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Version 1.1, (the "License"); you may not use this file except in
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under the License.
The C Client Back-end
2004-01-14
C
ch_c_client.xml
Introduction
With the option {be, c_client} the IDL Compiler generates
C client stubs according to the IDL to C mapping, on top of the
Erlang distribution and gen_server protocols.
The developer has to write additional code, that together with
the generated C client stubs, form a hidden Erlang node. That
additional code uses erl_interface functions for defining
the hidden node, and for establishing connections to other
Erlang nodes.
Generated Stub Files
The generated stub files are:
-
For each IDL interface, a C source file, the name of which
is .c]]>. Each operation of the
IDL interface is mapped to a C function (with scoped name)
in that file;
-
C source files that contain functions for type conversion,
memory allocation, and data encoding/decoding;
-
C header files that contain function prototypes and type
definitions.
All C functions are exported (i.e. not declared static).
C Interface Functions
For each IDL operation a C interface function is
generated, the prototype of which is:
( oe_obj, , CORBA_Environment *oe_env);]]>
where
-
]]> is the value to be returned as defined
by the IDL specification;
-
oe_obj]]> is the client interface
object;
-
]]> is a list of parameters of the
operation, defined in the same order as defined by the IDL
specification;
-
CORBA_Environment *oe_env is a pointer to the current
client environment. It contains the current file descriptor,
the current input and output buffers, etc. For details see
CORBA_Environment C Structure.
Generating, Compiling and Linking
To generate the C client stubs type the following in an
appropriate shell:
,
where ICROOT is the root of the IC application. The
-I ICROOT/include is only needed if File.idl
refers to erlang.idl.
When compiling a generated C stub file, the directories
ICROOT/include and EICROOT/include, have to be
specified as include directories, where EIROOT is the
root directory of the Erl_interface application.
When linking object files the EIROOT/lib and
ICROOT/priv/lib directories have to be specified.
An Example
In this example the IDL specification file "random.idl" is used
for generating C client stubs (the file is contained in the IC
/examples/c-client directory):
Generate the C client stubs:
Six files are generated.
Compile the C client stubs:
Please read the ReadMe file att the
examples/c-client directory
In the same
directory you can find all the code for this example.
In particular you will find the client.c file that contains
all the additional code that must be written to obtain a complete
client.
In the examples/c-client directory you will also find
source code for an Erlang server, which can be used for testing
the C client.