1/* 2 * Copyright (c) 2015 ARM Limited 3 * All rights reserved 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software 9 * licensed hereunder. You may use the software subject to the license 10 * terms below provided that you ensure that this notice is replicated 11 * unmodified and in its entirety in all distributions of the software, 12 * modified or unmodified, in source code or in binary form. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions are 16 * met: redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer; 18 * redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution; 21 * neither the name of the copyright holders nor the names of its 22 * contributors may be used to endorse or promote products derived from 23 * this software without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 * 37 * Authors: Andreas Sandberg 38 */ 39 40#ifndef __BASE_CIRCLEBUF_HH__ 41#define __BASE_CIRCLEBUF_HH__ 42 43#include <algorithm> 44#include <cassert> 45#include <vector> 46 47#include "base/misc.hh" 48#include "sim/serialize.hh" 49 50/** 51 * Circular buffer backed by a vector 52 * 53 * The data in the cricular buffer is stored in a standard 54 * vector. _start designates the first element in the buffer and _stop 55 * points to the last element + 1 (i.e., the position of the next 56 * insertion). The _stop index may be outside the range of the backing 57 * store, which means that the actual index must be calculated as 58 * _stop % capacity. 59 * 60 * Invariants: 61 * <ul> 62 * <li>_start <= _stop 63 * <li>_start < capacity 64 * <li>_stop < 2 * capacity 65 * </ul> 66 */ 67template<typename T> 68class CircleBuf 69{ 70 public: 71 typedef T value_type; 72 73 public: 74 explicit CircleBuf(size_t size) 75 : buf(size), _start(0), _stop(0) {} 76 77 /** Is the buffer empty? */ 78 bool empty() const { return _stop == _start; } 79 /** 80 * Return the maximum number of elements that can be stored in 81 * the buffer at any one time. 82 */ 83 size_t capacity() const { return buf.size(); } 84 /** Return the number of elements stored in the buffer. */ 85 size_t size() const { return _stop - _start; } 86 87 /** 88 * Remove all the elements in the buffer. 89 * 90 * Note: This does not actually remove elements from the backing 91 * store. 92 */ 93 void flush() { 94 _start = 0; 95 _stop = 0; 96 } 97 98 /** 99 * Copy buffer contents without advancing the read pointer 100 * 101 * @param out Output iterator/pointer 102 * @param len Number of elements to copy 103 */ 104 template <class OutputIterator> 105 void peek(OutputIterator out, size_t len) const { 106 peek(out, 0, len); 107 } 108 109 /** 110 * Copy buffer contents without advancing the read pointer 111 * 112 * @param out Output iterator/pointer 113 * @param offset Offset into the ring buffer 114 * @param len Number of elements to copy 115 */ 116 template <class OutputIterator> 117 void peek(OutputIterator out, off_t offset, size_t len) const { 118 panic_if(offset + len > size(), 119 "Trying to read past end of circular buffer.\n"); 120 121 const off_t real_start((offset + _start) % buf.size()); 122 if (real_start + len <= buf.size()) { 123 std::copy(buf.begin() + real_start, 124 buf.begin() + real_start + len, 125 out); 126 } else { 127 const size_t head_size(buf.size() - real_start); 128 const size_t tail_size(len - head_size); 129 std::copy(buf.begin() + real_start, buf.end(), 130 out); 131 std::copy(buf.begin(), buf.begin() + tail_size, 132 out + head_size); 133 } 134 } 135 136 /** 137 * Copy buffer contents and advance the read pointer 138 * 139 * @param out Output iterator/pointer 140 * @param len Number of elements to read 141 */ 142 template <class OutputIterator> 143 void read(OutputIterator out, size_t len) { 144 peek(out, len); 145 146 _start += len; 147 normalize(); 148 } 149 150 /** 151 * Add elements to the end of the ring buffers and advance. 152 * 153 * @param in Input iterator/pointer 154 * @param len Number of elements to read 155 */ 156 template <class InputIterator> 157 void write(InputIterator in, size_t len) { 158 // Writes that are larger than the backing store are allowed, 159 // but only the last part of the buffer will be written. 160 if (len > buf.size()) { 161 in += len - buf.size(); 162 len = buf.size(); 163 } 164 165 const size_t next(_stop % buf.size()); 166 const size_t head_len(std::min(buf.size() - next, len)); 167 168 std::copy(in, in + head_len, buf.begin() + next); 169 std::copy(in + head_len, in + len, buf.begin()); 170 171 _stop += len; 172 // We may have written past the old _start pointer. Readjust 173 // the _start pointer to remove the oldest entries in that 174 // case. 175 if (size() > buf.size()) 176 _start = _stop - buf.size(); 177 178 normalize(); 179 } 180 181 protected: 182 /** 183 * Normalize the start and stop pointers to ensure that pointer 184 * invariants hold after updates. 185 */ 186 void normalize() { 187 if (_start >= buf.size()) { 188 _stop -= buf.size(); 189 _start -= buf.size(); 190 } 191 192 assert(_start < buf.size()); 193 assert(_stop < 2 * buf.size()); 194 assert(_start <= _stop); 195 } 196 197 protected: 198 std::vector<value_type> buf; 199 size_t _start; 200 size_t _stop; 201 202}; 203 204 205/** 206 * Simple FIFO implementation backed by a circular buffer. 207 * 208 * This class provides the same basic functionallity as the circular 209 * buffer with the folling differences: 210 * <ul> 211 * <li>Writes are checked to ensure that overflows can't happen. 212 * <li>Unserialization ensures that the data in the checkpoint fits 213 * in the buffer. 214 * </ul> 215 */ 216template<typename T> 217class Fifo 218{ 219 public: 220 typedef T value_type; 221 222 public: 223 Fifo(size_t size) 224 : buf(size) {} 225 226 bool empty() const { return buf.empty(); } 227 size_t size() const { return buf.size(); } 228 size_t capacity() const { return buf.capacity(); } 229 230 void flush() { buf.flush(); } 231 232 template <class OutputIterator> 233 void peek(OutputIterator out, size_t len) const { buf.peek(out, len); } 234 template <class OutputIterator> 235 void read(OutputIterator out, size_t len) { buf.read(out, len); } 236 237 template <class InputIterator> 238 void write(InputIterator in, size_t len) { 239 panic_if(size() + len > capacity(), 240 "Trying to overfill FIFO buffer.\n"); 241 buf.write(in, len); 242 } 243 244 private: 245 CircleBuf<value_type> buf; 246}; 247 248 249template <typename T>
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