DSK_READTRACK
- Category
- IOCTL_DISK (08h)
- Function
- DSK_READTRACK (64h)
- Description
- Read Logical Track
Description
Reads a logical track.
Command Information
A byte with bit 0 defined as follows:
- Bit 0: If clear (0), the track layout contains non-consecutive sectors or does not start with Sector 1. If set (1), the track layout starts with Sector 1 and contains only consecutive sectors.
- All other bits are reserved and must be set to 0.
Parameter Packet Format
| Field | Length | C Datatype |
|---|---|---|
| Command Information | BYTE | BYTE |
| Head | WORD | USHORT |
| Cylinder | WORD | USHORT |
| First Sector | WORD | USHORT |
| Number of Sectors | WORD | USHORT |
| Track Layout Table | BYTES | BYTE[] |
Track Layout Table
The Track Layout Table has the following format:
| Field | Length |
|---|---|
| Sector Number for Sector 1 | WORD |
| Sector Size for Sector 1 | WORD |
| Sector Number for Sector 2 | WORD |
| Sector Size for Sector 2 | WORD |
| Sector Number for Sector 3 | WORD |
| Sector Size for Sector 3 | WORD |
| ... | ... |
| Sector Number for Sector n | WORD |
| Sector Size for Sector n | WORD |
The sector table that is specified provides information that is used during the READ track operation.
Data Packet Format
| Field | Length | C Datatype |
|---|---|---|
| Buffer | BYTES | UCHAR[] |
The Data Packet is a buffer. The buffer must be large enough to hold requested data.
Returns
Possible values are shown in the following list:
| Code | Description |
|---|---|
| 0 | NO_ERROR |
| 1 | ERROR_INVALID_FUNCTION |
| 6 | ERROR_INVALID_HANDLE |
| 15 | ERROR_INVALID_DRIVE |
| 31 | ERROR_GEN_FAILURE |
| 87 | ERROR_INVALID_PARAMETER |
| 111 | ERROR_BUFFER_OVERFLOW |
| 115 | ERROR_PROTECTION_VIOLATION |
| 117 | ERROR_INVALID_CATEGORY |
| 119 | ERROR_BAD_DRIVER_LEVEL |
| 163 | ERROR_UNCERTAIN_MEDIA |
| 165 | ERROR_MONITORS_NOT_SUPPORTED |
Remarks
This function is used to perform a read of sectors on the media and to perform the operations on the device that is specified in this request. The track table passed in on the call is used to determine the sector number, which is passed to the disk controller for the operation. In cases where the sectors are oddly numbered or are non-consecutive, this request breaks into n single sector operations and reads one sector at a time. This DosDevIOCtl is typically used when performing I/O outside of the normal file system data area on the media. The Head field specifies the physical head on the drive that performs the operation. The Cylinder field indicates the cylinder for the read. The First Sector field specifies the logical sector number within the Track Layout Table that starts the I/O operation (sector numbers start with 0, e.g., the third sector is number 2). The Number of Sectors field indicates the number of sectors to read (up to the maximum specified in the track table; the IOCtl subfunctions do not step heads/tracks). The TRACKLAYOUT data structure can be used by C programmers. To include this data structure in your file, make sure INCL_DOSDEVIOCTL is defined before including OS2.H.