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// ----------------------------------------------------------------------------
 
// Debug Unit memory cache: definition
 
// Copyright (C) 2008  Embecosm Limited <info@embecosm.com>
 
// Contributor Jeremy Bennett <jeremy.bennett@embecosm.com>
 
// This file is part of the GDB interface to the cycle accurate model of the
// OpenRISC 1000 based system-on-chip, ORPSoC, built using Verilator.
 
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or (at your
// option) any later version.
 
// This program 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 Lesser General Public
// License for more details.
 
// You should have received a copy of the GNU Lesser General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
// ----------------------------------------------------------------------------
 
// $Id: MemCache.h 326 2009-03-07 16:47:31Z jeremy $
 
#ifndef MEM_CACHE__H
#define MEM_CACHE__H
 
#include <stdint.h>
 
 
//! Module for cacheing memory accesses by the debug unit
 
//! Memory reads and writes through the Debug Unit via JTAG are time
//! consuming - of the order of 1000 CPU clock cycles. However when the
//! processor is stalled the values cannot change, other than through the
//! debug unit, so it makes sense to cache values.
 
//! Cacheing the entire memory is too much (it does need to be cleared when
//! the processor is unstalled. This class provides a cacheing function using
//! a closed hash table.
 
//! In the event of a clash on write, the old value is replaced by the new
//! value.
 
class MemCache
{
public:
 
  // Constructor and destructor
  MemCache (int  _tableSize = 1009);
  ~MemCache ();
 
  // Functions
  void  clear ();
  void  write (uint32_t  addr,
	       uint32_t  value);
  bool  read (uint32_t  addr,
	      uint32_t &value);
 
private:
 
  //! The size of the hash table. A prime number is a good choice.
  int  tableSize;
 
  // The hash table, keyed by address. Done as three parallel vectors,
  // allowing unambiguous clearing by use of memset for efficiency.
  bool     *tabIsValid;
  uint32_t *tabKeyAddr;
  uint32_t *tabValue;
 
 
};	// MemCache ()
 
#endif	// MEM_CACHE__H