How to pass a structure in PL/SQL external proc.

Question

This is for educational purpose only. I am trying to implement kernel32.dll and shell32.dll in PL/SQL using external proc. Everything is working fine, except When there is a structure in OUT parameter.
My database version.
SQL> SELECT * FROM v$version;
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Prod
PL/SQL Release 10.2.0.3.0 - Production
CORE    10.2.0.3.0      Production
TNS for 32-bit Windows: Version 10.2.0.3.0 - Production
NLSRTL Version 10.2.0.3.0 - ProductionI have set up the listner.ora and tnsnames.ora and written a package called dbms_kernel32sb.
There are 9 program units.
1. CreateFile -- working fine
2. CloseFile -- working fine
3. GetSize -- working fine
4. FindFirstFile -- NOT working, because one OUT parameter has the structure type WIN32_FIND_DATA.
5. GetFileTime -- NOT working, because one OUT parameter has the structure type FILETIME
6. GetDiskFreeSpace -- working fine
7. GetDriveType -- working fine.
8. GetLastError -- working fine
9. ExecuteCommand -- working fine.
Here is the package specification:
CREATE OR REPLACE PACKAGE dbms_kernel32sb AS
    Name: dbms_kernel32sb.pks
    Author: Saubhik Banerjee
    Date: 24th Jan 2011
    Version: 1.0
    Comment: This package is to implement some functionality from kernel32.dll.
             Usng extproc
OPEN_EXISTING_FILE CONSTANT PLS_INTEGER :=3;
FILE_ATTRIBUTE_NORMAL CONSTANT PLS_INTEGER :=128;
DISABLE_FILE_SHARE_MODE CONSTANT PLS_INTEGER :=0;
NO_FILE_SECURITY_ATTRIBUTE CONSTANT PLS_INTEGER :=0;
NO_TEMPLATE_FILE CONSTANT PLS_INTEGER :=0;
GENERIC_FILE_ACCESS CONSTANT PLS_INTEGER :=0;
FILE_SIZE_HIGH CONSTANT PLS_INTEGER :=400000000;
EXECUTE_FILE CONSTANT VARCHAR2(4):='open';
PRINT_FILE CONSTANT VARCHAR2(5):='print';
NO_PARAMATER CONSTANT VARCHAR2(2):=' ';
FUNCTION CreateFile(pi_FileName VARCHAR2 --1, File name
            ,pi_DesiredAccess BINARY_INTEGER --2, Type of access required (read/write ect)
            ,pi_ShareMode BINARY_INTEGER --3,  share mode
            ,pi_SecurityAttributes BINARY_INTEGER --4, securoty attribute
            ,pi_CreationDisposition BINARY_INTEGER --5, open existing, create new etc
            ,pi_FlagsAndAttributes BINARY_INTEGER --6, File attribute- normal
            ,pi_TemplateFile BINARY_INTEGER) --Not required.
    Return BINARY_INTEGER;
FUNCTION CloseFile (pi_FileHandle BINARY_INTEGER)
                     Return BINARY_INTEGER;
FUNCTION GetSize (pi_FileHandle BINARY_INTEGER,
                   pio_FileSizeHigh IN OUT BINARY_INTEGER)
               RETURN BINARY_INTEGER;
FUNCTION FindFirstFile ( pi_FileName VARCHAR2
                         ,pio_Win32_Find_data OUT 
                             WIN32_FIND_DATA
RETURN BINARY_INTEGER;                                             
FUNCTION GetFileTime ( pi_FileHandle BINARY_INTEGER
                       ,pio_FileCreationTime IN OUT FILETIME
                       ,pio_LastAccessTime   IN OUT FILETIME
                       ,pio_LastWriteTime    IN OUT FILETIME
RETURN BINARY_INTEGER;
FUNCTION GetDiskFreeSpace ( pi_RootPathName VARCHAR2
                            ,pio_SectorsPerCluster  OUT BINARY_INTEGER
                            ,pio_BytesPerSector   OUT BINARY_INTEGER
                            ,pio_NumberOfFreeClusters  OUT BINARY_INTEGER
                            ,pio_TotalNumberOfClusters  OUT BINARY_INTEGER
RETURN BINARY_INTEGER;    
FUNCTION GetDriveType( pi_driveLetter VARCHAR2) RETURN VARCHAR2;
FUNCTION GetLastError RETURN BINARY_INTEGER;   
FUNCTION ExecuteCommand ( pi_OperationType VARCHAR2
                          ,pi_FileName VARCHAR2
                          ,pi_Parameters VARCHAR2
                          ,pi_DefaultDirectory VARCHAR2
RETURN VARCHAR2;
END dbms_kernel32sb;
Here is the package body:
CREATE OR REPLACE PACKAGE BODY dbms_kernel32sb AS
/* Name: dbms_kernel32sb.pkb
    Author: Saubhik Banerjee
    Date: 24th Jan 2011
    Version: 1.0
    Comment: This package is to implement some functionality from kernel32.dll.
             Usng extproc
  FUNCTION
  CreateFile( pi_FileName VARCHAR2 --1
            , pi_DesiredAccess BINARY_INTEGER --2
            , pi_ShareMode BINARY_INTEGER --3
            , pi_SecurityAttributes BINARY_INTEGER --4
            , pi_CreationDisposition BINARY_INTEGER --5
            , pi_FlagsAndAttributes BINARY_INTEGER --6
            , pi_TemplateFile BINARY_INTEGER) --7
    Return BINARY_INTEGER IS EXTERNAL LIBRARY kernel32 Name "CreateFileA"
    PARAMETERS(  pi_FileName STRING
               , pi_DesiredAccess long
               , pi_ShareMode long
               , pi_SecurityAttributes long
               , pi_CreationDisposition long
               , pi_FlagsAndAttributes long
               , pi_TemplateFile long
               , return long);
FUNCTION CloseFile (pi_FileHandle BINARY_INTEGER)
                     Return BINARY_INTEGER
     IS EXTERNAL
     LIBRARY kernel32 Name "CloseHandle"
     PARAMETERS (pi_FileHandle long, return long);
FUNCTION GetSize (pi_FileHandle BINARY_INTEGER,
                   pio_FileSizeHigh IN OUT BINARY_INTEGER)
               RETURN BINARY_INTEGER
     IS EXTERNAL
    LIBRARY kernel32 NAME "GetFileSize"
    PARAMETERS (pi_FileHandle long, pio_FileSizeHigh long, return long );
  FUNCTION GetFileTime ( pi_FileHandle BINARY_INTEGER
                       ,pio_FileCreationTime IN OUT FILETIME
                       ,pio_LastAccessTime   IN OUT FILETIME
                       ,pio_LastWriteTime    IN OUT FILETIME
   RETURN BINARY_INTEGER
     IS EXTERNAL
    LIBRARY kernel32 NAME "GetFileTime"
    WITH CONTEXT
    PARAMETERS ( CONTEXT,
                  pi_FileHandle long
                , pio_FileCreationTime  OCIColl
                , pio_FileCreationTime INDICATOR SHORT
                , pio_LastAccessTime  OCIColl
               , pio_LastAccessTime INDICATOR SHORT
                , pio_LastWriteTime OCIColl
                , pio_LastWriteTime INDICATOR SHORT
                , return long );                  
FUNCTION FindFirstFile ( pi_FileName VARCHAR2
                         ,pio_Win32_Find_data OUT 
                             WIN32_FIND_DATA
RETURN BINARY_INTEGER
IS EXTERNAL
    LIBRARY kernel32 NAME "FindFirstFileA"
    --WITH CONTEXT
    PARAMETERS
                ( --CONTEXT,
                 pi_FileName STRING--, pi_FileName INDICATOR SHORT
                , pio_Win32_Find_data  BY REFERENCE OCIColl--,pio_Win32_Find_data INDICATOR long
                , return long );
FUNCTION GetDiskFreeSpace ( pi_RootPathName VARCHAR2
                            ,pio_SectorsPerCluster  OUT BINARY_INTEGER
                            ,pio_BytesPerSector   OUT BINARY_INTEGER
                            ,pio_NumberOfFreeClusters  OUT BINARY_INTEGER
                            ,pio_TotalNumberOfClusters  OUT BINARY_INTEGER
RETURN BINARY_INTEGER
  IS EXTERNAL
    LIBRARY kernel32 NAME "GetDiskFreeSpaceA"
    PARAMETERS (  pi_RootPathName STRING
                , pio_SectorsPerCluster BY REFERENCE long
                , pio_BytesPerSector BY REFERENCE long
                , pio_NumberOfFreeClusters BY REFERENCE long
                , pio_TotalNumberOfClusters BY REFERENCE long
                , return long );   
  FUNCTION GetDriveTypeA( pi_driveLetter VARCHAR2) RETURN BINARY_INTEGER   
  IS EXTERNAL
  LIBRARY kernel32 NAME "GetDriveTypeA"
  PARAMETERS (pi_driveLetter STRING, RETURN long);
FUNCTION GetDriveType( pi_driveLetter VARCHAR2) RETURN VARCHAR2 IS
BEGIN
  CASE  GetDriveTypeA(pi_driveLetter) 
   WHEN 2 THEN RETURN 'Removable';
   WHEN 3 THEN RETURN 'Drive Fixed';
   WHEN 4 THEN RETURN 'Remote';
   WHEN 5 THEN RETURN 'Cd-Rom';
   WHEN 6 THEN RETURN 'Ram disk';
   ELSE RETURN 'Unrecognized';
END CASE;                              
END;
FUNCTION GetLastError  RETURN BINARY_INTEGER
IS EXTERNAL
LIBRARY kernel32 NAME "GetLastError"
PARAMETERS (return long);
FUNCTION ShellExecute( pi_Hwnd BINARY_INTEGER
                      ,pi_Operation VARCHAR2
                      ,pi_FileName VARCHAR2
                      ,pi_Parameters VARCHAR2
                      ,pi_DefaultDirectory  VARCHAR2
                      ,pi_ShowCmd BINARY_INTEGER
                      ) RETURN BINARY_INTEGER
IS EXTERNAL
LIBRARY SHELL32 NAME "ShellExecuteA"
PARAMETERS (pi_Hwnd long,pi_Operation STRING,pi_FileName STRING
             ,pi_Parameters STRING,pi_DefaultDirectory STRING
             ,pi_ShowCmd long, return long
FUNCTION ExecuteCommand ( pi_OperationType VARCHAR2
                          ,pi_FileName VARCHAR2
                          ,pi_Parameters VARCHAR2
                          ,pi_DefaultDirectory VARCHAR2
RETURN VARCHAR2 IS
  v_return_val BINARY_INTEGER;
BEGIN
  v_return_val:= ShellExecute(0,pi_OperationType
                             ,pi_FileName,pi_Parameters
                             ,pi_DefaultDirectory,0
  IF v_return_val <=32 THEN
   RETURN 'Error!';
  ELSE RETURN 'Success!';
  END IF;
END;
END dbms_kernel32sb;
Now the working demos:
SQL> SET SERVEROUT ON
SQL> /* Demo I:- How to obtain file size */
SQL> DECLARE
  2    v_FileSize BINARY_INTEGER;
  3    v_FileSizeHigh PLS_INTEGER;
  4    v_FileHandle BINARY_INTEGER;
  5    v_filename VARCHAR2(500) :='C:\test2.csv';
  6    v_dummy BINARY_INTEGER;
  7  BEGIN
  8    v_FileSizeHigh := DBMS_KERNEL32SB.FILE_SIZE_HIGH;
  9    v_FileHandle:=DBMS_KERNEL32SB.CreateFile(v_filename -- File name
10                            ,DBMS_KERNEL32SB.GENERIC_FILE_ACCESS
11                            ,DBMS_KERNEL32SB.DISABLE_FILE_SHARE_MODE
12                            ,DBMS_KERNEL32SB.NO_FILE_SECURITY_ATTRIBUT
13                            ,DBMS_KERNEL32SB.OPEN_EXISTING_FILE
14                            ,DBMS_KERNEL32SB.FILE_ATTRIBUTE_NORMAL
15                            ,DBMS_KERNEL32SB.NO_TEMPLATE_FILE);
16   v_FileSize := DBMS_KERNEL32SB.Getsize(v_FileHandle, v_FileSizeHigh)
17   DBMS_OUTPUT.put_line('File Size in Bytes: ' ||v_FileSize);
18   v_dummy:=DBMS_KERNEL32SB.CloseFile(v_FileHandle);
19  END;
20  /
File Size in Bytes: 61
PL/SQL procedure successfully completed.
SQL>
SQL> /* Demo II:- How to find free disk space  */
SQL> DECLARE
  2    v_rootpath VARCHAR2(500) :='C:\';
  3    v_dummy BINARY_INTEGER;
  4    v_sectorspercluster BINARY_INTEGER;
  5    v_bytespersector BINARY_INTEGER;
  6    v_numberoffreeclusters BINARY_INTEGER;
  7    v_totalnumberofclusters BINARY_INTEGER;
  8    v_freespace NUMBER;
  9    v_totalspace NUMBER;
10  BEGIN
11    v_dummy:=DBMS_KERNEL32SB.GetDiskFreeSpace(v_rootpath
12                                              ,v_sectorspercluster
13                                              ,v_bytespersector
14                                              ,v_numberoffreeclusters
15                                              ,v_totalnumberofclusters
16                                              );
17                                              
18    DBMS_OUTPUT.put_line('Sector pre Cluster: ' ||v_sectorspercluster);
19    DBMS_OUTPUT.put_line('Bytes per sector: ' ||v_bytespersector);
20    DBMS_OUTPUT.put_line('Number Of Free Clusters: ' ||v_numberoffreeclusters);
21    DBMS_OUTPUT.put_line('Total Number Of Clusters: ' ||v_totalnumberofclusters);
22    v_freespace:=v_numberoffreeclusters/1024/1024/1024;
23    v_freespace:=ROUND(v_freespace*v_sectorspercluster*v_bytespersector,3);
24    v_totalspace:=v_totalnumberofclusters/1024/1024/1024;
25    v_totalspace:=ROUND(v_totalspace*v_sectorspercluster*v_bytespersector,3);
26    DBMS_OUTPUT.put_line('Total Space (GB):' ||v_totalspace);
27    DBMS_OUTPUT.put_line('Total number of Free space (GB): '||v_freespace );
28  END;
29  /
Sector pre Cluster: 8
Bytes per sector: 512
Number Of Free Clusters: 739477
Total Number Of Clusters: 9765622
Total Space (GB):37.253
Total number of Free space (GB): 2.821
PL/SQL procedure successfully completed.
SQL>
SQL> /* Demo IV:- How to get drive type*/
SQL> SELECT dbms_kernel32sb.GetDriveType('C:\') FROM dual;
DBMS_KERNEL32SB.GETDRIVETYPE('C:\')
Drive Fixed
SQL> SELECT dbms_kernel32sb.GetDriveType('D:\') FROM dual;
DBMS_KERNEL32SB.GETDRIVETYPE('D:\')
Cd-Rom
SQL> SELECT dbms_kernel32sb.GetDriveType('E:\') FROM dual;
DBMS_KERNEL32SB.GETDRIVETYPE('E:\')
Unrecognized
SQL>
SQL> /* Demo V:- How to execute an Operating System Command*/
SQL> DECLARE
  2   v_FileToExecute VARCHAR2(20):='test.bat';
  3   v_Parameter VARCHAR2(20):='test1.csv';--dbms_kernel32sb.NO_PARAMATER
  4   v_DefaultDirectory VARCHAR2(20):='C:\';
  5   v_ReturnValue VARCHAR2(20);
  6  BEGIN
  7    v_ReturnValue:=dbms_kernel32sb.ExecuteCommand(dbms_kernel32sb.EXECUTE_FILE
  8                                                  ,v_FileToExecute
  9                                                  ,v_Parameter
10                                                  ,v_DefaultDirectory
11                                                  );
12   DBMS_OUTPUT.put_line('Status: '||v_ReturnValue);                               
13  END;
14  /
Status: Success!
PL/SQL procedure successfully completed.
SQL> Now the sub programs with structures are NOT getting called successfully.
SQL> /* Demo III:- How to obtain file time */
SQL> DECLARE
  2    v_FileHandle BINARY_INTEGER;
  3    v_filename VARCHAR2(500) :='C:\test2.csv';
  4    v_dummy BINARY_INTEGER;
  5    v_filecreationtime FILETIME;
  6    v_lastaccesstime FILETIME;
  7    v_lastwritetime FILETIME;
  8    v_err BINARY_INTEGER;
  9  BEGIN
10    v_FileHandle:=DBMS_KERNEL32SB.CreateFile(v_filename -- File name
11                            ,DBMS_KERNEL32SB.GENERIC_FILE_ACCESS
12                            ,DBMS_KERNEL32SB.DISABLE_FILE_SHARE_MODE
13                            ,DBMS_KERNEL32SB.NO_FILE_SECURITY_ATTRIBUTE
14                            ,DBMS_KERNEL32SB.OPEN_EXISTING_FILE
15                            ,DBMS_KERNEL32SB.FILE_ATTRIBUTE_NORMAL
16                            ,DBMS_KERNEL32SB.NO_TEMPLATE_FILE);
17   v_dummy := DBMS_KERNEL32SB.GetFileTime( v_FileHandle
18                                          ,v_filecreationtime
19                                          ,v_lastaccesstime
20                                          ,v_lastwritetime
21                                          );
22   v_err:=DBMS_KERNEL32SB.GetLastError;                                
23   DBMS_OUTPUT.put_line('File Size in Bytes: ' ||v_dummy);
24   DBMS_OUTPUT.put_line('Error:'||v_err);
25   v_dummy:=DBMS_KERNEL32SB.CloseFile(v_FileHandle);
26  END;
27  /
File Size in Bytes: 0
Error:203
PL/SQL procedure successfully completed.
SQL> So, I have noticed that, Where ever a STRUCTURE is involved in external routine, there is a problem. I want to know, How to implement functions with STRUCTURE as OUT parameter.
Forgot to mention: This is my FILETIME object which corresponds to FILETIME structure of win32.
CREATE OR REPLACE TYPE FILETIME_rec IS OBJECT
                          ( LowDateTime NUMBER
                           ,HighDateTime NUMBER
CREATE OR REPLACE TYPE FILETIME IS TABLE OF  FILETIME_rec;Edited by: Saubhik on Feb 1, 2011 4:15 PM

Answer 1

Saubhik wrote:
This is for educational purpose only. I am trying to implement kernel32.dll and shell32.dll in PL/SQL using external proc. Interesting. Familiar with the Wn32 API, but do not run Oracle on Windows and never looked at this aspect of integration.
So, I have noticed that, Where ever a STRUCTURE is involved in external routine, there is a problem. I want to know, How to implement functions with STRUCTURE as OUT parameter.
Forgot to mention: This is my FILETIME object which corresponds to FILETIME structure of win32.The problem is that this passes the parameter by reference and not value. In a vanilla C/C++/Delphi program, you will create a variable of that struct and then pass a long pointer to that variable when making the API call. That pointer will be dereferenced and the memory it points to, populated. This is not a problem as the underlying DLL you call that does this, uses your process's data segment.
Extproc is different. In order to protect the integrity of the database server process, an external call is done by a "proxy" process. It acts as the interface between your PL/SQL code and the actual external call.
In this case, this "proxy" process will be doing the implicit LoadLibrary() call to load kernel32.dll interface - and the DLL will expect to dereference and access this process's memory struct to populate it. This "proxy" process in turn needs to know that despite it calling the interface by reference, it needs to return that parameter to PL/SQL by value - as your PL/SQL code cannot dereference a pointer passed back by that "proxy" process and access its memory to gain access to that struct.
In basic terms - that argument is a 32 bit number containing a pointer. That is what the "proxy" process needs to pass to the interface call. Your code is passing a struct and not a pointer, right?
And that is the basic problem I believe. How to address this.. not sure. You can have your own DLL as interface that does not use pointers but expect arguments to be passed by value. But this will suck as you then need to include a custom DLL to deploy and have PL/SQL call that, instead of simply accessing and calling the native kernel interface.
Doubt that many Win32 programmers with OCI (Oracle Call Interface) frequents this forum. So perhaps this is not the best place to ask. I would be hitting Metalink (support.oracle.com) search function in your sho3s though as there should be support notes dealing with this subject matter.