netwerk/base/public/nsICachingChannel.idl

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  15  * The Original Code is mozilla.org code.
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  20  * the Initial Developer. All Rights Reserved.
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  22  * Contributor(s):
  23  *   Darin Fisher <darin@netscape.com> (original author)
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  38
  39 #include "nsISupports.idl"
  40
  41 interface nsIFile;
  42
  43 /**
  44  * A channel may optionally implement this interface to allow clients
  45  * to affect its behavior with respect to how it uses the cache service.
  46  *
  47  * This interface provides:
  48  *   1) Support for "stream as file" semantics (for JAR and plugins).
  49  *   2) Support for "pinning" cached data in the cache (for printing and save-as).
  50  *   3) Support for uniquely identifying cached data in cases when the URL
  51  *      is insufficient (e.g., HTTP form submission).
  52  */
  53 [scriptable, uuid(830D4BCB-3E46-4011-9BDA-51A5D1AF891F)]
  54 interface nsICachingChannel : nsISupports
  55 {
  56     /**
  57      * Set/get the cache token... uniquely identifies the data in the cache.
  58      * Holding a reference to this token prevents the cached data from being
  59      * removed.
  60      *
  61      * A cache token retrieved from a particular instance of nsICachingChannel
  62      * could be set on another instance of nsICachingChannel provided the
  63      * underlying implementations are compatible.  The implementation of
  64      * nsICachingChannel would be expected to only read from the cache entry
  65      * identified by the cache token and not try to validate it.
  66      *
  67      * The cache token can be QI'd to a nsICacheEntryInfo if more detail
  68      * about the cache entry is needed (e.g., expiration time).
  69      */
  70     attribute nsISupports cacheToken;
  71
  72     /**
  73      * The same as above but accessing the offline app cache token if there
  74      * is any.
  75      *
  76      * @throws
  77      *      NS_ERROR_NOT_AVAILABLE when there is not offline cache token
  78      */
  79     attribute nsISupports offlineCacheToken;
  80
  81     /**
  82      * Set/get the cache key... uniquely identifies the data in the cache
  83      * for this channel.  Holding a reference to this key does NOT prevent
  84      * the cached data from being removed.
  85      *
  86      * A cache key retrieved from a particular instance of nsICachingChannel
  87      * could be set on another instance of nsICachingChannel provided the
  88      * underlying implementations are compatible and provided the new
  89      * channel instance was created with the same URI.  The implementation of
  90      * nsICachingChannel would be expected to use the cache entry identified
  91      * by the cache token.  Depending on the value of nsIRequest::loadFlags,
  92      * the cache entry may be validated, overwritten, or simply read.
  93      *
  94      * The cache key may be NULL indicating that the URI of the channel is
  95      * sufficient to locate the same cache entry.  Setting a NULL cache key
  96      * is likewise valid.
  97      */
  98     attribute nsISupports cacheKey;
  99
 100     /**
 101      * Specifies whether or not the data should be cached to a file.  This
 102      * may fail if the disk cache is not present.  The value of this attribute
 103      * is usually only settable during the processing of a channel's
 104      * OnStartRequest.  The default value of this attribute depends on the
 105      * particular implementation of nsICachingChannel.
 106      */
 107     attribute boolean cacheAsFile;
 108
 109     /**
 110      * Specifies whether or not the data should be placed in the offline cache,
 111      * in addition to normal memory/disk caching.  This may fail if the offline
 112      * cache is not present.  The value of this attribute should be set before
 113      * opening the channel.
 114      */
 115     attribute boolean cacheForOfflineUse;
 116
 117     /**
 118      * The session into which to cache offline data.  If not specified,
 119      * data will be placed in "HTTP-offline"
 120      */
 121     attribute ACString offlineCacheClientID;
 122
 123     /**
 124      * Get the "file" where the cached data can be found.  This is valid for
 125      * as long as a reference to the cache token is held.  This may return
 126      * an error if cacheAsFile is false.
 127      */
 128     readonly attribute nsIFile cacheFile;
 129
 130     /**
 131      * TRUE if this channel's data is being loaded from the cache.  This value
 132      * is undefined before the channel fires its OnStartRequest notification
 133      * and after the channel fires its OnStopRequest notification.
 134      */
 135     boolean isFromCache();
 136
 137     /**************************************************************************
 138      * Caching channel specific load flags:
 139      */
 140
 141     /**
 142      * This load flag inhibits fetching from the net.  An error of
 143      * NS_ERROR_DOCUMENT_NOT_CACHED will be sent to the listener's
 144      * onStopRequest if network IO is necessary to complete the request.
 145      *
 146      * This flag can be used to find out whether fetching this URL would
 147      * cause validation of the cache entry via the network.
 148      *
 149      * Combining this flag with LOAD_BYPASS_LOCAL_CACHE will cause all
 150      * loads to fail. This flag differs from LOAD_ONLY_FROM_CACHE in that
 151      * this flag fails the load if validation is required while
 152      * LOAD_ONLY_FROM_CACHE skips validation where possible.
 153      */
 154     const unsigned long LOAD_NO_NETWORK_IO = 1 << 26;
 155
 156     /**
 157      * This load flag causes the offline cache to be checked when fetching
 158      * a request.  It will be set automatically if the browser is offline.
 159      *
 160      * This flag will not be transferred through a redirect.
 161      */
 162     const unsigned long LOAD_CHECK_OFFLINE_CACHE = 1 << 27;
 163
 164     /**
 165      * This load flag causes the local cache to be skipped when fetching a
 166      * request.  Unlike LOAD_BYPASS_CACHE, it does not force an end-to-end load
 167      * (i.e., it does not affect proxy caches).
 168      */
 169     const unsigned long LOAD_BYPASS_LOCAL_CACHE = 1 << 28;
 170
 171     /**
 172      * This load flag causes the local cache to be skipped if the request
 173      * would otherwise block waiting to access the cache.
 174      */
 175     const unsigned long LOAD_BYPASS_LOCAL_CACHE_IF_BUSY = 1 << 29;
 176
 177     /**
 178      * This load flag inhibits fetching from the net if the data in the cache
 179      * has been evicted.  An error of NS_ERROR_DOCUMENT_NOT_CACHED will be sent
 180      * to the listener's onStopRequest in this case.  This flag is set
 181      * automatically when the application is offline.
 182      */
 183     const unsigned long LOAD_ONLY_FROM_CACHE = 1 << 30;
 184
 185     /**
 186      * This load flag controls what happens when a document would be loaded
 187      * from the cache to satisfy a call to AsyncOpen.  If this attribute is
 188      * set to TRUE, then the document will not be loaded from the cache.  A
 189      * stream listener can check nsICachingChannel::isFromCache to determine
 190      * if the AsyncOpen will actually result in data being streamed.
 191      *
 192      * If this flag has been set, and the request can be satisfied via the
 193      * cache, then the OnDataAvailable events will be skipped.  The listener
 194      * will only see OnStartRequest followed by OnStopRequest.
 195      */
 196     const unsigned long LOAD_ONLY_IF_MODIFIED = 1 << 31;
 197 };