0
>
>
> Given a memory address and a size, we should be able to construct an Arrow buffer from this. The additional base object will be used to hold a reference to the underlying, original buffer so that it does not go out of scope before the Arrow buffer.



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