chunk_generator.hh revision 2418 
1/*
2 * Copyright (c) 2001-2005 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef __BASE__CHUNK_GENERATOR_HH__
30#define __BASE__CHUNK_GENERATOR_HH__
31
32/**
33 * @file
34 * Declaration and inline definition of ChunkGenerator object.
35 */
36
37#include <algorithm>
38#include "base/intmath.hh"
39#include "targetarch/isa_traits.hh" // for Addr
40
41/**
42 * This class takes an arbitrary memory region (address/length pair)
43 * and generates a series of appropriately (e.g. block- or page-)
44 * aligned chunks covering the same region.
45 *
46 * Example usage:
47
48\code
49    for (ChunkGenerator gen(addr, size, chunkSize); !gen.done(); gen.next()) {
50        doSomethingChunky(gen.addr(), gen.size());
51    }
52\endcode
53 */
54class ChunkGenerator
55{
56  private:
57    /** The starting address of the current chunk. */
58    Addr curAddr;
59    /** The starting address of the next chunk (after the current one). */
60    Addr nextAddr;
61    /** The size of the current chunk (in bytes). */
62    int  curSize;
63    /** The number of bytes remaining in the region after the current chunk. */
64    int  sizeLeft;
65    /** The maximum chunk size, e.g., the cache block size or page size. */
66    const int chunkSize;
67
68  public:
69    /**
70     * Constructor.
71     * @param startAddr The starting address of the region.
72     * @param totalSize The total size of the region.
73     * @param _chunkSize The size/alignment of chunks into which
74     *    the region should be decomposed.
75     */
76    ChunkGenerator(Addr startAddr, int totalSize, int _chunkSize)
77        : chunkSize(_chunkSize)
78    {
79        // chunkSize must be a power of two
80        assert(chunkSize == 0 || isPowerOf2(chunkSize));
81
82        // set up initial chunk.
83        curAddr = startAddr;
84
85        if (chunkSize == 0) //Special Case, if we see 0, assume no chuncking
86        {
87            nextAddr = startAddr + totalSize;
88        }
89        else
90        {
91            // nextAddr should be *next* chunk start
92            nextAddr = roundUp(startAddr, chunkSize);
93            if (curAddr == nextAddr) {
94                // ... even if startAddr is already chunk-aligned
95                nextAddr += chunkSize;
96            }
97        }
98
99        // how many bytes are left between curAddr and the end of this chunk?
100        int left_in_chunk = nextAddr - curAddr;
101        curSize = std::min(totalSize, left_in_chunk);
102        sizeLeft = totalSize - curSize;
103    }
104
105    /** Return starting address of current chunk. */
106    Addr addr() { return curAddr; }
107    /** Return size in bytes of current chunk. */
108    int  size() { return curSize; }
109
110    /**
111     * Are we done?  That is, did the last call to next() advance
112     * past the end of the region?
113     * @return True if yes, false if more to go.
114     */
115    bool done() { return (curSize == 0); }
116
117    /**
118     * Advance generator to next chunk.
119     * @return True if successful, false if unsuccessful
120     * (because we were at the last chunk).
121     */
122    bool next()
123    {
124        if (sizeLeft == 0) {
125            curSize = 0;
126            return false;
127        }
128
129        curAddr = nextAddr;
130        curSize = std::min(sizeLeft, chunkSize);
131        sizeLeft -= curSize;
132        nextAddr += curSize;
133        return true;
134    }
135};
136
137#endif // __BASE__CHUNK_GENERATOR_HH__
138