Package com.unboundid.ldap.sdk.unboundidds.controls

Class MatchingEntryCountRequestControl

java.lang.Object
com.unboundid.ldap.sdk.Control
com.unboundid.ldap.sdk.unboundidds.controls.MatchingEntryCountRequestControl
All Implemented Interfaces:
Serializable
@NotMutable @ThreadSafety(level=COMPLETELY_THREADSAFE) public final class MatchingEntryCountRequestControl extends Control
This class provides a request control which may be included in a search request to indicate that the server should provide the number of entries that match the search criteria. The count will be included in the search result done message, and all search result entries will be suppressed.
NOTE: This class, and other classes within the com.unboundid.ldap.sdk.unboundidds package structure, are only supported for use against Ping Identity, UnboundID, and Nokia/Alcatel-Lucent 8661 server products. These classes provide support for proprietary functionality or for external specifications that are not considered stable or mature enough to be guaranteed to work in an interoperable way with other types of LDAP servers.

Whenever possible, the server will use index information to quickly identify entries matching the criteria of the associated search request. However, if the count is only determined using index information, then that count may include entries that would not actually be returned to the client in the course of processing that search (e.g., because the client doesn't have permission to access the entry, or because it is a special "operational" entry like an LDAP subentry, replication conflict entry, or soft-deleted entry). Indicating that the server should always examine candidate entries will increase the length of time to obtain the matching entry count, but will ensure that the count will not include entries that would not otherwise be returned by that search.

Also note that this control is not compatible for use with other controls that may cause only a subset of entries to be returned, including the simple paged results control and the virtual list view control. It is also not compatible for use with other controls that may cause the server to return more entries than those that match the search criteria, like the LDAP join control.

The OID for a matching entry count request control is "1.3.6.1.4.1.30221.2.5.36", and it may have a criticality of either true or false. It must include a value with the following encoding: 
   MatchingEntryCountRequest ::= SEQUENCE {
        maxCandidatesToExamine           [0] INTEGER (0 .. MAX) DEFAULT 0,
        alwaysExamineCandidates          [1] BOOLEAN DEFAULT FALSE,
        processSearchIfUnindexed         [2] BOOLEAN DEFAULT FALSE,
        includeDebugInfo                 [3] BOOLEAN DEFAULT FALSE,
        skipResolvingExplodedIndexes     [4] BOOLEAN DEFAULT FALSE,
        fastShortCircuitThreshold        [5] INTEGER (0 .. MAX) OPTIONAL,
        slowShortCircuitThreshold        [6] INTEGER (0 .. MAX) OPTIONAL,
        includeExtendedResponseData      [7] BOOLEAN DEFAULT FALSE,
        ... }
See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final String
    EXTENDED_RESPONSE_DATA_FEATURE_OID
    The OID (1.3.6.1.4.1.30221.2.12.7) for the supportedFeature value that a server should advertise in its root DSE if it supports returning extended information in the response control that older clients may not be able to handle.
    static final String
    MATCHING_ENTRY_COUNT_REQUEST_OID
    The OID (1.3.6.1.4.1.30221.2.5.36) for the matching entry count request control.

  • Constructor Summary

    Constructors
    Constructor
    Description
    MatchingEntryCountRequestControl()
    Creates a new matching entry count request control with the default settings.
    MatchingEntryCountRequestControl(boolean isCritical, int maxCandidatesToExamine, boolean alwaysExamineCandidates, boolean processSearchIfUnindexed, boolean includeDebugInfo)
    Creates a new matching entry count request control with the provided information.
    MatchingEntryCountRequestControl(boolean isCritical, int maxCandidatesToExamine, boolean alwaysExamineCandidates, boolean processSearchIfUnindexed, boolean skipResolvingExplodedIndexes, Long fastShortCircuitThreshold, Long slowShortCircuitThreshold, boolean includeDebugInfo)
    Creates a new matching entry count request control with the provided information.
    MatchingEntryCountRequestControl(boolean isCritical, MatchingEntryCountRequestControlProperties properties)
    Creates a new matching entry count request control with the provided properties.
    MatchingEntryCountRequestControl(Control control)
    Creates a new matching entry count request control that is decoded from the provided generic control.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    alwaysExamineCandidates()
    Indicates whether the server should always examine candidate entries in fully-indexed searches to determine whether they would actually be returned to the client in a normal search with the same criteria.
    static MatchingEntryCountRequestControl
    decodeJSONControl(JSONObject controlObject, boolean strict)
    Attempts to decode the provided object as a JSON representation of a matching entry count request control.
    String
    getControlName()
    Retrieves the user-friendly name for this control, if available.
    Long
    getFastShortCircuitThreshold()
    Retrieves the short-circuit threshold that the server should use when determining whether to continue with index processing in an attempt to further pare down a candidate set that already has a defined superset of the entries that actually match the filter.
    int
    getMaxCandidatesToExamine()
    Retrieves the maximum number of candidate entries that should be examined in order to determine accurate count of the number of matching entries.
    Long
    getSlowShortCircuitThreshold()
    Retrieves the short-circuit threshold that the server should use when determining whether to continue with index processing in an attempt to further pare down a candidate set that already has a defined superset of the entries that actually match the filter.
    boolean
    includeDebugInfo()
    Indicates whether the server should include debug information in the response control that provides additional information about how the server arrived at the result.
    boolean
    includeExtendedResponseData()
    Indicates whether the server may include extended response data in the corresponding response control, which may provide information like whether all of the identified candidate entries are within the scope of the search and any unindexed or unevaluated portion of the search filter.
    boolean
    processSearchIfUnindexed()
    Indicates whether the server should internally retrieve and examine all entries within the search scope in order to obtain an exact matching entry count for an unindexed search.
    static boolean
    serverSupportsExtendedResponseData(LDAPInterface connection)
    Attempts to determine whether the server to which the provided connection is established supports including extended response data in the matching entry count response control.
    static boolean
    serverSupportsExtendedResponseData(RootDSE rootDSE)
    Determines whether the provided root DSE indicates that the associated server supports including extended response data in the matching entry count response control.
    boolean
    skipResolvingExplodedIndexes()
    Indicates whether the server should skip the effort of actually retrieving the candidate entry IDs for exploded index keys in which the number of matching entries is known.
    JSONObject
    toJSONControl()
    Retrieves a representation of this matching entry count request control as a JSON object.
    void
    toString(StringBuilder buffer)
    Appends a string representation of this LDAP control to the provided buffer.

    Methods inherited from class com.unboundid.ldap.sdk.Control

    decode, decode, decodeControls, decodeJSONControl, deregisterDecodeableControl, encode, encodeControls, equals, getOID, getValue, hashCode, hasValue, isCritical, readFrom, registerDecodeableControl, registerDecodeableControl, toString, writeTo

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Field Details

    • MATCHING_ENTRY_COUNT_REQUEST_OID

      @NotNull public static final String MATCHING_ENTRY_COUNT_REQUEST_OID
      The OID (1.3.6.1.4.1.30221.2.5.36) for the matching entry count request control.
      See Also:

    • EXTENDED_RESPONSE_DATA_FEATURE_OID

      @NotNull public static final String EXTENDED_RESPONSE_DATA_FEATURE_OID
      The OID (1.3.6.1.4.1.30221.2.12.7) for the supportedFeature value that a server should advertise in its root DSE if it supports returning extended information in the response control that older clients may not be able to handle. Clients that wish to use the includeExtendedResponseData element of the request control should check the target server's root DSE to determine whether it supports this feature before requesting it because older versions of the server that do not support it may not accept a control that requests it.
      See Also:

  • Constructor Details

    • MatchingEntryCountRequestControl

      public MatchingEntryCountRequestControl()
      Creates a new matching entry count request control with the default settings. The control will be critical, no candidate entries will be examined, and the search will not be processed if it is unindexed.

    • MatchingEntryCountRequestControl

      public MatchingEntryCountRequestControl(boolean isCritical, int maxCandidatesToExamine, boolean alwaysExamineCandidates, boolean processSearchIfUnindexed, boolean includeDebugInfo)
      Creates a new matching entry count request control with the provided information.
      Parameters:
      isCritical - Indicates whether this control should be critical.
      maxCandidatesToExamine - The maximum number of candidate entries that the server should retrieve and examine to determine whether they actually match the search criteria. If the search is partially indexed and the total number of candidate entries is less than or equal to this value, then these candidate entries will be examined to determine which of them match the search criteria so that an accurate count can be determined. If the search is fully indexed such that the all candidate entries are known to match the search criteria, then the server may still examine each of these entries if the number of candidates is less than maxCandidatesToExamine and alwaysExamineCandidates is true in order to allow the entry count that is returned to be restricted to only those entries that would actually be returned to the client. This will be ignored for searches that are completely unindexed.

      The value for this argument must be greater than or equal to zero. If it is zero, then the server will not examine any entries, so a partially-indexed search will only be able to return a count that is an upper bound, and a fully-indexed search will only be able to return an unexamined exact count. If there should be no bound on the number of entries to retrieve, then a value of Integer.MAX_VALUE may be specified.
      alwaysExamineCandidates - Indicates whether the server should always examine candidate entries to determine whether they would actually be returned to the client in a normal search. This will only be used for fully-indexed searches in which the set of matching entries is known. If the value is true and the number of candidates is smaller than maxCandidatesToExamine, then each matching entry will be internally retrieved and examined to determine whether it would be returned to the client based on the details of the search request (e.g., whether the requester has permission to access the entry, whether it's an LDAP subentry, replication conflict entry, soft-deleted entry, or other type of entry that is normally hidden) so that an exact count can be returned. If this is false or the number of candidates exceeds maxCandidatesToExamine, then the server will only be able to return an unexamined count which may include entries that match the search criteria but that would not normally be returned to the requester.
      processSearchIfUnindexed - Indicates whether the server should attempt to determine the number of matching entries if the search criteria is completely unindexed. If this is true and the requester has the unindexed-search privilege, then the server will iterate through all entries in the scope (which may take a very long time to complete) in order to to determine which of them match the search criteria so that it can return an accurate count. If this is false or the requester does not have the unindexed-search privilege, then the server will not spend any time attempting to determine the number of matching entries and will instead return a matching entry count response control indicating that the entry count is unknown.
      includeDebugInfo - Indicates whether the server should include debug information in the response that may help better understand how it arrived at the result. If any debug information is returned, it will be in the form of human-readable text that is not intended to be machine-parsable.

    • MatchingEntryCountRequestControl

      public MatchingEntryCountRequestControl(boolean isCritical, int maxCandidatesToExamine, boolean alwaysExamineCandidates, boolean processSearchIfUnindexed, boolean skipResolvingExplodedIndexes, @Nullable Long fastShortCircuitThreshold, @Nullable Long slowShortCircuitThreshold, boolean includeDebugInfo)
      Creates a new matching entry count request control with the provided information.
      Parameters:
      isCritical - Indicates whether this control should be critical.
      maxCandidatesToExamine - The maximum number of candidate entries that the server should retrieve and examine to determine whether they actually match the search criteria. If the search is partially indexed and the total number of candidate entries is less than or equal to this value, then these candidate entries will be examined to determine which of them match the search criteria so that an accurate count can be determined. If the search is fully indexed such that the all candidate entries are known to match the search criteria, then the server may still examine each of these entries if the number of candidates is less than maxCandidatesToExamine and alwaysExamineCandidates is true in order to allow the entry count that is returned to be restricted to only those entries that would actually be returned to the client. This will be ignored for searches that are completely unindexed.

      The value for this argument must be greater than or equal to zero. If it is zero, then the server will not examine any entries, so a partially-indexed search will only be able to return a count that is an upper bound, and a fully-indexed search will only be able to return an unexamined exact count. If there should be no bound on the number of entries to retrieve, then a value of Integer.MAX_VALUE may be specified.
      alwaysExamineCandidates - Indicates whether the server should always examine candidate entries to determine whether they would actually be returned to the client in a normal search. This will only be used for fully-indexed searches in which the set of matching entries is known. If the value is true and the number of candidates is smaller than maxCandidatesToExamine, then each matching entry will be internally retrieved and examined to determine whether it would be returned to the client based on the details of the search request (e.g., whether the requester has permission to access the entry, whether it's an LDAP subentry, replication conflict entry, soft-deleted entry, or other type of entry that is normally hidden, etc.) so that an exact count can be returned. If this is false or the number of candidates exceeds maxCandidatesToExamine, then the server will only be able to return an unexamined count which may include entries that match the search criteria but that would not normally be returned to the requester.
      processSearchIfUnindexed - Indicates whether the server should attempt to determine the number of matching entries if the search criteria is completely unindexed. If this is true and the requester has the unindexed-search privilege, then the server will iterate through all entries in the scope (which may take a very long time to complete) in order to to determine which of them match the search criteria so that it can return an accurate count. If this is false or the requester does not have the unindexed-search privilege, then the server will not spend any time attempting to determine the number of matching entries and will instead return a matching entry count response control indicating that the entry count is unknown.
      skipResolvingExplodedIndexes - Indicates whether the server should skip the effort of actually retrieving the candidate entry IDs for exploded index keys in which the number of matching entries is known. Skipping the process of retrieving the candidate entry IDs can allow the server to more quickly estimate the matching entry count, but the resulting estimate may be less accurate.
      fastShortCircuitThreshold - Specifies the short-circuit threshold that the server should use when determining whether to continue with index processing in an attempt to further pare down a candidate set that already has a defined superset of the entries that actually match the filter. Short-circuiting may allow the server to skip potentially-costly index processing and allow it to obtain the matching entry count estimate faster, but the resulting estimate may be less accurate. The fast short-circuit threshold will be used for index processing that is expected to be very fast (e.g., when performing index lookups for presence, equality, and approximate-match components, which should only require accessing a single index key). A value that is less than or equal to zero indicates that the server should never short circuit when performing fast index processing. A value of null indicates that the server should determine the appropriate fast short-circuit threshold to use.
      slowShortCircuitThreshold - Specifies the short-circuit threshold that the server should use when determining whether to continue with index processing for evaluation that may be more expensive than what falls into the "fast" category (e.g., substring and range filter components). A value that is less than or equal to zero indicates that the server should never short circuit when performing slow index processing. A value of null indicates that the server should determine the appropriate slow short-circuit threshold to use.
      includeDebugInfo - Indicates whether the server should include debug information in the response that may help better understand how it arrived at the result. If any debug information is returned, it will be in the form of human-readable text that is not intended to be machine-parsable.

    • MatchingEntryCountRequestControl

      public MatchingEntryCountRequestControl(boolean isCritical, @NotNull MatchingEntryCountRequestControlProperties properties)
      Creates a new matching entry count request control with the provided properties.
      Parameters:
      isCritical - Indicates whether the control should be critical.
      properties - The properties that should be used to create this matching entry count request control. It must not be null.

    • MatchingEntryCountRequestControl

      public MatchingEntryCountRequestControl(@NotNull Control control) throws LDAPException
      Creates a new matching entry count request control that is decoded from the provided generic control.
      Parameters:
      control - The control to decode as a matching entry count request control.
      Throws:
      LDAPException - If the provided control cannot be decoded as a matching entry count request control.

  • Method Details

    • getMaxCandidatesToExamine

      public int getMaxCandidatesToExamine()
      Retrieves the maximum number of candidate entries that should be examined in order to determine accurate count of the number of matching entries.

      For a fully-indexed search, this property will only be used if alwaysExamineCandidates is true. If the number of candidate entries identified is less than the maximum number of candidates to examine, then the server will return an EXAMINED_COUNT result that indicates the number of entries matching the criteria that would actually be returned in a normal search with the same criteria. If the number of candidate entries exceeds the maximum number of candidates to examine, then the server will return an UNEXAMINED_COUNT result that indicates the number of entries matching the search criteria but that may include entries that would not actually be returned to the client.

      For a partially-indexed search, if the upper bound on the number of candidates is less than or equal to the maximum number of candidates to examine, then the server will internally retrieve and examine each of those candidates to determine which of them match the search criteria and would actually be returned to the client, and will then return an EXAMINED_COUNT result with that count. If the upper bound on the number of candidates is greater than the maximum number of candidates to examine, then the server will return an UPPER_BOUND result to indicate that the exact count is not known but an upper bound is available.
      Returns:
      The maximum number of candidate entries to examine in order to determine an accurate count of the number of matching entries.

    • alwaysExamineCandidates

      public boolean alwaysExamineCandidates()
      Indicates whether the server should always examine candidate entries in fully-indexed searches to determine whether they would actually be returned to the client in a normal search with the same criteria.
      Returns:
      true if the server should attempt to internally retrieve and examine matching entries to determine whether they would normally be returned to the client (e.g., that the client has permission to access the entry and that it is not a normally-hidden entry like an LDAP subentry, a replication conflict entry, or a soft-deleted entry), or false if the server should return an unverified count.

    • processSearchIfUnindexed

      public boolean processSearchIfUnindexed()
      Indicates whether the server should internally retrieve and examine all entries within the search scope in order to obtain an exact matching entry count for an unindexed search. Note that this value will not be considered for completely-indexed or partially-indexed searches, nor for searches in which matching entries should be returned.
      Returns:
      true if the server should internally retrieve and examine all entries within the search scope in order to obtain an exact matching entry count for an unindexed search, or false if not.

    • skipResolvingExplodedIndexes

      public boolean skipResolvingExplodedIndexes()
      Indicates whether the server should skip the effort of actually retrieving the candidate entry IDs for exploded index keys in which the number of matching entries is known. Skipping the process of accessing an exploded index can allow the server to more quickly arrive at the matching entry count estimate, but that estimate may be less accurate than if it had actually retrieved those candidates.
      Returns:
      true if the server should skip the effort of actually retrieving the candidate entry IDs for exploded index keys in which the number of matching entries is known, or false if it may retrieve candidates from an exploded index in the course of determining the matching entry count.

    • getFastShortCircuitThreshold

      @Nullable public Long getFastShortCircuitThreshold()
      Retrieves the short-circuit threshold that the server should use when determining whether to continue with index processing in an attempt to further pare down a candidate set that already has a defined superset of the entries that actually match the filter. If the number of entries in that candidate set is less than or equal to the short-circuit threshold, then the server may simply use that candidate set in the course of determining the matching entry count, even if there may be additional processing that can be performed (e.g., further filter components to evaluate) that may allow the server to pare down the results even further. Short-circuiting may allow the server to obtain the matching entry count estimate faster, but may also cause the resulting estimate to be less accurate.

      The value returned by this method will be used for cases in which the server is performing the fastest types of index processing. For example, this may include evaluating presence, equality, or approximate match components, which should only require retrieving a single index key to obtain the candidate set.
      Returns:
      The short-circuit threshold that should be used for fast index processing, zero if the server should not short-circuit at all during fast index processing, or null if the server should determine the appropriate fast short-circuit threshold to use.

    • getSlowShortCircuitThreshold

      @Nullable public Long getSlowShortCircuitThreshold()
      Retrieves the short-circuit threshold that the server should use when determining whether to continue with index processing in an attempt to further pare down a candidate set that already has a defined superset of the entries that actually match the filter. If the number of entries in that candidate set is less than or equal to the short-circuit threshold, then the server may simply use that candidate set in the course of determining the matching entry count, even if there may be additional processing that can be performed (e.g., further filter components to evaluate) that may allow the server to pare down the results even further. Short-circuiting may allow the server to obtain the matching entry count estimate faster, but may also cause the resulting estimate to be less accurate.

      The value returned by this method will be used for cases in which the server is performing index processing that is not considered to be among the fastest types of processing. For example, this may include evaluating substring and range components, as they may require retrieving many index keys to obtain the full candidate set.
      Returns:
      The short-circuit threshold that should be used for slow index processing, or zero if the server should not short-circuit at all during slow index processing, or null if the server should determine the appropriate slow short-circuit threshold to use.

    • includeExtendedResponseData

      public boolean includeExtendedResponseData()
      Indicates whether the server may include extended response data in the corresponding response control, which may provide information like whether all of the identified candidate entries are within the scope of the search and any unindexed or unevaluated portion of the search filter.
      Returns:
      true if the server may include extended response data in the corresponding response control, or false if not.

    • serverSupportsExtendedResponseData

      public static boolean serverSupportsExtendedResponseData(@NotNull LDAPInterface connection) throws LDAPException
      Attempts to determine whether the server to which the provided connection is established supports including extended response data in the matching entry count response control.
      Parameters:
      connection - The connection (or connection pool or other interface) to use to communicate with the server. It must not be null and must be established.
      Returns:
      true if the server reports that supports including extended response data in the matching entry count response control, or false if it does not indicate that it is supported.
      Throws:
      LDAPException - If a problem occurs while attempting to communicate with the server.

    • serverSupportsExtendedResponseData

      public static boolean serverSupportsExtendedResponseData(@NotNull RootDSE rootDSE)
      Determines whether the provided root DSE indicates that the associated server supports including extended response data in the matching entry count response control.
      Parameters:
      rootDSE - The root DSE retrieved from the server for which to make the determination. It must not be null.
      Returns:
      true if the root DSE indicates that supports including extended response data in the matching entry count response control, or false if not.

    • includeDebugInfo

      public boolean includeDebugInfo()
      Indicates whether the server should include debug information in the response control that provides additional information about how the server arrived at the result. If debug information is to be provided, it will be in a human-readable rather than machine-parsable form.
      Returns:
      true if the server should include debug information in the response control, or false if not.

    • getControlName

      @NotNull public String getControlName()
      Retrieves the user-friendly name for this control, if available. If no user-friendly name has been defined, then the OID will be returned.
      Overrides:
      getControlName in class Control
      Returns:
      The user-friendly name for this control, or the OID if no user-friendly name is available.

    • toJSONControl

      @NotNull public JSONObject toJSONControl()
      Retrieves a representation of this matching entry count request control as a JSON object. The JSON object uses the following fields:
      • oid -- A mandatory string field whose value is the object identifier for this control. For the matching entry count request control, the OID is "1.3.6.1.4.1.30221.2.5.36".
      • control-name -- An optional string field whose value is a human-readable name for this control. This field is only intended for descriptive purposes, and when decoding a control, the oid field should be used to identify the type of control.
      • criticality -- A mandatory Boolean field used to indicate whether this control is considered critical.
      • value-base64 -- An optional string field whose value is a base64-encoded representation of the raw value for this matching entry count request control. Exactly one of the value-base64 and value-json fields must be present.
      • value-json -- An optional JSON object field whose value is a user-friendly representation of the value for this matching entry count request control. Exactly one of the value-base64 and value-json fields must be present, and if the value-json field is used, then it will use the following fields:
        • maximum-candidates-to-examine -- An optional integer field whose value indicates the maximum number of entries that the server should retrieve and examine to determine whether they actually match the search criteria and would be returned to the client.
        • always-examine-candidates -- An optional Boolean field that indicates whether the server should always examine candidates to determine whether they would actually be returned to the client, even if the search is fully indexed and the server knows that all candidates match the search criteria.
        • process-search-if-unindexed -- An optional Boolean field that indicates whether the server should attempt to process the search even if the search criteria is completely unindexed.
        • include-debug-info -- An optional Boolean field that indicates whether the server should return debug information in the response control about the processing it performed in the course of determining the matching entry count estimate.
        • skip-resolving-exploded-indexes -- An optional Boolean field that indicates whether the server should skip the step of resolving exploded indexes in cases where the size of the ID set is known.
        • fast-short-circuit-threshold -- An optional integer field whose value is the short-circuit threshold that the server should use for "fast" filter components.
        • slow-short-circuit-threshold -- An optional integer field whose value is the short-circuit threshold that the server should use for "slow" filter components.
        • include-extended-response-data -- An optional Boolean field that indicates whether the server should include extended information in the response control.
      Overrides:
      toJSONControl in class Control
      Returns:
      A JSON object that contains a representation of this control.

    • decodeJSONControl

      @NotNull public static MatchingEntryCountRequestControl decodeJSONControl(@NotNull JSONObject controlObject, boolean strict) throws LDAPException
      Attempts to decode the provided object as a JSON representation of a matching entry count request control.
      Parameters:
      controlObject - The JSON object to be decoded. It must not be null.
      strict - Indicates whether to use strict mode when decoding the provided JSON object. If this is true, then this method will throw an exception if the provided JSON object contains any unrecognized fields. If this is false, then unrecognized fields will be ignored.
      Returns:
      The matching entry count request control that was decoded from the provided JSON object.
      Throws:
      LDAPException - If the provided JSON object cannot be parsed as a valid matching entry count request control.

    • toString

      public void toString(@NotNull StringBuilder buffer)
      Appends a string representation of this LDAP control to the provided buffer.
      Overrides:
      toString in class Control
      Parameters:
      buffer - The buffer to which to append the string representation of this buffer.