Requesting Information About an Open Blob

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After an application opens a Blob, it can obtain information about the Blob. The isc_blob_info() call enables an application to query for Blob information such as the total number of segments in the Blob, or the length, in bytes, of the longest segment.

In addition to a pointer to the error status vector and a Blob handle, isc_blob_info() requires two application-provided buffers, an item-list buffer, where the application specifies the information it needs, and a result buffer, where InterBase returns the requested information. An application populates the item-list buffer with information requests prior to calling isc_blob_info(), and passes it both a pointer to the item-list buffer, and the size, in bytes, of that buffer.

The application must also create a result buffer large enough to hold the information returned by InterBase. It passes both a pointer to the result buffer, and the size, in bytes, of that buffer to isc_blob_info(). If InterBase attempts to pass back more information than can fit in the result buffer, it puts the value, ­isc_info_truncated, defined in ibase.h, in the final byte of the result buffer.

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