} dav_if_state_list;

typedef struct dav_if_header
{
    const char *uri;
    apr_size_t uri_len;
    struct dav_if_state_list *state;
    struct dav_if_header *next;

    int dummy_header;   /* used internally by the lock/etag validation */
} dav_if_header;

typedef struct dav_locktoken_list 
{
    dav_locktoken *locktoken;
    struct dav_locktoken_list *next;
} dav_locktoken_list;

DAV_DECLARE(dav_error *) dav_get_locktoken_list(request_rec *r,
                                                dav_locktoken_list **ltl);


/* --------------------------------------------------------------------
**
** LIVE PROPERTY HANDLING
*/

/* opaque type for PROPPATCH rollback information */
typedef struct dav_liveprop_rollback dav_liveprop_rollback;

struct dav_hooks_liveprop
{
    /*
    ** Insert property information into a text block. The property to
    ** insert is identified by the propid value. The information to insert
    ** is identified by the "what" argument, as follows:
    **   DAV_PROP_INSERT_NAME
    **      property name, as an empty XML element
    **   DAV_PROP_INSERT_VALUE
    **      property name/value, as an XML element
    **   DAV_PROP_INSERT_SUPPORTED
    **      if the property is defined on the resource, then
    **      a DAV:supported-live-property element, as defined
    **      by the DeltaV extensions to RFC2518.
    **                      
    ** Providers should return DAV_PROP_INSERT_NOTDEF if the property is
    ** known and not defined for this resource, so should be handled as a
    ** dead property. If a provider recognizes, but does not support, a
    ** property, and does not want it handled as a dead property, it should
    ** return DAV_PROP_INSERT_NOTSUPP.
    **
    ** Returns one of DAV_PROP_INSERT_* based on what happened.
    **
    ** ### we may need more context... ie. the lock database
    */
    dav_prop_insert (*insert_prop)(const dav_resource *resource,
                                   int propid, dav_prop_insert what,
                                   apr_text_header *phdr);

    /*
    ** Determine whether a given property is writable.
    **
    ** ### we may want a different semantic. i.e. maybe it should be
    ** ### "can we write <value> into this property?"
    **
    ** Returns 1 if the live property can be written, 0 if read-only.
    */
    int (*is_writable)(const dav_resource *resource, int propid);

    /*
    ** This member defines the set of namespace URIs that the provider
    ** uses for its properties. When insert_all is called, it will be
    ** passed a list of integers that map from indices into this list
    ** to namespace IDs for output generation.
    **
    ** The last entry in this list should be a NULL value (sentinel).
    */
    const char * const * namespace_uris;

    /*
    ** ### this is not the final design. we want an open-ended way for
    ** ### liveprop providers to attach *new* properties. To this end,
    ** ### we'll have a "give me a list of the props you define", a way
    ** ### to check for a prop's existence, a way to validate a set/remove
    ** ### of a prop, and a way to execute/commit/rollback that change.
    */

    /*
    ** Validate that the live property can be assigned a value, and that
    ** the provided value is valid.
    **
    ** elem will point to the XML element that names the property. For
    ** example:
    **     <lp1:executable>T</lp1:executable>
    **
    ** The provider can access the cdata fields and the child elements
    ** to extract the relevant pieces.
    **
    ** operation is one of DAV_PROP_OP_SET or _DELETE.
    **
    ** The provider may return a value in *context which will be passed
    ** to each of the exec/commit/rollback functions. For example, this
    ** may contain an internal value which has been processed from the
    ** input element.
    **
    ** The provider must set defer_to_dead to true (non-zero) or false.
    ** If true, then the set/remove is deferred to the dead property
    ** database. Note: it will be set to zero on entry.
    */
    dav_error * (*patch_validate)(const dav_resource *resource,
                                  const apr_xml_elem *elem,
                                  int operation,
                                  void **context,
                                  int *defer_to_dead);

    /* ### doc... */
    dav_error * (*patch_exec)(const dav_resource *resource,
                              const apr_xml_elem *elem,
                              int operation,
                              void *context,
                              dav_liveprop_rollback **rollback_ctx);

    /* ### doc... */
    void (*patch_commit)(const dav_resource *resource,
                         int operation,
                         void *context,
                         dav_liveprop_rollback *rollback_ctx);

    /* ### doc... */
    dav_error * (*patch_rollback)(const dav_resource *resource,
                                  int operation,
                                  void *context,
                                  dav_liveprop_rollback *rollback_ctx);

    /*
    ** If a provider needs a context to associate with this hooks structure,
    ** then this field may be used. In most cases, it will just be NULL.
    */
    void *ctx;
};

/*
** dav_liveprop_spec: specify a live property
**
** This structure is used as a standard way to determine if a particular
** property is a live property. Its use is not part of the mandated liveprop
** interface, but can be used by liveprop providers in conjuction with the
** utility routines below.
**
** spec->name == NULL is the defined end-sentinel for a list of specs.
*/
typedef struct {
    int ns;             /* provider-local namespace index */
    const char *name;   /* name of the property */

    int propid;         /* provider-local property ID */

    int is_writable;    /* is the property writable? */

} dav_liveprop_spec;

/*
** dav_liveprop_group: specify a group of liveprops
**
** This structure specifies a group of live properties, their namespaces,
** and how to handle them.
*/
typedef struct {
    const dav_liveprop_spec *specs;
    const char * const *namespace_uris;
    const dav_hooks_liveprop *hooks;

} dav_liveprop_group;

/* ### docco */
DAV_DECLARE(int) dav_do_find_liveprop(const char *ns_uri, const char *name,
                                      const dav_liveprop_group *group,
                                      const dav_hooks_liveprop **hooks);

/* ### docco */
DAV_DECLARE(int) dav_get_liveprop_info(int propid,
                                       const dav_liveprop_group *group,
                                       const dav_liveprop_spec **info);

/* ### docco */
DAV_DECLARE(void) dav_register_liveprop_group(apr_pool_t *pool, 
                                              const dav_liveprop_group *group);

/* ### docco */
DAV_DECLARE(int) dav_get_liveprop_ns_index(const char *uri);

/* ### docco */
DAV_DECLARE(int) dav_get_liveprop_ns_count(void);

/* ### docco */
DAV_DECLARE(void) dav_add_all_liveprop_xmlns(apr_pool_t *p,
                                             apr_text_header *phdr);

/*
** The following three functions are part of mod_dav's internal handling
** for the core WebDAV properties. They are not part of mod_dav's API.
*/
DAV_DECLARE_NONSTD(int) dav_core_find_liveprop(
    const dav_resource *resource,
    const char *ns_uri,
    const char *name,
    const dav_hooks_liveprop **hooks);
DAV_DECLARE_NONSTD(void) dav_core_insert_all_liveprops(
    request_rec *r,
    const dav_resource *resource,
    dav_prop_insert what,
    apr_text_header *phdr);
DAV_DECLARE_NONSTD(void) dav_core_register_uris(apr_pool_t *p);


/*
** Standard WebDAV Property Identifiers
**
** A live property provider does not need to use these; they are simply
** provided for convenience.
**
** Property identifiers need to be unique within a given provider, but not
** *across* providers (note: this uniqueness constraint was different in
** older versions of mod_dav).
**
** The identifiers start at 20000 to make it easier for providers to avoid
** conflicts with the standard properties. The properties are arranged
** alphabetically, and may be reordered from time to time (as properties
** are introduced).
**
** NOTE: there is no problem with reordering (e.g. binary compat) since the
** identifiers are only used within a given provider, which would pick up
** the entire set of changes upon a recompile.
*/
enum {
    DAV_PROPID_BEGIN = 20000,

    /* Standard WebDAV properties (RFC 2518) */
    DAV_PROPID_creationdate,
    DAV_PROPID_displayname,
    DAV_PROPID_getcontentlanguage,
    DAV_PROPID_getcontentlength,
    DAV_PROPID_getcontenttype,
    DAV_PROPID_getetag,
    DAV_PROPID_getlastmodified,
    DAV_PROPID_lockdiscovery,
    DAV_PROPID_resourcetype,
    DAV_PROPID_source,
    DAV_PROPID_supportedlock,

    /* DeltaV properties (from the I-D (#14)) */
    DAV_PROPID_activity_checkout_set,
    DAV_PROPID_activity_set,
    DAV_PROPID_activity_version_set,
    DAV_PROPID_auto_merge_set,
    DAV_PROPID_auto_version,
    DAV_PROPID_baseline_collection,
    DAV_PROPID_baseline_controlled_collection,
    DAV_PROPID_baseline_controlled_collection_set,
    DAV_PROPID_checked_in,
    DAV_PROPID_checked_out,
    DAV_PROPID_checkin_fork,
    DAV_PROPID_checkout_fork,
    DAV_PROPID_checkout_set,
    DAV_PROPID_comment,
    DAV_PROPID_creator_displayname,
    DAV_PROPID_current_activity_set,
    DAV_PROPID_current_workspace_set,
    DAV_PROPID_default_variant,
    DAV_PROPID_eclipsed_set,
    DAV_PROPID_label_name_set,
    DAV_PROPID_merge_set,
    DAV_PROPID_precursor_set,
    DAV_PROPID_predecessor_set,
    DAV_PROPID_root_version,
    DAV_PROPID_subactivity_set,
    DAV_PROPID_subbaseline_set,
    DAV_PROPID_successor_set,
    DAV_PROPID_supported_method_set,
    DAV_PROPID_supported_live_property_set,
    DAV_PROPID_supported_report_set,
    DAV_PROPID_unreserved,
    DAV_PROPID_variant_set,
    DAV_PROPID_version_controlled_binding_set,
    DAV_PROPID_version_controlled_configuration,
    DAV_PROPID_version_history,
    DAV_PROPID_version_name,
    DAV_PROPID_workspace,
    DAV_PROPID_workspace_checkout_set,

    DAV_PROPID_END
};

/*
** Property Identifier Registration
**
** At the moment, mod_dav requires live property providers to ensure that
** each property returned has a unique value. For now, this is done through
** central registration (there are no known providers other than the default,
** so this remains manageable).
**
** WARNING: the TEST ranges should never be "shipped".
*/
#define DAV_PROPID_CORE         10000   /* ..10099. defined by mod_dav */
#define DAV_PROPID_FS           10100   /* ..10299.
                                           mod_dav filesystem provider. */
#define DAV_PROPID_TEST1        10300   /* ..10399 */
#define DAV_PROPID_TEST2        10400   /* ..10499 */
#define DAV_PROPID_TEST3        10500   /* ..10599 */
/* Next: 10600 */


/* --------------------------------------------------------------------
**
** DATABASE FUNCTIONS
*/

typedef struct dav_db dav_db;
typedef struct dav_namespace_map dav_namespace_map;
typedef struct dav_deadprop_rollback dav_deadprop_rollback;

typedef struct {
    const char *ns;     /* "" signals "no namespace" */
    const char *name;
} dav_prop_name;

/* hook functions to enable pluggable databases */
struct dav_hooks_propdb
{
    dav_error * (*open)(apr_pool_t *p, const dav_resource *resource, int ro,
                        dav_db **pdb);
    void (*close)(dav_db *db);

    /*
    ** In bulk, define any namespaces that the values and their name
    ** elements may need.
    **
    ** Note: sometimes mod_dav will defer calling this until output_value
    ** returns found==1. If the output process needs the dav_xmlns_info
    ** filled for its work, then it will need to fill it on demand rather
    ** than depending upon this hook to fill in the structure.
    **
    ** Note: this will *always* be called during an output sequence. Thus,
    ** the provider may rely solely on using this to fill the xmlns info.
    */
    dav_error * (*define_namespaces)(dav_db *db, dav_xmlns_info *xi);

    /*
    ** Output the value from the database (i.e. add an element name and