FileCore_DiscOp64 (changes)
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FileCore
» SWI Calls
» FileCore_DiscOp64
FileCore_DiscOp64
(SWI &4054C)
| Entry | |
|---|---|
| R1 | Reason code + Options |
| R2 | Pointer to disc address |
| R3 | Pointer to buffer (or scatter list) |
| R4 | Length in bytes |
| R5 | Pointer to |
| R6 | Cache handle |
| R8 | Pointer to Filecore instance private word |
| Exit | |
|---|---|
| R1 | Preserved |
| R2 | Preserved, disc address pointed to is updated to point to the next byte to be transferred |
| R3 | Pointer to next buffer location to be transferred |
| R4 | Number of bytes not transferred |
| R5 | Preserved ? |
| R6 | Preserved ? |
| R8 | Preserved ? |
Use
The purpose of this call is to provide a number of low-level disc operations using the more advanced Disc Operation DiscOp64.
Reason Codes
| # | Hex # | Action |
|---|---|---|
| 0 | &00 | Verify? |
| 1 | &01 | Read sectors? |
| 2 | &02 | Write sectors? |
| 3 | &03 | Read track/ID? |
| 4 | &04 | Write/format track? |
| 5 | &05 | Seek? |
| 6 | &06 | Restore? |
| 7 | &07 | Step in? |
| 8 | &08 | Step out? |
| 9 | &09 | Read sectors via cache? |
| 15 | &0F | Specify Hard disc? |
Options
| Bit | Meaning |
|---|---|
| 4 | Given alternative defect list |
| 5 | Given sector list |
| 6 | Ignore escape |
| 7 | Ignore timeout |
| 8 – 31 | Reserved, must be zero) |
Notes
The action performed depends on the reason code value in R1.
This call is just like FileCore_DiscOp except that it attacks a number of shortcomings in old versions of FileCore:
- Alternative disc record pointers passed in to various SWIs currently only have a 26-bit range so will not work in 32 bit systems.
- FileCore_SectorDiscOp limits discs to 2^29 sectors, i.e. 256GB for drives with 512 byte sectors.
In the future, this will allow for up to 16 exbibytes (over 16 billion GB) per disc, and many more discs per filing system.
As high (top-bit set) addresses are possible in a scatter list, only negative numbers smaller or equal to than -64K (ie >= unsigned &FFFF0000) should be interpreted as the end of list marker.
This applies to any FileCore module for RISC OS 3.50 or later.
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