56 lines
2.3 KiB
Markdown
56 lines
2.3 KiB
Markdown
Implementing a shared library dynamic load using the oai loader is a two steps task:
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1. define the `loader_shlibfunc_t` array, describing the list of externally available functions implemented in the library. This is the interface of the module.
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1. Call the `load_module_shlib` function, passing it the previously defined array and the number of items in this array. The first argument to `load_module_shlib` is the name identifying the module, which is also used to format the corresponding library name, as described [here](loader/rtusage#shared-library-names)
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After a successful `load__module_shlib` call, the function pointer of each `loader_shlibfunc_t` array item has been set and can be used to call the corresponding function.
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Typical loader usage looks like:
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```c
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/* shared library loader include file */
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#include "common/utils/load_module_shlib.h"
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.............
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/*
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define and initialize the array, describing the list of functions
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implemented in "mymodule"
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*/
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loader_shlibfunc_t mymodule_fdesc[2];
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mymodule_fdesc[0].fname="mymodule_f1";
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mymodule_fdesc[1].fname="mymodule_f2";
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/*
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load the library, it's name must be libmymod.so. Configuration can be
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used to specify a specific path to look for libmymod.so. Configuration
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can also specify a version, for example "V1", in this case the loader
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will look for libmymodV1.so
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*/
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ret=load_module_shlib("mymod",mymodule_fdesc, sizeof(mymodule_fdesc)/sizeof(loader_shlibfunc_t));
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if (ret < 0) {
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fprintf(stderr,"Library couldn't be loaded\n");
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} else {
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/*
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library has been loaded, we probably want to call some functions...
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*/
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ret=((funcf1_t)mymodule_fdesc[0].fptr)();
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..................
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/*
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later and/or somewhere else in the code you may want to call function "mymodule_f2"
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You can use the loader get_shlibmodule_fptr(char *modname, char *fname) function
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to retrieve the pointer to that function
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*/
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funcf2_t *f2;
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int ret;
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int intarg1;
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char *strarg;
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........................
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f2 = (funcf2_t)get_shlibmodule_fptr("mymodule", "mymodule_f2")
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if (f2 != NULL) {
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ret = f2(intarg1,strarg);
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}
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...............
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```
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When loading a shared library the loader looks for a symbol named `< module name > _autoinit` and, if it finds it, calls it. The `autoinit` function is called without any argument and the returned value, if any, is not tested.
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[loader home page](loader)
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[loader developer home page](loader/devusage) |