backing_store.h

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/*
 * Copyright 2014 Vincent Sanders <vince@netsurf-browser.org>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * NetSurf is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
/**
 * \file
 * Low-level source data cache backing store interface.
 */
 
#ifndef NETSURF_CONTENT_LLCACHE_PRIVATE_H_
#define NETSURF_CONTENT_LLCACHE_PRIVATE_H_
 
#include "content/llcache.h"
 
/** storage control flags */
enum backing_store_flags {
        /** no special processing */
        BACKING_STORE_NONE = 0,
        /** data is metadata */
        BACKING_STORE_META = 1,
};
 
/**
 * low level cache backing store operation table
 *
 * The low level cache (source objects) has the capability to make
 * objects and their metadata (headers etc) persistent by writing to a
 * backing store using these operations.
 */
struct gui_llcache_table {
        /**
         * Initialise the backing store.
         *
         * @param parameters to configure backing store.
         * @return NSERROR_OK on success or error code on failure.
         */
        nserror (*initialise)(const struct llcache_store_parameters *parameters);
 
        /**
         * Finalise the backing store.
         *
         * @return NSERROR_OK on success or error code on failure.
         */
        nserror (*finalise)(void);
 
        /**
         * Place an object in the backing store.
         *
         * The object is placed in the persistent store and may be
         *  retrieved with the fetch method.
         *
         * The backing store will take a reference to the
         *  passed data, subsequently the caller should explicitly
         *  release the allocation using the release method and not
         *  free the data itself.
         *
         * The caller may not assume that the persistent storage has
         *  been completely written on return.
         *
         * @param[in] url The url is used as the unique primary key for the data.
         * @param[in] flags The flags to control how the object is stored.
         * @param[in] data The objects data.
         * @param[in] datalen The length of the \a data.
         * @return NSERROR_OK on success or error code on failure.
         */
        nserror (*store)(struct nsurl *url, enum backing_store_flags flags,
                         uint8_t *data, const size_t datalen);
 
        /**
         * Retrieve an object from the backing store.
         *
         * The backing store will manage its own memory and the
         * allocations returned in \a data *must* not be altered.
         *
         * The caller must assume nothing about the backing store
         *  allocated buffers and the storage and *must* be freed by
         *  calling the release method.
         *
         * @param[in] url The url is used as the unique primary key for the data.
         * @param[in] flags The flags to control how the object is retrieved.
         * @param[out] data The retrieved objects data.
         * @param[out] datalen The length of the \a data retrieved.
         * @return NSERROR_OK on success or error code on failure.
         */
        nserror (*fetch)(struct nsurl *url, enum backing_store_flags flags,
                         uint8_t **data, size_t *datalen);
 
        /**
         * release a previously fetched or stored memory object.
         *
         * @param url The url is used as the unique primary key to invalidate.
         * @param[in] flags The flags to control how the object data is released.
         * @return NSERROR_OK on success or error code on failure.
         */
        nserror (*release)(struct nsurl *url, enum backing_store_flags flags);
 
        /**
         * Invalidate a source object from the backing store.
         *
         * The entry (if present in the backing store) must no longer
         * be returned as a result to the fetch or meta operations.
         *
         * If the entry had data allocated it will be released.
         *
         * @param url The url is used as the unique primary key to invalidate.
         * @return NSERROR_OK on success or error code on failure.
         */
        nserror (*invalidate)(struct nsurl *url);
 
};
 
extern struct gui_llcache_table* null_llcache_table;
extern struct gui_llcache_table* filesystem_llcache_table;
 
#endif