Anachronaut
87d819847e
SWI osExit takes a status in A, and the shell keeps it. Fifty eight exits across twenty three programs now say deliberately whether they worked: 25 did what they were asked, 24 did not, 9 were asked wrongly. Compare is the exception and says so - one there means the files differ, which is a result rather than a failure, the way diff has always had it. IN A RATHER THAN Q, which is not a departure from the rule that a service answers in Q. This one takes an ARGUMENT, the way osPrintNumber takes A and B, and it never returns to answer anything. A is free precisely because a return would have put it back - and Q is the ALU's output, so a small number costs four instructions there against one in A. The shell does not print it. A program that failed has already said so in words and a number beside that is noise, so osLastStatus hands it back and Status is the program that shows it. That indirection is the point: the number exists for the thing that cannot read words. MARKING THE EXITS FOUND A DEFECT ON THE FIRST RUN. Type and More printed why they had failed and then fell through into the success exit, reporting that all was well. Nobody had noticed, because while the only reader was a person, the person could see both the complaint and the claim. Two smaller things. Snake sets the console to line mode and then exits with zero, and the linter flagged the second RSTA as redundant - an exit status and a console mode, equal by accident, which is the class that must never be collapsed. And the README still taught answering by writing into the frame, three months of habit that SRET replaced yesterday; that section is gone and the one describing SRET stands in its place.
108 lines
2.1 KiB
NASM
108 lines
2.1 KiB
NASM
; Tries to commit a file bigger than the room it reserved.
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;
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; osFileStart sets aside an extent and osFileWrite refuses a block index outside it, so the
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; obvious way to reach a neighbouring file - writing off the end - is already barred. This
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; is the other way to the same place: reserve one block, write the one block, and then tell
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; osFileDone the file came to two.
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;
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; NOTHING WOULD SAY SO IF THAT WERE ALLOWED. A directory entry is the only record of what a
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; file owns, so an entry claiming a block it was never given simply owns it, and whatever
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; owned it before owns it too. Both files then look perfectly well formed.
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;
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; Correct behaviour is a refusal, and the file left as it was. The reservation is one block
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; and a tail of ten, so:
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;
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; two blocks and no tail more than was reserved refused
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; one block and a tail exactly what was reserved allowed
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;
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; Written by Anachronaut
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#Include services.asm
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#Program
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#Base 0x4000
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start:
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; One block, and ten bytes after it.
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SETD.0 Name
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SETD.3 0x00 0x01
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INIA 0d10
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SWI osFileStart
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BNQ noStart
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SETD.1 Block
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RSTA
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RSTB
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SWI osFileWrite
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BNQ noWrite
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SETD.1 Block
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RSTA
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INIB 0d1
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SWI osFileWrite
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BNQ noWrite
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; Two whole blocks, which is more than one block and a tail.
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SETD.3 0x00 0x02
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RSTA
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SWI osFileDone
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BNQ refused
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SETD.0 Allowed
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SWI osPrintString
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RSTA
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SWI osExit
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refused:
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SETD.0 Refused
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SWI osPrintString
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; And the honest size, which is what was reserved.
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SETD.3 0x00 0x01
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INIA 0d10
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SWI osFileDone
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BNQ noHonest
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SETD.0 Honest
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SWI osPrintString
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RSTA
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SWI osExit
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noHonest:
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SETD.0 NoHonest
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SWI osPrintString
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INIA 0d1
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SWI osExit
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noStart:
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SETD.0 NoStart
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SWI osPrintString
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INIA 0d1
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SWI osExit
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noWrite:
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SETD.0 NoWrite
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SWI osPrintString
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INIA 0d1
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SWI osExit
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#Data
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#Base 0x2000
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Name:
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"claim.dat"
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Block:
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#Reserve 0d256
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Allowed:
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"claiming more than was reserved was ALLOWED
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"
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Refused:
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"claiming more than was reserved was refused
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"
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Honest:
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"and the size it really came to was taken
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"
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NoHonest:
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"the honest size was refused too
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"
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NoStart:
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"no start
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"
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NoWrite:
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"no write
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"
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