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.
183 lines
3.8 KiB
NASM
183 lines
3.8 KiB
NASM
; A program that keeps a file without knowing how a filesystem works.
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;
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; INCLUDES NOTHING BUT THE SERVICE NAMES. No sbfs.asm, no console.asm - the system has both
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; of those running already, and this asks it rather than carrying a second copy. That is the
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; whole point of the program: if it works, a tool that edits documents does not need two and
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; a half kilobytes of filesystem bound into it.
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;
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; It writes a file, reads it back, says how big it was, renames it, and takes it away again,
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; which is every file service there is.
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;
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; ---- What you will see before the handlers are written ----
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;
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; The numbers are pinned but nothing answers to them yet, so the first call dispatches
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; through an empty vector and the machine stops:
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;
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; Fault: Software vector 21, dispatched from Program Address 0x200B, has no handler
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; installed.
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;
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; That is the fault working properly rather than the program being broken. A vector with
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; nothing in it is not a jump to address zero; it is a stop, with the vector named and the
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; place it was called from named, which is as much as the machine can know.
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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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; ---- Write it ----
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;
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; A and B together are how many bytes there are, most significant first, which is the
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; same sixteen bits a length always is on this machine.
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SETD.0 Name
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SETD.1 Body
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RSTA
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INIB 0d22 ; The text and its newline. NOT the zero the assembler put
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SWI osFileSave ; after it: a text file ends where the text ends.
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BNQ noSave
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SETD.0 SavedText
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SWI osPrintString
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; ---- Read it back ----
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;
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; DP3 comes back holding how many bytes there were, because that is one of the two things
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; a service is allowed to answer in and a file that fits in memory has a length that fits
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; in a pointer.
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SETD.0 Name
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SETD.1 Landing
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SWI osFileRead
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BNQ noRead
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SETD.0 ReadText
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SWI osPrintString
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PSHD.3
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POPB ; The low byte is on top, the way a pointer is pushed.
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POPA
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SWI osPrintNumber
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SETD.0 BytesText
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SWI osPrintString
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; And now the length is needed for something rather than just reported. What came back is
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; a file, not a string: nothing on the disk ends in a zero byte, because the entry says
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; where it stops instead. So a zero goes on the end before it can be printed as one.
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SETD.1 Landing
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PSHD.3
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POPB
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POPA
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walkToEnd:
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BRB atEnd
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INCD.1
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DECB
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BRI walkToEnd
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atEnd:
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RSTA
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STA.1
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SETD.0 Landing
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SWI osPrintString
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; ---- Call it something else ----
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SETD.0 Name
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SETD.1 OtherName
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SWI osFileRename
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BNQ noRename
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SETD.0 RenamedText
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SWI osPrintString
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; ---- And take it away ----
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SETD.0 OtherName
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SWI osFileDelete
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BNQ noDelete
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SETD.0 DeletedText
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SWI osPrintString
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; Reading it now should fail, and a service saying no is not the same as one that is not
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; there: this comes back with an answer rather than stopping the machine.
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SETD.0 OtherName
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SETD.1 Landing
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SWI osFileRead
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BRQ stillThere
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SETD.0 GoneText
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SWI osPrintString
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RSTA
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SWI osExit
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stillThere:
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SETD.0 StillText
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SWI osPrintString
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RSTA
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SWI osExit
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noSave:
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SETD.0 NoSaveText
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SWI osPrintString
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INIA 0d1
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SWI osExit
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noRead:
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SETD.0 NoReadText
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SWI osPrintString
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INIA 0d1
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SWI osExit
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noRename:
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SETD.0 NoRenameText
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SWI osPrintString
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INIA 0d1
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SWI osExit
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noDelete:
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SETD.0 NoDeleteText
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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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"kept.txt"
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OtherName:
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"moved.txt"
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Body:
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"a file kept by asking
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"
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SavedText:
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"saved it
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"
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ReadText:
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"read it back, "
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BytesText:
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" bytes:
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"
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RenamedText:
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"renamed it
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"
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DeletedText:
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"deleted it
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"
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GoneText:
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"and it is gone
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"
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StillText:
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"but it is still there
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"
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NoSaveText:
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"it would not save
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"
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NoReadText:
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"it would not read
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"
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NoRenameText:
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"it would not rename
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"
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NoDeleteText:
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"it would not delete
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"
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Landing:
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#Reserve 0d256
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