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include/platform/filesystem/io_cache.h

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+/* -----------------------------------------------------------------------------
+	GSFramework
+	Copyright 2001-2013 Emmanuel Julien. All Rights Reserved.
+----------------------------------------------------------------------------- */
+
+
+#ifndef	__NIOCACHE__
+#define	__NIOCACHE__
+
+
+		#include "filesystem/data_store.h"
+		#include "filesystem/io_handle.h"
+		#include "memory/nauto_ptr.h"
+		#include "container/nlist.h"
+		#include "nstring/nstring.h"
+		#include "time/ntime.h"
+		#include "unit/nunit.h"
+
+
+namespace GS {
+	namespace IO {
+
+//
+class	CacheHandle : public Handle
+{
+		friend class Cache;
+
+protected:
+
+		String		path;
+		AutoPtr <Handle> handle;
+
+public:
+
+		CacheHandle(Base *io, const char *p, Handle *h) : Handle(io), path(p), handle(h) {}
+		~CacheHandle();
+};
+
+/*!
+	@short	Cached I/O filesystem wrapper.
+	Implements a transparent file cache on top of another filesystem.
+	@author	Emmanuel Julien (ejulien@nworks.fr)
+*/
+class	Cache : public Base
+{
+		SharedPtr <Base> io;
+		DataStore	store;
+
+public:
+
+struct	Entry
+{
+	String		path, id;
+	String		hash;
+
+	uint		refc;
+	size_t		size;
+
+	Time		last_use;
+
+	Entry() : refc(0), size(0) {}
+};
+
+private:
+
+		Threading::Mutex mutex;
+
+		size_t		cache_size;
+		AutoList <Entry *> entries;
+
+		int			ComputeEntryRecyclingScore(const Entry *) const;
+		String		ReserveOnStore(size_t size);
+
+		Entry		*GetCacheEntry(const char *path) const;
+		Entry		*CreateCacheEntry(const char *path);
+		bool		UpdateCacheEntry(Entry *entry, Array <char> *preloaded_data = 0);
+		bool		DeleteCacheEntry(Entry *entry);
+
+public:
+
+virtual	uint		GetCaps() const;
+
+virtual	Handle		*Open(const char *, Mode = ModeRead);
+virtual	void		Close(Handle *);
+
+virtual	bool		Delete(const char *);
+
+virtual	size_t		Tell(Handle *);
+virtual	size_t		Seek(Handle *, ptrdiff_t offset, SeekRef = SeekCurrent);
+
+virtual	size_t		Read(Handle *, void *, size_t);
+virtual	size_t		Write(Handle *, const void *, size_t);
+
+virtual	bool		MkDir(const char *);
+
+		/// Test if a given path is in cache.
+		bool		IsInCache(const char *path) const { return asbool(GetCacheEntry(path)); }
+
+		/// Reload cache state from its store.
+		bool		SynchronizeWithStore(const char *store_path = "store.db");
+
+		Cache(Base *base, Base *store, size_t cache_size = Units::MB(32));
+};
+
+	}	// IO
+}	// GS
+
+
+#endif	// __NIOCACHE__