Here is a piece of code below for writing and reading blobs in SQLITE
database.
I ' ve a problem to read from blob struct called 'Points'
Any help would be appreciated
Reagards
Greg
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include "sqlite3.h"
typedef unsigned char uchar;
char dbname[1000];
static sqlite3 *db1;
void
exec_simple (char *stm)
{
int rc;
char *errMsg = 0;
rc = sqlite3_exec (db1, stm, NULL, 0, &errMsg);
if (rc != SQLITE_OK)
{
fprintf (stderr, "SQL error: %s\n", errMsg);
}
}
typedef struct points
{
long numPoints;
double *x;
}Points;
int
main (int argc, char **argv)
{
char *errMsg = 0;
int rc;
sqlite3_stmt *stmt = NULL;
Points *pointsP;
long numPoints;
long size;
int iii;
char text[32];
uchar *pabyRec;
int nRecordSize;
int num_punkt;
int nOffset;
strcpy(dbname,".\\test.db");
unlink (dbname);
rc = sqlite3_open (dbname, &db1);
if (rc)
{
fprintf (stderr, "Can't open database: %s\n", sqlite3_errmsg (db1));
exit (1);
}
exec_simple ("PRAGMA page_size=8192");
exec_simple ("PRAGMA synchronous = OFF");
exec_simple ("PRAGMA count_changes = OFF");
exec_simple ("PRAGMA temp_store = MEMORY");
exec_simple ("CREATE TABLE punkty(id INTEGER PRIMARY KEY, value BLOB)");
// write record
numPoints=5;
size = numPoints * 1 * sizeof(double) + sizeof(int);
pointsP = (Points *) malloc(size);
memcpy( pointsP, &numPoints, sizeof(int));
nRecordSize = 4;
pointsP->x = (double *) calloc(numPoints, sizeof(double));
for( iii = 0; iii < numPoints; iii++ )
{
pointsP->x[iii] = (double)iii*100+0.01;
}
for( iii = 0; iii < numPoints; iii++ )
{
memcpy( pointsP + nRecordSize, pointsP->x + iii, sizeof(double));
nRecordSize += 1 * 8;
}
rc = sqlite3_prepare(db1, "insert into punkty values (1,?);", -1, &stmt,
NULL);
if (rc)
{
fprintf (stderr, "ERORR: %s\n", sqlite3_errmsg (db1));
exit (1);
}
rc =sqlite3_bind_blob(stmt, 1, pointsP, size, NULL);
if (rc)
{
fprintf (stderr, "ERORR: %s\n", sqlite3_errmsg (db1));
exit (1);
}
sqlite3_step(stmt);
rc =sqlite3_finalize(stmt);
if (rc)
{
fprintf (stderr, "ERORR: %s\n", sqlite3_errmsg (db1));
exit (1);
}
if( pointsP->x != NULL )
{
free( pointsP->x );
pointsP->x=NULL;
}
free(pointsP);
pointsP=NULL;
// read record
rc = sqlite3_prepare (db1, "select *from punkty", -1, &stmt, NULL);
if (rc != SQLITE_OK)
{
fprintf (stderr, " %s\n", sqlite3_errmsg (db1));
}
while (sqlite3_step (stmt) == SQLITE_ROW)
{
if (rc != SQLITE_OK)
{
fprintf (stderr, "SQL error: %s\n", errMsg);
}
size = sqlite3_column_bytes(stmt, 1);
pointsP= (Points *)malloc(size);
memcpy(pointsP,sqlite3_column_blob(stmt, 1),size);
printf("size=%ld\n",size);
memcpy( &num_punkt, pointsP, 4 );
printf("pointsP->numPoints=%ld\n",num_punkt);
nOffset = 4;
pointsP->x = (double *) calloc(num_punkt, sizeof(double));
for( iii = 0; iii < num_punkt; iii++ )
{
memcpy(pointsP->x + iii, pointsP + nOffset + iii * 8, 8); //maybe here
is a fault
}
for(iii=0;iii<num_punkt;iii++)
{
printf("x=%.2f\n",pointsP->x[iii]); // here prints rubbish
}
printf("ID=%ld\n", sqlite3_column_int(stmt,0));
}
sqlite3_finalize (stmt);
}
