1 files changed, 252 insertions, 0 deletions
diff --git a/src/VBox/Runtime/common/misc/circbuf.cpp b/src/VBox/Runtime/common/misc/circbuf.cpp
new file mode 100644
index 00000000..03ac0a88
--- /dev/null
+++ b/src/VBox/Runtime/common/misc/circbuf.cpp
@@ -0,0 +1,252 @@
+/* $Id: circbuf.cpp $ */
+/** @file
+ * IPRT - Lock Free Circular Buffer
+ */
+
+/*
+ * Copyright (C) 2011-2019 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+ * VirtualBox OSE distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <iprt/circbuf.h>
+#include <iprt/mem.h>
+#include <iprt/assert.h>
+#include <iprt/asm.h>
+#include <iprt/errcore.h>
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+/** @todo r=bird: this is missing docs and magic. */
+typedef struct RTCIRCBUF
+{
+    /** The current read position in the buffer. */
+    size_t          offRead;
+    /** Is a read block acquired currently? */
+    bool            fReading;
+    /** Is a write block acquired currently? */
+    bool            fWriting;
+    /** The current write position in the buffer. */
+    size_t          offWrite;
+    /** How much space of the buffer is currently in use. */
+    volatile size_t cbUsed;
+    /** How big is the buffer. */
+    size_t          cbBuf;
+    /** The buffer itself. */
+    void           *pvBuf;
+} RTCIRCBUF, *PRTCIRCBUF;
+
+
+RTDECL(int) RTCircBufCreate(PRTCIRCBUF *ppBuf, size_t cbSize)
+{
+    /* Validate input. */
+    AssertPtrReturn(ppBuf, VERR_INVALID_POINTER);
+    AssertReturn(cbSize > 0, VERR_INVALID_PARAMETER);
+
+    PRTCIRCBUF pTmpBuf;
+    pTmpBuf = (PRTCIRCBUF)RTMemAllocZ(sizeof(RTCIRCBUF));
+    if (!pTmpBuf)
+        return VERR_NO_MEMORY;
+
+    pTmpBuf->pvBuf = RTMemAlloc(cbSize);
+    if (pTmpBuf->pvBuf)
+    {
+        pTmpBuf->cbBuf = cbSize;
+        *ppBuf = pTmpBuf;
+        return VINF_SUCCESS;
+    }
+
+    RTMemFree(pTmpBuf);
+    return VERR_NO_MEMORY;
+}
+
+
+RTDECL(void) RTCircBufDestroy(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    if (!pBuf)
+        return;
+    AssertPtr(pBuf);
+    RTMemFree(pBuf->pvBuf);
+    RTMemFree(pBuf);
+}
+
+
+RTDECL(void) RTCircBufReset(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtr(pBuf);
+
+    pBuf->offRead  = 0;
+    pBuf->offWrite = 0;
+    pBuf->cbUsed   = 0;
+    pBuf->fReading = false;
+    pBuf->fWriting = false;
+}
+
+
+RTDECL(size_t) RTCircBufFree(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtrReturn(pBuf, 0);
+
+    return pBuf->cbBuf - ASMAtomicReadZ(&pBuf->cbUsed);
+}
+
+
+RTDECL(size_t) RTCircBufUsed(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtrReturn(pBuf, 0);
+
+    return ASMAtomicReadZ(&pBuf->cbUsed);
+}
+
+RTDECL(size_t) RTCircBufSize(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtrReturn(pBuf, 0);
+
+    return pBuf->cbBuf;
+}
+
+RTDECL(bool) RTCircBufIsReading(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtrReturn(pBuf, 0);
+
+    return ASMAtomicReadBool(&pBuf->fReading);
+}
+
+RTDECL(bool) RTCircBufIsWriting(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtrReturn(pBuf, 0);
+
+    return ASMAtomicReadBool(&pBuf->fWriting);
+}
+
+RTDECL(size_t) RTCircBufOffsetRead(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtrReturn(pBuf, 0);
+
+    return ASMAtomicReadZ(&pBuf->offRead);
+}
+
+RTDECL(size_t) RTCircBufOffsetWrite(PRTCIRCBUF pBuf)
+{
+    /* Validate input. */
+    AssertPtrReturn(pBuf, 0);
+
+    return ASMAtomicReadZ(&pBuf->offWrite);
+}
+
+RTDECL(void) RTCircBufAcquireReadBlock(PRTCIRCBUF pBuf, size_t cbReqSize, void **ppvStart, size_t *pcbSize)
+{
+    /* Validate input. */
+    AssertPtr(pBuf);
+    Assert(cbReqSize > 0);
+    AssertPtr(ppvStart);
+    AssertPtr(pcbSize);
+
+    *ppvStart = 0;
+    *pcbSize = 0;
+
+    /* How much is in use? */
+    size_t cbUsed = ASMAtomicReadZ(&pBuf->cbUsed);
+    if (cbUsed > 0)
+    {
+        /* Get the size out of the requested size, the read block till the end
+         * of the buffer & the currently used size. */
+        size_t cbSize = RT_MIN(cbReqSize, RT_MIN(pBuf->cbBuf - pBuf->offRead, cbUsed));
+        if (cbSize > 0)
+        {
+            /* Return the pointer address which point to the current read
+             * position. */
+            *ppvStart = (char *)pBuf->pvBuf + pBuf->offRead;
+            *pcbSize = cbSize;
+
+            ASMAtomicWriteBool(&pBuf->fReading, true);
+        }
+    }
+}
+
+
+RTDECL(void) RTCircBufReleaseReadBlock(PRTCIRCBUF pBuf, size_t cbSize)
+{
+    /* Validate input. */
+    AssertPtr(pBuf);
+
+    /* Split at the end of the buffer. */
+    pBuf->offRead = (pBuf->offRead + cbSize) % pBuf->cbBuf;
+
+    ASMAtomicSubZ(&pBuf->cbUsed, cbSize);
+    ASMAtomicWriteBool(&pBuf->fReading, false);
+}
+
+
+RTDECL(void) RTCircBufAcquireWriteBlock(PRTCIRCBUF pBuf, size_t cbReqSize, void **ppvStart, size_t *pcbSize)
+{
+    /* Validate input. */
+    AssertPtr(pBuf);
+    Assert(cbReqSize > 0);
+    AssertPtr(ppvStart);
+    AssertPtr(pcbSize);
+
+    *ppvStart = 0;
+    *pcbSize = 0;
+
+    /* How much is free? */
+    size_t cbFree = pBuf->cbBuf - ASMAtomicReadZ(&pBuf->cbUsed);
+    if (cbFree > 0)
+    {
+        /* Get the size out of the requested size, then write block till the end
+         * of the buffer & the currently free size. */
+        size_t cbSize = RT_MIN(cbReqSize, RT_MIN(pBuf->cbBuf - pBuf->offWrite, cbFree));
+        if (cbSize > 0)
+        {
+            /* Return the pointer address which point to the current write
+             * position. */
+            *ppvStart = (char*)pBuf->pvBuf + pBuf->offWrite;
+            *pcbSize = cbSize;
+
+            ASMAtomicWriteBool(&pBuf->fWriting, true);
+        }
+    }
+}
+
+
+RTDECL(void) RTCircBufReleaseWriteBlock(PRTCIRCBUF pBuf, size_t cbSize)
+{
+    /* Validate input. */
+    AssertPtr(pBuf);
+
+    /* Split at the end of the buffer. */
+    pBuf->offWrite = (pBuf->offWrite + cbSize) % pBuf->cbBuf;
+
+    ASMAtomicAddZ(&pBuf->cbUsed, cbSize);
+    ASMAtomicWriteBool(&pBuf->fWriting, false);
+}
+