common/misc/circbuf.cpp

	circbuf.cpp revision 41802163cf830caf53a1a619fed55afb52246eac
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync/* $Id$ */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync/** @file
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * IPRT - Lock Free Circular Buffer
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync/*
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * Copyright (C) 2010 Oracle Corporation
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync *
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * This file is part of VirtualBox Open Source Edition (OSE), as
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * available from http://www.virtualbox.org. This file is free software;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * you can redistribute it and/or modify it under the terms of the GNU
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * General Public License (GPL) as published by the Free Software
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * Foundation, in version 2 as it comes in the "COPYING" file of the
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync *
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * The contents of this file may alternatively be used under the terms
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * of the Common Development and Distribution License Version 1.0
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * VirtualBox OSE distribution, in which case the provisions of the
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * CDDL are applicable instead of those of the GPL.
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync *
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * You may elect to license modified versions of this file under the
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync * terms and conditions of either the GPL or the CDDL or both.
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync/*******************************************************************************
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync*   Header Files                                                               *
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync*******************************************************************************/
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync#include <iprt/circbuf.h>
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync#include <iprt/mem.h>
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync#include <iprt/assert.h>
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync#include <iprt/asm.h>
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync#include <iprt/err.h>
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(int) RTCircBufCreate(PRTCIRCBUF *ppBuf, size_t cbSize)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtrReturn(ppBuf, VERR_INVALID_POINTER);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertReturn(cbSize > 0, VERR_INVALID_PARAMETER);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    PRTCIRCBUF pTmpBuf;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    pTmpBuf = (PRTCIRCBUF)RTMemAllocZ(sizeof(RTCIRCBUF));
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    if (!pTmpBuf)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        return VERR_NO_MEMORY;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    pTmpBuf->pvBuf = RTMemAlloc(cbSize);
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    if (pTmpBuf->pvBuf)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    {
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        pTmpBuf->cbBufSize = cbSize;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        *ppBuf = pTmpBuf;
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync        return VINF_SUCCESS;
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    }
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    RTMemFree(pTmpBuf);
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    return VERR_NO_MEMORY;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(void) RTCircBufDestroy(PRTCIRCBUF pBuf)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    if (!pBuf)
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync        return;
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    AssertPtr(pBuf);
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    RTMemFree(pBuf->pvBuf);
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    RTMemFree(pBuf);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(void) RTCircBufReset(PRTCIRCBUF pBuf)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(pBuf);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    pBuf->uReadPos  = 0;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    pBuf->uWritePos = 0;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    pBuf->cbBufUsed = 0;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(size_t) RTCircBufFree(PRTCIRCBUF pBuf)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtrReturn(pBuf, 0);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
41802163cf830caf53a1a619fed55afb52246eacvboxsync    return pBuf->cbBufSize - ASMAtomicReadZ(&pBuf->cbBufUsed);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(size_t) RTCircBufUsed(PRTCIRCBUF pBuf)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtrReturn(pBuf, 0);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
41802163cf830caf53a1a619fed55afb52246eacvboxsync    return ASMAtomicReadZ(&pBuf->cbBufUsed);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(size_t) RTCircBufSize(PRTCIRCBUF pBuf)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtrReturn(pBuf, 0);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    return pBuf->cbBufSize;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(void) RTCircBufAcquireReadBlock(PRTCIRCBUF pBuf, size_t cbReqSize, void **ppvStart, size_t *pcbSize)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(pBuf);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    Assert(cbReqSize > 0);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(ppvStart);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(pcbSize);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    *ppvStart = 0;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    *pcbSize = 0;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* How much is in use? */
41802163cf830caf53a1a619fed55afb52246eacvboxsync    size_t cbUsed = ASMAtomicReadZ(&pBuf->cbBufUsed);
41802163cf830caf53a1a619fed55afb52246eacvboxsync    if (cbUsed > 0)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    {
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        /* Get the size out of the requested size, the read block till the end
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync         * of the buffer & the currently used size. */
41802163cf830caf53a1a619fed55afb52246eacvboxsync        size_t cbSize = RT_MIN(cbReqSize, RT_MIN(pBuf->cbBufSize - pBuf->uReadPos, cbUsed));
41802163cf830caf53a1a619fed55afb52246eacvboxsync        if (cbSize > 0)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        {
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync            /* Return the pointer address which point to the current read
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync             * position. */
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync            *ppvStart = (char *)pBuf->pvBuf + pBuf->uReadPos;
41802163cf830caf53a1a619fed55afb52246eacvboxsync            *pcbSize = cbSize;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        }
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    }
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(void) RTCircBufReleaseReadBlock(PRTCIRCBUF pBuf, size_t cbSize)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(pBuf);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Split at the end of the buffer. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    pBuf->uReadPos = (pBuf->uReadPos + cbSize) % pBuf->cbBufSize;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
41802163cf830caf53a1a619fed55afb52246eacvboxsync    ASMAtomicSubZ(&pBuf->cbBufUsed, cbSize);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(void) RTCircBufAcquireWriteBlock(PRTCIRCBUF pBuf, size_t cbReqSize, void **ppvStart, size_t *pcbSize)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(pBuf);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    Assert(cbReqSize > 0);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(ppvStart);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(pcbSize);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    *ppvStart = 0;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    *pcbSize = 0;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* How much is free? */
41802163cf830caf53a1a619fed55afb52246eacvboxsync    size_t cbFree = pBuf->cbBufSize - ASMAtomicReadZ(&pBuf->cbBufUsed);
41802163cf830caf53a1a619fed55afb52246eacvboxsync    if (cbFree > 0)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    {
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        /* Get the size out of the requested size, the write block till the end
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync         * of the buffer & the currently free size. */
41802163cf830caf53a1a619fed55afb52246eacvboxsync        size_t cbSize = RT_MIN(cbReqSize, RT_MIN(pBuf->cbBufSize - pBuf->uWritePos, cbFree));
41802163cf830caf53a1a619fed55afb52246eacvboxsync        if (cbSize > 0)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        {
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync            /* Return the pointer address which point to the current write
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync             * position. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync            *ppvStart = (char*)pBuf->pvBuf + pBuf->uWritePos;
41802163cf830caf53a1a619fed55afb52246eacvboxsync            *pcbSize = cbSize;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync        }
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    }
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsyncRTDECL(void) RTCircBufReleaseWriteBlock(PRTCIRCBUF pBuf, size_t cbSize)
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync{
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Validate input. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    AssertPtr(pBuf);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    /* Split at the end of the buffer. */
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync    pBuf->uWritePos = (pBuf->uWritePos + cbSize) % pBuf->cbBufSize;
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync
078edd33e3a22f968a7aee5a9e042bca314c2f03vboxsync    size_t cbOldIgnored = 0;
41802163cf830caf53a1a619fed55afb52246eacvboxsync    ASMAtomicAddZ(&pBuf->cbBufUsed, cbSize);
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync}
97f795f0be0c10aae9b31cc8f8d5cdf8ea2ab421vboxsync