Passing Parameters to External C Procedures with Call Specifications

NAME "C_demoExternal"

LIBRARY SomeLib

WITH CONTEXT

PARAMETERS(CONTEXT, x INT, y STRING, z OCIDATE);

END;

CREATE OR REPLACE PACKAGE BODY Demo_pack AS

PROCEDURE plsToC_InBodyOld_proc (x BINARY_INTEGER, y VARCHAR2, z DATE) AS EXTERNAL

LANGUAGE C

NAME "C_InBodyOld" LIBRARY SomeLib WITH CONTEXT

PARAMETERS(CONTEXT, x INT, y STRING, z OCIDATE);

PROCEDURE plsToC_demoExternal_proc (x BINARY_INTEGER, y VARCHAR2, z DATE) AS LANGUAGE C

NAME "C_demoExternal" LIBRARY SomeLib

WITH CONTEXT

PARAMETERS(CONTEXT, x INT, y STRING, z OCIDATE);

PROCEDURE plsToC_InBody_proc (x BINARY_INTEGER, y VARCHAR2, z DATE) AS LANGUAGE C

NAME "C_InBody"

LIBRARY SomeLib WITH CONTEXT

PARAMETERS(CONTEXT, x INT, y STRING, z OCIDATE);

PROCEDURE plsToJ_InBody_proc (x BINARY_INTEGER, y VARCHAR2, z DATE) IS LANGUAGE JAVA

NAME 'pkg1.class4.J_InBody_meth(int,java.lang.String,java.sql.Date)';

END;

Passing Parameters to External C Procedures with Call Specifications

Call specifications allows a mapping between PL/SQL and C datatypes. See "Specifying Datatypes" for datatype mappings.

Passing parameters to an external C procedure is complicated by several circumstances:

■The available set of PL/SQL datatypes does not correspond one-to-one with the set of C datatypes.

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Passing Parameters to External C Procedures with Call Specifications

■Unlike C, PL/SQL includes the RDBMS concept of nullity. Therefore, PL/SQL parameters can be NULL, whereas C parameters cannot.

■The external procedure might need the current length or maximum length of

CHAR, LONG RAW, RAW, and VARCHAR2 parameters.

■The external procedure might need character set information about CHAR, VARCHAR2, and CLOB parameters.

■PL/SQL might need the current length, maximum length, or null status of values returned by the external procedure.

In the following sections, you learn how to specify a parameter list that deals with these circumstances.

Note: The maximum number of parameters that you can pass to a C external procedure is 128. However, if you pass float or double parameters by value, then the maximum is less than 128. How much less depends on the number of such parameters and your operating system. To get a rough estimate, count each float or double passed by value as two parameters.

Specifying Datatypes

Do not pass parameters to an external procedure directly. Instead, pass them to the PL/SQL subprogram that published the external procedure. Therefore, you must specify PL/SQL datatypes for the parameters. PL/SQL datatypes map to default external datatypes, as shown in Table 8–1.

Table 8–1 Parameter Datatype Mappings

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Passing Parameters to External C Procedures with Call Specifications

TIMESTAMP WITH TIME

ZONE

TIMESTAMP WITH LOCAL

TIME ZONE

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Passing Parameters to External C Procedures with Call Specifications

Table 8–1 (Cont.) Parameter Datatype Mappings

1 This PL/SQL type will only compile if you use AS EXTERNAL in your callspec.

External Datatype Mappings

Each external datatype maps to a C datatype, and the datatype conversions are performed implicitly. To avoid errors when declaring C prototype parameters, refer to Table 8–2, which shows the C datatype to specify for a given external datatype and PL/SQL parameter mode. For example, if the external datatype of an OUT parameter is STRING, then specify the datatype char * in your C prototype.

Table 8–2 External Datatype Mappings

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Passing Parameters to External C Procedures with Call Specifications

Table 8–2 (Cont.) External Datatype Mappings

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