Merge branch 'vince/llcache'

Docs/source-object-backing-store

@@ -0,0 +1,194 @@
+Source Object (low level) cache backing store
+=============================================
+
+Introduction
+------------
+
+The source object cache provides a system to extend the life of source
+objects (html files, images etc.) after they are no longer immediately
+being used.
+
+Only fetch types where we have well defined rules on caching are
+considered, in practice this limits us to HTTP(S). The section in
+RFC2616 [1] on caching specifies these rules.
+
+To futher extend the objects lifetime they can be pushed into a
+backing store where the objects are available for reuse less quickly
+than from RAM but faster than retriving from the network again.
+
+The backing store implementation provides a key:value infrastructure
+with a simple store, retrive and invalidate interface.
+
+Generic filesystem backing store
+--------------------------------
+
+Although the backing store interface is fully pluggable a generic
+implementation based on storing objects on the filesystem in a
+heirachy of directories.
+
+The option to alter the backing store format exists and is controled
+by a version field. It is implementation defined what happens if a
+version mis-match occours.
+
+As the backing store only holds cache data one should not expect a
+great deal of effort to be expended converting formats (i.e. the cache
+may simply be discarded).
+
+Layout version 1
+----------------
+
+An object has an identifier value generated from the url (NetSurf
+backing stores uses the url as the unique key). The value used is
+obtained using nsurl_hash() which is currently a 32 bit FNV so is
+directly usable.
+
+This identifier is adequate to ensure the collision rate for the
+hashed url values (a collision for every 2^16 urls added) is
+sufficiently low the overhead of returning the wrong object (which
+backing stores are permitted to do) is not significat.
+
+An entry list is maintained which contains all the metadata about a
+given identifier. This list is limited in length to constrain the
+resources necessary to maintain it. It is made persistant to avoid the
+overhead of reconstructing it at initialisation and to keep the data
+used to improve the eviction decisions.
+
+Each object is stored and retrived directly into the filesystem using
+a filename generated from a base64url encoding of an address
+value. The objects address is derived from the identifier by cropping
+it to a shorter length.
+
+A mapping between the object address and its entry is maintained which
+uses storage directly proportional to the size of the address length.
+
+The cropping length is stored in the control file with the default
+values set at compile time. This allows existing backing stores to
+continue operating with existing data independantly of new default
+setting. This setting gives some ability to tune the default cache
+index size to values suitable for a specific host operating system.
+
+E.g. Linux based systems can easily cope with several megabytes of
+mmaped index but RISC OS might want to limit this to a few megabytes
+of heap at most.
+
+The files are stored on disc using their base64url address value.
+By creating a directory for each character of the encoded filename
+(except the last which is of course the leafname) we create a
+directory structure where no directory has more than 64 entries.
+
+E.g. A 19bit address of 0x1 would be base64url encoded into AAAB
+resulting in the data being stored in a file path of
+"/store/prefix/data/B/A/A/BAAAAA".
+
+An address of 0x00040001 encodes to BAAB and a file path of
+"/store/prefix/meta/B/A/A/BAABAA"
+
+Control files
+~~~~~~~~~~~~~
+
+control
++++++++
+A control file is used to hold a list of values describing how the
+other files in the backing store should be used.
+
+entries
++++++++
+
+this file contains a table of entries describing the files held on the
+filesystem.
+
+Each control file table entry is 28 bytes and consists of
+
+ - signed 64 but value for last use time
+
+ - 32bit full url hash allowing for index reconstruction and
+   addiitonal collision detection. Also the possibility of increasing
+   the ADDRESS_LENGTH although this would require renaming all the
+   existing files in the cache and is not currently implemented.
+
+ - unsigned 32bit length for data
+
+ - unsigned 32bit length for metadata
+
+ - unsigned 16bit value for number of times used.
+
+ - unsigned 16bit value for flags
+
+ - unsigned 16bit value for data block index (unused)
+
+ - unsigned 16bit value for metatdata block index (unused)
+
+Address to entry index
+~~~~~~~~~~~~~~~~~~~~~~
+
+An entry index is held in RAM that allows looking up the address to
+map to an entry in the control file.
+
+The index is the only data structure whose size is directly depndant
+on the length of the hash specificaly:
+
+(2 ^ (ADDRESS_BITS - 3)) * ENTRY_BITS) in bytes
+
+where ADDRESS_BITS is how long the address is in bits and ENTRY_BITS
+is how many entries the control file (and hence the while
+cache) may hold.
+
+RISCOS values
++++++++++++++
+
+By limiting the ENTRY_BITS size to 14 (16,384 entries) the entries
+list is limited to 448kilobytes.
+
+The typical values for RISC OS would set ADDRESS_BITS to 18. This
+spreads the entries over 262144 hash values which uses 512 kilobytes
+for the index. Limiting the hash space like this reduces the
+efectiveness of the cache.
+
+A small ADDRESS_LENGTH causes a collision (two urls with the same
+address) to happen roughly for every 2 ^ (ADDRESS_BITS / 2) = 2 ^ 9 =
+512 objects stored. This roughly translates to a cache miss due to
+collision every ten pages navigated to.
+
+Larger systems
+++++++++++++++
+
+In general ENTRY_BITS set to 16 as this limits the store to 65536
+objects which given the average size of an object at 8 kilobytes
+yeilds half a gigabyte of disc used which is judged to be sufficient.
+
+For larger systems e.g. those using GTK frontend we would most likely
+select ADDRESS_BITS as 22 resulting in a collision every 2048 objects
+but the index using some 8 Megabytes
+
+Typical values
+--------------
+
+Example 1
+~~~~~~~~~
+
+For a store with 1034 objects genrated from a random navigation of
+pages linked from the about:welcome page.
+
+Metadata total size is 593608 bytes an average of 574 bytes. The
+majority of the storage is used to hold the urls and headers.
+
+Data total size is 9180475 bytes a mean of 8879 bytes 1648726 in the
+largest 10 entries which if excluded gives 7355 bytes average size
+
+Example 2
+~~~~~~~~~
+
+355 pages navigated in 80 minutes from about:welcome page and a
+handful of additional sites (google image search and reddit)
+
+2018 objects in cache at quit. 400 objects from news.bbc.co.uk alone
+
+Metadata total 987,439 bytes mean of 489 bytes
+
+data total 33,127,831 bytes mean of 16,416 bytes
+
+with one single 5,000,811 byte gif
+
+data totals without gif is 28,127,020 mean 13,945
+
+[1] http://tools.ietf.org/html/rfc2616#section-13

Makefile.defaults

@@ -86,6 +86,11 @@ NETSURF_HOMEPAGE := "about:welcome"
 # Valid options: YES, NO
 NETSURF_USE_LIBICONV_PLUG := YES
 
+# Enable building the source object cache filesystem based backing store.
+# implementation.
+# Valid options: YES, NO
+NETSURF_FS_BACKING_STORE := NO
+
 # Initial CFLAGS. Optimisation level etc. tend to be target specific.
 CFLAGS :=
 

amiga/gui.c

@@ -5294,7 +5294,7 @@ int main(int argc, char** argv)
 
 	if (ami_locate_resource(messages, "Messages") == false)
 		die("Cannot open Messages file");
-	ret = netsurf_init(messages);
+	ret = netsurf_init(messages, NULL);
 	if (ret != NSERROR_OK) {
 		die("NetSurf failed to initialise");
 	}

atari/gui.c

@@ -1126,7 +1126,7 @@ int main(int argc, char** argv)
 
     /* common initialisation */
     LOG(("Initialising core..."));
-    ret = netsurf_init(messages);
+    ret = netsurf_init(messages, NULL);
     if (ret != NSERROR_OK) {
 	die("NetSurf failed to initialise");
     }

beos/gui.cpp

@@ -1062,7 +1062,7 @@ int main(int argc, char** argv)
 
 	/* common initialisation */
 	BPath messages = get_messages_path();
-	ret = netsurf_init(messages.Path());
+        ret = netsurf_init(messages.Path(), NULL);
 	if (ret != NSERROR_OK) {
 		die("NetSurf failed to initialise");
 	}
@@ -1115,7 +1115,7 @@ int gui_init_replicant(int argc, char** argv)
 
 	/* common initialisation */
 	BPath messages = get_messages_path();
-	ret = netsurf_init(messages.Path());
+        ret = netsurf_init(messages.Path(), NULL);
 	if (ret != NSERROR_OK) {
 		// FIXME: must not die when in replicant!
 		die("NetSurf failed to initialise");

cocoa/NetsurfApp.m

@@ -217,7 +217,7 @@ int main( int argc, char **argv )
 	nsoption_commandline(&argc, argv, NULL);
 
 	/* common initialisation */
-	error = netsurf_init(messages);
+        error = netsurf_init(messages, NULL);
 	if (error != NSERROR_OK) {
 		die("NetSurf failed to initialise");
 	}

content/Makefile

@@ -1,6 +1,11 @@
 # Content sources
 
 S_CONTENT := content.c content_factory.c dirlist.c fetch.c hlcache.c	\
-	llcache.c mimesniff.c urldb.c
+	llcache.c mimesniff.c urldb.c no_backing_store.c
+
+# Make filesystem backing store available
+ifeq ($(NETSURF_FS_BACKING_STORE),YES)
+	S_CONTENT += fs_backing_store.c
+endif
 
 S_CONTENT := $(addprefix content/,$(S_CONTENT))

content/backing_store.h

@@ -0,0 +1,100 @@
+/*
+ * 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 {
+	BACKING_STORE_NONE = 0, /**< no special processing */
+	BACKING_STORE_META = 1, /**< data is metadata */
+	BACKING_STORE_MMAP = 2, /**< when data is retrived this indicates the
+				 * returned buffer may be memory mapped,
+				 * flag must be cleared if the storage is
+				 * allocated and is not memory mapped.
+				 */
+};
+
+/** low level cache backing store operation table
+ *
+ * The low level cache (source objects) has the capability to make
+ * objects and their metadata (headers etc) persistant 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 faliure.
+	 */
+	nserror (*initialise)(const struct llcache_store_parameters *parameters);
+
+	/**
+	 * Finalise the backing store.
+	 *
+	 * @return NSERROR_OK on success or error code on faliure.
+	 */
+	nserror (*finalise)(void);
+
+	/**
+	 * Place an object in the backing store.
+	 *
+	 * @param url The url is used as the unique primary key for the data.
+	 * @param flags The flags to control how the obejct is stored.
+	 * @param data The objects data.
+	 * @param datalen The length of the \a data.
+	 * @return NSERROR_OK on success or error code on faliure.
+	 */
+	nserror (*store)(struct nsurl *url, enum backing_store_flags flags,
+			 const uint8_t *data, const size_t datalen);
+
+	/**
+	 * Retrive an object from the backing store.
+	 *
+	 * @param url The url is used as the unique primary key for the data.
+	 * @param flags The flags to control how the object is retrived.
+	 * @param data The objects data.
+	 * @param datalen The length of the \a data retrieved.
+	 * @return NSERROR_OK on success or error code on faliure.
+	 */
+	nserror (*fetch)(struct nsurl *url, enum backing_store_flags *flags,
+			 uint8_t **data, size_t *datalen);
+
+	/**
+	 * 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.
+	 *
+	 * @param url The url is used as the unique primary key to invalidate.
+	 * @return NSERROR_OK on success or error code on faliure.
+	 */
+	nserror (*invalidate)(struct nsurl *url);
+};
+
+extern struct gui_llcache_table* null_llcache_table;
+extern struct gui_llcache_table* filesystem_llcache_table;
+
+#endif

content/hlcache.c

@@ -339,9 +339,10 @@ static nserror hlcache_migrate_ctx(hlcache_retrieval_ctx *ctx,
 
 	ctx->migrate_target = true;
 
-	if (effective_type != NULL &&
+	if ((effective_type != NULL) &&
 	    hlcache_type_is_acceptable(effective_type,
-			ctx->accepted_types, &type)) {
+				       ctx->accepted_types,
+				       &type)) {
 		error = hlcache_find_content(ctx, effective_type);
 		if (error != NSERROR_OK && error != NSERROR_NEED_DATA) {
 			if (ctx->handle->cb != NULL) {
@@ -524,9 +525,7 @@ hlcache_initialise(const struct hlcache_parameters *hlcache_parameters)
 		return NSERROR_NOMEM;
 	}
 
-	ret = llcache_initialise(hlcache_parameters->cb,
+	ret = llcache_initialise(&hlcache_parameters->llcache);
-				 hlcache_parameters->cb_ctx,
-				 hlcache_parameters->limit);
 	if (ret != NSERROR_OK) {
 		free(hlcache);
 		hlcache = NULL;

content/hlcache.h

@@ -23,11 +23,12 @@
 #ifndef NETSURF_CONTENT_HLCACHE_H_
 #define NETSURF_CONTENT_HLCACHE_H_
 
-#include "content/content.h"
-#include "content/llcache.h"
 #include "utils/errors.h"
 #include "utils/nsurl.h"
 
+#include "content/content.h"
+#include "content/llcache.h"
+
 /** High-level cache handle */
 typedef struct hlcache_handle hlcache_handle;
 
@@ -44,18 +45,10 @@ typedef struct {
 } hlcache_event;
 
 struct hlcache_parameters {
-	llcache_query_callback cb; /**< Query handler for llcache */
-	void *cb_ctx; /**< Pointer to llcache query handler data */
-
 	/** How frequently the background cache clean process is run (ms) */
 	unsigned int bg_clean_time;
 
-	/** The target upper bound for the cache size */
+	struct llcache_parameters llcache;
-	size_t limit;
-
-	/** The hysteresis allowed round the target size */
-	size_t hysteresis;
-
 };
 
 /**

content/llcache.h

@@ -156,6 +156,74 @@ typedef nserror (*llcache_query_response)(bool proceed, void *cbpw);
 typedef nserror (*llcache_query_callback)(const llcache_query *query, void *pw,
 		llcache_query_response cb, void *cbpw);
 
+/**
+ * Parameters to configure the low level cache backing store.
+ */
+struct llcache_store_parameters {
+	const char *path; /**< The path to the backing store */
+
+	size_t limit; /**< The backing store upper bound target size */
+	size_t hysteresis; /**< The hysteresis around the target size */
+
+	/** log2 of the default maximum number of entries the cache
+	 * can track.
+	 *
+	 * If unset this defaults to 16 (65536 entries) The cache
+	 * control file takes precedence so cache data remains
+	 * portable between builds with differing defaults.
+	 */
+	unsigned int entry_size;
+
+	/** log2 of the default number of entries in the mapping between
+	 * the url and cache entries.
+	 *
+	 * @note This is exposing an internal implementation detail of
+	 * the filesystem based default backing store implementation.
+	 * However it is likely any backing store implementation will
+	 * need some way to map url to cache entries so it is a
+	 * generally useful configuration value.
+	 *
+	 * Too small a value will cause unecessary collisions and
+	 * cache misses and larger values cause proportionaly larger
+	 * amounts of memory to be used.
+	 *
+	 * The "birthday paradox" means that the hash will experience
+	 * a collision in every 2^(address_size/2) urls the cache
+	 * stores.
+	 *
+	 * A value of 20 means one object stored in every 1024 will
+	 * cause a collion and a cache miss while using two megabytes
+	 * of storage.
+	 *
+	 * If unset this defaults to 20 (1048576 entries using two
+	 * megabytes) The cache control file takes precedence so cache
+	 * data remains portable between builds with differing
+	 * defaults.
+	 */
+	unsigned int address_size;
+};
+
+/**
+ * Parameters to configure the low level cache.
+ */
+struct llcache_parameters {
+	llcache_query_callback cb; /**< Query handler for llcache */
+	void *cb_ctx; /**< Pointer to llcache query handler data */
+
+	size_t limit; /**< The target upper bound for the RAM cache size */
+	size_t hysteresis; /**< The hysteresis around the target size */
+
+	int minimum_lifetime; /**< The minimum lifetime to consider
+			       * sending objects to backing store.
+			       */
+
+	size_t bandwidth; /**< The maximum bandwidth to allow the
+			   * backing store to use.
+			   */
+
+	struct llcache_store_parameters store;
+};
+
 /**
  * Initialise the low-level cache
  *
@@ -163,7 +231,7 @@ typedef nserror (*llcache_query_callback)(const llcache_query *query, void *pw,
  * \param pw  Pointer to query handler data
  * \return NSERROR_OK on success, appropriate error otherwise.
  */
-nserror llcache_initialise(llcache_query_callback cb, void *pw, uint32_t llcache_limit);
+nserror llcache_initialise(const struct llcache_parameters *parameters);
 
 /**
  * Finalise the low-level cache

content/no_backing_store.c

@@ -0,0 +1,68 @@
+/*
+ * 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 resource cache null persistant storage implementation.
+ */
+
+#include "utils/nsurl.h"
+
+#include "content/backing_store.h"
+
+
+/* default to disabled backing store */
+static nserror initialise(const struct llcache_store_parameters *parameters)
+{
+	return NSERROR_OK;
+}
+
+static nserror finalise(void)
+{
+	return NSERROR_OK;
+}
+
+static nserror store(nsurl *url,
+		     enum backing_store_flags flags,
+		     const uint8_t *data,
+		     const size_t datalen)
+{
+	return NSERROR_SAVE_FAILED;
+}
+
+static nserror fetch(nsurl *url,
+		     enum backing_store_flags *flags,
+		     uint8_t **data_out,
+		     size_t *datalen_out)
+{
+	return NSERROR_NOT_FOUND;
+}
+
+static nserror invalidate(nsurl *url)
+{
+	return NSERROR_NOT_FOUND;
+}
+
+static struct gui_llcache_table llcache_table = {
+	.initialise = initialise,
+	.finalise = finalise,
+	.store = store,
+	.fetch = fetch,
+	.invalidate = invalidate,
+};
+
+struct gui_llcache_table *null_llcache_table = &llcache_table;

desktop/gui.h

@@ -69,6 +69,7 @@ struct hlcache_handle;
 struct download_context;
 struct nsurl;
 struct gui_file_table;
+struct gui_llcache_table;
 
 typedef struct nsnsclipboard_styles {
 	size_t start;			/**< Start of run */
@@ -520,7 +521,6 @@ struct gui_browser_table {
 
 };
 
-
 /**
  * NetSurf operation function table
  *
@@ -572,6 +572,15 @@ struct netsurf_table {
 	 * Provides routines for the interactive text search on a page.
 	 */
 	struct gui_search_table *search;
+
+	/**
+	 * Low level cache table.
+	 *
+	 * Used by the low level cache to push objects to persistant
+	 * storage. The table is optional and may be NULL which
+	 * uses the default implementation.
+	 */
+	struct gui_llcache_table *llcache;
 };
 
 

desktop/gui_factory.c

@@ -17,6 +17,8 @@
  */
 
 #include "content/hlcache.h"
+#include "content/backing_store.h"
+
 #include "desktop/download.h"
 #include "desktop/gui_factory.h"
 #include "utils/file.h"
@@ -25,7 +27,6 @@
 struct netsurf_table *guit = NULL;
 
 
-
 static void gui_default_window_set_title(struct gui_window *g, const char *title)
 {
 }
@@ -400,6 +401,34 @@ static nserror verify_search_register(struct gui_search_table *gst)
 	return NSERROR_OK;
 }
 
+/** verify low level cache persistant backing store table is valid */
+static nserror verify_llcache_register(struct gui_llcache_table *glt)
+{
+	/* check table is present */
+	if (glt == NULL) {
+		return NSERROR_BAD_PARAMETER;
+	}
+
+	/* mandantory operations */
+	if (glt->store == NULL) {
+		return NSERROR_BAD_PARAMETER;
+	}
+	if (glt->fetch == NULL) {
+		return NSERROR_BAD_PARAMETER;
+	}
+	if (glt->invalidate == NULL) {
+		return NSERROR_BAD_PARAMETER;
+	}
+	if (glt->initialise == NULL) {
+		return NSERROR_BAD_PARAMETER;
+	}
+	if (glt->finalise == NULL) {
+		return NSERROR_BAD_PARAMETER;
+	}
+
+	return NSERROR_OK;
+}
+
 static nsurl *gui_default_get_resource_url(const char *path)
 {
 	return NULL;
@@ -622,6 +651,16 @@ nserror gui_factory_register(struct netsurf_table *gt)
 		return err;
 	}
 
+	/* llcache table */
+	if (gt->llcache == NULL) {
+		/* set default backing store table */
+		gt->llcache = null_llcache_table;
+	}
+	err = verify_llcache_register(gt->llcache);
+	if (err != NSERROR_OK) {
+		return err;
+	}
+
 	guit = gt;
 
 	return NSERROR_OK;

desktop/netsurf.c

@@ -67,11 +67,23 @@
 */
 #define SPECULATE_SMALL 4096
 
-/* the time between cache clean runs in ms */
+/** the time between image cache clean runs in ms. */
 #define IMAGE_CACHE_CLEAN_TIME (10 * 1000)
 
+/** default time between content cache cleans. */
 #define HL_CACHE_CLEAN_TIME (2 * IMAGE_CACHE_CLEAN_TIME)
 
+/** default minimum object time before object is pushed to backing store. */
+#define LLCACHE_MIN_DISC_LIFETIME (60 * 30)
+
+/** default maximum bandwidth for backing store writeout. */
+#define LLCACHE_MAX_DISC_BANDWIDTH (128 * 1024)
+
+/** ensure there is a minimal amount of memory for source objetcs and
+ * decoded bitmaps.
+ */
+#define MINIMUM_MEMORY_CACHE_SIZE (2 * 1024 * 1024)
+
 bool netsurf_quit = false;
 
 static void netsurf_lwc_iterator(lwc_string *str, void *pw)
@@ -108,8 +120,6 @@ static nserror netsurf_llcache_query_handler(const llcache_query *query,
 	return NSERROR_OK;
 }
 
-#define MINIMUM_MEMORY_CACHE_SIZE (2 * 1024 * 1024)
-
 /* exported interface documented in desktop/netsurf.h */
 nserror netsurf_register(struct netsurf_table *table)
 {
@@ -118,14 +128,17 @@ nserror netsurf_register(struct netsurf_table *table)
 }
 
 /* exported interface documented in desktop/netsurf.h */
-nserror netsurf_init(const char *messages)
+nserror netsurf_init(const char *messages, const char *store_path)
 {
-	nserror error;
+	nserror ret;
 	struct utsname utsname;
-	nserror ret = NSERROR_OK;
 	struct hlcache_parameters hlcache_parameters = {
 		.bg_clean_time = HL_CACHE_CLEAN_TIME,
+		.llcache = {
 			.cb = netsurf_llcache_query_handler,
+			.minimum_lifetime = LLCACHE_MIN_DISC_LIFETIME,
+			.bandwidth = LLCACHE_MAX_DISC_BANDWIDTH,
+		}
 	}; 
 	struct image_cache_parameters image_cache_parameters = {
 		.bg_clean_time = IMAGE_CACHE_CLEAN_TIME,
@@ -155,75 +168,86 @@ nserror netsurf_init(const char *messages)
 	messages_load(messages);
 
 	/* corestrings init */
-	error = corestrings_init();
+	ret = corestrings_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
 	/* set up cache limits based on the memory cache size option */
-	hlcache_parameters.limit = nsoption_int(memory_cache_size);
+	hlcache_parameters.llcache.limit = nsoption_int(memory_cache_size);
 
-	if (hlcache_parameters.limit < MINIMUM_MEMORY_CACHE_SIZE) {
+	if (hlcache_parameters.llcache.limit < MINIMUM_MEMORY_CACHE_SIZE) {
-		hlcache_parameters.limit = MINIMUM_MEMORY_CACHE_SIZE;
+		hlcache_parameters.llcache.limit = MINIMUM_MEMORY_CACHE_SIZE;
-		LOG(("Setting minimum memory cache size to %d",
+		LOG(("Setting minimum memory cache size %d",
-		     hlcache_parameters.limit));
+		     hlcache_parameters.llcache.limit));
 	} 
 
 	/* image cache is 25% of total memory cache size */
-	image_cache_parameters.limit = (hlcache_parameters.limit * 25) / 100;
+	image_cache_parameters.limit = (hlcache_parameters.llcache.limit * 25) / 100;
 
 	/* image cache hysteresis is 20% of the image cache size */
 	image_cache_parameters.hysteresis = (image_cache_parameters.limit * 20) / 100;
 
 	/* account for image cache use from total */
-	hlcache_parameters.limit -= image_cache_parameters.limit;
+	hlcache_parameters.llcache.limit -= image_cache_parameters.limit;
+
+	/* set backing store target limit */
+	hlcache_parameters.llcache.store.limit = nsoption_int(disc_cache_size);
+
+	/* set backing store hysterissi to 20% */
+	hlcache_parameters.llcache.store.hysteresis = (hlcache_parameters.llcache.store.limit * 20) / 100;;
+
+	/* set the path to the backing store */
+	hlcache_parameters.llcache.store.path = store_path;
 
 	/* image handler bitmap cache */
-	error = image_cache_init(&image_cache_parameters);
+	ret = image_cache_init(&image_cache_parameters);
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
 	/* content handler initialisation */
-	error = nscss_init();
+	ret = nscss_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
-	error = html_init();
+	ret = html_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
-	error = image_init();
+	ret = image_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
-	error = textplain_init();
+	ret = textplain_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
 
-	error = mimesniff_init();
+	ret = mimesniff_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
 	url_init();
 
 	setlocale(LC_ALL, "C");
 
 	/* initialise the fetchers */
-	error = fetch_init();
+	ret = fetch_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 	
 	/* Initialise the hlcache and allow it to init the llcache for us */
-	hlcache_initialise(&hlcache_parameters);
+	ret = hlcache_initialise(&hlcache_parameters);
+	if (ret != NSERROR_OK)
+		return ret;
 
 	/* Initialize system colours */
-	error = ns_system_colour_init();
+	ret = ns_system_colour_init();
-	if (error != NSERROR_OK)
+	if (ret != NSERROR_OK)
-		return error;
+		return ret;
 
 	js_initialise();
 
-	return ret;
+	return NSERROR_OK;
 }
 
 

desktop/netsurf.h

@@ -43,7 +43,7 @@ nserror netsurf_register(struct netsurf_table *table);
  * @param messages path to translation mesage file.
  * @return NSERROR_OK on success or error code on faliure.
  */
-nserror netsurf_init(const char *messages);
+nserror netsurf_init(const char *messages, const char *store_path);
 
 /**
  * Run event loop.

framebuffer/gui.c

@@ -1837,7 +1837,7 @@ main(int argc, char** argv)
 
 	/* common initialisation */
 	messages = filepath_find(respaths, "Messages");
-	ret = netsurf_init(messages);
+	ret = netsurf_init(messages, NULL);
 	free(messages);
 	if (ret != NSERROR_OK) {
 		die("NetSurf failed to initialise");

gtk/Makefile.defaults

@@ -21,6 +21,9 @@ NETSURF_USE_NSSVG := AUTO
 # Valid options: YES, NO, AUTO
 NETSURF_USE_ROSPRITE := AUTO
 
+# Enable building the source object cache filesystem based backing store.
+NETSURF_FS_BACKING_STORE := YES
+
 # Configuration overrides for Mac OS X
 ifeq ($(HOST),macosx)
     NETSURF_USE_LIBICONV_PLUG := NO

gtk/gui.c

@@ -44,6 +44,7 @@
 #include "content/fetchers/resource.h"
 #include "content/hlcache.h"
 #include "content/urldb.h"
+#include "content/backing_store.h"
 #include "desktop/browser.h"
 #include "desktop/gui.h"
 #include "desktop/netsurf.h"
@@ -1100,11 +1101,111 @@ static nserror create_config_home(char **config_home_out)
 	/* strip the trailing separator */
 	config_home[strlen(config_home) - 1] = 0;
 
+	LOG(("\"%s\"", config_home));
+
 	*config_home_out = config_home;
 
 	return NSERROR_OK;
 }
 
+/**
+ * Get the path to the cache directory.
+ *
+ * @param cache_home_out Path to cache directory.
+ * @return NSERROR_OK on sucess and \a cache_home_out updated else error code.
+ */
+static nserror get_cache_home(char **cache_home_out)
+{
+	nserror ret;
+	char *xdg_cache_dir;
+	char *cache_home;
+	char *home_dir;
+
+	/* $XDG_CACHE_HOME defines the base directory relative to
+	 * which user specific non-essential data files should be
+	 * stored.
+	 */
+	xdg_cache_dir = getenv("XDG_CACHE_HOME");
+
+	if ((xdg_cache_dir == NULL) || (*xdg_cache_dir == 0)) {
+		/* If $XDG_CACHE_HOME is either not set or empty, a
+		 * default equal to $HOME/.cache should be used.
+		 */
+
+		home_dir = getenv("HOME");
+
+		/* the HOME envvar is required */
+		if (home_dir == NULL) {
+			return NSERROR_NOT_DIRECTORY;
+		}
+
+		ret = check_dirname(home_dir, ".cache/netsurf", &cache_home);
+		if (ret != NSERROR_OK) {
+			return ret;
+		}
+	} else {
+		ret = check_dirname(xdg_cache_dir, "netsurf", &cache_home);
+		if (ret != NSERROR_OK) {
+			return ret;
+		}
+	}
+
+	LOG(("\"%s\"", cache_home));
+
+	*cache_home_out = cache_home;
+	return NSERROR_OK;
+}
+
+static nserror create_cache_home(char **cache_home_out)
+{
+	char *cache_home = NULL;
+	char *home_dir;
+	char *xdg_cache_dir;
+	nserror ret;
+
+	LOG(("Attempting to create configuration directory"));
+
+	/* $XDG_CACHE_HOME defines the base directory
+	 * relative to which user specific cache files
+	 * should be stored.
+	 */
+	xdg_cache_dir = getenv("XDG_CACHE_HOME");
+
+	if ((xdg_cache_dir == NULL) || (*xdg_cache_dir == 0)) {
+		home_dir = getenv("HOME");
+
+		if ((home_dir == NULL) || (*home_dir == 0)) {
+			return NSERROR_NOT_DIRECTORY;
+		}
+
+		ret = netsurf_mkpath(&cache_home, NULL, 4, home_dir, ".cache", "netsurf", "/");
+		if (ret != NSERROR_OK) {
+			return ret;
+		}
+	} else {
+		ret = netsurf_mkpath(&cache_home, NULL, 3, xdg_cache_dir, "netsurf", "/");
+		if (ret != NSERROR_OK) {
+			return ret;
+		}
+	}
+
+	/* ensure all elements of path exist (the trailing / is required) */
+	ret = filepath_mkdir_all(cache_home);
+	if (ret != NSERROR_OK) {
+		free(cache_home);
+		return ret;
+	}
+
+	/* strip the trailing separator */
+	cache_home[strlen(cache_home) - 1] = 0;
+
+	LOG(("\"%s\"", cache_home));
+
+	*cache_home_out = cache_home;
+
+	return NSERROR_OK;
+}
+
 static nserror nsgtk_option_init(int *pargc, char** argv)
 {
 	nserror ret;
@@ -1162,6 +1263,7 @@ static struct gui_browser_table nsgtk_browser_table = {
 int main(int argc, char** argv)
 {
 	char *messages;
+	char *cache_home = NULL;
 	nserror ret;
 	struct netsurf_table nsgtk_table = {
 		.browser = &nsgtk_browser_table,
@@ -1170,6 +1272,7 @@ int main(int argc, char** argv)
 		.download = nsgtk_download_table,
 		.fetch = nsgtk_fetch_table,
 		.search = nsgtk_search_table,
+		.llcache = filesystem_llcache_table,
 	};
 
         ret = netsurf_register(&nsgtk_table);
@@ -1210,9 +1313,20 @@ int main(int argc, char** argv)
 	/* Obtain path to messages */
 	messages = filepath_find(respaths, "Messages");
 
+	/* Locate the correct user cache directory path */
+	ret = get_cache_home(&cache_home);
+	if (ret == NSERROR_NOT_FOUND) {
+		/* no cache directory exists yet so try to create one */
+		ret = create_cache_home(&cache_home);
+	}
+	if (ret != NSERROR_OK) {
+		LOG(("Unable to locate a cache directory."));
+	}
+
 	/* core initialisation */
-	ret = netsurf_init(messages);
+	ret = netsurf_init(messages, cache_home);
 	free(messages);
+	free(cache_home);
 	if (ret != NSERROR_OK) {
 		fprintf(stderr, "NetSurf core failed to initialise (%s)\n",
 			messages_get_errorcode(ret));

monkey/main.c

@@ -155,7 +155,7 @@ main(int argc, char **argv)
 
   /* common initialisation */
   messages = filepath_find(respaths, "Messages");
-  ret = netsurf_init(messages);
+  ret = netsurf_init(messages, NULL);
   free(messages);
   if (ret != NSERROR_OK) {
     die("NetSurf failed to initialise");

riscos/gui.c

@@ -2542,7 +2542,7 @@ int main(int argc, char** argv)
 	}
 
 	/* common initialisation */
-	ret = netsurf_init(path);
+	ret = netsurf_init(path, NULL);
 	if (ret != NSERROR_OK) {
 		die("NetSurf failed to initialise");
 	}

windows/main.c

@@ -164,7 +164,7 @@ WinMain(HINSTANCE hInstance, HINSTANCE hLastInstance, LPSTR lpcli, int ncmd)
 
 	/* common initialisation */
 	messages = filepath_find(respaths, "messages");
-	ret = netsurf_init(messages);
+	ret = netsurf_init(messages, NULL);
 	free(messages);
 	if (ret != NSERROR_OK) {
 		free(options_file_location);