stg_bigblockfile.c

这是一个开放源代码的与WINNT/WIN2K/WIN2003兼容的操作系统

  LPBIGBLOCKFILE This,
  DWORD          page_index)
{
    MappedPage *page;

    page = BIGBLOCKFILE_FindPageInList(This->maplist, page_index);
    if (!page)
    {
	page = BIGBLOCKFILE_FindPageInList(This->victimhead, page_index);
	if (page)
	{
	    This->num_victim_pages--;

	    BIGBLOCKFILE_Zero(&page->readable_blocks);
	    BIGBLOCKFILE_Zero(&page->writable_blocks);
	}
    }

    if (page)
    {
	/* If the page is not already at the head of the list, move
	 * it there. (Also moves pages from victim to main list.) */
	if (This->maplist != page)
	{
	    if (This->victimhead == page) This->victimhead = page->next;
	    if (This->victimtail == page) This->victimtail = page->prev;

	    BIGBLOCKFILE_UnlinkPage(page);

	    BIGBLOCKFILE_LinkHeadPage(&This->maplist, page);
	}

	return page;
    }

    page = BIGBLOCKFILE_CreatePage(This, page_index);
    if (!page) return NULL;

    BIGBLOCKFILE_LinkHeadPage(&This->maplist, page);

    return page;
}

static BOOL BIGBLOCKFILE_MapPage(LPBIGBLOCKFILE This, MappedPage *page)
{
    DWORD lowoffset = PAGE_SIZE * page->page_index;

    if (This->fileBased)
    {
	DWORD numBytesToMap;
	DWORD desired_access;

        if( !This->hfilemap )
            return FALSE;

	if (lowoffset + PAGE_SIZE > This->filesize.u.LowPart)
	    numBytesToMap = This->filesize.u.LowPart - lowoffset;
	else
	    numBytesToMap = PAGE_SIZE;

	if (This->flProtect == PAGE_READONLY)
	    desired_access = FILE_MAP_READ;
	else
	    desired_access = FILE_MAP_WRITE;

	page->lpBytes = MapViewOfFile(This->hfilemap, desired_access, 0,
				      lowoffset, numBytesToMap);
        page->mapped_bytes = numBytesToMap;
    }
    else
    {
	page->lpBytes = (LPBYTE)This->pbytearray + lowoffset;
        page->mapped_bytes = PAGE_SIZE;
    }

    TRACE("mapped page %u to %p\n", page->page_index, page->lpBytes);

    return page->lpBytes != NULL;
}

static MappedPage *BIGBLOCKFILE_CreatePage(LPBIGBLOCKFILE This,
					   ULONG page_index)
{
    MappedPage *page;

    page = HeapAlloc(GetProcessHeap(), 0, sizeof(MappedPage));
    if (page == NULL)
      return NULL;

    page->page_index = page_index;
    page->refcnt = 1;

    page->next = NULL;
    page->prev = NULL;

    if (!BIGBLOCKFILE_MapPage(This, page))
    {
        HeapFree(GetProcessHeap(),0,page);
        return NULL;
    }

    BIGBLOCKFILE_Zero(&page->readable_blocks);
    BIGBLOCKFILE_Zero(&page->writable_blocks);

    return page;
}

static void BIGBLOCKFILE_UnmapPage(LPBIGBLOCKFILE This, MappedPage *page)
{
    TRACE("%d at %p\n", page->page_index, page->lpBytes);
    if (page->refcnt > 0)
	ERR("unmapping inuse page %p\n", page->lpBytes);

    if (This->fileBased && page->lpBytes)
	UnmapViewOfFile(page->lpBytes);

    page->lpBytes = NULL;
}

static void BIGBLOCKFILE_DeletePage(LPBIGBLOCKFILE This, MappedPage *page)
{
    BIGBLOCKFILE_UnmapPage(This, page);

    HeapFree(GetProcessHeap(), 0, page);
}

/******************************************************************************
 *      BIGBLOCKFILE_ReleaseMappedPage      [PRIVATE]
 *
 * Decrements the reference count of the mapped page.
 */
static void BIGBLOCKFILE_ReleaseMappedPage(
  LPBIGBLOCKFILE This,
  MappedPage    *page)
{
    assert(This != NULL);
    assert(page != NULL);

    /* If the page is no longer refenced, move it to the victim list.
     * If the victim list is too long, kick somebody off. */
    if (!InterlockedDecrement(&page->refcnt))
    {
	if (This->maplist == page) This->maplist = page->next;

	BIGBLOCKFILE_UnlinkPage(page);

	if (MAX_VICTIM_PAGES > 0)
	{
	    if (This->num_victim_pages >= MAX_VICTIM_PAGES)
	    {
		MappedPage *victim = This->victimtail;
		if (victim)
		{
		    This->victimtail = victim->prev;
		    if (This->victimhead == victim)
			This->victimhead = victim->next;

		    BIGBLOCKFILE_UnlinkPage(victim);
		    BIGBLOCKFILE_DeletePage(This, victim);
		}
	    }
	    else This->num_victim_pages++;

	    BIGBLOCKFILE_LinkHeadPage(&This->victimhead, page);
	    if (This->victimtail == NULL) This->victimtail = page;
	}
	else
	    BIGBLOCKFILE_DeletePage(This, page);
    }
}

static void BIGBLOCKFILE_DeleteList(LPBIGBLOCKFILE This, MappedPage *list)
{
    while (list != NULL)
    {
	MappedPage *next = list->next;

	BIGBLOCKFILE_DeletePage(This, list);

	list = next;
    }
}

/******************************************************************************
 *      BIGBLOCKFILE_FreeAllMappedPages     [PRIVATE]
 *
 * Unmap all currently mapped pages.
 * Empty mapped pages list.
 */
static void BIGBLOCKFILE_FreeAllMappedPages(
  LPBIGBLOCKFILE This)
{
    BIGBLOCKFILE_DeleteList(This, This->maplist);
    BIGBLOCKFILE_DeleteList(This, This->victimhead);

    This->maplist = NULL;
    This->victimhead = NULL;
    This->victimtail = NULL;
    This->num_victim_pages = 0;
}

static void BIGBLOCKFILE_UnmapList(LPBIGBLOCKFILE This, MappedPage *list)
{
    for (; list != NULL; list = list->next)
    {
	BIGBLOCKFILE_UnmapPage(This, list);
    }
}

static void BIGBLOCKFILE_UnmapAllMappedPages(LPBIGBLOCKFILE This)
{
    BIGBLOCKFILE_UnmapList(This, This->maplist);
    BIGBLOCKFILE_UnmapList(This, This->victimhead);
}

static void BIGBLOCKFILE_RemapList(LPBIGBLOCKFILE This, MappedPage *list)
{
    while (list != NULL)
    {
	MappedPage *next = list->next;

	if (list->page_index * PAGE_SIZE > This->filesize.u.LowPart)
	{
            TRACE("discarding %u\n", list->page_index);

	    /* page is entirely outside of the file, delete it */
	    BIGBLOCKFILE_UnlinkPage(list);
	    BIGBLOCKFILE_DeletePage(This, list);
	}
	else
	{
	    /* otherwise, remap it */
	    BIGBLOCKFILE_MapPage(This, list);
	}

	list = next;
    }
}

static void BIGBLOCKFILE_RemapAllMappedPages(LPBIGBLOCKFILE This)
{
    BIGBLOCKFILE_RemapList(This, This->maplist);
    BIGBLOCKFILE_RemapList(This, This->victimhead);
}

/****************************************************************************
 *      BIGBLOCKFILE_GetProtectMode
 *
 * This function will return a protection mode flag for a file-mapping object
 * from the open flags of a file.
 */
static DWORD BIGBLOCKFILE_GetProtectMode(DWORD openFlags)
{
    switch(STGM_ACCESS_MODE(openFlags))
    {
    case STGM_WRITE:
    case STGM_READWRITE:
        return PAGE_READWRITE;
    }
    return PAGE_READONLY;
}


/* ILockByte Interfaces */

/******************************************************************************
 * This method is part of the ILockBytes interface.
 *
 * It reads a block of information from the byte array at the specified
 * offset.
 *
 * See the documentation of ILockBytes for more info.
 */
static HRESULT WINAPI ImplBIGBLOCKFILE_ReadAt(
      BigBlockFile* const This,
      ULARGE_INTEGER ulOffset,  /* [in] */
      void*          pv,        /* [length_is][size_is][out] */
      ULONG          cb,        /* [in] */
      ULONG*         pcbRead)   /* [out] */
{
    ULONG first_page = ulOffset.u.LowPart / PAGE_SIZE;
    ULONG offset_in_page = ulOffset.u.LowPart % PAGE_SIZE;
    ULONG bytes_left = cb;
    ULONG page_index = first_page;
    ULONG bytes_from_page;
    LPVOID writePtr = pv;

    HRESULT rc = S_OK;

    TRACE("(%p)-> %i %p %i %p\n",This, ulOffset.u.LowPart, pv, cb, pcbRead);

    /* verify a sane environment */
    if (!This) return E_FAIL;

    if (offset_in_page + bytes_left > PAGE_SIZE)
        bytes_from_page = PAGE_SIZE - offset_in_page;
    else
        bytes_from_page = bytes_left;

    if (pcbRead)
        *pcbRead = 0;

    while (bytes_left)
    {
        LPBYTE readPtr;
        BOOL eof = FALSE;
        MappedPage *page = BIGBLOCKFILE_GetMappedView(This, page_index);

        if (!page || !page->lpBytes)
        {
            rc = STG_E_READFAULT;
            break;
        }

        TRACE("page %i,  offset %u, bytes_from_page %u, bytes_left %u\n",
            page->page_index, offset_in_page, bytes_from_page, bytes_left);

        if (page->mapped_bytes < bytes_from_page)
        {
            eof = TRUE;
            bytes_from_page = page->mapped_bytes;
        }

        readPtr = (BYTE*)page->lpBytes + offset_in_page;
        memcpy(writePtr,readPtr,bytes_from_page);
        BIGBLOCKFILE_ReleaseMappedPage(This, page);

        if (pcbRead)
            *pcbRead += bytes_from_page;
        bytes_left -= bytes_from_page;

        if (bytes_left && !eof)
        {
            writePtr = (LPBYTE)writePtr + bytes_from_page;
            page_index ++;
            offset_in_page = 0;
            if (bytes_left > PAGE_SIZE)
                bytes_from_page = PAGE_SIZE;
            else
                bytes_from_page = bytes_left;
        }
        if (eof)
        {
            rc = STG_E_READFAULT;
            break;
        }
    }

    TRACE("finished\n");
    return rc;
}

/******************************************************************************
 * This method is part of the ILockBytes interface.
 *
 * It writes the specified bytes at the specified offset.
 * position. If the file is too small, it will be resized.
 *
 * See the documentation of ILockBytes for more info.
 */
static HRESULT WINAPI ImplBIGBLOCKFILE_WriteAt(
      BigBlockFile* const This,
      ULARGE_INTEGER ulOffset,    /* [in] */
      const void*    pv,          /* [size_is][in] */
      ULONG          cb,          /* [in] */
      ULONG*         pcbWritten)  /* [out] */
{
    ULONG size_needed = ulOffset.u.LowPart + cb;
    ULONG first_page = ulOffset.u.LowPart / PAGE_SIZE;
    ULONG offset_in_page = ulOffset.u.LowPart % PAGE_SIZE;
    ULONG bytes_left = cb;
    ULONG page_index = first_page;
    ULONG bytes_to_page;
    LPCVOID readPtr = pv;

    HRESULT rc = S_OK;

    TRACE("(%p)-> %i %p %i %p\n",This, ulOffset.u.LowPart, pv, cb, pcbWritten);

    /* verify a sane environment */
    if (!This) return E_FAIL;

    if (This->flProtect != PAGE_READWRITE)
        return STG_E_ACCESSDENIED;

    if (size_needed > This->filesize.u.LowPart)
    {
        ULARGE_INTEGER newSize;
        newSize.u.HighPart = 0;
        newSize.u.LowPart = size_needed;
        BIGBLOCKFILE_SetSize(This, newSize);
    }

    if (offset_in_page + bytes_left > PAGE_SIZE)
        bytes_to_page = PAGE_SIZE - offset_in_page;
    else
        bytes_to_page = bytes_left;

    if (pcbWritten)
        *pcbWritten = 0;

    while (bytes_left)
    {
        LPBYTE writePtr;
        MappedPage *page = BIGBLOCKFILE_GetMappedView(This, page_index);

        TRACE("page %i,  offset %u, bytes_to_page %u, bytes_left %u\n",
            page ? page->page_index : 0, offset_in_page, bytes_to_page, bytes_left);

        if (!page)
        {
            ERR("Unable to get a page to write. This should never happen\n");
            rc = E_FAIL;
            break;
        }

        if (page->mapped_bytes < bytes_to_page)
        {
            ERR("Not enough bytes mapped to the page. This should never happen\n");
            rc = E_FAIL;
            break;
        }

        writePtr = (BYTE*)page->lpBytes + offset_in_page;
        memcpy(writePtr,readPtr,bytes_to_page);
        BIGBLOCKFILE_ReleaseMappedPage(This, page);

        if (pcbWritten)
            *pcbWritten += bytes_to_page;
        bytes_left -= bytes_to_page;

        if (bytes_left)
        {
            readPtr = (const BYTE *)readPtr + bytes_to_page;
            page_index ++;
            offset_in_page = 0;
            if (bytes_left > PAGE_SIZE)
                bytes_to_page = PAGE_SIZE;
            else
                bytes_to_page = bytes_left;
        }
    }

    return rc;
}


HRESULT     BIGBLOCKFILE_ReadAt(LPBIGBLOCKFILE This, ULARGE_INTEGER offset,
                void* buffer, ULONG size, ULONG* bytesRead)
{
    if (This->fileBased)
        return ImplBIGBLOCKFILE_ReadAt(This,offset,buffer,size,bytesRead);
    else
        return ILockBytes_ReadAt(This->pLkbyt,offset,buffer,size,bytesRead);
}

HRESULT    BIGBLOCKFILE_WriteAt(LPBIGBLOCKFILE This, ULARGE_INTEGER offset,
                const void* buffer, ULONG size, ULONG* bytesRead)
{
    if (This->fileBased)
        return ImplBIGBLOCKFILE_WriteAt(This,offset,buffer,size,bytesRead);
    else
        return ILockBytes_WriteAt(This->pLkbyt,offset,buffer,size,bytesRead);
}