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C syntax

DBIResult DBIFN DbiGetBlobHeading (hCursor, iField, pRecBuf, pDest);

Delphi syntax

function DbiGetBlobHeading (hCursor: hDBICur; iField: Word; pRecBuf: Pointer; pDest: Pointer): DBIResult stdcall;

Description

DbiGetBlobHeading retrieves information about a BLOB field from the BLOB heading in the record buffer.

Parameters

hCursor                Type: hDBICur                (Input)
Specifies the cursor handle.

iField                Type: UINT16                (Input)
Specifies the ordinal number of the BLOB field within the record.

pRecBuf                Type: pBYTE                (Input)
Pointer to the client buffer containing the BLOB heading.

pDest                Type: pBYTE                (Output)
Pointer to the client buffer that receives the retrieved BLOB heading. The client buffer must be large enough to accommodate the retrieved information.

Usage

This function is valid only for table types that support BLOB headings, that is, Paradox only. When the table is created, the client can specify the number of bytes of the BLOB field information to be stored in the tuple itself. This information is also contained in the normal storage area of the BLOB; it is actually duplicated. The benefit of storing some of the BLOB field in the tuple is that the BLOB field does not have to be opened to retrieve this information. If the BLOB is small, it can be contained fully in the record making access faster.

Paradox: With formatted BLOB fields, the formatting information in the first eight bytes of the field is not stored within the tuple. It is functionally the same as if DbiGetBlob were called with an iOffSet of 8 and an iLen the length of the tuple area.

dBASE or FoxPro: This function is not supported for dBASE or FoxPro tables.

Access: This function is not supported for Access tables.

SQL: This function is not supported for SQL tables.

Prerequisites

This call does not require a prior call to DbiOpenBlob. (This call can be understood as the functional equivalent of a DbiGetField call for BLOB fields).

Completion state

If the BLOB does not have a heading, DbiGetBlobHeading returns an error.

See also

DbiPutBlob, DbiTruncateBlob, DbiFreeBlob, DbiGetBlob, DbiGetBlobSize