117 lines
4.3 KiB
C
117 lines
4.3 KiB
C
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/************************************************************************
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* Copyright (c) 2005-2006 tok@openlinux.org.uk *
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* *
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* This software is provided as-is, without any express or implied *
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* warranty. In no event will the authors be held liable for any *
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* damages arising from the use of this software. *
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* *
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* Permission is granted to anyone to use this software for any purpose, *
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* including commercial applications, and to alter it and redistribute *
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* it freely, subject to the following restrictions: *
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* *
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* 1. The origin of this software must not be misrepresented; you must *
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* not claim that you wrote the original software. If you use this *
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* software in a product, an acknowledgment in the product documentation *
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* would be appreciated but is not required. *
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* *
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* 2. Altered source versions must be plainly marked as such, and must *
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* not be misrepresented as being the original software. *
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* *
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* 3. This notice may not be removed or altered from any source *
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* distribution. *
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************************************************************************/
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#ifndef BUFFER_CACHE_H
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#define BUFFER_CACHE_H
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#include <map>
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#include "Singleton.h"
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using namespace Loki;
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namespace Util {
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/** A simple memory-buffer pool.
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*
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* - You should never manually delete a buffer created through the cache.
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* - You should however \e unlock buffers that were locked once you
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* no longer need them.
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* - You don't need to check for NULL pointers; exceptions are used for
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* errors.
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* - Buffers are initialised with zeroes.
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*
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* Beware:
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* \code
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* // assuming the cache is empty
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*
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* a = requestBuffer(10)
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* b = requestBuffer(5)
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*
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* a == b
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* ----------------------
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* a = requestBuffer(5)
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* b = requestBuffer(6)
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*
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* a != b
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* \endcode
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*/
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class BufferCache {
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public:
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BufferCache();
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~BufferCache();
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/** Returns a buffer of (at least) len bytes.
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*
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* @param Length of requested buffer in bytes.
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* @return The buffer.
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* @note May throw a OutOfMemory exception.
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*/
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unsigned char* requestBuffer(unsigned int len);
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/** Returns a locked buffer of (at least) len bytes.
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* Just a convenience function.
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*
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* @see requestBuffer
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* @see lockBuffer
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*/
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unsigned char* requestLockedBuffer(unsigned int len);
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/** Lock a buffer (which was allocated by this cache).
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*
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* @param Pointer to the buffer.
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*
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* You need this when you request multiple buffers at the same time; lock
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* the current buffer before requesting the next one.
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*/
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void lockBuffer(unsigned char* tb);
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/** Unlock a buffer (which was previously locked).
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* @param Pointer to the buffer.
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*
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* Returns the buffer to the shared pool.
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*/
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void unlockBuffer(unsigned char* tb);
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class LockedBuffer {
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public:
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LockedBuffer(unsigned char* b);
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LockedBuffer(unsigned int len);
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~LockedBuffer();
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inline unsigned char* operator()() { return buf_p; }
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private:
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unsigned char* buf_p;
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};
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void printStatus();
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private:
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typedef std::map<unsigned int, unsigned char*> BufferMap_t;
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typedef std::map<unsigned char*, unsigned int> BufferMap_T;
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BufferMap_t allocated;
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BufferMap_T locked;
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BufferMap_t::const_iterator findMatchingBuffer(unsigned int len);
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BufferMap_t::iterator findLockedBuffer(unsigned char* tb);
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unsigned char* createBuffer(unsigned int len);
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void freeBuffer(BufferMap_t::const_iterator pos);
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unsigned int total_bytes;
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};
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/** Instance of BufferCache.
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*/
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typedef SingletonHolder<BufferCache, CreateUsingNew, DefaultLifetime,
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SingleThreaded> BufferCacheHolder;
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}
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#endif
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