This document describes the specific mapping of Software AG IDL data types, groups, arrays and structures to the C programming language. Please note also the remarks and hints on the IDL data types valid for all language bindings found in the IDL file.
This document covers the following topics:
In the table below, the following metasymbols and informal terms are used for the IDL.
The metasymbols "[" and "]" enclose optional lexical entities.
The informal term number (or in some cases number1.number2) is a sequence of numeric characters, for example 123.
| Software AG IDL | Description | C Data Type | Note |
|---|---|---|---|
Anumber |
Alphanumeric | unsigned char [number] |
1,3 |
char [number + 1] |
1,3 | ||
AV |
Alphanumeric variable length | ERX_HVDATA |
4 |
AVnumber |
Alphanumeric variable length with maximum length | ERX_HVDATA |
3,4 |
Bnumber |
Binary | unsigned char [number] |
3 |
BV |
Binary variable length | ERX_HVDATA |
4 |
BVnumber |
Binary variable length with maximum length | ERX_HVDATA |
4 |
D |
Date | unsigned char [ERX_GET_PACKED_LEN(7)] |
3,5,8,12,14,15 |
F4 |
Floating point (small) | float |
11 |
F8 |
Floating point (large) | double |
11 |
I1 |
Integer (small) | signed char |
|
I2 |
Integer (medium) | signed short |
|
I4 |
Integer (large) | signed long |
|
Knumber |
Kanji | unsigned char [number] |
3 |
KV |
Kanji variable length | ERX_HVDATA |
4 |
KVnumber |
Kanji variable length with maximum length | ERX_HVDATA |
3,4 |
L |
Logical | unsigned char |
6 |
Nnumber1[.number2] |
Unpacked decimal | double |
9 |
unsigned char[number1 +
number2] |
7,9 | ||
NUnumber1[.number2] |
Unpacked decimal unsigned | double |
9 |
unsigned char[number1 +
number2] |
7,9 | ||
Pnumber1[.number2] |
Packed decimal | double |
10 |
unsigned char[ERX_GET_PACKED_LEN(number1 + number2)] |
8,10 | ||
PUnumber1[.number2] |
Packed decimal unsigned | double |
10 |
unsigned char[ERX_GET_PACKED_LEN(number1 + number2)] |
8,10 | ||
T |
Time | unsigned char[ERX_GET_PACKED_LEN(13)] |
5,8,13,14,16 |
Unumber |
Unicode | wchar_t[number] |
2,17,18 |
wchar [number + 1] |
2,17,18 | ||
UV |
Unicode variable length | ERX_HVDATA |
4,17 |
UVnumber |
Unicode variable length with maximum length | ERX_HVDATA |
4,17,19 |
See also the hints and restrictions valid for all language bindings under IDL Data Types.
Notes:
unsigned char[..] without null termination (mainframe
Natural, COBOL, PL/I style) or C style string (C data type char[.. + 1] with
null termination). The mapping is controlled with the
Mapping Options when you
generate source files from IDL. See Generate C Source Files from Software AG IDL Files.
wchar_t[..] without null termination (mainframe
Natural, COBOL, PL/I style) or to a C style wide character string ( C data type
wchar_t[.. + 1] with null termination). The mapping is controlled with the
Mapping Options when you
generate source files from IDL. See Generate C Source Files from Software AG IDL Files.
ERX_HVDATA is an
RPC-specific data type in the header file erxVData.h for
handling variable-length data types. See
API Function Descriptions for Variable-length Data Types AV, BV, KV and UV.
FALSE.
Contents other than a binary zero are treated as TRUE.
ERX_GET_PACKED_LENGTH is a macro within the header file
erx.h used to evaluate the length of a field in bytes with
packed contents.
For unpacked, the total number of digits (number1+number2) is 99.
For double, it depends on your target environment how many significant digits are supported. In most environments 15 - 16
digits, which means for exact results the total number of digits (number1+number2) should be less than 16.
If you connect two endpoints, the total number of digits used must be lower or equal than the maxima of both endpoints. For the supported total number of digits for endpoints, see the notes under data types N, NU, P and PU in section Mapping IDL Data Types to target language environment C | CL | COBOL | DCOM | .NET | Java | Natural | PL/I | RPG | XML.
double or packed.
The mapping is controlled with the
Mapping Options when you
generate source files from IDL. See Generate C Source Files from Software AG IDL Files.
For unpacked the total number of digits (number1+number2) is 99.
For double, it depends on your target environment how many significant digits are supported. In most environments 15 - 16
digits, which means for exact results the total number of digits (number1+number2) should be less than 16.
If you connect two endpoints, the total number of digits used must be lower or equal than the maxima of both endpoints. For the supported total number of digits for endpoints, see the notes under data types N, NU, P and PU in section Mapping IDL Data Types to target language environment C | CL | COBOL | DCOM | .NET | Java | Natural | PL/I | RPG | XML.
float and double, rounding errors can occur, so that the values of senders and receivers
might differ.
| 1. | Years that are evenly divisible by 4 are leap years. |
| 2. | Years that are evenly divisible by 100 are not leap years unless rule 3, below, is true. |
| 3. | Years that are evenly divisible by 400 are leap years. |
| 4. | Before the year 1582 AD, rule 1 from the Julian calendar is used. After the year 1582 AD, rules 1, 2 and 3 of the Gregorian calendar are used. |
See the following table for the relation of the packed number to a real date:
| Date / Range of Dates | Value / Range of Values |
| 1.1.0000 | 0 (special value - no date) |
| undefined dates | 1 - 364 (do not use) |
| 1.1.0001 | 365 |
| 1.1.1970 | 719527 (start of C-time functions) |
| 28.11.2737 | 999999 (maximum date) |
| Time / Range of Times | Value / Range of Values |
| 1.1.0000 00:00:00.0 | 0 (special value - no time) |
| undefined times | 1 - 315359999 |
| 1.1.0001 00:00:00.0 | 315360000 |
| 1.1.1970 00:00:00.0 | 621671328000 (start of C-time functions) |
| tenths of a second per day | =24*60*60*10 = 864000 | ||
| number of time | = number of date | * 864000 | |
| 315360000 | = 365 | * 864000 | 1.1.0001 00:00:00.0 |
| 621671328000 | = 719527 | * 864000 | 1.1.1970 00:00:00.0 |
| number of date | = number of time | / 864000 | |
| 365 | = 315360000 | / 864000 | 1.1.0001 |
| 719527 | = 621671328000 | / 864000 | 1.1.1970 |
no date value is the
internal state of a #DATE (Natural type D) variable after a RESET #DATE is
executed within Natural programs. This internal state is not a valid date. The
no date value can be transferred as the invalid date 1.1.0 from RPC
clients to servers and vice versa. C Wrapper supports Natural no
date value. C Wrapper passes 0 to the C application when no
date is received. With the same value of 0, the C application can send
no date to its partner (client or server).
no time value is the
internal state of a #TIME (Natural type T) variable after a RESET #TIME is
executed within Natural programs. This internal state is not a valid time. The
no time value can be transferred as the invalid time 1.1.0 0:00:00.0
from RPC clients to servers and vice versa. C Wrapper supports
Natural no time value. C Wrapper passes 0 to the C application when
no time is received. With the same value of 0, the C application can
send no time to its partner (client or server).
wchar_t data type in your environment:
Size of wchar_t |
UTF Version Used |
|---|---|
| 2 bytes (Windows and some UNIX environments) | UTF-16 |
| 4 bytes (some other UNIX environments) | UTF-32 |
The endianness (big endian or little endian) of the Unicode encoding that is used (UTF-16-LE, UTF-16-BE, UTF32-LE or UTF32-BE) is the same as the hardware architecture of the machine.
sizeof(wchar_t) is 4 bytes, only Unicode characters from the
Basic Multilingual Plane are supported (code points U+0000 to U+FFFF except U+D800 to U+DFFF reserved for leading and trailing
surrogates). Unicode characters from Supplementary Planes (code points U+10000 to U+10FFFF)
are not supported.
sizeof(wchar_t) is 4 bytes,
the number of UTF-16 Unicode code points (after character conversion from UTF-32 to UTF-16)
must be less than or equal to number. Please note the following:
Unicode characters from the Basic Multilingual Plane (code points U+0000 to U+FFFF except U+D800 to U+DFFF, reserved for leading and trailing surrogates) require one code point in UTF-16
Unicode characters from Supplementary Planes (code points U+10000 to U+10FFFF) require two code points in UTF-16
The library name as specified in the IDL file is sent from a client to the server. Special characters are not replaced. The library alias is not sent to the server.
In the RPC server, the IDL library name sent may be used to locate the target server. See Locating and Calling the Target Server under z/OS (CICS, Batch, IMS) | C | .NET | Micro Focus | BS2000 | z/VSE (CICS, Batch).
The library name as given in the IDL file is used to compose the names
of the generated output files. See library-definition under Software AG IDL Grammar in the IDL Editor documentation.
Therefore the allowed characters are restricted by the underlying file
system.
For the server interface object, the name is composed with a prefix D
as Dlibrary-name.c and for the
server as library-name.c. For
the client interface object the name is composed with a prefix C as
Clibrary name.c. For both
interface objects the same header file
Clibrary-name.h is also used.
When the name of the generated sources is built, lower and uppercase characters
are considered and the special characters '#', '$', '&', '+', '-', '.', '/'
and '@' used in the name for libraries are replaced by the character underscore
'_'. Other special characters used in the library name are not changed and may
lead to problems with your underlying file system.
Aliases for the library name in the IDL file are not supported in
C Wrapper language binding. See library-definition.
Examples:
A library name of #HU$GO. results in C_HU_GO_.c and C_HU_GO_.h as the
client interface object file name for the generated source.
A library name of #HU$GO. results in D_HU_GO_.c and C_HU_GO_.h as the
server interface object file name for the generated source.
The program name is sent from a client to the server. Special characters are not replaced. The program alias is not sent to the server.
In the RPC server, the IDL program name sent is used to locate the target server. See Locating and Calling the Target Server under z/OS (CICS, Batch, IMS) | C | .NET | Micro Focus | BS2000 | z/VSE (CICS, Batch).
The program names as given in the IDL file are mapped to functions
within the generated C sources. See program-definition under Software AG IDL Grammar in the IDL Editor documentation. When building function names,
lower and uppercase characters are considered and the special characters '#',
'$', '&', '+', '-', '.', '/' and '@' are replaced by the character
underscore '_' valid for C names. Other special characters used in the program
name are not changed and may lead to compilation errors when compiling the
generated sources.
Aliases for the program name in the
program-definition are not supported in C Wrapper
language binding.
A parameter name of #HU$GO. results in _HU_GO_ as the function name
for the C programming language.
The parameter names as given in the IDL file are mapped to parameters
of the generated C functions. See parameter-data-definition under Software AG IDL Grammar in the IDL Editor documentation. When building parameters,
lower and uppercase characters are considered and the special characters '#',
'$', '&', '+', '-', '.', '/' and '@' are replaced by the character
underscore '_' valid for C names.
Examples:
A parameter name of #HU$GO. results in _HU_GO_ as the parameter name
for the C programming language.
Fixed arrays within the IDL file are mapped to fixed C arrays. The
upper bound given in the IDL file is decremented by 1 because C arrays always
start with the lower bound 0. For example the number (I2/5) in the IDL
file will be mapped to signed short number [4].
See the array-definition under Software AG IDL Grammar in the IDL Editor documentation for the syntax on
how to describe fixed arrays within the IDL file and refer to
fixed-bound-array-index.
Unbounded arrays within the IDL file are mapped to the ERX_HARRAY
data type found in the header file erxArray.h. See
Using Unbounded Arrays for more information.
See the array-definition for the syntax of
unbounded arrays within the IDL file and refer to
unbounded-array-index.
Groups within the IDL file are mapped to the C data type
struct. See the group-parameter-definition under Software AG IDL Grammar in the IDL Editor documentation
for the syntax on how to describe groups within the IDL file.
Structures within the IDL file are mapped to the C data type
struct like groups. See structure-definition for
the syntax on how to describe structures within the IDL file.
The IDL syntax allows you to define parameters as IN parameters, OUT
parameters, or IN OUT parameters (which is the default if nothing is
specified). This direction specification is reflected in the generated C
interface object as follows:
Parameters with the IN attribute are
sent from the RPC client to the RPC server. When the parameter is a simple
parameter (that is, no fixed or unbounded array, no group and no structure) the
parameter is provided with the method call by value. Complex parameters such as
fixed and unbounded arrays, groups and structures are provided with the call by
reference method.
Parameters with the OUT attribute are
sent from the RPC server to the RPC client. They are always provided with the
call by reference method.
Parameters with the IN and
OUT attribute are sent from the RPC client to
the RPC server and then back to the RPC client. They are always provided with
the call by reference method.
Note that only the direction information of the top-level fields (level 1) is relevant. Group fields always inherit the specification from their parent. A different specification is ignored.
See the attribute-list for the syntax on how to
describe attributes within the IDL file and refer to direction
attribute.
The ALIGNED Attribute is not relevant for the programming language C.
However, a C client can send the ALIGNED attribute to an RPC server where it
might be needed.
See the attribute-list for the syntax of attributes
in the IDL file and refer to the aligned attribute.
The IDL syntax allows definitions of procedures only. It does not have the concept of a function. A function is a procedure which, in addition to the parameters, returns a value. Procedures and functions are transparent between clients and servers. This means a client using a function can call a server implemented as a procedure and vice versa.
It is possible to call the remote procedure as a function and not as a procedure, if you prefer it and if it suits your interface.
The function float sin(float x) will be called
as a function - and not as a procedure - when defined in the IDL file as
follows:
Library ... is
Program 'sin' is
Define Data Parameter
1 x (F4) In
1 Function_Result (F4) Out
End-Define
it can be invoked as :
y = sin(x);
When you generate source files from IDL (see Generate C Source Files from Software AG IDL Files), a C function instead of a C procedure is generated if the following is true for the interface description in the IDL file:
The last parameter's name is function_result.
The name function_result is not case-sensitive.
The last parameter's direction is Out. See attribute-list.
The last parameter is a scalar variable, that is, not an array.
The last parameter is of type and length:
| Software AG IDL | Description | Note |
|---|---|---|
I1 |
Integer (small) | 2 |
I2 |
Integer (medium) | 2 |
I4 |
Integer (large) | 2 |
A1 |
Alphanumeric with length 1 | 2 |
B1 |
Binary with length 1 | 2 |
L |
Logical | 2 |
Nnumber
[.number] |
Unpacked decimal | 1, 2 |
Pnumber [.number] |
Packed decimal | 1, 2 |
NUnumber [.number] |
Unpacked decimal unsigned | 1, 2 |
PUnumber [.number] |
Packed decimal unsigned | 1, 2 |
Notes: