VirtualBox

source: vbox/trunk/src/VBox/Runtime/common/misc/circbuf.cpp

Last change on this file was 106061, checked in by vboxsync, 8 weeks ago

Copyright year updates by scm.

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