nsICachingChannel Interface

 A channel may optionally implement this interface to allow clients
 to affect its behavior with respect to how it uses the cache service.

 This interface provides:
   1) Support for "stream as file" semantics (for JAR and plugins).
   2) Support for "pinning" cached data in the cache (for printing and save-as).
   3) Support for uniquely identifying cached data in cases when the URL
      is insufficient (e.g., HTTP form submission).

[scriptable, uuid(b1f95f5e-ee05-4434-9d34-89a935d7feef)]

Constants

 Caching channel specific load flags:


 This load flag causes the local cache to be skipped when fetching a
 request.  Unlike LOAD_BYPASS_CACHE, it does not force an end-to-end load
 (i.e., it does not affect proxy caches).

const unsigned long LOAD_BYPASS_LOCAL_CACHE = 268435456

 This load flag causes the local cache to be skipped if the request
 would otherwise block waiting to access the cache.

const unsigned long LOAD_BYPASS_LOCAL_CACHE_IF_BUSY = 536870912

 This load flag inhibits fetching from the net if the data in the cache
 has been evicted.  An error of NS_ERROR_DOCUMENT_NOT_CACHED will be sent
 to the listener's onStopRequest in this case.

const unsigned long LOAD_ONLY_FROM_CACHE = 1073741824

 This load flag controls what happens when a document would be loaded
 from the cache to satisfy a call to AsyncOpen.  If this attribute is
 set to TRUE, then the document will not be loaded from the cache.  A
 stream listener can check nsICachingChannel::isFromCache to determine
 if the AsyncOpen will actually result in data being streamed.

 If this flag has been set, and the request can be satisfied via the
 cache, then the OnDataAvailable events will be skipped.  The listener
 will only see OnStartRequest followed by OnStopRequest.

const unsigned long LOAD_ONLY_IF_MODIFIED = 2147483648

Attributes

 Specifies whether or not the data should be cached to a file.  This
 may fail if the disk cache is not present.  The value of this attribute
 is usually only settable during the processing of a channel's
 OnStartRequest.  The default value of this attribute depends on the
 particular implementation of nsICachingChannel.

attribute boolean cacheAsFile

 Get the "file" where the cached data can be found.  This is valid for
 as long as a reference to the cache token is held.  This may return
 an error if cacheAsFile is false.

readonly attribute nsIFile cacheFile

 Set/get the cache key... uniquely identifies the data in the cache
 for this channel.  Holding a reference to this key does NOT prevent
 the cached data from being removed.
 
 A cache key retrieved from a particular instance of nsICachingChannel
 could be set on another instance of nsICachingChannel provided the
 underlying implementations are compatible and provided the new 
 channel instance was created with the same URI.  The implementation of
 nsICachingChannel would be expected to use the cache entry identified
 by the cache token.  Depending on the value of nsIRequest::loadFlags,
 the cache entry may be validated, overwritten, or simply read.

 The cache key may be NULL indicating that the URI of the channel is
 sufficient to locate the same cache entry.  Setting a NULL cache key
 is likewise valid.

attribute nsISupports cacheKey

 Set/get the cache token... uniquely identifies the data in the cache.
 Holding a reference to this token prevents the cached data from being
 removed.
 
 A cache token retrieved from a particular instance of nsICachingChannel
 could be set on another instance of nsICachingChannel provided the
 underlying implementations are compatible.  The implementation of
 nsICachingChannel would be expected to only read from the cache entry
 identified by the cache token and not try to validate it.

 The cache token can be QI'd to a nsICacheEntryInfo if more detail
 about the cache entry is needed (e.g., expiration time).

attribute nsISupports cacheToken

Methods

 TRUE if this channel's data is being loaded from the cache.  This value
 is undefined before the channel fires its OnStartRequest notification
 and after the channel fires its OnStopRequest notification.

boolean isFromCache()