gecko-dev/netwerk/cache/nsICacheEntryDescriptor.idl

/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsICacheVisitor.idl"
#include "nsICache.idl"

interface nsISimpleEnumerator;
interface nsICacheListener;
interface nsIInputStream;
interface nsIOutputStream;
interface nsIFile;
interface nsICacheMetaDataVisitor;


[scriptable, uuid(49c1a11d-f5d2-4f09-8262-551e64908ada)]
interface nsICacheEntryDescriptor : nsICacheEntryInfo
{
    /**
     * Set the time at which the cache entry should be considered invalid (in
     * seconds since the Epoch).
     */
    void setExpirationTime(in uint32_t expirationTime);

    /**
     * Set the cache entry data size.  This will fail if the cache entry
     * IS stream based.
     */
    void setDataSize(in unsigned long size);

    /**
     * Open blocking input stream to cache data.  This will fail if the cache
     * entry IS NOT stream based.  Use the stream transport service to
     * asynchronously read this stream on a background thread.  The returned
     * stream MAY implement nsISeekableStream.
     *
     * @param offset
     *        read starting from this offset into the cached data.  an offset
     *        beyond the end of the stream has undefined consequences.
     *
     * @return blocking, unbuffered input stream.
     */
    nsIInputStream openInputStream(in unsigned long offset);

    /**
     * Open blocking output stream to cache data.  This will fail if the cache
     * entry IS NOT stream based.  Use the stream transport service to
     * asynchronously write to this stream on a background thread.  The returned
     * stream MAY implement nsISeekableStream.
     *
     * If opening an output stream to existing cached data, the data will be
     * truncated to the specified offset.
     *
     * @param offset
     *        write starting from this offset into the cached data.  an offset
     *        beyond the end of the stream has undefined consequences.
     *
     * @return blocking, unbuffered output stream.
     */
    nsIOutputStream openOutputStream(in unsigned long offset);

    /**
     * Get/set the cache data element.  This will fail if the cache entry
     * IS stream based.  The cache entry holds a strong reference to this
     * object.  The object will be released when the cache entry is destroyed.
     */
    attribute nsISupports cacheElement;
    
    /**
      * Stores the Content-Length specified in the HTTP header for this
      * entry. Checked before we write to the cache entry, to prevent ever
      * taking up space in the cache for an entry that we know up front 
      * is going to have to be evicted anyway. See bug 588507.
      */
    attribute int64_t    predictedDataSize;

    /**
     * Get the access granted to this descriptor.  See nsICache.idl for the
     * definitions of the access modes and a thorough description of their
     * corresponding meanings.
     */
    readonly attribute nsCacheAccessMode accessGranted;
    
    /**
     * Get/set the storage policy of the cache entry.  See nsICache.idl for
     * the definitions of the storage policies.
     */
    attribute nsCacheStoragePolicy storagePolicy;

    /**
     * Get the disk file associated with the cache entry.
     */
    readonly attribute nsIFile file;

    /**
     * Get/set security info on the cache entry for this descriptor.  This fails
     * if the storage policy is not STORE_IN_MEMORY.
     */
    attribute nsISupports securityInfo;
    
    /**
     * Get the size of the cache entry data, as stored. This may differ
     * from the entry's dataSize, if the entry is compressed.
     */
    readonly attribute unsigned long storageDataSize;

    /**
     * Doom the cache entry this descriptor references in order to slate it for 
     * removal.  Once doomed a cache entry cannot be undoomed.
     *
     * A descriptor with WRITE access can doom the cache entry and choose to
     * fail pending requests.  This means that pending requests will not get
     * a cache descriptor.  This is meant as a tool for clients that wish to
     * instruct pending requests to skip the cache.
     */
    void doom();
    void doomAndFailPendingRequests(in nsresult status);
    
    /**
     * A writer must validate this cache object before any readers are given
     * a descriptor to the object.
     */
    void markValid();

    /**
     *  Explicitly close the descriptor (optional).
     */
    
    void close();

    /**
     * Methods for accessing meta data.  Meta data is a table of key/value
     * string pairs.  The strings do not have to conform to any particular
     * charset, but they must be null terminated.
     */
    string getMetaDataElement(in string key);
    void   setMetaDataElement(in string key, in string value);
    
    /**
     * Visitor will be called with key/value pair for each meta data element.
     */
    void   visitMetaData(in nsICacheMetaDataVisitor  visitor);
};



[scriptable, uuid(22f9a49c-3cf8-4c23-8006-54efb11ac562)]
interface nsICacheMetaDataVisitor : nsISupports
{
    /**
     * Called for each key/value pair in the meta data for a cache entry
     */
    boolean visitMetaDataElement(in string  key,
                                 in string  value);
};