Copyright Digital Equipment Corp. All rights reserved.
DL_DataGetFirst
NAME
DL_DataGetFirst, CSSM_DL_DataGetFirst - Get first data record (CDSA)
SYNOPSIS
# include <cssm.h>
API:
CSSM_RETURN CSSMAPI CSSM_DL_DataGetFirst
(CSSM_DL_DB_HANDLE DLDBHandle,
const CSSM_QUERY *Query,
CSSM_HANDLE_PTR ResultsHandle,
CSSM_DB_RECORD_ATTRIBUTE_DATA_PTR Attributes,
CSSM_DATA_PTR Data,
CSSM_DB_UNIQUE_RECORD_PTR *UniqueId)
SPI:
CSSM_RETURN CSSMDLI DL_DataGetFirst
(CSSM_DL_DB_HANDLE DLDBHandle,
const CSSM_QUERY *Query,
CSSM_HANDLE_PTR ResultsHandle,
CSSM_DB_RECORD_ATTRIBUTE_DATA_PTR Attributes,
CSSM_DATA_PTR Data,
CSSM_DB_UNIQUE_RECORD_PTR *UniqueId)
LIBRARY
Common Security Services Manager library (CDSA$INCSSM300_SHR.EXE)
PARAMETERS
DLDBHandle (input)
The handle pair that describes the add-in data storage
library module to be used to perform this function and
the open data store to search for records satisfying the
query.
Query (input/optional)
The query structure specifying the selection predicate(s)
used to query the data store. The structure contains meta
information about the search fields and the relational and
conjunctive operators forming the selection predicate. The
comparison values to be used in the search are specified in
the Attributes field of this Query structure. If a search
attribute is of type CSSM_DB_ATTRIBUTE_FORMAT_STRING and the
search value specified for that string includes a null-
terminator, then the length count for that string should
include the terminating character. (If null-terminators
are used they should be used consistently, storing the
terminator as part of the string in the data store, otherwise
selection predicates will not locate expected matches.) The
Query structure attributes also identify the particular
attributes to be searched by this query. If no query is
specified, the DL module can return the first record in the
data store, performing sequential retrieval, or return an
error. If no selection predicates are specified, the DL
module can return the first record in the data store,
performing sequential retrieval, or return an error
(CSSM_DL_UNSUPPORTED_NUM_SELECTION_PREDS). When selection
predicates are specified, the NumberOfValues of the Attribute
of each selection predicate must be 1. If any selection
predicate does not satisfy this requirement, the error
CSSMERR_DL_INVALID_QUERY is returned.
ResultsHandle (output)
This handle should be used to retrieve subsequent records
that satisfied this query.
Attributes (optional-input/output)
If the Attributes structure pointer is NULL, no values are
returned.
Otherwise, the DataRecordType, NumberOfAttributes and
AttributeData fields are read. AttributeData must be an
array of NumberOfAttributes CSSM_DB_RECORD_ATTRIBUTE
elements. Only the Info field of each element is used on
input. The AttributeFormat field of the Info field is
ignored on input.
On output, a CSSM_DB_RECORD_ATTRIBUTE structure containing
a list of all or the requested attribute values (subset) from
the retrieved record. The SemanticInformation field is set.
For each CSSM_DB_ATTRIBUTE_DATA contained in the AttributeData
array, the NumberOfValues field is set to reflect the size of
the Value array which is allocated by the DL using the
application specified allocators. Each CSSM_DATA in the Value
array will have it's Data field as a pointer to data allocated
using the application specified allocators containing the
attributes value, and have it's Length set to the length of the
value.
All values for an attribute are returned (this could be 0).
All fields in the Info field of the CSSM_DB_ATTRIBUTE_DATA
are left unchanged except for the AttributeFormat field,
which is set to reflect the schema.
Data (optional-input/output)
Data values contained in the referenced memory are ignored
during processing and are overwritten with the retrieved
opaque object. On output, a CSSM_DATA structure containing
the opaque object stored in the retrieved record.
UniqueId (output)
If successful and (at least) a record satisfying the query has
been found, then this parameter returns a pointer to a
CSSM_UNIQUE_RECORD_PTR structure containing a unique
identifier associated with the retrieved record. This unique
identifier structure can be used in future references to this
record using this DLDBHandle pairing. It may not be valid for
other DLHandles targeted to this DL module or to other
DBHandles targeted to this data store. If there are no records
satisfying the query, then this pointer is NULL and
CSSM_DL_DataGetFirst() must return CSSM_DL_ENDOFDATA; in this
case a normal termination condition has occurred. The
CSSM_DL_FreeUniqueRecord() must be used to de-allocate this
structure.
DESCRIPTION
This function retrieves the first data record in the data store that
matches the selection criteria. The selection criteria (including
selection predicate and comparison values) is specified in the Query
structure. If the Query specifies an attribute that is not defined
in the database's meta-information, an error condition is returned.
The DL module can use internally-managed indexing structures to enhance
the performance of the retrieval operation. This function selects the
first record satisfying the query based on the list of Attributes and
the opaque Data object. The output buffers for the retrieved record
are allocated by this function using the memory management functions
provided during the module attach operation. This function also
returns a results handle to be used when retrieving subsequent records
satisfying the query.
Additional matching records are iteratively retrieved using the
CSSM_DL_DataGetNext() function . The data storage module supports
one of two retrieval models:
· Transactional - all query results are determined at initial
query evaluation. Results do not change during an incremental
retrieval process.
· File System Scan - query results are selected during the
incremental retrieval process. Records matching the query may
be added to or deleted from the underlying data store during
the iterative retrieval. The caller may receive the new
matching records and not received the deleted records.
The caller can determine which retrieval model is supported by
examining the encapsulated product description for this data
storage module.
If the query selection criteria also specifies time for space limits
for executing the query, those limits also apply ro retrieval of the
additional selected data records retrieved using the
CSSM_DL_DataGetNext() function. Finally, this function returns a
unique record identifier associated with the retrieved record. This
structure can be used in future references to the retrieved data
record. Once a user has finished using a certain query, it must call
CSSM_DataAbortQuery() for releasing resources that CSSM uses. If all
records satisfying the query have been retrieved, then query is
automatically terminated.
RETURN VALUE
A CSSM_RETURN value indicating success or specifying a particular
error condition. The value CSSM_OK indicates success. All other
values represent an error condition.
ERRORS
Errors are described in the CDSA technical standard. See CDSA.
CSSMERR_DL_ENDOFDATA
CSSMERR_DL_FIELD_SPECIFIED_MULTIPLE
CSSMERR_DL_INCOMPATIBLE_FIELD_FORMAT
CSSMERR_DL_INVALID_DB_HANDLE
CSSMERR_DL_INVALID_FIELD_NAME
CSSMERR_DL_INVALID_PARSING_MODULE
CSSMERR_DL_INVALID_QUERY
CSSMERR_DL_INVALID_RECORDTYPE
CSSMERR_DL_INVALID_RECORD_UID
CSSMERR_DL_UNSUPPORTED_FIELD_FORMAT
CSSMERR_DL_UNSUPPORTED_NUM_SELECTION_PREDS
CSSMERR_DL_UNSUPPORTED_OPERATOR
CSSMERR_DL_UNSUPPORTED_QUERY
CSSMERR_DL_UNSUPPORTED_QUERY_LIMITS
SEE ALSO
Books
Intel CDSA Application Developer's Guide (see CDSA)
Other Help Topics
Functions for the CSSM API:
CSSM_DL_DataGetNext
CSSM_DL_DataAbortQuery
Functions for the DL SPI:
DL_DataGetNext
DL_DataAbortQuery