| mmioOpen The mmioOpen function opens a file for unbuffered or buffered I/O. The file can be a standard file, a memory file, or an element of a custom storage system. The handle returned by mmioOpen is not a standard file handle; do not use it with any file I/O functions other than multimedia file I/O functions. VB4-32,5,6
Declare Function mmioOpen Lib "winmm.dll" Alias "mmioOpenA" (ByVal szFileName As String, lpmmioinfo As MMIOINFO, ByVal dwOpenFlags As Long) As Long |
| Operating Systems Supported |
| Requires Windows NT 3.1 or later; Requires Windows 95 or later |
· szFilename
Address of a string containing the filename of the file to open. If no I/O procedure is specified to open the file, the filename determines how the file is opened, as follows:
· If the filename does not contain a plus sign (+), it is assumed to be the name of a standard file (that is, a file whose type is not HMMIO).
· If the filename is of the form EXAMPLE.EXT+ABC, the extension EXT is assumed to identify an installed I/O procedure which is called to perform I/O on the file. For more information, see mmioInstallIOProc.
· If the filename is NULL and no I/O procedure is given, the adwInfo member of the MMIOINFO structure is assumed to be the standard (non-HMMIO) file handle of a currently open file.
The filename should not be longer than 128 bytes, including the terminating NULL character.
When opening a memory file, set szFilename to NULL.
· lpmmioinfo
Address of an MMIOINFO structure containing extra parameters used by mmioOpen. Unless you are opening a memory file, specifying the size of a buffer for buffered I/O, or specifying an uninstalled I/O procedure to open a file, this parameter should be NULL. If this parameter is not NULL, all unused members of the MMIOINFO structure it references must be set to zero, including the reserved members.
· dwOpenFlags
Flags for the open operation. The MMIO_READ, MMIO_WRITE, and MMIO_READWRITE flags are mutually exclusive ¾ only one should be specified. The MMIO_COMPAT, MMIO_EXCLUSIVE, MMIO_DENYWRITE, MMIO_DENYREAD, and MMIO_DENYNONE flags are file-sharing flags. The following values are defined:
MMIO_ALLOCBUF
Opens a file for buffered I/O. To allocate a buffer larger or smaller than the default buffer size (8K, defined as MMIO_DEFAULTBUFFER), set the cchBuffer member of the MMIOINFO structure to the desired buffer size. If cchBuffer is zero, the default buffer size is used. If you are providing your own I/O buffer, this flag should not be used.
MMIO_COMPAT
Opens the file with compatibility mode, allowing any process on a given machine to open the file any number of times. If the file has been opened with any of the other sharing modes, mmioOpen fails.
MMIO_CREATE
Creates a new file. If the file already exists, it is truncated to zero length. For memory files, this flag indicates the end of the file is initially at the start of the buffer.
MMIO_DELETE
Deletes a file. If this flag is specified, szFilename should not be NULL. The return value is TRUE (cast to HMMIO) if the file was deleted successfully or FALSE otherwise. Do not call the mmioClose function for a file that has been deleted. If this flag is specified, all other flags that open files are ignored.
MMIO_DENYNONE
Opens the file without denying other processes read or write access to the file. If the file has been opened in compatibility mode by any other process, mmioOpen fails.
MMIO_DENYREAD
Opens the file and denies other processes read access to the file. If the file has been opened in compatibility mode or for read access by any other process, mmioOpen fails.
MMIO_DENYWRITE
Opens the file and denies other processes write access to the file. If the file has been opened in compatibility mode or for write access by any other process, mmioOpen fails.
MMIO_EXCLUSIVE
Opens the file and denies other processes read and write access to the file. If the file has been opened in any other mode for read or write access, even by the current process, mmioOpen fails.
MMIO_EXIST
Determines whether the specified file exists and creates a fully qualified filename from the path specified in szFilename. The filename is placed back into szFilename. The return value is TRUE (cast to HMMIO) if the qualification was successful and the file exists or FALSE otherwise. The file is not opened, and the function does not return a valid multimedia file I/O file handle, so do not attempt to close the file.
MMIO_GETTEMP
Creates a temporary filename, optionally using the parameters passed in szFilename. For example, you can specify “C:F” to create a temporary file residing on drive C, starting with letter “F”. The resulting filename is placed in the buffer pointed to by szFilename. The return value is MMSYSERR_NOERROR (cast to HMMIO) if the temporary filename was created successfully or MMIOERR_FILENOTFOUND otherwise. The file is not opened, and the function does not return a valid multimedia file I/O file handle, so do not attempt to close the file. This flag overrides all other flags.
MMIO_PARSE
Creates a fully qualified filename from the path specified in szFilename. The filename is placed back into szFilename. The return value is TRUE (cast to HMMIO) if the qualification was successful or FALSE otherwise. The file is not opened, and the function does not return a valid multimedia file I/O file handle, so do not attempt to close the file. If this flag is specified, all flags that open files are ignored.
MMIO_READ
Opens the file for reading only. This is the default if MMIO_WRITE and MMIO_READWRITE are not specified.
MMIO_READWRITE
Opens the file for reading and writing.
MMIO_WRITE
Opens the file for writing only. |
Returns a handle of the opened file. If the file cannot be opened, the return value is NULL. If lpmmioinfo is not NULL, the wErrorRet member of the MMIOINFO structure will contain one of the following error values:
MMIOERR_ACCESSDENIED
The file is protected and cannot be opened.
MMIOERR_INVALIDFILE
Another failure condition occurred. This is the default error for an open-file failure.
MMIOERR_NETWORKERROR
The network is not responding to the request to open a remote file.
MMIOERR_PATHNOTFOUND
The directory specification is incorrect.
MMIOERR_SHARINGVIOLATION
The file is being used by another application and is unavailable.
MMIOERR_TOOMANYOPENFILES
The number of files simultaneously open is at a maximum level. The system has run out of available file handles. |
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