147 lines
5 KiB
C++
147 lines
5 KiB
C++
/*
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* Copyright (c) 2001-2005 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Steve Reinhardt
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*/
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#ifndef __BASE__CHUNK_GENERATOR_HH__
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#define __BASE__CHUNK_GENERATOR_HH__
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/**
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* @file
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* Declaration and inline definition of ChunkGenerator object.
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*/
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#include <algorithm>
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#include "base/intmath.hh"
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#include "base/types.hh"
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/**
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* This class takes an arbitrary memory region (address/length pair)
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* and generates a series of appropriately (e.g. block- or page-)
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* aligned chunks covering the same region.
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*
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* Example usage:
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\code
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for (ChunkGenerator gen(addr, size, chunkSize); !gen.done(); gen.next()) {
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doSomethingChunky(gen.addr(), gen.size());
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}
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\endcode
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*/
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class ChunkGenerator
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{
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private:
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/** The starting address of the current chunk. */
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Addr curAddr;
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/** The starting address of the next chunk (after the current one). */
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Addr nextAddr;
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/** The size of the current chunk (in bytes). */
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unsigned curSize;
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/** The number of bytes remaining in the region after the current chunk. */
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unsigned sizeLeft;
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/** The start address so we can calculate offset in writing block. */
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const Addr startAddr;
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/** The maximum chunk size, e.g., the cache block size or page size. */
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const unsigned chunkSize;
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public:
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/**
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* Constructor.
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* @param _startAddr The starting address of the region.
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* @param totalSize The total size of the region.
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* @param _chunkSize The size/alignment of chunks into which
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* the region should be decomposed.
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*/
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ChunkGenerator(Addr _startAddr, unsigned totalSize, unsigned _chunkSize)
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: startAddr(_startAddr), chunkSize(_chunkSize)
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{
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// chunkSize must be a power of two
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assert(chunkSize == 0 || isPowerOf2(chunkSize));
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assert(totalSize >= 0);
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// set up initial chunk.
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curAddr = startAddr;
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if (chunkSize == 0) //Special Case, if we see 0, assume no chuncking
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{
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nextAddr = startAddr + totalSize;
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}
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else
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{
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// nextAddr should be *next* chunk start
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nextAddr = roundUp(startAddr, chunkSize);
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if (curAddr == nextAddr) {
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// ... even if startAddr is already chunk-aligned
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nextAddr += chunkSize;
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}
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}
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// how many bytes are left between curAddr and the end of this chunk?
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unsigned left_in_chunk = nextAddr - curAddr;
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curSize = std::min(totalSize, left_in_chunk);
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sizeLeft = totalSize - curSize;
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}
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/** Return starting address of current chunk. */
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Addr addr() const { return curAddr; }
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/** Return size in bytes of current chunk. */
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unsigned size() const { return curSize; }
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/** Number of bytes we have already chunked up. */
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unsigned complete() const { return curAddr - startAddr; }
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/**
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* Are we done? That is, did the last call to next() advance
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* past the end of the region?
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* @return True if yes, false if more to go.
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*/
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bool done() const { return (curSize == 0); }
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/**
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* Advance generator to next chunk.
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* @return True if successful, false if unsuccessful
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* (because we were at the last chunk).
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*/
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bool
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next()
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{
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if (sizeLeft == 0) {
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curSize = 0;
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return false;
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}
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curAddr = nextAddr;
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curSize = std::min(sizeLeft, chunkSize);
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sizeLeft -= curSize;
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nextAddr += curSize;
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return true;
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}
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};
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#endif // __BASE__CHUNK_GENERATOR_HH__
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