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NAME
- TFStartUnitTagList
-
Start a trackfile.device unit, so that it may be used with TFInsertMediaTagList().
SYNOPSIS
unit = TFStartUnitTagList(which_unit, tags)
LONG TFStartUnitTagList(LONG which_unit, CONST struct TagItem *tags);
LONG TFStartUnitTags(LONG which_unit, ...);
D0 D0 A0
LONG TFStartUnitTags(LONG which_unit, ...);
FUNCTION
Before a trackfile.device unit can take control of an ADF disk image file it first needs to be started. Starting a unit involves allocating memory for the maintenance of the unit as well as creating a Process which will respond to the commands the unit has to perform.
INPUTS
- which_unit
-
Which unit to start. Unit numbers must be >= 0. If you do not have a preference for a specific unit number, use TFSU_NextAvailableUnit instead which will pick the next currently unused unit number for you.
- tags
-
Pointer to a list of TagItems; this may be NULL.
TAGS
- TF_DriveType (LONG)
-
You may request that the unit to be started should be specific type. The type must either be DRIVE3_5 (for a double-density 3.5" disk) or DRIVE3_5_150RPM (for a high-density 3.5" disk). Defaults to DRIVE3_5.
- TF_EnableChecksums (BOOL)
-
As a disk is being used, a checksum may be calculated over all the tracks which can be useful to identify specific disk contents. This checksum is updated in real time as disk data is being modified. Additional memory may need to be allocated in order to keep track of the checksums, and a small overhead may be incurred when track data is being modified.
The primary purpose of the checksums is to detect if disk image files with identical contents are to be inserted. If this is detected, the attempt will be aborted with an error code returned by the TFInsertMediaTagList() function.
The TF_EnableChecksums tag value defaults to FALSE.
- TF_MaxCacheMemory (ULONG)
-
trackfile.device may make use of a cache which is shared by all units, speeding up disk file read accesses. How much memory (in bytes) may be used by the cache at a time for all the units may be preset once.
Please note that TF_MaxCacheMemory is only supported if the unit is TFUNIT_CONTROL and the cache has not been set up yet. Defaults to 0 (the cache is not set up).
RESULT
- unit
-
If successful, the number of the unit started (a value >= 0) or otherwise a negative value indicating an error.
- TFERROR_Denied
-
TFStartUnitTagList() can only be called by a Process, never by a Task.
- TFERROR_InvalidDriveType
-
The TF_DriveType tag value is not known or supported.
- TFERROR_UnitBusy
-
The unit you wanted to start is already operational.
- TFERROR_OutOfMemory
-
Memory allocation has failed.
- TFERROR_ProcessFailed
-
The unit Process could not be started, e.g. because of memory allocation failure. Check with dos.library/IoErr() to learn more.
SEE ALSO
<exec/errors.h>, <devices/trackdisk.h>, <devices/trackfile.h>, TFInsertMediaTagList(), TFStopUnitTagList(), TFGetUnitData()