chunk_generator.hh

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/*
 * Copyright (c) 2001-2005 The Regents of The University of Michigan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#ifndef __BASE_CHUNK_GENERATOR_HH__
#define __BASE_CHUNK_GENERATOR_HH__
 
#include <algorithm>
#include <cassert>
 
#include "base/intmath.hh"
#include "base/types.hh"
 
class ChunkGenerator
{
  private:
    Addr curAddr;
    Addr nextAddr;
    Addr curSize;
    Addr nextSize;
    Addr sizeLeft;
    const Addr startAddr;
    const Addr chunkSize;
 
  public:
    ChunkGenerator(Addr _startAddr, Addr totalSize, Addr _chunkSize) :
        startAddr(_startAddr), chunkSize(_chunkSize)
    {
        // chunkSize must be a power of two
        assert(chunkSize == 0 || isPowerOf2(chunkSize));
 
        // set up initial chunk.
        curAddr = startAddr;
 
        if (chunkSize == 0) { // Special Case, if we see 0, assume no chunking.
            nextAddr = startAddr + totalSize;
        } else {
            // nextAddr should be *next* chunk start.
            nextAddr = roundUp(startAddr, chunkSize);
            if (curAddr == nextAddr) {
                // ... even if startAddr is already chunk-aligned
                nextAddr += chunkSize;
            }
            nextAddr = std::min(nextAddr, startAddr + totalSize);
        }
 
        // How many bytes are left between curAddr and the end of this chunk?
        curSize = nextAddr - curAddr;
        sizeLeft = totalSize - curSize;
        nextSize = std::min(sizeLeft, chunkSize);
    }
 
    Addr addr() const { return curAddr; }
    Addr size() const { return curSize; }
 
    Addr complete() const { return curAddr - startAddr; }
 
    bool done() const { return curSize == 0; }
 
    bool last() const { return sizeLeft == 0; }
 
    void
    setNext(Addr next)
    {
        assert(next >= nextAddr);
 
        const Addr skipping = std::min(next - nextAddr, sizeLeft);
 
        sizeLeft -= skipping;
        curSize += skipping;
        nextAddr = next;
 
        assert(chunkSize);
 
        // nextSize will be enough to get to an alignment boundary,
        nextSize = roundUp(next, chunkSize) - next;
        // or if it's already aligned, to the following boundary or the end.
        if (!nextSize)
            nextSize = std::min(sizeLeft, chunkSize);
    }
 
    bool
    next()
    {
        if (last()) {
            curSize = 0;
            return false;
        }
 
        curAddr = nextAddr;
        curSize = nextSize;
        sizeLeft -= curSize;
        nextAddr += curSize;
        nextSize = std::min(sizeLeft, chunkSize);
        return true;
    }
};
 
#endif // __BASE_CHUNK_GENERATOR_HH__