Hardware Design: SIE

Hardware Design: SIE Git Source Tree

1	Examples from http://www.wellho.net/mouth/1844_Calling-functions-in-C-from-your-Lua-script-a-first-HowTo.html
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3	If you may with to pass a table from your Lua script into a C function, so that the C function can make use of a value from the table code like this:
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5	stuff = {hotel = 48, hq = 404, town = 1}
6	....
7	summat = extratasks.dothis(stuff)
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9	This isn't as easy as just passing a value, since the size of a table can vary, and Lua's dynamic memory allocation doesn't sit well, in a simple interface, with C's static model. The "trick" is to tackle it within the C code by using function calls to get (and if necessary) reset values from the table - with the data required by those function calls being processed via the Lua stack.
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11	/* Looking up based on the key */
12	/* Add key we're interested in to the stack*/
13	lua_pushstring(L,"hq");
14	/* Have Lua functions look up the keyed value */
15	lua_gettable(L, -2 );
16	/* Extract the result which is on the stack */
17	double workon = lua_tonumber(L,-1);
18	/* Tidy up the stack - get rid of the extra we added*/
19	lua_pop(L,1);
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21	That code retrieves the "hq" value from the table that's been passed in (called stuff in my Lua example above) and stores it into a C variable called workon ... objective achieved!
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