1 | /* $Id: circbuf.cpp 106061 2024-09-16 14:03:52Z vboxsync $ */
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2 | /** @file
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3 | * IPRT - Lock Free Circular Buffer
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4 | */
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5 |
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6 | /*
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7 | * Copyright (C) 2011-2024 Oracle and/or its affiliates.
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8 | *
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9 | * This file is part of VirtualBox base platform packages, as
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10 | * available from https://www.virtualbox.org.
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11 | *
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12 | * This program is free software; you can redistribute it and/or
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13 | * modify it under the terms of the GNU General Public License
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14 | * as published by the Free Software Foundation, in version 3 of the
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15 | * License.
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16 | *
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17 | * This program is distributed in the hope that it will be useful, but
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18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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20 | * General Public License for more details.
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21 | *
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22 | * You should have received a copy of the GNU General Public License
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23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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24 | *
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25 | * The contents of this file may alternatively be used under the terms
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26 | * of the Common Development and Distribution License Version 1.0
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27 | * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
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28 | * in the VirtualBox distribution, in which case the provisions of the
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29 | * CDDL are applicable instead of those of the GPL.
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30 | *
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31 | * You may elect to license modified versions of this file under the
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32 | * terms and conditions of either the GPL or the CDDL or both.
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33 | *
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34 | * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
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35 | */
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36 |
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37 |
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38 | /*********************************************************************************************************************************
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39 | * Header Files *
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40 | *********************************************************************************************************************************/
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41 | #include <iprt/circbuf.h>
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42 | #include <iprt/mem.h>
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43 | #include <iprt/assert.h>
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44 | #include <iprt/asm.h>
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45 | #include <iprt/errcore.h>
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46 |
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47 |
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48 | /*********************************************************************************************************************************
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49 | * Structures and Typedefs *
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50 | *********************************************************************************************************************************/
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51 | /** @todo r=bird: this is missing docs and magic. */
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52 | typedef struct RTCIRCBUF
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53 | {
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54 | /** The current read position in the buffer. */
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55 | size_t offRead;
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56 | /** Is a read block acquired currently? */
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57 | bool fReading;
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58 | /** Is a write block acquired currently? */
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59 | bool fWriting;
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60 | /** The current write position in the buffer. */
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61 | size_t offWrite;
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62 | /** How much space of the buffer is currently in use. */
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63 | volatile size_t cbUsed;
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64 | /** How big is the buffer. */
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65 | size_t cbBuf;
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66 | /** The buffer itself. */
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67 | void *pvBuf;
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68 | } RTCIRCBUF, *PRTCIRCBUF;
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69 |
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70 |
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71 | RTDECL(int) RTCircBufCreate(PRTCIRCBUF *ppBuf, size_t cbSize)
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72 | {
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73 | /* Validate input. */
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74 | AssertPtrReturn(ppBuf, VERR_INVALID_POINTER);
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75 | AssertReturn(cbSize > 0, VERR_INVALID_PARAMETER);
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76 |
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77 | PRTCIRCBUF pTmpBuf;
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78 | pTmpBuf = (PRTCIRCBUF)RTMemAllocZ(sizeof(RTCIRCBUF));
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79 | if (!pTmpBuf)
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80 | return VERR_NO_MEMORY;
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81 |
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82 | pTmpBuf->pvBuf = RTMemAlloc(cbSize);
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83 | if (pTmpBuf->pvBuf)
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84 | {
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85 | pTmpBuf->cbBuf = cbSize;
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86 | *ppBuf = pTmpBuf;
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87 | return VINF_SUCCESS;
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88 | }
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89 |
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90 | RTMemFree(pTmpBuf);
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91 | return VERR_NO_MEMORY;
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92 | }
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93 |
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94 |
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95 | RTDECL(void) RTCircBufDestroy(PRTCIRCBUF pBuf)
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96 | {
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97 | /* Validate input. */
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98 | if (!pBuf)
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99 | return;
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100 | AssertPtr(pBuf);
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101 | RTMemFree(pBuf->pvBuf);
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102 | RTMemFree(pBuf);
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103 | }
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104 |
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105 |
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106 | RTDECL(void) RTCircBufReset(PRTCIRCBUF pBuf)
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107 | {
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108 | /* Validate input. */
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109 | AssertPtr(pBuf);
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110 |
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111 | pBuf->offRead = 0;
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112 | pBuf->offWrite = 0;
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113 | pBuf->cbUsed = 0;
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114 | pBuf->fReading = false;
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115 | pBuf->fWriting = false;
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116 | }
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117 |
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118 |
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119 | RTDECL(size_t) RTCircBufFree(PRTCIRCBUF pBuf)
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120 | {
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121 | /* Validate input. */
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122 | AssertPtrReturn(pBuf, 0);
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123 |
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124 | return pBuf->cbBuf - ASMAtomicReadZ(&pBuf->cbUsed);
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125 | }
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126 |
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127 |
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128 | RTDECL(size_t) RTCircBufUsed(PRTCIRCBUF pBuf)
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129 | {
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130 | /* Validate input. */
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131 | AssertPtrReturn(pBuf, 0);
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132 |
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133 | return ASMAtomicReadZ(&pBuf->cbUsed);
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134 | }
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135 |
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136 | RTDECL(size_t) RTCircBufSize(PRTCIRCBUF pBuf)
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137 | {
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138 | /* Validate input. */
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139 | AssertPtrReturn(pBuf, 0);
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140 |
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141 | return pBuf->cbBuf;
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142 | }
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143 |
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144 | RTDECL(bool) RTCircBufIsReading(PRTCIRCBUF pBuf)
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145 | {
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146 | /* Validate input. */
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147 | AssertPtrReturn(pBuf, 0);
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148 |
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149 | return ASMAtomicReadBool(&pBuf->fReading);
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150 | }
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151 |
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152 | RTDECL(bool) RTCircBufIsWriting(PRTCIRCBUF pBuf)
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153 | {
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154 | /* Validate input. */
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155 | AssertPtrReturn(pBuf, 0);
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156 |
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157 | return ASMAtomicReadBool(&pBuf->fWriting);
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158 | }
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159 |
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160 | RTDECL(size_t) RTCircBufOffsetRead(PRTCIRCBUF pBuf)
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161 | {
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162 | /* Validate input. */
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163 | AssertPtrReturn(pBuf, 0);
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164 |
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165 | return ASMAtomicReadZ(&pBuf->offRead);
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166 | }
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167 |
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168 | RTDECL(size_t) RTCircBufOffsetWrite(PRTCIRCBUF pBuf)
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169 | {
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170 | /* Validate input. */
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171 | AssertPtrReturn(pBuf, 0);
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172 |
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173 | return ASMAtomicReadZ(&pBuf->offWrite);
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174 | }
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175 |
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176 | RTDECL(void) RTCircBufAcquireReadBlock(PRTCIRCBUF pBuf, size_t cbReqSize, void **ppvStart, size_t *pcbSize)
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177 | {
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178 | /* Validate input. */
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179 | AssertPtr(pBuf);
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180 | Assert(cbReqSize > 0);
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181 | AssertPtr(ppvStart);
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182 | AssertPtr(pcbSize);
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183 |
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184 | *ppvStart = 0;
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185 | *pcbSize = 0;
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186 |
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187 | /* How much is in use? */
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188 | size_t cbUsed = ASMAtomicReadZ(&pBuf->cbUsed);
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189 | if (cbUsed > 0)
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190 | {
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191 | /* Get the size out of the requested size, the read block till the end
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192 | * of the buffer & the currently used size. */
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193 | size_t cbSize = RT_MIN(cbReqSize, RT_MIN(pBuf->cbBuf - pBuf->offRead, cbUsed));
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194 | if (cbSize > 0)
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195 | {
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196 | /* Return the pointer address which point to the current read
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197 | * position. */
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198 | *ppvStart = (char *)pBuf->pvBuf + pBuf->offRead;
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199 | *pcbSize = cbSize;
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200 |
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201 | ASMAtomicWriteBool(&pBuf->fReading, true);
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202 | }
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203 | }
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204 | }
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205 |
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206 |
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207 | RTDECL(void) RTCircBufReleaseReadBlock(PRTCIRCBUF pBuf, size_t cbSize)
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208 | {
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209 | /* Validate input. */
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210 | AssertPtr(pBuf);
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211 |
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212 | /* Split at the end of the buffer. */
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213 | pBuf->offRead = (pBuf->offRead + cbSize) % pBuf->cbBuf;
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214 |
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215 | ASMAtomicSubZ(&pBuf->cbUsed, cbSize);
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216 | ASMAtomicWriteBool(&pBuf->fReading, false);
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217 | }
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218 |
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219 |
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220 | RTDECL(void) RTCircBufAcquireWriteBlock(PRTCIRCBUF pBuf, size_t cbReqSize, void **ppvStart, size_t *pcbSize)
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221 | {
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222 | /* Validate input. */
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223 | AssertPtr(pBuf);
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224 | Assert(cbReqSize > 0);
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225 | AssertPtr(ppvStart);
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226 | AssertPtr(pcbSize);
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227 |
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228 | *ppvStart = 0;
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229 | *pcbSize = 0;
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230 |
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231 | /* How much is free? */
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232 | size_t cbFree = pBuf->cbBuf - ASMAtomicReadZ(&pBuf->cbUsed);
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233 | if (cbFree > 0)
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234 | {
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235 | /* Get the size out of the requested size, then write block till the end
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236 | * of the buffer & the currently free size. */
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237 | size_t cbSize = RT_MIN(cbReqSize, RT_MIN(pBuf->cbBuf - pBuf->offWrite, cbFree));
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238 | if (cbSize > 0)
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239 | {
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240 | /* Return the pointer address which point to the current write
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241 | * position. */
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242 | *ppvStart = (char*)pBuf->pvBuf + pBuf->offWrite;
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243 | *pcbSize = cbSize;
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244 |
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245 | ASMAtomicWriteBool(&pBuf->fWriting, true);
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246 | }
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247 | }
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248 | }
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249 |
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250 |
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251 | RTDECL(void) RTCircBufReleaseWriteBlock(PRTCIRCBUF pBuf, size_t cbSize)
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252 | {
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253 | /* Validate input. */
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254 | AssertPtr(pBuf);
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255 |
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256 | /* Split at the end of the buffer. */
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257 | pBuf->offWrite = (pBuf->offWrite + cbSize) % pBuf->cbBuf;
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258 |
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259 | ASMAtomicAddZ(&pBuf->cbUsed, cbSize);
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260 | ASMAtomicWriteBool(&pBuf->fWriting, false);
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261 | }
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262 |
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