Extra features of FileSwitch, introduced in version 1.70

i) Path variables work properly. Whenever <thing>: prefixes a path the relevant path variable will be used (<thing>$Path). Paths in path variables will be resolved in the same way. The following new errors may occur:

• Path variable had multiple entries and was used for a write operation
• One of the path variables used refers to itself

ii) FileSwitch manages directories. From now on FileSwitch will process a path, resolving out wildcards, absolute directory references (%, @, \ and &) and sorting out parent references (^). There should be minimal impact on how things work, except for the following:

• All filing systems will get all absolute directories working the same.
• It may be possible to delete current and library directories.
• Paths which go through non-existant directories, but end up at an existing object will work (eg a.b.c.d.^.^.^.f will end at a.f even if b, c or d don't exist).

iii) FileSwitch provides support for MultiFS-like filing systems. The support provided by FileSwitch means that 'seamless' access to MS-DOS hard disc partition files, or MS-DOS discs, can be implemented. In effect, the foreign disc format is not noticed by the user when it is accessed from the desktop. As a consequence of this the object type has been extended:

Object type Meaning
0 Not present
1 File
2 Directory
3 File and Directory - this means this file has been
 identified as a MultiFS file, and hence can be treated as a
 directory too. Objects of this type may be treated as both
 files and directories.

An alternative way to think of the object type is as a bit field:

Bit Meaning when set
0 Object may have file-like operations done to it
1 Object may have directory-like operations done to it

iv) Given a filename, FileSwitch can be asked to process it to produce a mostly canonical form (mostly in the sense that the case may be different, and wildcards may not be sorted out if the wildcarded object doesn't exist!). So

• 'a' may be resolved to 'adfs::HardDisc4.$.current.a' if the current directory is 'adfs::HardDisc4.$.current'.
• 'a*' may be resolved to the same thing if 'a' exists and is the first match for 'a*', but, if there is no match for 'a*', then 'adfs::HardDisc4.$.current.a*' will be returned.
• 'A' may be resolved to 'adfs::HardDisc4.$.current.A', which should be considered the same as 'adfs::HardDisc4.$.current.a'.

OS_FSControl 37 (FSControl_CanonicalisePath)

On entry
r0 = 37
r1 = Pointer to path to be canonicalised r2 = Pointer to buffer to be filled in r3 = Pointer to system variable name of path to use, or 0 if none r4 = Pointer to default path to use if no system variable is specified

 or if that variable doesn't exist, or 0 if no path is the default

r5 = Buffer length

On exit
Buffer filled in with 0-terminated canonicalised name, and r5 = number of spare bytes in the buffer after and including

 the 0 terminator. If the buffer would have overflowed,
 then this will be taken to negative the overflow, but
 the overflow won't actually have happened. This
 provides a machanism for finding out how much buffer
 is needed.

This may be used as a two-pass process: Pass 1:
In:

 r0 = 37
 r1 = Pointer to path
 r2 = 0
 r5 = 0

Out:

 r5 = -(length of canonicalised path)

Pass 2:
Claim buffer of the right size (1-r5, not just -r5 as a space for the terminator is needed) In:

 r0 = 37
 r1 = Pointer to path
 r2 = Pointer to claimed buffer
 r5 = size of claimed buffer

Out:

 r5 should be 0, but check to make sure!

v) Given a file handle, fileswitch will return the name of the file.

OS_Args 7 (OSArgs_ReadPath)
On entry
r0 = 7
r1 = file handle
r2 = Pointer to buffer to be filled in r5 = Buffer length
On exit
Buffer filled in with 0-terminated canonicalised name, and r5 = number of spare bytes in the buffer after the 0 terminator.

 If the buffer would have overflowed, then this will be
 taken to negative the overflow, but the overflow won't
 actually have happened. This provides a machanism for
 finding out how much buffer is needed.

This call can be used in the same way as OS_FSControl 37.

vi) FileSwitch now processes the conversion of file info into filetype information.

OS_FSControl 38 (FSControl_InfoToFileType) On entry
r0 = 38
r1 = a pointer to the object's name
r2 = object's load address
r3 = object's execute address
r4 = object's length
r5 = objects's attributes
r6 = object's type (file/directory)
On exit
r2 = object's type:

 Special values:
 -1 untyped
 &1000 directory
 &2000 application directory (directory whose name starts with a '!').

OS_File 20-23 (OSFile_ReadWithType, _ReadWithTypePath, _ReadWithTypePathVar

 and _ReadWithTypeNoPath)

On Entry
r0 = 20, 21, 22 or 23
r1 = Pointer to name of object
On exit
r0 = object's type
r1 unchanged
r2 = Object's load address or top word of date stamp r3 = Object's execute address or bottom word of date stamp r4 = Object's length
r5 = object's attributes
r6 = Object's type:

 Special values:
 -1 untyped (r2, r3 are load and execute address)
 &1000 directory
 &2000 application directory (directory whose name starts with a '!').

OS_GBPB 12 (OSGBPB_ReadDirEntriesFileType)

On entry
r0 = 12
r1 = pointer to directory name
r2 = start address of data in memory (word aligned) r3 = number of names to read from directory r4 = offset of first item to read from directory (0 for start) r5 = buffer length
r6 = Pointer to (Wildcarded) name to match

On exit
r0-r2 unchanged
r3 = number of objects read
r4 = offset of next item to read
r5, r6 unchanged

This call is similar in function to OS_GBPB 10, except the buffer is filled in with entries like this:

Offset Contents

0 Load address or high word of date stamp
4 Execute address of low word of date stamp
8 Length
12 File attributes
16 Object type
20 Object's file type (as for OS_File 20-23)
24 Object's name (null terminated)