Accessing Blob Data with API Calls

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In addition to accessing Blob data using SQL as described in this chapter, the InterBase API provides routines for accessing Blob data. The following API calls are provided for accessing and managing Blob data:

API Blob calls
Function	Description
`isc_blob_default_desc2()`	Loads a Blob descriptor data structure with default information about a Blob.
`isc_blob_gen_bpb2()`	Generates a Blob parameter buffer (BPB) from source and target Blob descriptors to allow dynamic access to Blob sub-type and character set information.
`isc_blob_info()`	Returns information about an open Blob.
`isc_blob_lookup_desc2()`	Looks up and stores into a Blob descriptor the sub-type, character set, and segment size of a Blob.
`isc_blob_set_desc2()`	Sets the fields of a Blob descriptor to values specified in parameters to `isc_blob_set_desc()`.
`isc_cancel_blob()`	Discards a Blob and frees internal storage.
`isc_close_blob()`	Closes an open Blob.
`isc_create_blob2()`	Creates a context for storing a Blob, opens the Blob for write access, and optionally specifies a filter to be used to translate the Blob data from one sub-type to another.
`isc_get_segment()`	Reads a segment from an open Blob.
`isc_open_blob2()`	Opens an existing Blob for retrieval and optional filtering.
`isc_put_segment()`	Writes a Blob segment.

isc_blob_default_desc2(), isc_blob_gen_bpb2(), isc_blob_lookup_desc2(), and isc_blob_set_desc2(), support long metadata names of length METADATALENGTH . The older calls, such as isc_blob_default_desc() support only metadata names of 32 bytes or less.

For details on using the API calls to access Blob data, see the API Guide.

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Filtering Blob Data