source: vbox/trunk/src/VBox/HostServices/SharedFolders/shflhandle.cpp@ 36501

/** @file
 *
 * Shared Folders:
 * Handles helper functions.
 */

/*
 * Copyright (C) 2006-2007 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.
 */

#include "shflhandle.h"
#include <iprt/alloc.h>
#include <iprt/assert.h>
#include <iprt/critsect.h>


/*
 * Very basic and primitive handle management. Should be sufficient for our needs.
 * Handle allocation can be rather slow, but at least lookup is fast.
 *
 */
typedef struct
{
    uint32_t    uFlags;
    uintptr_t   pvUserData;
} SHFLINTHANDLE, *PSHFLINTHANDLE;

static SHFLINTHANDLE *pHandles = NULL;
static int32_t        lastHandleIndex = 0;
static RTCRITSECT     lock;

int vbsfInitHandleTable()
{
    pHandles = (SHFLINTHANDLE *)RTMemAllocZ (sizeof (SHFLINTHANDLE) * SHFLHANDLE_MAX);
    if (pHandles == NULL)
    {
        AssertFailed();
        return VERR_NO_MEMORY;
    }

    /* Never return handle 0 */
    pHandles[0].uFlags = SHFL_HF_TYPE_DONTUSE;
    lastHandleIndex    = 1;

    return RTCritSectInit(&lock);
}

int vbsfFreeHandleTable()
{
    if (pHandles)
        RTMemFree(pHandles);

    pHandles = NULL;

    if (RTCritSectIsInitialized(&lock))
        RTCritSectDelete(&lock);

    return VINF_SUCCESS;
}

SHFLHANDLE  vbsfAllocHandle(uint32_t uType, uintptr_t pvUserData)
{
    SHFLHANDLE handle;

    Assert((uType & SHFL_HF_TYPE_MASK) != 0 && pvUserData);

    RTCritSectEnter(&lock);

    /* Find next free handle */
    if(lastHandleIndex >= SHFLHANDLE_MAX-1)
    {
        lastHandleIndex = 1;
    }

    /* Nice linear search */
    for(handle=lastHandleIndex;handle<SHFLHANDLE_MAX;handle++)
    {
        if(pHandles[handle].pvUserData == 0)
        {
            lastHandleIndex = handle;
            break;
        }
    }

    if(handle == SHFLHANDLE_MAX)
    {
        /* Try once more from the start */
        for(handle=1;handle<SHFLHANDLE_MAX;handle++)
        {
            if(pHandles[handle].pvUserData == 0)
            {
                lastHandleIndex = handle;
                break;
            }
        }
        if(handle == SHFLHANDLE_MAX)
        { /* Out of handles */
            RTCritSectLeave(&lock);
            AssertFailed();
            return SHFL_HANDLE_NIL;
        }
    }
    pHandles[handle].uFlags     = (uType & SHFL_HF_TYPE_MASK) | SHFL_HF_VALID;
    pHandles[handle].pvUserData = pvUserData;

    lastHandleIndex++;

    RTCritSectLeave(&lock);

    return handle;
}

int vbsfFreeHandle(SHFLHANDLE handle)
{
    if (handle < SHFLHANDLE_MAX && (pHandles[handle].uFlags & SHFL_HF_VALID))
    {
        pHandles[handle].uFlags     = 0;
        pHandles[handle].pvUserData = 0;
        return VINF_SUCCESS;
    }
    return VERR_INVALID_HANDLE;
}

uintptr_t vbsfQueryHandle(SHFLHANDLE handle, uint32_t uType)
{
    if (handle < SHFLHANDLE_MAX && (pHandles[handle].uFlags & SHFL_HF_VALID))
    {
        Assert((uType & SHFL_HF_TYPE_MASK) != 0);

        if (pHandles[handle].uFlags & uType)
            return pHandles[handle].pvUserData;
    }
    return 0;
}

SHFLHANDLE vbsfAllocDirHandle (void)
{
    SHFLFILEHANDLE *pHandle = (SHFLFILEHANDLE *)RTMemAllocZ (sizeof (SHFLFILEHANDLE));

    if (pHandle)
    {
        pHandle->Header.u32Flags = SHFL_HF_TYPE_DIR;
        return vbsfAllocHandle(pHandle->Header.u32Flags, (uintptr_t)pHandle);
    }

    return SHFL_HANDLE_NIL;
}

SHFLHANDLE vbsfAllocFileHandle (void)
{
    SHFLFILEHANDLE *pHandle = (SHFLFILEHANDLE *)RTMemAllocZ (sizeof (SHFLFILEHANDLE));

    if (pHandle)
    {
        pHandle->Header.u32Flags = SHFL_HF_TYPE_FILE;
        return vbsfAllocHandle(pHandle->Header.u32Flags, (uintptr_t)pHandle);
    }

    return SHFL_HANDLE_NIL;
}

void vbsfFreeFileHandle (SHFLHANDLE hHandle)
{
    SHFLFILEHANDLE *pHandle = (SHFLFILEHANDLE *)vbsfQueryHandle(hHandle, SHFL_HF_TYPE_DIR|SHFL_HF_TYPE_FILE);

    if (pHandle)
    {
        vbsfFreeHandle(hHandle);
        RTMemFree (pHandle);
    }
    else
        AssertFailed();

    return;
}