[IronPython] What is .AppendChunk expecting?

[Shri Borde]

I think you are going to need Curt's solution #2 and explicitly create a "byte array".

Let us know if that works. If it does, we could also consider adding to IronPython.Runtime.PythonBuffer (the class which implements buffer<http://www.python.org/doc/2.5.1/api/bufferObjects.html>) an implicit conversion operator to "byte array". With a few tweaks to System.Scripting.Com.VarEnumSelector, we could get to a point where you should be able to just do "p.AppendChunk<http://msdn.microsoft.com/en-us/library/ms678268(VS.85).aspx>(elem)" and have elem converted from a buffer<http://www.python.org/doc/2.5.1/api/bufferObjects.html> to "VT_ARRAY | VT_I1"

From: users-bounces at lists.ironpython.com [mailto:users-bounces at lists.ironpython.com] On Behalf Of Curt Hagenlocher
Sent: Wednesday, August 27, 2008 8:51 PM
To: Discussion of IronPython
Subject: Re: [IronPython] What is .AppendChunk expecting?

Two more ideas:

1) Try passing a list of numbers.  You can trivially get this from the buffer by saying
a = map(lambda c: ord(c), buf)
2) Try passing a BCL array of bytes.  This is almost as easy:
import System
a = System.Array[System.Byte](map(lambda c: ord(c), b))
On Wed, Aug 27, 2008 at 7:36 PM, Vernon Cole <vernondcole at gmail.com<mailto:vernondcole at gmail.com>> wrote:
I tried both
p.AppendChunk(str(elem))
and
p.AppendChunk(unicode(elem))
both of which work, but then the execution fails with:
<console output>
   File "C:\Program Files\IronPython 2.0 Beta4\lib\site-packages\adodbapi\adodbapi.py", line 675, in _executeHelper
    rs = self.cmd.Execute(ra)
 EnvironmentError: The field is too small to accept the amount of data you attempted to add.  Try inserting or pasting less data.

-- on command: "INSERT INTO tblTemp (fldId,fldData) VALUES (?,?)"
-- with parameters: (2, <read-only buffer for 0x000000000000003A, size 4, offset
 0 at 0x000000000000003B>)
</console output>
which lead me to believe that I'm not giving .AppendChunk() the argument it expects.

I even tried
p.Value = elem
which results in:
 StandardError: Exception has been thrown by the target of an invocation.

--
Vernon

On Wed, Aug 27, 2008 at 7:40 PM, Curt Hagenlocher <curt at hagenlocher.org<mailto:curt at hagenlocher.org>> wrote:
This will probably need to be a string.  I don't think we do any automatic conversions of buffer objects for CLR or COM calls.
On Wed, Aug 27, 2008 at 6:28 PM, Vernon Cole <vernondcole at gmail.com<mailto:vernondcole at gmail.com>> wrote:
Dear miracle workers:
  This may actually be the last failed unittest for adodbapai. Progress has been remarkable.
Can you help with one more?

Situation: filling in the parameter list for an ADO execute.  The second parameter (parameter 1) is a python "buffer" to be loaded into a binary(4) column.
"elem" contains the value of the parameter.
"p" is the parameter object.
Pywin32 uses p.AppendChunk successfully to pass the buffer to SQL, but Iron objects:

<console output>
DatabaseError:
--ADODBAPI
-- Trying parameter 1 = <read-only buffer for 0x000000000000003A, size 4, offset
 0 at 0x000000000000003B>
Traceback (most recent call last):
   File "C:\Program Files\IronPython 2.0 Beta4\lib\site-packages\adodbapi\adodba
pi.py", line 659, in _executeHelper
    p.AppendChunk(elem)
 TypeError: Specified cast is not valid.
-- on command: "INSERT INTO tblTemp (fldId,fldData) VALUES (?,?)"
-- with parameters: (2, <read-only buffer for 0x000000000000003A, size 4, offset
 0 at 0x000000000000003B>)
</console output>

What coercion should be supplied to make AppendChunk happy to accept the buffer contents without trying to cast it?
--
Vernon Cole


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