RRDS example

The sample program (CCNGVS4) in Figure 1 illustrates the use of an RRDS file. It performs the following operations:

Opens an RRDS file in record mode (the cluster must be defined)
Writes three records (RRN 2, RRN 10, and RRN 32)
Sets the file position to the first record
Reads the first record in the file
Deletes it
Locates the last record in the file and sets the access direction to backwards
Reads the record
Updates the record
Sets the _EDC_RRDS_HIDE_KEY environment variable
Reads the next record in sequence (RRN 10) into a character string

Figure 1. RRDS example

/* this example illustrates the use
of an RRDS file */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <env.h>

struct rrds_struct {
__
rrds_key_type   rrds_key;
   char             *rrds_buf;
};

typedef struct rrds_struct RRDS_STRUCT;

main() {

FILE              *fileptr;
RRDS_STRUCT        RRDSstruct;
RRDS_STRUCT       *rrds_rec = &RRDSstruct;
char               buffer1[80] =
                      "THIS IS THE FIRST RECORD IN THE FILE.  I"
                      "T WILL BE WRITTEN AT RRN POSITION 2.   ";
char               buffer2[80] =
                      "THIS IS THE SECOND RECORD IN THE FILE. I"
                      "T WILL BE WRITTEN AT RRN POSITION 10.  ";
char               buffer3[80] =
                      "THIS IS THE THIRD RECORD IN THE FILE.  I"
                      "T WILL BE WRITTEN AT RRN POSITION 32.  ";
char               outputbuf[80];
unsigned long      flocate_key = 0;

/*------------------------------------------------------------------*/
/*| select RRDS record structure 2 by setting __fill to 1           */
/*|                                                                 */
/*| 1. open an RRDS file record mode  (the cluster must be defined) */
/*| 2. write three records (RRN 2, RRN 10, RRN 32)                  */
/*------------------------------------------------------------------*/
    rrds_rec->rrds_key.__fill = 1;

    fileptr = fopen("DD:RRDSFILE", "wb+,type=record");
    if (fileptr == NULL) {
       perror("fopen");
       exit(99);
    }
    rrds_rec->rrds_key.__recnum = 2;
    rrds_rec->rrds_buf = buffer1;
    fwrite(rrds_rec,1,88, fileptr);

    rrds_rec->rrds_key.__recnum = 10;
    rrds_rec->rrds_buf = buffer2;
    fwrite(rrds_rec,1,88, fileptr);

    rrds_rec->rrds_key.__recnum = 32;
    rrds_rec->rrds_buf = buffer3;
    fwrite(rrds_rec,1,88, fileptr);

/*------------------------------------------------------------------*/
/*| 3. set file position to the first record                        */
/*| 4. read the first record in the file                            */
/*| 5. delete it                                                    */
/*------------------------------------------------------------------*/
    flocate(fileptr, &flocate_key,; sizeof(unsigned long), __KEY_FIRST);

    memset(outputbuf,0x00,80);
    rrds_rec->rrds_buf = outputbuf;

    fread(rrds_rec,1, 88, fileptr);
    printf("The first record in the file (this will be deleted):\n");
    printf("RRN %d: %s\n\n",rrds_rec->rrds_key.__recnum,outputbuf);

    fdelrec(fileptr);

/*------------------------------------------------------------------*/
/*| 6. locate last record in file and set access direction backwards*/
/*| 7. read the record                                              */
/*| 8. update the record                                            */
/*------------------------------------------------------------------*/
    flocate(fileptr, &flocate_key,; sizeof(unsigned long), __KEY_LAST);

    memset(outputbuf,0x00,80);
    rrds_rec->rrds_buf = outputbuf;

    fread(rrds_rec,1, 88, fileptr);
    printf("The last record in the file (this one will be updated):\n");
    printf("RRN %d: %s\n\n",rrds_rec->rrds_key.__recnum,outputbuf);

    memset(outputbuf,0x00,80);
    memcpy(outputbuf,"THIS IS THE UPDATED STRING... ",30);
    fupdate(rrds_rec,88,fileptr);

/*------------------------------------------------------------------*/
/*| 9. set _EDC_RRDS_HIDE_KEY environment variable                  */
/*|10. read the next record in sequence (ie. RRN 10) into a         */
/*|    + character string                                           */
/*------------------------------------------------------------------*/

    setenv("_EDC_RRDS_HIDE_KEY","Y",1);
    memset(outputbuf,0x00,80);
    fread(outputbuf, 1, 80, fileptr);
    printf("The middle record in the file (read into char string):\n");
    printf("%80s\n\n",outputbuf);

    fclose(fileptr);
}