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https://github.com/servalproject/serval-dna.git
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67 lines
2.8 KiB
C
67 lines
2.8 KiB
C
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/*
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Serval DNA features
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Copyright (C) 2016 Flinders University
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef __SERVAL_DNA__FEATURE_H
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#define __SERVAL_DNA__FEATURE_H
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/* These are macros for assembling an executable out of an explicitly-listed
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* subset of "features". A feature is an object file (.o file) that contains
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* the entire implementation of the feature, and is optional, ie, can be
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* omitted from an executable without breaking the build.
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*
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* In Serval DNA, features are joined up with their infrastructure using
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* linkage sections; see "sections.h" for more details.
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*
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* For example, a source file can add its own static function to the list of
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* all URL path-to-function mappings for the HTTPD server using
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* DECLARE_HANDLER() macro defined in "httpd.h". There is no
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* explicitly-initialised array that lists all the URL paths; the array is
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* constructed implicitly by the linker when it assembles the "httpd" section.
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* Simply including the relevant object files in the link brings their
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* functions into the array.
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*
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* Features are also used to add commands to the CLI interface and to add
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* port-number handlers to the MDP interface.
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*
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* In order to build an executable from libservald.a, the executable needs a
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* way to specify which optional features it wishes to link in, otherwise they
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* will be omitted from the build, and as a result it will offer few or no CLI
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* commands, no MDP services, and no HTTP services.
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*
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* Each source file that implements a feature must contain a DEFINE_FEATURE()
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* macro, with the name of the feature as its argument.
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*
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* Every executable that links against libservald.a must contain a source file
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* that invokes the USE_FEATURE() macro once for every defined feature it
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* wishes to link in. This is typically done inside the main() function, but
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* may be done within any function that is guaranteed to be included in the
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* link.
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*/
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#define DEFINE_FEATURE(name) \
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void _serval_feature__ ## name () {} \
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#define USE_FEATURE(name) \
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do { \
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extern void _serval_feature__ ## name (); \
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_serval_feature__ ## name (); \
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} while (0)
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#endif // __SERVAL_DNA__FEATURE_H
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