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/*
traversing a flat pre-built (in speed15.c) pointer list of 10 million records
of 5 fields in a 1 GB database:
a pointer to the previous record is stored in field 3 of each record,
a pointer to the last record is stored in field 2 of first record.
Observe that we use standard C int 0 for the NULL pointer,
this is also what wg_encode_null(db,0) always gives.
Database was created earlier by speed15.
Do not forget to delete database later, a la: wgdb 15 free
real 0m0.153s
user 0m0.110s
sys 0m0.043s
*/
#include <whitedb/dbapi.h>
#include <stdlib.h>
#include <stdio.h>
int main(int argc, char **argv) {
void *db, *rec;
char *name="15";
int i;
wg_int encptr;
db = wg_attach_database(name, 1000000000);
if (!db) { printf("db creation failed \n"); exit(0); }
rec=wg_get_first_record(db);
// get a pointer to the last record
rec=wg_decode_record(db,wg_get_field(db,rec,2));
i=1;
while(1) {
encptr=wg_get_field(db,rec,3); // encptr is not yet decoded
if (encptr==(wg_int)0) break; // encoded null is always standard 0
rec=wg_decode_record(db,encptr); // get a pointer to the previous record
i++;
}
printf("i %d\n", i);
wg_detach_database(db);
return 0;
}
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