private sqlite3_context get_context(IntPtr context, IntPtr agg_context)
{
// agg_context is a pointer to 8 bytes of storage, obtained from
// sqlite3_aggregate_context(). we will use it to store the
// sqlite3_context object so we can use the same object for all
// calls to xStep and xFinal for this instance/invocation of the
// aggregate function.
agg_sqlite3_context ctx;
IntPtr c = Marshal.ReadIntPtr(agg_context);
if (c == IntPtr.Zero)
{
// this is the first call to xStep or xFinal. we need a new
// sqlite3_context object to pass to the user's callback.
ctx = new agg_sqlite3_context(_user_data);
// and store a handle in the agg_context storage area so we
// can get this back next time.
GCHandle h = GCHandle.Alloc(ctx);
Marshal.WriteIntPtr(agg_context, (IntPtr)h);
}
else
{
// we've been through here before. retrieve the sqlite3_context
// object from the agg_context storage area.
GCHandle h = (GCHandle)c;
ctx = h.Target as agg_sqlite3_context;
}
// we are reusing the same sqlite3_context object for each call
// to xStep/xFinal within the same instance/invocation of the
// user's agg function. but SQLite actually gives us a different
// context pointer on each call. so we need to fix it up.
ctx.fix_ptr(context);
return(ctx);
}
private sqlite3_context get_context(IntPtr context, IntPtr agg_context)
{
// agg_context is a pointer to 8 bytes of storage, obtained from
// sqlite3_aggregate_context(). we will use it to store the
// sqlite3_context object so we can use the same object for all
// calls to xStep and xFinal for this instance/invocation of the
// aggregate function.
agg_sqlite3_context ctx;
IntPtr c = Marshal.ReadIntPtr(agg_context);
if (c == IntPtr.Zero)
{
// this is the first call to xStep or xFinal. we need a new
// sqlite3_context object to pass to the user's callback.
ctx = new agg_sqlite3_context(_user_data);
// and store a handle in the agg_context storage area so we
// can get this back next time.
GCHandle h = GCHandle.Alloc(ctx);
Marshal.WriteIntPtr(agg_context, (IntPtr) h);
}
else
{
// we've been through here before. retrieve the sqlite3_context
// object from the agg_context storage area.
GCHandle h = (GCHandle) c;
ctx = h.Target as agg_sqlite3_context;
}
// we are reusing the same sqlite3_context object for each call
// to xStep/xFinal within the same instance/invocation of the
// user's agg function. but SQLite actually gives us a different
// context pointer on each call. so we need to fix it up.
ctx.fix_ptr(context);
return ctx;
}
