Recent Posts

Topic: General / What game should I write ?

Topic: Community Support / How to cope with a faulty Territory module

Depends whether you think there’s a serious problem with module help strings containing a VDU31 after the first 16 characters. On balance I’m inclined to not worry… but also to not repeat it.

However, the permissiveness of the handling of the first 16 characters is surprising and not defensible really, though I have duplicated it. It’s possible to create a module that changes mode or redefines a character when you type *Help Modules ¹. I’m struggling to think of a justification for that, other than existing (early) badly-formed examples (that somehow still have a valid version number, hmm…).

I thought carefully about the VDU31 bit, but since the algorithm is regarding all other ctrls as a terminator by that stage, it’s got to be an off-by-one.

¹ Oh, no it doesn’t. Didn’t notice that change but it did, Quite Some Time Ago. Must be malformed strings.

Topic: Bugs / Filetype corruption with SparkFS on recent 5.25 builds

I’m afraid that the documentation has always been so ropey that actual implementation has always outranked theoretical API.

Find a way to retain compatibility even if it has to be special-cased by FS number. There is precedent in FileSwitch with regard to pathname processing.

Topic: Community Support / How to cope with a faulty Territory module

If you look more closely you’ll find it is not a snippet of RMEnsure but is compatible with it except for the obvious bug I fixed.

For differing values of “obvious”!

Has the bugfix been fed back into the sources?

Topic: General / What game should I write ?

What about a Crazee Rider type game

https://en.wikipedia.org/wiki/Crazee_Rider

Topic: Bugs / Filetype corruption with SparkFS on recent 5.25 builds

Reading the referenced bits of the PRMs (I never implemented an FS myself!), I would conclude that both the current SparkFS implementation as well as the current FileSwitch implementation follow what the PRMs say. Both interpretations are valid. So unless there are very very very good reasons for the new FileSwitch behaviour, I would prefer to reinstate old behaviour. FileSwitch is extremely critical. Even if very specific behaviour is changed, this needs a very good reason, especially if both the old behaviour and the new behaviour matches the docs.

I would even argue that if we are going to significantly change FileSwitch in the future (64bit file size, non-blocking I/O, file caching and possibly a lot of other things), we need to make sure that “new” clients wanting to use the new features need to register specifically as “new” with FileSwitch so that the old stuff can be left unchanged. It is extremely complicated to keep things working unchanged when changing things!

There are a lot of FSes to be tested if the changed behaviour stays as it is. TBAFS. ArcFS. LanManFS. LanMan98. ShareFS. Sunfush. ImageNFS. NFS. X-Files. Win95FS. Memphis. HostFS in V-RPC. LayerFS. raFS. These are just those that come to my mind immediately (and yes, this is a bit sad…).

Topic: Community Support / How to cope with a faulty Territory module

If you look more closely you’ll find it is not a snippet of RMEnsure but is compatible with it except for the obvious bug I fixed.

Topic: Community Support / How to cope with a faulty Territory module

Very much so. Code ought to already exist – RMEnsure must read the version in some form…

The previous thread I linked to, you posted a link to the sources which showed exactly how RMEnsure did it! Just the same as Nemo has posted a snippet of the RMEnsure code above :-) Yes, it has to parse the help string to get the version number. I wonder if OS_Module 20 parses the help string too?

Topic: Bugs / Filetype corruption with SparkFS on recent 5.25 builds

Fat32Fs also gets this right. There is a comment which says “R2=R3=0 means don’t restamp file” in FSEntry_Close.

Topic: Aldershot / Was 2015 the end of RISC OS?

Personally, I think we need to code an OS from scratch, and implement necessary 32-bit ABI/API to support legacy RO apps, but encourage new apps to the modern API. Would have to still be an ARM-based system unless you plan of writing an emulator on top of things. I think the current code-base is stopping progression.

Topic: Community Support / How to cope with a faulty Territory module

And yes, it ought to be an OS_Module call.

Very much so. Code ought to already exist – RMEnsure must read the version in some form…

Topic: Aldershot / Was 2015 the end of RISC OS?

The continued lack of a decent standards-compliant browser is by far the biggest impediment. Lack of WiFi is #2, but academic in the light of #1.

“Programming language XYZ” is irrelevant – you need bums on seats before you start worrying about what to serve them. Without Facebook, Twitter, Instagram, Netflix, iPlayer, Spotify, banking etc, there will not be bums on seats.

Topic: Bugs / Zap Disassemble

your latest version of !Zap ok to use?

I think the best I can say is “it should have a few less bugs than other builds”. ;-)

Topic: Bugs / DeskTopTracker

What decides when vrpc-dl slows down?
Is this the Tracker mod job?

It’s mainly the Wimp – it contains some code which counts the number of idle poll events per second, and then drops CPU speed + starts using Portable_Idle if the number of events reaches a certain threshold.

Topic: Community Support / How to cope with a faulty Territory module

I’m sure you’re not the first person to ask about finding a module version number

It is especially galling that *RMEnsure has to do exactly that.

Since module help string rules are slightly strange, here’s how to read the BCD version number of a module:

; > r0  module name
;   r0  module version or 0 if no help string
;    V  set if module not present

GetModuleVerBCD STMFD   R13!, {R1-R5,R14}
                MOV     R1, R0
                MOV     R0, #18
                SWI     XOS_Module
                LDMVSFD R13!, {R1-R5,PC}        ; return error

                LDR     R0, [R3,#20]
                TEQ     R0, #0                  ; no help?
                LDMEQFD R13!, {R1-R5,PC}        ; return 0
                ADD     R3, R3, R0

; 1st 16 chrs can contain ctrl codes, strangely
                MOV     R0, #0
                MOV     R1, #0
skipname        LDRB    R14, [R3],#1
                TEQ     R14, #0                 ; no version?
                LDMEQFD R13!, {R1-R5,PC}        ; return 0
                TEQ     R14, #9                 ; expand tabs
                ADDEQ   R1, R1, #8
                ADDNE   R1, R1, #1
                BICEQ   R1, R1, #7
                CMP     R1, #16
                BLT     skipname

; thereafter any ctrl (except tab) terminates the string
skiptodigit     LDRB    R14, [R3],#1
                CMP     R14, #9
                CMPGT   R14, #32
                LDMCCFD R13!, {R1-R5,PC}        ; return 0
                SUB     R14, R14, #"0"
                CMP     R14, #10
                BCS     skiptodigit

major           ORR     R0, R14, R0, LSL#4
                LDRB    R14, [R3],#1
                SUB     R14, R14, #"0"
                CMP     R14, #10
                BCC     major
                MOV     R0, R0, LSL#16
                CMP     R14, #"."-"0"           ; decimal point?
                LDMNEFD R13!, {R1-R5,PC}        ; return MMMM.0000

                MOV     R1, #12
minor           LDRB    R14, [R3],#1
                SUB     R14, R14, #"0"
                CMP     R14, #10
                LDMCSFD R13!, {R1-R5,PC}        ; return MMMM.mm00
                ORR     R0, R0, R14, LSL R1
                SUBS    R1, R1, #4
                BPL     minor
                LDMFD   R13!, {R1-R5,PC}        ; return MMMM.mmmm

And yes, it ought to be an OS_Module call.

Topic: Bugs / DeskTopTracker

Mmm – something about a squadron of ‘pigs’ comes to mind :-(

Running ’Rick’s ‘C’ article on ‘USBeep’ in !TextEase – with it being read out – the Mips range between 60Mips and about 150Mips – drops to about 2Mips when doing nothing.

So the system works.

In the ‘Portable_Idle’ there seems to be a loop calling a address in the podule area – until a certain value is returned.

What decides when vrpc-dl slows down?
Is this the Tracker mod job?

[edit 1]
Just tried !DigitalCD – that works with the same tracker – Mips go up/down as required.
(uses TimPlayer)

Topic: Bugs / DeskTopTracker

Sounds like VRPC is being over-eager with how long Portable_Idle puts the system to sleep for. A problem to take up with the VRPC developers.

Topic: Bugs / DeskTopTracker

Just had a go with ‘Wimp Zarch’ (vrpc-dl ro5.25 – in a Window-windows mode) – able to read Mips.

When started up – ‘Wimp Zarch’ goes like the clappers – 370Mips.

When it stops to take a breather – it drops down to about 40Mips – and when it continues slow (auto mode).

When I move another window – away it goes again.

With ‘DeskTracker’ – when it starts playing a tune – it drops to about 5Mips.
(no wonder the sound drops off)

Topic: Announcements / RiscLua 7

Unfortunately you’ve broken that link, Gavin.

Sorry. I think the Textile help is wrong.

Lua is not special here.

I think Lua’s tables are special in that keys and values can be any non-nil value. Also, I do not think other languages have the concept of metatables .

I have just updated the Utilities in the RiscLua 7 distribution with !Linker and !Absolua. These let you create standalone Absolute versions your Lua programs, which will run on computers that do not have the RiscLua interpreter.

Topic: Announcements / RiscLua 7

Rick parted with

you can’t cast a string number into an integer in C, if you tried the best you’d get is the ASCII code of the first number

You’re guaranteed to never get that. Since “a string” in C is a char * (or in Windows programs, often a wchar_t *) then casting it to int will probably result in (an integer directly correlated with) the address of the string, dependent on your int and ptr sizes. If you used an intptr_t you’d be certain of it.

Topic: Announcements / RiscLua 7

Gavin wrote

More on tables

Unfortunately you’ve broken that link, Gavin.

However, on your actual page you claim

[Tables] combine many ideas that are separate, or do not exist, in other programming languages

A straw man argument. May not exist in some other programming languages, but in others they definitely do. Tables are associate arrays and are available under various names in many languages, such as Python, Javascript, PostScript, Ruby, and even Perl.

Lua is not special here. There’s a much stronger argument that Javascript objects are unlike other associative arrays because of their prototypical inheritance, but that can be implemented using a magic key in other languages too.

Topic: Announcements / RiscLua 7

Rick complained of dynamic typing

The point is, it’s a variable that’s a string, a real, and number, a date, or whatever else the just language supports. Which is which?

And yet:

DEFFNjustLikeBasicThen(T%)
CASET%OF
WHEN1:=TRUE
WHEN2:=2
WHEN3:=PI
WHEN4:="For?"
ENDCASE

Topic: Announcements / RiscLua 7

Steffen said

common programming errors. Try dangling pointers, off-by-one, invalid cast, failed malloc

• Assumption of success (absence of failure handling)
• Missing break;
• Sanity checking of parameters
• Undefined behaviour
• False corollary
• int/ptr/bool confusion

Topic: Community Support / Pi shutdown, restart - cannot move memory

So I think the crucial question (as it isn’t 100% repeatable for everyone) is: Has anyone had a “cannot move memory” error when doing a shutdown/restart on a Pi with RTC using 5.24 or 5.25?

Topic: Community Support / How to cope with a faulty Territory module

I’m sure you’re not the first person to ask about finding a module version number. I guess something like OS_Module 20 that works on softloaded modules as well as ROM modules might be handy?

Edited to add: Last discussed here