MMIOM_GETFORMATNAME
The MMIOM_GETFORMATNAME message is sent to a Multimedia I/O (MMIO) procedure to retrieve a human-readable text string representing the media format name (e.g., "AVC Image File Format" or "WAVE Audio File"). This message is handled at the global driver level and does not require an active file handle or an initialized open instance.
Syntax
bytesRead = mmioSendMessage(hmmio, MMIOM_GETFORMATNAME, (LONG)pszBuffer, lParam2);
Parameters
- ulReserved (ULONG)
- In place of the standard `pmmioinfo` parameter, this field is reserved and set to zero. An MMIOINFO runtime instance block is not required to process this request.
- usMsg (USHORT)
- The message identifier, set to `MMIOM_GETFORMATNAME`.
- lParam1 (LONG)
- A pointer to a caller-allocated null-terminated string buffer (`PSZ`) where the I/O procedure will write the format name string.
- lParam2 (LONG)
- The size, in bytes, of the output buffer provided in lParam1.
Return Value
- rc (ULONG)
- Returns structural transaction metrics:
- Greater than 0: The exact number of bytes successfully copied into the destination string buffer (including or bounding the string layout footprint).
- 0: The inquiry failed, or the I/O procedure could not supply a localized format identification label.
Remarks
- **Subsystem Dispatch**: The MMIO Manager issues this message automatically when an application calls the mmioGetFormatName function.
- **Truncation Safeguard**: The I/O procedure must respect the buffer size constraints specified in lParam2. If the target format name string length exceeds the value of lParam2, the I/O procedure will truncate the text string data to fit the specified number of bytes cleanly, ensuring it remains safe from buffer overrun conditions.