Get Example source ABAP code based on a different SAP table
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ABAP_OBJ - Kernel Methods For internal use, kernel methods can be implemented in the ABAP kernel instead of in the ABAP language.
Introduction Kernel methods provide the option of directly calling the ABAP kernel functions implemented in C or C++. Kernel methods replace the previous concepts of C calls and system calls. The introduction of new C calls and system calls should be avoided. Kernel methods offer the same checks and security features as regular ABAP methods. Except for the constructors and the C destructor, all ABAP methods can be implemented as kernel methods. An ABAP method can furthermore be redefined as a kernel method and a kernel method can still be redefined as an ABAP method within a path of the inheritance hierarchy. For C developers who want to implement a kernel method, an API is available that enables simple, high-performance, and secure access to arguments. Class-based exceptions also continue to be supported.
Defining Kernel Methods
Declaration in ABAP A kernel method is declared like a regular ABAP method, either in the Class Builder or in the declaration part of a local class. Whether a method is implemented as a kernel method is completely irrelevant for the declaration. In ABAP, this means that a kernel method can be used just like a regular ABAP method.
Implementation in ABAP The determination of a method as a kernel method is made in the implementation part of the class using the optional addition BY KERNEL MODULE kmod1 kmod2 ... of the statement METHOD. kmod1 , kmod2, ... are the names of kernel modules that implement the method. The ABAP implementation of a kernel method must be empty, which means that there must be no ABAP statements between METHOD and ENDMETHOD: METHOD meth BY KERNEL MODULE kmod1 kmod2 ... ENDMETHOD. Constructors and the C destructor cannot be implemented as kernel methods. There is a separate mechanism for the C Destructor. After ABAP_KEY KERNEL MODULE, a list of kernel modules kmod1 , kmod2, ... can be specified. Currently, only C functions of the kernel can be specified for kmod1, kmod2, ....The list after KERNEL MODULE is evaluated by the compiler from left to right. The first kernel module in the list that is registered in the kernel (see below) is used during generation. If no valid kernel module is found in the list, a syntax error occurs. There are also two standard C functions that can appear at the end of the list: FAIL and IGNORE. If one of these functions is specified at the end of the list, a syntax error is avoided if no valid module is found in the previous list. IGNORE is used to ignore the call of a kernel method of this type (behavior as in an empty ABAP implementation); for FAIL, a catchable exception of the class CX_SY_DYN_CALL_ILLEGAL_METHOD is raised.
ABAP_EXAMPLES METHOD meth BY KERNEL MODULE xx_impl_630 xx_impl_620 xx_impl_610. First, the kernel is searched for xx_impl_630. Then the kernel is searched for xx_impl_620, and finally for xx_impl_610. If none of these functions are found, a syntax error occurs. METHOD meth BY KERNEL MODULE xx_impl_630 xx_impl_620 FAIL. First, the kernel is searched for xx_impl_630. Then the kernel is searched for xx_impl_620. If neither of these functions are found, a syntax error is not raised, but a catchable exception of the class CX_SY_DYN_CALL_ILLEGAL_METHOD is raised when the method is called. METHOD meth BY KERNEL MODULE xx_impl_620 xx_impl_610 IGNORE. First, the kernel is searched for xx_impl_620. Then the kernel is searched for xx_impl_620. If none of the functions are found, a syntax error is not raised, but the empty ABAP implementation is called instead, when the method is called. ABAP_EXAMPLE_END
Implementation in the Kernel Currently, only C functions can be used as kernel modules of kernel methods. The C functions can have any position in the kernel. No special includes of the ABAP runtime framework are required for implementing the C function. The C functions must have a specific interface. The interface itself is wrapped by a macro called ARGUMENTS. All required definitions and prototypes are in the include //src/include/abkmeth.h. This is the only include needed for defining C functions for kernel methods. Since C functions can be defined in C and C++, you must use externC in C++: #include 'abkmeth.h' ... externC void name_of_cmodule( ARGUMENTS ) { ... } A C function that implements a kernel method must be registered for the kernel method. If, after METHOD meth BY KERNEL MODULE, the name of a C function is specified that was not registered for the kernel method, the syntax error mentioned above occurs. Multiple C functions can be registered for a kernel method. The sequence of the kernel modules kmod1, kmod2, ... specified in the list after METHOD meth BY KERNEL MODULE defines which of the registered C functions is used. This allows further downward-compatible development of kernel methods. To make changes to the registration active, the target lib of the project krn/runt must be recompiled and the kernel relinked.
Registration C functions are registered in the signature file //src/krn/runt/abkmeth.sig using the following syntax for kernel methods where all ABAP IDs must be specified in uppercase letters: KERNEL_METHOD('CLASS','METH', cfunc,argcnt) This definition registers the C function cfunc for the kernel method meth of a global class class. The C function expects a number of argcnt arguments. Kernel methods of local classes in class pools or other ABAP programs are registered using the following macros: KERNEL_METHOD_CLASS_LOCAL('GCLASS','CLASS','METH',cmodule,argcnt) KERNEL_METHOD_PROGRAM_LOCAL('PROG','CLASS','METH',cmodule,argcnt) The effect is the same as with KERNEL_METHOD, except that the global class gclass must be specified for local classes in class pools and the program prog for program-local classes.
Registering Arguments All ABAP data objects, such as parameters, attributes, or global data, which are to be accessed in C functions for kernel methods, are handled as arguments of the C function. The argument list of a C function for a kernel method is not limited to the interface parameters of the ABAP method and does not have to contain these completely. Before arguments can be accessed within C functions for kernel methods, they must also be registered. The argcnt arguments must be registered immediately after the C function is registered using KERNEL_METHOD. A single argument is defined (registered) using one of the following macros: ARGUMENT_basetype(index,'name',type_kind,'type',read_write) ARGUMENT_$[C$|N$|X$](index,'name',type_kind,'type',read_write ,length) ARGUMENT_P(index,'name',type_kind,'type',read_write,length,decimals) ARGUMENT_STRUCT(index,'name',type_kind,'type',read_write,ctype) These macros define an argument with the name name and an index index. basetype must be used to assign the actual type of the ABAP data object according to the following table. If the basetype is C , N, X, P, or STRUCT , more parameters must be specified than for the other types. basetypeABAP Data TypeType in C Cc with specified lengthSAP_CHAR (*) $[Length$] C_GENERICc without specified lengthSAP_CHAR* Xx with specified lengthSAP_RAW (*) $[Length$] X_GENERICx without specified lengthSAP_RAW* Nn with specified lengthSAP_CHAR (*) $[Length$] N_GENERICn without specified lengthSAP_CHAR* Pp with specified length and decimalsSAP_BCD (*) $[Length$] P_GENERICp without specified length and decimals SAP_BCD* DdSAP_DATE* TtSAP_TIME* UTCLONGutclongSAP_LLONG* IiSAP_INT* INT1bSAP_INT1* INT2sSAP_SHORT* INT8int8SAP_LLONG* FfSAP_DOUBLE* DECFLOAT16decfloat16DecFloat16 DECFLOAT34decfloat34DecFloat34 STRINGstringStrRef* XSTRINGxstringStrRef* TABLEAll table typesTABH_REF* OBJ_REFAll object referencesObjRef* DATA_REFAll data referencesFldRef* STRUCTAll structure typesRegistered type ctype* ANYanyvoid* DATAdatavoid* SIMPLEsimplevoid* CSEQUENCEcsequencevoid* XSEQUENCExsequencevoid* NUMERICnumericvoid* CLIKEclikeSAP_CHAR* C_POINTER%_c_pointervoid** The macro parameters have the following meanings:
name is the identification of any ABAP data object in uppercase letters that could also be used in an ABAP implementation of the kernel method. In particular, the identifier can contain relationships specified using component selectors, for example me->attr or struc-comp.
index is a sequential number from 1 to argcnt. The arguments are accessed using this index.
For type_kind you can specify either TYPE or TYPE_REF_TO.
type is the identifier of any ABAP data type in uppercase letters that could also be used in an ABAP implementation of the kernel method. type_kind and type are used to check the interface of the kernel method in ABAP.
For read_write, either READ or WRITE can be specified. This determines whether there is read or write access to the argument and is evaluated in the access macros.
In the case of ARGUMENT_$[C$|N$|X$|P$], length must be used to specify the length of all ABAP data types with a generic length. For c and n in characters and in bytes for x and p.
When using ARGUMENT_P, decimals must be used to specify the number of decimal places.
For ARGUMENT_STRUCT, ctype must be used to specify a suitable C type. This type should be generated from an ABAP type definition using saphfile.
Accessing Arguments After registering the arguments, the following macros can be used to access them within the C function. Except for direct access to the data control block, the access macros do not require any includes from the ABAP runtime framework. ARGUMENT_basetype_READ(index,'name'); This macro returns the read address of an argument with the type const ctype, where ctype is defined by basetype according to the table above. The index and name of the argument must be passed. Additional parameters must be specified for the generic types (see below). Only the index is needed to access the argument. However, to make the C function more legible to execute additional consistency checks, the name must also be specified. If the kernel is compiled in debugging mode, the system performs a consistency check between the index and name; the specified C type and the ABAP type of the argument are still checked. In the case of an error, an appropriate ABAP runtime error is raised (KMETH_INVALID_ARGUMENT_ID , KMETH_INVALID_ARGUMENT_NAME, or KMETH_INVALID_CTYPE_LENG ). No checks are performed in the optimized kernel. ARGUMENT_basetype_WRITE(index,'name'); This macro has the same semantics as ARGUMENT_basetype_READ. However, the system returns the write address. The system also checks whether the argument was defined as a write argument. Write access to a read-only argument (for example, a constant), this raises the ABAP runtime error KMETH_ARGUMENT_READ_ONLY. ARGUMENT_$[C$|N$]_READ(index,'name',lengthU); ARGUMENT_$[C$|N$]_WRITE(index,'name',lengthU); ARGUMENT_X_READ(index,'name',lengthR); ARGUMENT_X_WRITE(index,'name',lengthR); If these macros are used, the expected length in bytes lengthR or in characters lengthU must be specified for the generic types c, x, and n. ARGUMENT_P_READ(index,'name',lengthR,decimals); ARGUMENT_P_WRITE(index,'name',lengthR,decimals); If these macros are used, the expected length must be specified in bytes (lengthR) and the number of decimal places (decimals ) for the generic type p. ARGUMENT_$[C_GENERIC$|N_GENERIC$|CLIKE$]_READ(index,'name',size_tU); ARGUMENT_$[C_GENERIC$|N_GENERIC$|CLIKE$]_WRITE(index,'name' ,size_tU); ARGUMENT_X_GENRIC_READ(index,'name',size_tR); ARGUMENT_X_GENERIC_WRITE(index,'name',size_tR); If these macros are used, a variable of the type size_tU or size_tR containing the length in bytes or characters must be specified for the types C_GENERIC, X_GENERIC, N_GENERIC, and CLIKE. ARGUMENT_P_GENERIC_READ(index,'name',size_tR,decimals); ARGUMENT_P_GENERIC_WRITE(index,'name',size_tR,decimals); If these macros are used, a variable decimals for the decimal places, as well as the length size_tR must be specified for the type P_GENERIC.
