Teradata provides the following library functions for accessing the value of a large object:
- FNC_LobOpen
- FNC_LobRead
- FNC_LobClose
To access the value of a large object, follow these steps:
- Call FNC_LobOpen to establish a read context for the large object.
FNC_LobOpen returns a read context handle for the large object through an output argument of type LOB_CONTEXT_ID. The sqltypes_td.h header file defines LOB_CONTEXT_ID like this:
typedef long LOB_CONTEXT_ID;
- Call FNC_LobRead to read the large object and place the data into a BYTE buffer.
One of the input arguments to FNC_LobRead is the read context handle that was returned by FNC_LobOpen.
- Call FNC_Close to release all resources associated with the read context.
For detailed information on each function, see C Library Functions.
Here is a code excerpt that shows how to access the value of a large object:
#define BUFFER_SIZE 500
void do_something ( LOB_LOCATOR *a,
LOB_RESULT_LOCATOR *result,
char sqlstate[6] )
{
BYTE buffer[BUFFER_SIZE];
FNC_LobLength_t actlen;
LOB_CONTEXT_ID id;
/* Establish a read context for the LOB input argument */
FNC_LobOpen(*a, &id, 0, BUFFER_SIZE);
/* Read the LOB and place the data into a BYTE buffer */
FNC_LobRead(id, buffer, BUFFER_SIZE, &actlen);
/* Release the resources associated with the read context */
FNC_LobClose(id);
...
}
For a complete example, see C Scalar Function Using LOBs.