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<HEAD>
  <TITLE>IDL to C mapping</TITLE>
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<A NAME="6"><!-- Empty --></A>
<H2>6 IDL to C mapping</H2>
<A NAME="6.1"><!-- Empty --></A>
<H3>6.1 Introduction</H3>

<P> The IC C mapping (used by the C client and C server back-ends) follows
the <STRONG>OMG C Language Mapping Specification</STRONG>. 

<P> The C mapping supports the following:

<P>
<UL>

<LI>
                 All OMG IDL basic types except <CODE>long double</CODE> and <CODE>any</CODE>.
        <BR>


</LI>


<LI>
                 All OMG IDL constructed types.
        <BR>


</LI>


<LI>
                 OMG IDL constans.
        <BR>


</LI>


<LI>
                 Operations with passing of parameters and receiving of
         results. <CODE>inout</CODE> parameters are not supported.
        <BR>


</LI>


</UL>

<P>The following is not supported:


<P>
<UL>

<LI>
                 Access to attributes.
        <BR>


</LI>


<LI>
                 User defined exceptions.
        <BR>
 <BR>

</LI>


<LI>
                 User defined objects.
        <BR>
 <BR>

</LI>


</UL>
<A NAME="6.2"><!-- Empty --></A>
<H3>6.2 C Mapping Characteristics</H3>
<A NAME="6.2.1"><!-- Empty --></A>
<H4>6.2.1 Reserved Names</H4>

<P>     The IDL compiler reserves all identifiers starting with
        <CODE>OE_</CODE> and <CODE>oe_</CODE> for internal use.
<A NAME="6.2.2"><!-- Empty --></A>
<H4>6.2.2 Scoped Names</H4>

<P>     The C programmer must always use the global name for a type,
        constant or operation. The C global name corresponding to an
        OMG IDL global name is derived by converting occurrences of
        &#34;::&#34; to underscore, and eliminating the leading &#34;::&#34;. So, for
        example, an operation <CODE>op1</CODE> defined in interface
        <CODE>I1</CODE> which is defined in module <CODE>M1</CODE> would be
        written as <CODE>M1::I1::op1</CODE> in IDL and as <CODE>M1_I1_op1</CODE>
        in C.

<P>
<TABLE CELLPADDING=4>
  <TR>
    <TD VALIGN=TOP><IMG ALT="Warning!" SRC="warning.gif"></TD>
    <TD>

<P>      If underscores are used in IDL names it can lead to
         ambiguities due to the name mapping described above,
         therefore it is advisable to avoid underscores in
         identifiers.
            </TD>
  </TR>
</TABLE>
<A NAME="6.2.3"><!-- Empty --></A>
<H4>6.2.3 Generated Files</H4>

<P>     Two files will be generated for each scope. One set of files
        will be generated for each module and each interface scope.
        An extra set is generated for those definitions at top
        level scope. One of the files is a header file(<CODE>.h</CODE>), and the 
        other file is a C source code file (<CODE>.c</CODE>). In addition to these 
        files a number of C source files will be generated for type encodings,
        they are named according to the following template:
        <CODE>oe_code_&#60;type&#62;.c</CODE>.

<P>     For example:

<PRE>
// IDL, in the file &#34;spec.idl&#34;
module m1 {

    typedef sequence&#60;long&#62; lseq;
   
    interface i1 {
        ...
    };
    ...
};
      
</PRE>

<P>     XXX This is C client specific.
        Will produce the files <CODE>oe_spec.h</CODE> and
        <CODE>oe_spec.c</CODE> for the top scope level. Then the files
        <CODE>m1.h</CODE> and <CODE>m1.c</CODE> for the module <CODE>m1</CODE> and
        files <CODE>m1_i1.h</CODE> and <CODE>m1_i1.c</CODE> for the interface
        <CODE>i1</CODE>. The typedef will produce <CODE>oe_code_m1_lseq.c</CODE>.

<P>     The header file contains type definitions for all
        <CODE>struct</CODE> types and sequences and constants in the IDL file. The
        c file contains all operation stubs if the the scope is an interface.

<P>     In addition to the scope-related files a C source file will
        be generated for encoding operations of all <CODE>struct</CODE> and
        sequence types.
<A NAME="6.3"><!-- Empty --></A>
<H3>6.3 Basic OMG IDL Types</H3>

<P> The mapping of basic types is as follows.

<P>
<CENTER>
<TABLE CELLSPACING=0 CELLPADDING=2 BORDER=1>
  <CAPTION ALIGN=BOTTOM><EM>OMG IDL Basic Types</EM></CAPTION>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
<STRONG>OMG IDL type</STRONG>
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
<STRONG>C type</STRONG>
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
<STRONG>Mapped to C type</STRONG>
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
float
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_float
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
float
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
double
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_double
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
double
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
short
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned short
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
char
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
char
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
wchar
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
boolean
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_boolean
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned char
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
octet
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_octet
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
char
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
any
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Not supported
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">

    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long double
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Not supported
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">

    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Object
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Not supported
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">

    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
void
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
void
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
void
    </TD>

  </TR>

</TABLE>
</CENTER>

<P> XXX Note that several mappings are not according to OMG C Language
mapping.
<A NAME="6.4"><!-- Empty --></A>
<H3>6.4 Constructed OMG IDL Types</H3>

<P> Constructed types have mappings as shown in the following table.

<P>
<CENTER>
<TABLE CELLSPACING=0 CELLPADDING=2 BORDER=1>
  <CAPTION ALIGN=BOTTOM><EM>OMG IDL Constructed Types</EM></CAPTION>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
OMG IDL type
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Mapped to C type
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
string
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
wstring
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
enum
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
enum
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
sequence
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct (see below)
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array
    </TD>

  </TR>

</TABLE>
</CENTER>

<P> An OMG IDL sequence (an array of variable length), 

<PRE>
// IDL
typedef sequence &#60;IDL_TYPE&#62; NAME;
    
</PRE>

<P> is mapped to a C struct as follows:

<PRE>
/* C */
typedef struct {
  CORBA_unsigned_long _maximum;
  CORBA_unsigned_long _length;
  C_TYPE* _buffer;
} C_NAME;
    
</PRE>

<P> where <CODE>C_TYPE</CODE> is the mapping of <CODE>IDL_TYPE</CODE>, and where
<CODE>C_NAME</CODE> is the scoped name of <CODE>NAME</CODE>.
<A NAME="6.5"><!-- Empty --></A>
<H3>6.5 OMG IDL Constants</H3>

<P> An IDL constant is mapped to a C constant through a C
<CODE>#define</CODE> macro, where the name of the macro is scoped.
Example:

<PRE>
// IDL
module M1 {
    const long c1 = 99;
};
    
</PRE>

<P>results in the following:
<PRE>
/* C */
#define M1_c1 99
    
</PRE>
<A NAME="6.6"><!-- Empty --></A>
<H3>6.6 OMG IDL Operations</H3>

<P> An OMG IDL operation is mapped to C function. Each C operation
function has two mandatory parameters: a first parameter of
<STRONG>interface object</STRONG> type, and a last parameter of
<STRONG>environment</STRONG> type.

<P>

<P> In a C operation function the the <CODE>in</CODE> and <CODE>out</CODE>
parameters are located between the first and last parameters
described above, and they appear in the same order as in the IDL
operation declaration.

<P> Notice that <CODE>inout</CODE> parameters are not supported. 

<P>

<P> The return value of an OMG IDL operation is mapped to a
corresponding return value of the C operation function.

<P> Mandatory C operation function parameters:

<P>
<UL>

<LI>
        <CODE>CORBA_Object oe_obj</CODE> - the first parameter of a C
        operation function. This parameter is required by the <STRONG>OMG
        C Language Mapping Specification</STRONG>, but in the current
        implementation there is no particular use for it.

</LI>


<LI>
        <CODE>CORBA_Environment* oe_env</CODE> - the last parameter of a C
        operation function. The parameter is defined in the C header
        file <CODE>ic.h</CODE> and has the following public fields:
        
<UL>

<LI>
         <CODE>CORBA_Exception_type _major</CODE> - indicates if an
         operation invocation was successful which will be one of
         the following:
         
<UL>

<LI>
CORBA_NO_EXCEPTION
</LI>


<LI>
CORBA_SYSTEM_EXCEPTION
</LI>


</UL>

         
</LI>


<LI>
         int <STRONG>_fd</STRONG> - a file descriptor returned from
         <STRONG>erl_connect</STRONG> function.
         
</LI>


<LI>
         int <STRONG>_inbufsz</STRONG> - size of input buffer.
         
</LI>


<LI>
         char* <STRONG>_inbuf</STRONG> - pointer to a buffer used for
         input.
         
</LI>


<LI>
         int <STRONG>_outbufsz</STRONG> - size of output buffer.
         
</LI>


<LI>
         char* <STRONG>_outbuf</STRONG> - pointer to a buffer used for
         output.
         
</LI>


<LI>
                        int <STRONG>_memchunk</STRONG> - expansion unit size for the
                output buffer. This is the size of memory chunks in
                bytes used for increasing the output in case of buffer
                expansion. The value of this field must be always set
                to &#62;= 32, should be at least 1024 for performance
                reasons.
         <BR>

         
</LI>


<LI>
         char <STRONG>regname[256]</STRONG> - a registered name for a
         process.
         
</LI>


<LI>
         erlang_pid* <STRONG>_to_pid</STRONG> - an Erlang process
         identifier, is only used if the registered_name parameter
         is the empty string.
         
</LI>


<LI>
         erlang_pid* <STRONG>_from_pid</STRONG> - your own process id so
         the answer can be returned
         
</LI>


</UL>
  Beside the public fields, other private fields
         are internally used but are not mentioned here. <BR>


</LI>


</UL>

<P>Example:
<PRE>
// IDL
interface i1 {
    long op1(in long a); 
    long op2(in string s, out long count);
};
    
</PRE>

<P> Is mapped to the following C functions
<PRE>
/* C */ 
CORBA_long i1_op1(i1 oe_obj, CORBA_long a, CORBA_Environment* oe_env)
{
    ...
}
CORBA_long i1_op2(i1 oe_obj, CORBA_char* s, CORBA_long *count,
CORBA_Environment* oe_env)
{
    ...
}
    
</PRE>
<A NAME="op_impl"><!-- Empty --></A><A NAME="6.6.1"><!-- Empty --></A>
<H4>6.6.1 Operation Implementation</H4>

<P>      There is no standard CORBA mapping for the C-server side,
        as it is implementation-dependent but built in a similar way.
        The current server side mapping is different from the client
        side mapping in several ways:

<P>
<UL>

<LI>
         Argument mappings
         
</LI>


<LI>
         Result values
         
</LI>


<LI>
         Structure
         
</LI>


<LI>
         Usage
         
</LI>


<LI>
         Exception handling
         
</LI>


</UL>
<A NAME="6.7"><!-- Empty --></A>
<H3>6.7 Exceptions</H3>

<P> Although exception mapping is not implemented, the stubs will
generate CORBA system exceptions in case of operation failure.
Thus, the only exceptions propagated by the system are built in
system exceptions.
<A NAME="6.8"><!-- Empty --></A>
<H3>6.8 Access to Attributes</H3>

<P> Not Supported
<A NAME="6.9"><!-- Empty --></A>
<H3>6.9 Summary of Argument/Result Passing for the C-client</H3>

<P> The user-defined parameters can only be <CODE>in</CODE> or <CODE>out</CODE>
parameters, as 
<CODE>inout</CODE> parameters are not supported.

<P> This table summarize the types a client passes as arguments to
a stub, and receives as a result.

<P>
<CENTER>
<TABLE CELLSPACING=0 CELLPADDING=2 BORDER=1>
  <CAPTION ALIGN=BOTTOM><EM>Basic Argument and Result passing</EM></CAPTION>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
OMG IDL type
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
In
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Out
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Return
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_short*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_short
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long_long*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_long_long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_short*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_short
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long_long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long_long*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_unsigned_long_long
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
float
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_float
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_float*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_float
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
double
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_double
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_double*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_double
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
boolean
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_boolean
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_boolean*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_boolean
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
char
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
wchar
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
octet
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_octet
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_octet*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_octet
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
enum
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_enum
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_enum*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_enum
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct, fixed
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct, variable
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct**
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union, fixed
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union, variable
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union**
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
union*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
string
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char**
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_char*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
wstring
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar**
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
CORBA_wchar*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
sequence
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
sequence*
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
sequence**
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
sequence*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array, fixed
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array_slice*
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array, variable
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array_slice**
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array_slice*
    </TD>

  </TR>

</TABLE>
</CENTER>

<P> A client is responsible for providing storage of all arguments passed 
as <STRONG>in</STRONG> arguments.

<P>
<CENTER>
<TABLE CELLSPACING=0 CELLPADDING=2 BORDER=1>
  <CAPTION ALIGN=BOTTOM><EM>Client argument storage responsibility</EM></CAPTION>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
OMG IDL type
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Out
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Return
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
long long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned short
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
unsigned long long
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
float
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
double
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
boolean
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
char
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
wchar
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
octet
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
enum
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct, fixed
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
struct, variable
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
string
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
wstring
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
sequence
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array, fixed
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
3
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
array, variable
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
3
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
3
    </TD>

  </TR>

</TABLE>
</CENTER>

<P>
<CENTER>
<TABLE CELLSPACING=0 CELLPADDING=2 BORDER=1>
  <CAPTION ALIGN=BOTTOM><EM>Argument passing cases</EM></CAPTION>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Case
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
Description
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
1
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
         Caller allocates all necessary storage, except that which may
         be encapsulated and managed within the parameter itself.
        
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
2
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
         The caller allocates a pointer and passes it by reference to the
         callee. The callee sets the pointer to point to a valid instance of
         the parameter's type. The caller is responsible for releasing the
         returned storage. Following completion of a request, the caller is 
         not allowed to modify any values in the returned storage. To do 
         so the caller must first copy the returned instance into a new 
         instance, then modify the new instance. 
        
    </TD>

  </TR>
  <TR>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
3
    </TD>
    <TD ALIGN="LEFT" VALIGN="MIDDLE">
         
         The caller allocates a pointer to an array slice which has all the 
         same dimensions of the original array except the first, and passes 
         it by reference to the callee. The callee sets the pointer to point 
         to a valid instance of the array. The caller is responsible for 
         releasing the returned storage. Following completion of a request, 
         the caller is not allowed to modify any values in the returned 
         storage. To do so the caller must first copy the returned instance 
         into a new instance, then modify the new instance. 
        
    </TD>

  </TR>

</TABLE>
</CENTER>

<P> The returned storage in case 2 and 3 is allocated as one block of memory
so it is possible to deallocate it with one call of CORBA_free.
<A NAME="6.10"><!-- Empty --></A>
<H3>6.10 Supported Memory Allocation Functions</H3>

<P>
<UL>

<LI>
<STRONG>CORBA_Environment</STRONG> can be allocated from the user by calling 
         <STRONG>CORBA_Environment_alloc()</STRONG>.<BR>

        The interface for this function is <BR>

        <CODE>CORBA_Environment *CORBA_Environment_alloc(int inbufsz, int outbufsz);</CODE>
        where :<BR>

        
<UL>

<LI>
         <STRONG>inbufsz</STRONG> is the desired size of input buffer<BR>

         
</LI>


<LI>
         <STRONG>outbufsz</STRONG> is the desired size of output buffer<BR>

         
</LI>


<LI>
         return value is a <STRONG>pointer</STRONG> to an allocated and initialized 
         <STRONG>CORBA_Environment</STRONG> structure<BR>
         <BR>

</LI>


</UL>


</LI>


<LI>
Strings can be allocated from the user by calling <STRONG>CORBA_string_alloc()</STRONG>.<BR>

        The interface for this function is <BR>

        <CODE>CORBA_char *CORBA_string_alloc(CORBA_unsigned_long len);</CODE>
         <BR>
where :<BR>

         
<UL>

<LI>
         <STRONG>len</STRONG> is the length of the string to be allocated.<BR>

         
</LI>


</UL>


</LI>


</UL>

<P>Thus far, no other type allocation function is supported.<A NAME="6.11"><!-- Empty --></A>
<H3>6.11 Special Memory Deallocation Functions</H3>

<P>
<UL>

<LI>
        <CODE>void CORBA_free(void *storage)</CODE><BR>

         This function will free storage allocated by the stub.<BR>


</LI>


<LI>
        <CODE>void CORBA_exception_free(CORBA_environment *ev)</CODE><BR>

        This function will free storage allocated under exception propagation. 
<BR>

</LI>


</UL>
<A NAME="6.12"><!-- Empty --></A>
<H3>6.12 Exception Access Functions</H3>

<P>
<UL>

<LI>
        <CODE>CORBA_char *CORBA_exception_id(CORBA_Environment *ev)</CODE><BR>

         This function will return raised exception identity.<BR>


</LI>


<LI>
        <CODE>void *CORBA_exception_value(CORBA_Environment *ev)</CODE><BR>

        This function will return the value of a raised exception. 
<BR>

</LI>


</UL>
<A NAME="6.13"><!-- Empty --></A>
<H3>6.13 Special Types</H3>

<P>
<UL>

<LI>
        The erlang binary type has some special features.<BR>
        <BR>
While the <CODE>erlang::binary</CODE> idl type has the same C-definition as 
         a generated sequence of octets :
        <BR>


        
<PRE>
          module erlang
          {

          ....

          // an erlang binary
          typedef sequence&#60;octet&#62; binary;
          
          };
        
</PRE>

         
                 it provides a way on sending trasparent data between C and Erlang.
        <BR>

                 The C-definition (ic.h) for an erlang binary is :
        <BR>
 
        
<PRE>
          typedef struct {
          CORBA_unsigned_long _maximum;
          CORBA_unsigned_long _length;
          CORBA_octet* _buffer;
          } erlang_binary;                        /* ERLANG BINARY */
        
</PRE>

                 The differences (between <CODE>erlang::binary</CODE> and <CODE>sequence&#60; octet &#62;</CODE>) are :
        <BR>

        
<UL>

<LI>
                 on the erlang side the user is sending/receiving typical 
         built in erlang binaries, using <CODE>term_to_binary() / binary_to_term()</CODE> 
         to create / extract binary structures.
         <BR>

         
</LI>


<LI>
                 no encoding/decoding functions are generated
         <BR>

         
</LI>


<LI>
                 the underlying protocol is more efficient than usual sequences of
         octets
         <BR>

         
</LI>


</UL>

                 The erlang binary IDL type is defined in <CODE>erlang.idl</CODE>, while it's 
         C definition is located in the <CODE>ic.h</CODE> header file, both in the 
         <CODE>IC-&#60; vsn &#62;/include</CODE> directory.
         The user will have to include the file <CODE>erlang.idl</CODE> in order to use the
         <CODE>erlang::binary</CODE> type.
        <BR>


</LI>


</UL>
<A NAME="6.14"><!-- Empty --></A>
<H3>6.14 A Mapping Example</H3>

<P> <A NAME="stack_idl"><!-- Empty --></A>
This is a small example of a simple stack. There are two
operations on the stack, push and pop. The example shows all
generated files as well as conceptual usage of the stack.

<PRE>
// The source IDL file: stack.idl

struct s {
      long l;
      string s;
};

interface stack {
    void push(in s val);
    s pop();
};

    
</PRE>

<P> When this file is compiled it produces four files, two for the
top scope and two for the stack interface scope. The important parts 
of the generated C code for the stack API is shown below.<A NAME="stack_serv"><!-- Empty --></A>

<P> stack.c

<PRE>

void push(stack oe_obj, s val, CORBA_Environment* oe_env) {
  ...
}


s* pop(stack oe_obj, CORBA_Environment* oe_env) {
  ...
}


    
</PRE>

<P> oe_stack.h

<PRE>
#ifndef OE_STACK_H
#define OE_STACK_H 


/*------------------------------------------------------------
 * Struct definition: s
 */
typedef struct {
   long l;
   char *s;
} s;



#endif
    
</PRE>

<P> stack.h just contains an include statement of <CODE>oe_stack.h</CODE>.

<P> oe_code_s.c

<PRE>

int oe_sizecalc_s(CORBA_Environment
      *oe_env, int* oe_size_count_index, int* oe_size) {
  ...
}

int oe_encode_s(CORBA_Environment *oe_env, s* oe_rec) {
  ...
}

int oe_decode_s(CORBA_Environment *oe_env, char *oe_first, 
                int* oe_outindex, s *oe_out) {
  ...
}

    
</PRE>

<P> The only files that are really important are the <CODE>.h</CODE>
files and the stack.c file.
<CENTER>
<HR>
<SMALL>
Copyright &copy; 1991-2006
<A HREF="http://www.erlang.se">Ericsson AB</A><BR>
</SMALL>
</CENTER>
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