See If a LOB Locator Is Initialized

Figure 9-30 Use Case Diagram: See If a LOB Locator Is Initialized

See: "Use Case Model: Internal Persistent LOBs Basic Operations", for all basic operations of Internal Persistent LOBs.

Purpose

This procedure describes how to see if a LOB locator is initialized.

Usage Notes

Not applicable.

Syntax

See Chapter 3, "LOB Programmatic Environments" for a list of available functions in each programmatic environment. Use the following syntax references for each programmatic environment:

• PL/SQL (DBMS_LOB Package): There is no applicable syntax reference for this use case.

• C (OCI): Oracle Call Interface Programmer's Guide Chapter 15, "Relational Functions" -- OciLobLocatorIsInit.

• COBOL (Pro*COBOL): There is no applicable syntax reference for this use case.

• C/C++ (Pro*C/C++) (Pro*C/C++ Precompiler Programmer's Guide): Appendix F, "Embedded SQL Statements and Directives". See C(OCI), OciLobLocatorIsInit.

• Visual Basic (OO4O): There is no applicable syntax reference for this use case.

• Java (JDBC): There is no applicable syntax reference for this use case.

Scenario

The operation allows you to determine if the locator has been initialized or not. In the example shown both locators are found to be initialized.

Examples

Examples are provided in the following programmatic environments:

• PL/SQL (DBMS_LOB Package): No example is provided with this release.

• C (OCI): See If a LOB Locator Is Initialized

• COBOL (Pro*COBOL): No example is provided with this release.

• C/C++ (Pro*C/C++): See If a LOB Locator Is Initialized

• Visual Basic (OO4O): No example is provided with this release.

• Java (JDBC): No example is provided with this release.

C (OCI): See If a LOB Locator Is Initialized

/* Select the locator: */
sb4 select_frame_locator(Lob_loc, errhp, svchp, stmthp)
OCILobLocator *Lob_loc;
OCIError      *errhp;
OCISvcCtx     *svchp;
OCIStmt       *stmthp;     
{
  text      *sqlstmt = 
                 (text *)"SELECT Frame FROM Multimedia_tab WHERE Clip_ID=1";
  OCIDefine *defnp1;
  checkerr (errhp, OCIStmtPrepare(stmthp, errhp, sqlstmt, 
                                  (ub4)strlen((char *)sqlstmt),
                                  (ub4) OCI_NTV_SYNTAX, (ub4) OCI_DEFAULT));
  checkerr (errhp, OCIDefineByPos(stmthp, &defnp1, errhp, (ub4) 1,
                                  (dvoid *)&Lob_loc, (sb4)0, 
                                  (ub2) SQLT_BLOB,(dvoid *) 0, 
                                  (ub2 *) 0, (ub2 *) 0, (ub4) OCI_DEFAULT));

  /* Execute the select and fetch one row: */
  checkerr(errhp, OCIStmtExecute(svchp, stmthp, errhp, (ub4) 1, (ub4) 0,
                                 (CONST OCISnapshot*) 0, (OCISnapshot*) 0,  
                                 (ub4) OCI_DEFAULT));
  return (0);
}

void isInitializedLob(envhp, errhp, svchp, stmthp)
OCIEnv    *envhp;
OCIError  *errhp;
OCISvcCtx *svchp;
OCIStmt   *stmthp;
{
  OCILobLocator *Lob_loc1, *Lob_loc2;
  boolean       isInitialized;

  /* Allocate the LOB locators: */
  printf(" allocate locator 1 and 2\n");
  (void) OCIDescriptorAlloc((dvoid *) envhp, (dvoid **) &Lob_loc1,
                         (ub4)OCI_DTYPE_LOB, (size_t) 0, (dvoid **) 0);
  (void) OCIDescriptorAlloc((dvoid *) envhp, (dvoid **) &Lob_loc2, 
                            (ub4)OCI_DTYPE_LOB, (size_t) 0, (dvoid **) 0);

  /* Select the LOBs: */
  printf (" select a frame locator into locator 1\n");
  select_frame_locator(Lob_loc1, errhp, svchp, stmthp);         /* locator 1 */

  /* Determine if the locator 1 is Initialized -: */
  checkerr(errhp, OCILobLocatorIsInit(envhp, errhp, Lob_loc1, &isInitialized));
                                    /* IsInitialized should return TRUE here */
  printf(" for Locator 1, isInitialized = %d\n", isInitialized);

  /* Determine if the locator 2 is Initialized -: */
  checkerr(errhp, OCILobLocatorIsInit(envhp, errhp, Lob_loc2, &isInitialized));
                                    /* IsInitialized should return FALSE here */
  printf(" for Locator 2, isInitialized = %d\n", isInitialized);

  /* Free resources held by the locators: */
  (void) OCIDescriptorFree((dvoid *) Lob_loc1, (ub4) OCI_DTYPE_LOB);
  (void) OCIDescriptorFree((dvoid *) Lob_loc2, (ub4) OCI_DTYPE_LOB);
  return;
  }

C/C++ (Pro*C/C++): See If a LOB Locator Is Initialized

/* Pro*C/C++ has no form of embedded SQL statement to determine if a LOB
   locator is initialized.  Locators in Pro*C/C++ are initialized when they
   are allocated via the EXEC SQL ALLOCATE statement. However, an example
   can be written that uses embedded SQL and the OCI as is shown here: */

#include <sql2oci.h>
#include <stdio.h>
#include <sqlca.h>

void Sample_Error()
{
  EXEC SQL WHENEVER SQLERROR CONTINUE;
  printf("%.*s\n", sqlca.sqlerrm.sqlerrml, sqlca.sqlerrm.sqlerrmc);
  EXEC SQL ROLLBACK WORK RELEASE;
  exit(1);
}

void LobLocatorIsInit_proc()
{
  OCIBlobLocator *Lob_loc;
  OCIEnv *oeh;
  OCIError *err;
  boolean isInitialized;

  EXEC SQL WHENEVER SQLERROR DO Sample_Error();
  EXEC SQL ALLOCATE :Lob_loc;
  EXEC SQL SELECT Frame INTO Lob_loc
           FROM Multimedia_tab where Clip_ID = 1;
  /* Get the OCI Environment Handle using a SQLLIB Routine: */
  (void) SQLEnvGet(SQL_SINGLE_RCTX, &oeh);
  /* Allocate the OCI Error Handle: */
  (void) OCIHandleAlloc((dvoid *)oeh, (dvoid **)&err,
                        (ub4)OCI_HTYPE_ERROR, (ub4)0, (dvoid **)0);
  /* Use the OCI to determine if the locator is Initialized: */
  (void) OCILobLocatorIsInit(oeh, err, Lob_loc, &isInitialized);
  if (isInitialized)
    printf("The locator is initialized\n");
  else
    printf("The locator is not initialized\n");
  /* Note that in this example, the locator is initialized */
  /* Deallocate the OCI Error Handle: */
  (void) OCIHandleFree(err, OCI_HTYPE_ERROR);
  /* Release resources held by the locator: */
  EXEC SQL FREE :Lob_loc;
}

void main()
{
  char *samp = "samp/samp";
  EXEC SQL CONNECT :samp;
  LobLocatorIsInit_proc();
  EXEC SQL ROLLBACK WORK RELEASE;
}