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 * Authors: Steve Reinhardt
29 */
30
31#ifndef __BASE__CHUNK_GENERATOR_HH__
32#define __BASE__CHUNK_GENERATOR_HH__
33
34/**
35 * @file
36 * Declaration and inline definition of ChunkGenerator object.
37 */
38
39#include <algorithm>
40
41#include "base/intmath.hh"
42#include "base/types.hh"
43
44/**
45 * This class takes an arbitrary memory region (address/length pair)
46 * and generates a series of appropriately (e.g. block- or page-)
47 * aligned chunks covering the same region.
48 *
49 * Example usage:
50
51\code
52    for (ChunkGenerator gen(addr, size, chunkSize); !gen.done(); gen.next()) {
53        doSomethingChunky(gen.addr(), gen.size());
54    }
55\endcode
56 */
57class ChunkGenerator
58{
59  private:
60    /** The starting address of the current chunk. */
61    Addr curAddr;
62    /** The starting address of the next chunk (after the current one). */
63    Addr nextAddr;
64    /** The size of the current chunk (in bytes). */
65    unsigned  curSize;
66    /** The number of bytes remaining in the region after the current chunk. */
67    unsigned  sizeLeft;
68    /** The start address so we can calculate offset in writing block. */
69    const Addr startAddr;
70    /** The maximum chunk size, e.g., the cache block size or page size. */
71    const unsigned chunkSize;
72
73  public:
74    /**
75     * Constructor.
76     * @param _startAddr The starting address of the region.
77     * @param totalSize The total size of the region.
78     * @param _chunkSize The size/alignment of chunks into which
79     *    the region should be decomposed.
80     */
81    ChunkGenerator(Addr _startAddr, unsigned totalSize, unsigned _chunkSize)
82        : startAddr(_startAddr), chunkSize(_chunkSize)
83    {
84        // chunkSize must be a power of two
85        assert(chunkSize == 0 || isPowerOf2(chunkSize));
86
87        // set up initial chunk.
88        curAddr = startAddr;
89
90        if (chunkSize == 0) //Special Case, if we see 0, assume no chuncking
91        {
92            nextAddr = startAddr + totalSize;
93        }
94        else
95        {
96            // nextAddr should be *next* chunk start
97            nextAddr = roundUp(startAddr, chunkSize);
98            if (curAddr == nextAddr) {
99                // ... even if startAddr is already chunk-aligned
100                nextAddr += chunkSize;
101            }
102        }
103
104        // how many bytes are left between curAddr and the end of this chunk?
105        unsigned left_in_chunk = nextAddr - curAddr;
106        curSize = std::min(totalSize, left_in_chunk);
107        sizeLeft = totalSize - curSize;
108    }
109
110    /** Return starting address of current chunk. */
111    Addr addr() const { return curAddr; }
112    /** Return size in bytes of current chunk. */
113    unsigned size() const { return curSize; }
114
115    /** Number of bytes we have already chunked up. */
116    unsigned complete() const { return curAddr - startAddr; }
117
118    /**
119     * Are we done?  That is, did the last call to next() advance
120     * past the end of the region?
121     * @return True if yes, false if more to go.
122     */
123    bool done() const { return (curSize == 0); }
124
125    /**
126     * Is this the last chunk?
127     * @return True if yes, false if more to go.
128     */
129    bool last() const { return (sizeLeft == 0); }
130
131    /**
132     * Advance generator to next chunk.
133     * @return True if successful, false if unsuccessful
134     * (because we were at the last chunk).
135     */
136    bool
137    next()
138    {
139        if (sizeLeft == 0) {
140            curSize = 0;
141            return false;
142        }
143
144        curAddr = nextAddr;
145        curSize = std::min(sizeLeft, chunkSize);
146        sizeLeft -= curSize;
147        nextAddr += curSize;
148        return true;
149    }
150};
151
152#endif // __BASE__CHUNK_GENERATOR_HH__
153