cython - Can someone tell me what this c code is doing? -

-

cansome tell me going in cython code. full code can seen at:

https://github.com/scipy/scipy/blob/master/scipy/spatial/ckdtree.pyx

# standard trick variable-size arrays: # malloc sizeof(nodeinfo)+self.m*sizeof(double) bytes. cdef struct nodeinfo:     innernode* node     double side_distances[0]

it's old c trick. if don't know how many side_distances needed, because varies 1 instance of nodeinfo another, declare array size zero. when allocate memory node, allocate size of struct as defined (sizeof(nodeinfo)), plus memory number of values want in particular instance (+something * sizeof(double)). result for instance, have enough memory array of size specified.

it's "trick" in sense uses allocate separate array , store pointer in array. keeping in 1 allocation (attempted) optimization.

iirc, though, zero-sized array allowed c++ standard, not c standard. in c, should define flexible-sized array side_distances[], although no doubt many compilers permit c++ version in c extension. either way, though, struct doesn't contain room elements, although correctly aligned double.


Comments

Post a Comment

Popular posts from this blog

objective c - Change font of selected text in UITextView -

-
can suggest me how change font of selected text in uitextview.i cannot use uiwebview since have edit text. have seen pages app.how possible in app. see formatting text within uilabel differently . since need editing, should @ javascript-based editors such ckeditor or tinymce . highly recommend wwdc 2011 video session 511: "rich text editing in safari on ios."
Read more

php - Accessing POST data in Facebook cavas app -

-
so i've got simple form in canvas / iframe facebook app, , i'm trying pass along values post. reading on s.o. , fb's latest docs, understand it, data send via post form can accessed on receiving end $_request object. i read on thread on s.o. in order post forms work need pass along input named "signed_request" value current signed_request (i have signed request working ok otherwise...all login , authentication stuff working fine). isnt mentioned anywhere in official fb docs. so problem comes in $_request object signed request, , bunch of other session stuff. form inputs found. the way can read them set method of form "request" isn't real form method. takes of inputs , sends them args in url. horrible. here's sample page canvas app form i'm using try debug (leaving out authentication stuff): <form enctype="application/x-www-form-urlencoded" method="post" target="_top" id="my_form" action=...
Read more

c# - Getting control value when switching a view as part of a multiview -

-
i have following code in aspx page: <asp:button id="display_button" runat="server" text="display" onclick="button1_click" /> &nbsp; <asp:button id="edit_button" runat="server" text="edit" onclick="button2_click" /> &nbsp; <asp:button id="save_button" runat="server" text="save" onclick="button3_click" visible="false" /> &nbsp; <asp:multiview id="multiview1" runat="server" activeviewindex="0"> <asp:view id="view1" runat="server"> <asp:formview id="view_program" runat="server"> <itemtemplate> <%# eval("status").tostring().trim() %> </itemtemplate> </asp:formview> </asp:view> <asp:view id="view2" runat="server"> ...
Read more