isc_open_blob2()
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Opens an existing Blob for retrieval and optional filtering.
Syntax
ISC_STATUS isc_open_blob2(
ISC_STATUS *status_vector,
isc_db_handle *db_handle,
isc_tr_handle *trans_handle,
isc_blob_handle *blob_handle,
ISC_QUAD *blob_id,
short bpb_length,
char *bpb_address);
| Parameter | Type | Description |
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Pointer to the error status vector |
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Pointer to a database handle set by a previous call to
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Pointer to a transaction handle whose value has been set by a previous |
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Pointer to the Blob handle, which must be NULL when you make this call. |
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Pointer to the 64-bit system-defined Blob ID, which is stored in a field in the table and points to the first segment of the Blob or to a page of pointers to Blob fragments. |
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Length of the Blob parameter buffer (BPB) |
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Pointer to the BPB |
Description
isc_open_blob2() opens an existing Blob for retrieval and optional filtering from one Blob subtype to another.
Input and output Blob filter types are passed to isc_open_blob2() as subtype information in a previously populated BPB, pointed to by bpb_address. If Blob filters are not needed or cannot be used, a BPB is not needed; pass 0 for bpb_length and NULL for bpb_address.
The blob_id identifies which particular Blob is to be opened. This blob_id is set by a sequence of DSQL function calls.
On success, isc_open_blob2() assigns a unique ID to blob_handle. Subsequent API calls use this handle to identify the Blob against which they operate.
After a blob is opened, its data can be read by a sequence of calls to isc_get_segment().
When finished accessing the Blob, close it with isc_close_blob().
For more information about opening a Blob for retrieval and optional filtering, see Working with Blob Data.
Example
The following fragment is excerpted from the example file, api9.c. The example program displays job descriptions that are passed through a filter.
while ((fetch_stat = isc_dsql_fetch(status, &stmt, 1, sqlda)) == 0) {
printf("\nJOB CODE: %5s GRADE: %d", job_code, job_grade);
printf(" COUNTRY: %-20s\n\n", job_country);
/* Open the blob with the fetched blob_id. */
isc_open_blob2(status, &DB, &trans, &blob_handle, &blob_id, 9, bpb);
if (status[0] == 1 && status[1]) {
isc_print_status(status);
return(1);
}
}
Return value
isc_open_blob2() returns the second element of the status vector. Zero indicates success. A nonzero value indicates an error. For InterBase errors, the first element of the status vector is set to 1, and the second element is set to an InterBase error code.
To check for an InterBase error, examine the first two elements of the status vector directly. For more information about examining the status vector, see Handling Error Conditions.