typedef struct _OLESTREAMVTBL { /* ostrv */
DWORD (CALLBACK* Get)(LPOLESTREAM, void FAR*, DWORD);
DWORD (CALLBACK* Put)(LPOLESTREAM, OLE_CONST void FAR*, DWORD);
} OLESTREAMVTBL;
The OLESTREAMVTBL structure points to functions the client library uses for stream operations on objects. This structure is allocated and initialized by client applications.
The stream is valid only for the duration of the function to which it is passed. The library obtains everything it requires while the stream is valid.
The return values for the stream functions may indicate that an error has occurred but do not indicate the nature of the error. The client application is responsible for any required error-recovery operations.
A client application can use these functions to provide variations on the standard stream procedures; for example, the client could change the permanent storage of some objects so that they were stored in a database instead of the client document.
| LONG Get(lpstream, lpszBuf, cbbuf) | |||
| LPOLESTREAM lpstream; | |||
| LPSTR lpszBuf; | |||
| DWORD cbbuf; |
The Get function gets data from the specified stream.
lpstream
Points to an OLESTREAM structure allocated by the client.
lpszBuf
Points to a buffer to fill with data from the stream.
cbbuf
Specifies the number of bytes to read into the buffer.
The return value is the number of bytes actually read into the buffer if the function is successful. If the end of the file is encountered, the return value is zero. If the return value is negative, an error occurred.
The value specified by the cbbuf parameter can be larger than 64K. If the client application uses a stream-reading function that is limited to 64K, it should call that function repeatedly until it has read the number of bytes specified by cbbuf. Whenever the data size is greater than 64K, the pointer to the data buffer is always at the beginning of the segment.
| LONG Put(lpstream, lpszBuf, cbbuf) | |||
| LPOLESTREAM lpstream; | |||
| LPSTR lpszBuf; | |||
| DWORD cbbuf; |
The Put function puts data into the specified stream.
lpstream
Points to an OLESTREAM structure allocated by the client.
lpszBuf
Points to a buffer from which to write data into the stream.
cbbuf
Specifies the number of bytes to write into the stream.
The return value is the number of bytes actually written to the stream. If the return value is less than the number specified in the cbbuf parameter, there was insufficient space in the stream or an error occurred.
The value specified by the cbbuf parameter can be larger than 64K. If the client application uses a stream-writing function that is limited to 64K, it should call that function repeatedly until it has written the number of bytes specified by cbbuf. Whenever the data size is greater than 64K, the pointer to the data buffer is always at the beginning of the segment.