Databases
StackOverflow2013
Postsdbo
POHow do I create a Python ctypes pointer to an array of pointers
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow do I create a Python ctypes pointer to an array of pointers
    primarykey
    data
    text
    <p>I need to learn how to handle the <code>char**</code> in the C++ method below through Python ctypes. I was doing fine calling other methods that only need single pointers by using <code>create_string_buffer()</code>, but this method requires a pointer to an array of pointers.</p> <pre><code>ladybugConvertToMultipleBGRU32( LadybugContext context, const LadybugImage * pImage, unsigned char** arpDestBuffers, LadybugImageInfo * pImageInfo ) </code></pre> <p>How do I create a pointer to an array of six <code>create_string_buffer(7963648)</code> buffers in ctypes to pass to this C++ method for writing?</p> <pre><code>arpDestBuffers = pointer to [create_string_buffer(7963648) for i in xrange(6)] </code></pre> <p>Thank you for any help.</p> <hr> <p>Both the answers given below work. I just didn't realize I had another problem in my code which prevented me from seeing the results right away. The first example is just as Luc wrote:</p> <pre><code>SixBuffers = c_char_p * 6 arpDestBuffers = SixBuffers( *[c_char_p(create_string_buffer(7963648).raw) for i in xrange(6)] ) </code></pre> <p>The second example coming from omu_negru's answer is:</p> <pre><code>arpDestBuffers = (POINTER(c_char) * 6)() arpDestBuffers[:] = [create_string_buffer(7963648) for i in xrange(6)] </code></pre> <p>Both are accepted by the function and overwritten. Typing <code>print repr(arpDestBuffers[4][:10])</code> before and after calling the function gives:</p> <pre><code>'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' '\x15\x10\x0e\xff\x15\x10\x0e\xff\x14\x0f' </code></pre> <p>which shows that the function successfully overwrote the buffer with data.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USuser6811
    1. USuser6811
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow do I create a Python ctypes pointer to an array of pointers
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow do I create a Python ctypes pointer to an array of pointers
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POHow do I create a Python ctypes pointer to an array of pointers
      1. US0xc0de
      1. VTFavorite
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload