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POWrapping a C library for Lua: how do I create nested tables of functions?
 

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  1. POWrapping a C library for Lua: how do I create nested tables of functions?
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    <p>The code related to this question is here: <a href="https://github.com/jchester/lua-polarssl/tree/master/src">https://github.com/jchester/lua-polarssl/tree/master/src</a></p> <p>Currently I'm trying to wrap one part of the PolarSSL library (http://polarssl.org) to give me access to SHA-512 HMACs (luacrypto does not provide this).</p> <p>The API I'm aiming for is of the form:</p> <pre><code>a_sha512_hash = polarssl.hash.sha512('text') </code></pre> <p>or more fully</p> <pre><code>local polarssl = require 'polarssl' local hash = polarssl.hash a_sha512_hash = hash.sha512('test') </code></pre> <p>If you refer to polarssl.c in the link above, you'll see I've written functions that wrap PolarSSL code. Then I'm trying to build the function tables thus:</p> <pre><code>LUA_API int luaopen_polarssl( lua_State *L ) { static const struct luaL_Reg core[] = { { NULL, NULL } }; static const struct luaL_Reg hash_functions[] = { { "sha512", hash_sha512 }, { "sha384", hash_sha384 }, { NULL, NULL } }; static const struct luaL_Reg hmac_functions[] = { { "sha512", hmac_sha512 }, { "sha384", hmac_sha384 }, { NULL, NULL } }; luaL_register( L, CORE_MOD_NAME, core ); luaL_register( L, HASH_MOD_NAME, hash_functions ); luaL_register( L, HMAC_MOD_NAME, hmac_functions ); return 1; } </code></pre> <p>Where CORE_MOD_NAME = 'polarssl', HASH_MOD_NAME = 'polarssl.hash', HMAC_MOD_NAME = 'polarssl.hmac'.</p> <p>When I run a test script similar to the Lua code at the top of this question, I get this:</p> <pre><code>lua: test.lua:23: attempt to index global 'polarssl' (a nil value) stack traceback: test.lua:23: in main chunk [C]: ? </code></pre> <p>I've tried looking for examples of how to achieve this module.submodule approach (eg <a href="https://github.com/jwise/naim/blob/lua-experimental/lua/moon.c#L180">naim</a> vs <a href="https://github.com/sam-github/luasocket/blob/master/src/luasocket.c#L47">luasockets</a>), but everyone seems to have a different way of achieving it. I'm completely lost.</p>
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    1. USDaniel Roethlisberger
    1. USJacques Chester
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    1. COI can't link to naim and luasockets because I hit the < 10 point limit on links.
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      1. USJacques Chester
    2. COLooks like karma is handed out like delicious lollies, so updated post with links.
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      1. USJacques Chester
 

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