dde支持传输的几种类型详解

Dynamic Data E xchange and XlT able F ormatMicrosoft Windows provides several methods for transferring data between applications.One way to transfer data is to use Wind ows dynamic data exchange (DDE). DDE is amessage protocol for data exchange between Windows prog rams. It allows softwaredevelopers to design applications that share data and thereby provide the user with a moreintegrated Wind ows environment.For complete information abou t DDE, see the documentation for the Microsoft WindowsSoftware Development Kit (SDK). This article describes the DDE formats that MicrosoftExcel supports, and it provides detailed information ab out the high-performance XlTableDDE format.DDE FormatsMicrosoft Excel supports several DDE formats. The formats are listed in the followingtable in the order of precedence defined by Microsoft Excel, from hig hest precedence(XlTable) to lowest precedence (CF_METAFILEPIC T). Clipboard formats that beginwith CF_ are formats that are alread y defined in Windows.h. Clipboard formats withou tCF_ must be registered before use. For more information abou t registering formats, seeRegistering Clipboard Formats.Clipboard format DescriptionXlTable Microsoft Excel fast table format. For more information, see Fast Table Format.Biff5 Binary interchange file format (B IFF) for Microsoft Excel version 5.0. For more information abou t the file format,see Microsoft Excel File Format.Biff4 Binary interchange file format (B IFF) for Microsoft Excel version 4.0.Biff3 BIFF for Microsoft Excel version 3.0.Biff BIFF for Microsoft Excel version 2.x.CF_SYLK Microsoft symb olic link (SYLK) format. Microsoft Excel for the Apple Macintosh was originally designed to use SYLK format, and this format is now supported by Microsoft Excel on both the Windows and Macintosh platforms.Wk1 Lotus® 1-2-3® Release 2.01 and Release 2.2 format.Csv Comma-separated values format, commonly used in B ASIC language I/O. This is similar to CF_TEXT format, except that Csv uses commas to separate fields.CF_TEXT The simplest form of Clipboard data. It is a null-terminated string containing a carriage return and linefeed at the end of each line. Rich Text Format A method of encoding formatted text and graphics for easy transfer between applications. Rich Text Format (R T F) is commonly used by document-processing programs such as Microsoft Word for Windows and Microsoft Word for the Macintosh.CF_DIF An ASCII format used by the VisiCalc™ spreadsheet program. The format is under the control of Lotus Development Corporation.CF_BITMAP A Wind ows version 2.x-compatible bitmap.CF_METAFILEPIC T A metafile picture structure. For complete information, see the documentation for the Microsoft Windows Software Development Kit.Registering Clipboard FormatsWhenever an application uses a private Clipboard format — such as XlTable, Biff5,Biff4, Biff3, Biff, Wk1, Csv, or Rich Text Format — it must register the format beforeusing it. Microsoft Excel registers these private Clipboard formats, and you r DDEapplication must also register any of these formats that you want to use to exchange data.For example, to register XlTable, use the following Windows API fu nction call.wCBformat = RegisterClipb oardFormat((LPSTR)"XlTable");If the function call is successful, the return value is equal to the format value for theXlTable format. This format value (type WORD) is between 0xC000 and 0xFFFF, andit's equal to the format value that Windows retu rned to Microsoft Excel when it registeredXlTable. If Windows cannot register XlTable, the function returns 0 (zero).Fast T able FormatThe fast table format, XlTable, is desig ned to maximize the DDE transfer speed ofMicrosoft Excel. XlTable consists of a sequence of data blocks that represent arectangular selection of cells (a table). Each data block has three parts:WORD tdt /* the table data type */WORD cb /* the size (count of b ytes) of the data */BYTE data[cb] /* the data */The first data block is always of type td tTable, which specifies the number of rows andthe number of colu mns in the table. The data blocks that follow td tTable represent all thecells in the table. Microsoft Excel renders the reference of the cells in the table (forexample, R1C1:R2C4) as the item part of the DDE message.The cells are always rendered row-wise. In other words, all the cells in the first row of thetable appear first, then all the cells in the second row, and so on. To minimize overhead,adjacent cells of the same type (td t) are represented together in one data block, even if thecells are in different rows. In other words, one td tFloat can contain several nu mbers, onetd tString can contain several strings, one tdtB ool can contain several B oolean values, andso on. For examples, see the following sections, "XlTable Example 1" and "XlTableExample 2."The data block types are described in the following table.Data block type Value Descriptiontd tTable 0x0010 The size of the table. The data (4 bytes, cb=4) consists of two words.The first word is the nu mber of rows, and the second word is the nu mber of columns.td tFloat 0x0001 IEEE-format floating-point number. The size of the number is 8 bytes per cell.td tString0x0002 String in st (byte-counted) format. The first byte contains the leng th of the string (cch). The string isn't null-terminated.td tBool 0x0003 Boolean value: 1 = TRUE0 = FALSEThe length of the data is 2 bytes per cell.td tError 0x0004 Error value: 0 = #NULL!7 = #DIV/0!15 = #VALUE!23 = #REF!29 = #NAME?36 = #NUM!42 = #N/AThe length of the data is 2 bytes per cell.td tBlank 0x0005 A count of the number of consecu tive undefined (blank) cells.The data (2 bytes, cb=2) contains the number of consecu tive blank cells.td tInt 0x0006 Unsigned integer. The leng th of the data is 2 b ytes per cell. Microsoft Excel can read a number in thisformat, but it never writes a number in this format.td tSkip 0x0007 Number of cells to skip. A skipped cell is a cell that retains its previous value. In other words, a skipped cell isn't changed b use td tSkip to increase DDE performance if your application changes only one or two cells in the middle of a large table. Mthe new cell data is part of a WM_DDE_POKE message. The leng th of the data is 2 bytes (cb=2).XlT able E xample 1The following selection of three cells . . .A1 EastA2 WestA3 North. . . produces the XlTable rendering shown in the following table.Data (hexadecimal) Description10 00 04 00 01 00 03 00 td tTable, cb=4, rows=1, columns=302 00 10 00 td tString, cb=1604 45 61 73 74 cch=4, East (td tString continued)04 57 65 73 74 cch=4, West (td tString continued)05 4e 6f 72 74 68 cch=5, North (td tString continued)Notice that the table contains three cells, but the XlTable rendering contains only onetd tString data block.XlT able E xample 2The XlTable format uses the td tBlank data block to represent blank cells in a table. Asequence of several blank cells may be represented by a single tdtBlank data block.For example, the following table . . .A1: 2 A2: 3B1: 4 B2: 5D1: 6 D2: 7. . . produces the following XlTable rendering.Data (hexadecimal) Description10 00 04 00 02 00 04 00 td tTable, cb=4, rows=4, columns=206 00 08 00 02 00 03 00 04 00 05 00 td tInt, cb=8, int[0]=2, int[1]=3, int[2]=4, int[3]=5 (Microsoft Excel can read td tInt as a client, bu t it would write td tF05 00 02 00 02 00 td tBlank, cb=2, data=2 (two cells are blank)06 00 04 00 06 00 08 00 td tInt, cb=4, int[0]=6, int[1]=8Biff5, Biff4, Biff3, and Biff FormatsThe Biff5, Biff4, Biff3, and Biff Clipboard formats contain a variable number of records.The records are identical to the corresponding records in the B IFF file. For moreinformation ab out the BIFF5 records, see Microsoft Excel File Format. The Biff4, Biff3,and Biff formats are available for backward compatibility with existing applications. TheBiff Clipboard format corresponds to the BIFF2 file format.If you implement one of the BIFF Clipb oard formats, your code should be prepared toreceive all B IFF records except file-specific records such as the following:WRITEPROTFILEPASSTEMPLATEWRITEACCESSFILESHARINGCODEPAGEPUBSUBEDGINDEXThe requisite B IFF records that your code must provide when it writes to the Clipboard are as follows:BOFDIMENSIONSCell record or records (B LANK, B OOLERR, and so on。