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ORDERS Database Model Program (Continued)
Updating an Entry
(USER SELECTS 7 TO DO AN UPDATE)
ROUTINE: Update_A_Customer
* OBJECTIVE: This routine updates a customer record interactively.
* Updating is achieved by using the key item value to
* locate the proper entry. It then displays the contents
* to be updated.
*
* To perform the actual update, a TurboIMAGE/XL
* transaction is started. The entry is retrieved using
* a re-read mode, and an item level lock is obtained using
* the search value. A contents check of the new values
* is done against the old values. If the contents have
* changed, the user can choose to abort the process. Otherwise,
* the transaction proceeds and the update takes place.
*
* ACCESS: Mode 1 - Shared Modify Access
*
* CALLED BY: Main Line
*
* CALLS: DBGET in mode 7 (calculated)
* DBLOCK in mode 5 (unconditional)
* DBBEGIN in mode 1 (transaction begin)
* DBGET in mode 1 (re-read)
* DBUPDATE in mode 1 (update)
* DBEND in mode 1 (transaction end)
* DBUNLOCK in mode 1 (unlock)
BEGIN ROUTINE
Customer_Buffer,
Customer_Buffer_New, and
Customer_Buffer_Old are made up of:
Account
Last-Name
First-Name
Initial
Street-Address
City
State
Zip
Credit-Rating
Lock_Descriptor_Customer_Type is made up of:
Length_Of_Descriptor
Data_Set_Of_Descriptor
Data_Item_Of_Descriptor
Relative_Operator_For_Data_Item
Value_For_Data_Item
Lock_Descriptor_Customer_Array_Type is made up of:
Number_Of_Elements
Lock_Descriptor_Customer_Type
OBTAIN List <---- "@;"
OBTAIN Key_Item_Value <---- user input
CALL DBGET (DBname, Customer_Master, Mode7_Calculated, Status, List,
Customer_Buffer, Key_Item_Value)
ERROR CHECKING
Customer_Buffer_Old <---- Customer_Buffer
DISPLAY Customer_Buffer
OBTAIN Customer_Buffer_New <---- user input
OBTAIN Number_Of_Elements <---- 1
OBTAIN Length_Of_Descriptor <---- 22
OBTAIN Data_Set_Of_Descriptor <---- "CUSTOMER;"
OBTAIN Data_Item_Of_Descriptor <---- "ACCOUNT;"
OBTAIN Relative_Operator_For_Data_Item <---- "_="
OBTAIN Value_For_Data_Item <---- Key_Item_Value
CALL DBLOCK (DBname, Lock_Descriptor_Customer_Array_Type,
Mode5_Unconditional, Status)
ERROR CHECKING
OBTAIN Text <---- "Update entry on Customer set Begin__"
OBTAIN Textlen <---- 18
CALL DBBEGIN (DBname, Text, Mode1_Xbegin, Status, Textlen)
ERROR CHECKING
CALL DBGET (DBname, Customer_Master, Mode1_Reread, Status, List,
Customer_Buffer, Not_Used_Parm)
ERROR CHECKING
If Customer_Buffer is the same as Customer_Buffer_Old
Then continue
Otherwise
Let the user know that the entry has been modified by
another user, end the transaction, and release the locks.
CALL DBUPDATE (DBname, Customer_Master, Mode1_Update, Status, List,
Customer_Buffer_New)
ERROR CHECKING
OBTAIN Text <---- "Update entry on Customer set End"
OBTAIN Textlen <---- 16
CALL DBEND (DBname, Text, Mode1_Xend, Status, Textlen)
ERROR CHECKING
CALL DBUNLOCK (DBname, Customer_Master, Mode1_Unlock, Status)
ERROR CHECKING
END ROUTINE
Deleting an Entry
(USER SELECTS 8 TO DELETE AN ENTRY)
ROUTINE: Delete_A_Product
* OBJECTIVE: This routine deletes an entry from the Product master
* data set. The entry is specified by its key item value.
* Identifying the entry and deleting it are preceded by
* calls to DBLOCK and DBBEGIN to obtain locks and to start
* a new transaction.
*
* When the entry is located, the deletion of the record
* at the current record pointer is done by a call to
* DBDELETE.
*
* The completion of a transaction is achieved by a call
* to DBEND, and outstanding locks on this data set are
* released by a call to DBUNLOCK.
*
* ACCESS: Mode 1 - Shared Modify Access
*
* CALLED BY: Main Line
*
* CALLS: DBLOCK in mode 3 (unconditional)
* DBBEGIN in mode 1 (transaction begin)
* DBGET in mode 7 (calculated read)
* DBDELETE in mode 1 (delete)
* DBEND in mode 1 (transaction end)
* DBUNLOCK in mode 1 (unlock)
BEGIN ROUTINE
Product_Buffer is made up of:
Stock#
Description
CALL DBLOCK (DBname, Product_Master, Mode3_Unconditional, Status)
ERROR CHECKING
OBTAIN List <---- "@;"
OBTAIN Text <---- "Delete entry from Product set Begin_"
OBTAIN Textlen <---- 18
OBTAIN Key_Item_Value <---- "STK30040"
CALL DBBEGIN (DBname, Text, Mode1_Xbegin, Status, Textlen)
ERROR CHECKING
CALL DBGET (DBname, Product_Master, Mode7_Calculated, Status, List,
Product_Buffer, Key_Item_Value)
ERROR CHECKING
CALL DBDELETE (DBname, Product_Master, Mode1_Delete, Status)
ERROR CHECKING
OBTAIN Text <---- "Delete entry from Product set End___"
OBTAIN Textlen <---- 18
CALL DBEND (DBname, Text, Mode1_Xend, Status, Textlen)
ERROR CHECKING
CALL DBUNLOCK (DBname, Product_Master, Mode1_Unlock, Status)
ERROR CHECKING
END ROUTINE
Rewinding a Data Set
(USER SELECTS 9 TO REWIND A DATA SET)
ROUTINE: Rewind_Customer_Set
* OBJECTIVE: This routine rewinds the customer data set by calling
* DBCLOSE in mode 2.
*
* ACCESS: Mode 1 - Shared Modify Access
*
* CALLED BY: Main Line
*
* CALLS: DBCLOSE in mode 2 (rewind)
BEGIN ROUTINE
CALL DBCLOSE (DBname, Customer_Master, Mode2_Rewind, Status)
ERROR CHECKING
END ROUTINE
Obtaining Database Information
(USER SELECTS 10 TO OBTAIN INFORMATION ABOUT A DATA ITEM)
ROUTINE: Get_Data_Item_Info
* OBJECTIVE: This routine obtains information about a data item
* by calling DBINFO in mode 102.
*
* ACCESS: Mode 1 - Shared Modify Access
*
* CALLED BY: Main Line
*
* CALLS: DBINFO in mode 102 (item access)
BEGIN ROUTINE
DBINFO_Buffer is made up of:
Data_Item_Name
Data_Type
Sub_Item_Length
Sub_Item_Count
OBTAIN Data_Item_Name <---- "PURCH-DATE;"
CALL DBINFO (DBname, Data_Item_Name, Mode102_Item, Status, DBINFO_Buffer)
ERROR CHECKING
DISPLAY the DBINFO_Buffer
____________________________________________________________________
Data_Item_Name Data_Type Sub_Item_Length Sub_Item_Count
END ROUTINE
Obtaining Error Messages and Explanations
(USER SELECTS 11 TO OBTAIN ERROR MESSAGES AND ADDITIONAL
ERROR-RELATED INFORMATION)
ROUTINE:Get_Error_And_Explain
* OBJECTIVE: This routine generates an error message, corresponding
* to the existing value in the first word of the status
* parameter, by calling the DBERROR intrinsic.
* Additionally, the routine generates a description
* regarding the outstanding error message by calling the
* DBEXPLAIN intrinsic.
*
* ACCESS: Mode 1 - Shared Modify Access
*
* CALLED BY: Main Line
*
* CALLS: DBERROR
* DBEXPLAIN
BEGIN ROUTINE
Error_Buffer is made up of:
Error_Message
CALL DBERROR (Status, Error_Buffer, Error_Length)
DISPLAY the Error_Buffer
____________________________________________________________________
Error_Message
CALL DBEXPLAIN (Status)
END ROUTINE
Closing the Database
(USER SELECTS 12 TO CLOSE THE DATABASE)
ROUTINE: Close_The_Database
* OBJECTIVE: This routine closes the ORDERS database by calling
* the DBCLOSE intrinsic.
*
* ACCESS: Mode 1 - Shared Modify Access
*
* CALLED BY: Main Line
*
* CALLS: DBCLOSE in mode 1 (close)
BEGIN ROUTINE
CALL DBCLOSE (DBname, Not_Used_Parm, Mode1_Close, Status)
ERROR CHECKING
END ROUTINE
C
This section shows, in C, portions of the model program presented at the
beginning of this chapter. The examples perform specific tasks to
illustrate the use of TurboIMAGE/XL intrinsics. The C example does not
illustrate everything in the COBOL example. Some blocks of code may be
appropriate only if expanded to a full program.
Data items are defined at the beginning of the sample program.
TurboIMAGE/XL intrinsics must be declared for C as external procedures.
The procedure name is identified by the word "Intrinsic."
Type declarations declare names for data structure forms that will be
used in allocating variables. Variable declarations allocate the
variables of the program. Variables are defined with precise types or
forms. C string literals are delimited with double quotation marks ("
"). Field and record names are separated with a dot (.) when referenced
(for example, base_name.baseid).
NOTE Because the Schema Processor, DBSCHEMA, upshifts alphabetic
characters, programs must specify data set and data item names in
all uppercase characters. Take note of this because C does not
require that you use uppercase characters.
For information on TurboIMAGE/XL data item lengths and type designators,
refer to chapter 3. Tables 3-2 and 3-3 show the TurboIMAGE/XL type
designators, sub-item lengths, and data types typically used to process
them in C.
NOTE All parameters must be on halfword boundaries.
Defining Data Types, Variables, and Intrinsics.
The following is part of the C example program; it defines type
declarations, variable declarations, and TurboIMAGE/XL intrinsics.
#pragma list off
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#pragma list on
/* Define all TurboIMAGE/XL procedure calls that */
/* will be used in your application program */
#pragma intrinsic DBBEGIN, DBEND, DBOPEN, DBCLOSE, DBGET, DBPUT,DBFIND, DBINFO
#pragma intrinsic DBEXPLAIN, DBERROR, DBDELETE, DBUPDATE, DBLOCK,DBUNLOCK
/* Define all your TurboIMAGE/XL constants */
#define End_Of_Chain 15 /* For DBGET Mode 5 */
#define End_Of_Data_Set 11 /* For DBGET Mode 2 */
#define No_Chain_Head 17 /* For DBFIND */
#define No_Such_Entry 17 /* For DBGET Mode 7 */
#define Entry_Has_No_Data 17 /* For DBGET Mode 4 */
short DBname[6]
Password[4]
Sales_D_Set[4];
char
*Purch_Date = "PURCH-DATE;",
*Equal_Op = " =",
*Item_List ="ACCOUNT,STOCK#,PRICE,TAX,TOTAL,PURCH-DATE;";
/* Define all your global variables. */
struct
Database_Status_Type { short Condition;
short Length;
int Record_Number;
int Chain_Count;
int Back_Pointer;
int Forward_Pointer;
} Status;
struct
Sales_Data_Set_Type {int Account_Number;
char Stock_Number[8];
int Price;
int Tax;
int Total;
char Purch_Date[6];
};
struct
Lock_Descriptor_Type {short Num_Of_Elements;
short Length_Of_Descriptor;
char Data_Set_Of_Descriptor[16];
char Data_Item_Of_Descriptor[16];
char Relop_For_Data_Item[2];
char Value_For_Data_Item[6];
};
short Mode;
Main Body of Program.
/* Beginning of the main program */
main()
{
/* Initialize the database and set information */
strcpy ((char *)DBname," ORDERS; ");
strcpy ((char *)Password,"DO-ALL;");
strcpy ((char *)Sales_D_Set,"SALES;");
Open_The_Database();
Get_Sales_For_Date();
exit (0);
}
Obtaining Error Messages and Explanations.
The following paragraph implements the GET-ERROR-AND-EXPLAIN routine of
the sample program. This routine calls DBEXPLAIN and DBERROR. DBEXPLAIN
interprets the contents of the status parameter and prints a message on
$STDLIST. DBERROR returns a message in the ERROR-BUFFER, explaining the
condition code returned by TurboIMAGE/XL. At the end the routine, users
can choose to abort or continue the execution of this program.
/* Beginning of subroutines */
Get_Error_And_Explain()
{
/*
Access : Mode 1 - Shared Modified Access
The Orders database was opened in mode 1
Called by: Open_The_Database
Get_Sales_For_Date
Get_A_Product_Record
List_All_Customers
Add_A_Product
Update_A_Customer
Delete_A_Product
Rewind_Customer_Set
Get_Data_Item_Info
Close_The_Database
Calls : DBERROR
DBEXPLAIN
*/
short Error_Buffer[80];
short Error_Length;
int Answer;
DBERROR(&Status,Error_Buffer,&Error_Length);
printf("-------------------------------------------\n");
printf("%.*s\n",Error_Length, (char *)Error_Buffer);
printf("-------------------------------------------\n");
DBEXPLAIN(&Status);
Answer=0;
printf("---Enter, <1> to ABORT..., <2> to Continue >\n");
scanf("%d",&Answer);
if (Answer != 1)
printf(" Continuing .........\n");
else
exit(0);
}