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POHow to use NIF to interact with C code that keeps state across calls (i.e., linked lists as NIF)
 

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  1. POHow to use NIF to interact with C code that keeps state across calls (i.e., linked lists as NIF)
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    <p>I wanted to create a linked-list data structure that was implemented in C. The idea was that one would create a linked list</p> <pre><code>ll:new() -&gt; listId. </code></pre> <p>ListId, above, represents a "pointer" of some type that would get passed back to the C code which would function as some type of handle on the list. I was hoping not to have to pass the list itself back and forth since I imagined lists could get very, very large. Once the linked list was created, users would then interact with it in obvious ways:</p> <pre><code>ll:add(ListId, Elt) ll:add_after(ListId, Pos, Elt) </code></pre> <p>I imagined I would do this via Erlang's NIF capabilities. Now, for this to work the C side has to maintain the list across multiple calls to add, add_after, etc.</p> <p>In straight C, I would have a main function that a user interacts with that would keep the program alive thereby keeping the linked list persisted for the life of the user's interaction with the program. As I understand it, NIFs utilizes C code with no main function. That is, that each call to a NIF is a one-and-done type of proposition. </p> <p>Can someone give me some pointers on how (assuming it is appropriate) one can utilize NIFs to interact with C code that needs keeps state across multiple calls? I hope that was clear!</p>
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    1. USHynek -Pichi- Vychodil
    1. USJr0
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    1. COjust for clarification: ListId -- it contains the whole list in some form, or just reference(direct or indirect) to memory in the C part?
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      1. USOdobenus Rosmarus
    2. CO@OdobenusRosmarus, the ListId was supposed to be a reference to the linked list, NOT the list itself
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