Configuration files, and boot.cfg as the first of them
One setting to a line: a key, a space, the rest of the line is the value. A semicolon starts a comment. The format was noticed rather than designed - textSplit already cuts the first word off a line and leaves the rest, and textSame already insists two strings end together, so reading a setting is those two routines and a loop. It is also what the shell reads, which makes a configuration line a command line the machine reads instead of a person typing one. The format was chosen by asking what the BOOT LOADER could manage, because it is the worst case in every direction: a few kilobytes, no operating system to report to, and if it fails the machine does not start. Two formats would be worse than one and the loader cannot have the richer one. CONFIGURATION IS ADVICE. A missing file, a missing key, an unusable value, a line too long to read: all of them mean use the default and none is a failure. BUT QUIET IS NOT SILENT - a setting somebody meant, which did not take effect, says so. That was the user's addition and it is the better rule: the default alone leaves the only symptom being that the machine did not do what somebody asked. So two routines. cfgGet reads and says nothing, because reading three settings should not report one bad line three times. cfgCheck reads the file once and reports, and is handed the caller's list of keys - whether a key means anything is the only part of this a shared reader cannot judge. /System/Boot/ holds the boot files, and stage two reads boot.cfg for what to start, with a fallback to try if it does not work and a name compiled in for when the file says nothing. THE TEST FOUND A REAL BUG, and it is the interaction I would not have thought to look for. First-match-wins met an empty value: a file with system system /System/Boot/bare.bin matched the first line, handed back nothing, and the machine tried to start a file with no name while a good setting sat underneath. An unusable value is an absent one - which is what "configuration is advice" says, and this is where it earns its keep. cfgBare starts an image with no operating system in it at all, which is what loading an ordinary boot image buys: a program wanting the whole machine is a file like any other, chosen the same way the system is. Three disks differing ONLY in boot.cfg, so each is a test of the file rather than of the machinery under it.
This commit is contained in:
Anachronaut
@@ -0,0 +1,36 @@
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; bare.asm
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; A machine with no operating system on it at all.
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;
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; THIS IS THE POINT OF LOADING AN ORDINARY IMAGE. The second stage does not know what
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; CosmOS is; it knows what a boot image is, and this is one. So a program that wants the
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; whole machine to itself - no shell, no filesystem, no services - is not a special case
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; needing a special path. It is a file, written under CosmOS like any other, and started by
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; naming it in /System/Boot/boot.cfg.
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;
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; It owns everything from address zero upward, and the only thing it can be sure of is the
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; console, because that is all it asked for.
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;
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; Written by Anachronaut
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#Program
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start:
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SETD.0 Said
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sayLoop:
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LDA.0
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BRA sayDone
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OUTA 0x00
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INCD.0
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BRI sayLoop
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sayDone:
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HALT
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#Data
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Said:
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"bare metal: no system, just this
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"
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#Vectors
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Boot start
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+131
-8
@@ -66,9 +66,74 @@ start:
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CALL sbfsMount
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BNQ noFilesystem
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; ---- What to start ----
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;
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; Read before the image is, because the configuration is staged where the image will go:
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; there is one large free area down here and no reason to have two.
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SETD.0 ConfigPath
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SETD.2 StageAt
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LDD.1.2
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INIA 0d4
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CALL cfgLoad
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; Said before anything is started, so that a setting somebody meant which did not happen
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; is on the screen above whatever happened instead.
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SETD.0 KnownKeys
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CALL cfgCheck
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SETD.0 KeySystem
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CALL cfgGet
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SETD.1 BootName
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BNQ systemDefault
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SETD.2 CfgValue
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LDD.0.2
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RCAL copyString
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BRI systemChosen
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systemDefault:
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SETD.0 SystemName
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RCAL copyString
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systemChosen:
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; And what to fall back to, kept now because the configuration is about to be written
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; over by the image itself.
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RSTA
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SETD.0 HaveFallback
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STA.0
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SETD.0 KeyFallback
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CALL cfgGet
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BNQ noFallbackSet
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SETD.1 FallbackName
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SETD.2 CfgValue
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LDD.0.2
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RCAL copyString
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INIA 0x01
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SETD.0 HaveFallback
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STA.0
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noFallbackSet:
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SETD.0 BootName
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RCAL tryImage
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; It did not start. Whatever went wrong has already said so, and if there is something
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; else to try then trying it is the whole reason for having said it rather than stopping.
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SETD.0 HaveFallback
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LDA.0
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BRA noSystem
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SETD.0 FallbackText
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RCAL say
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SETD.0 FallbackName
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RCAL tryImage
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BRI noSystem
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; ---- Starting one particular image ----
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;
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; DP0 names it. Returns only if it could not be started, having said why; everything that
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; works ends in the jump at the bottom and never comes back.
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tryImage:
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SETD.1 TryName
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STD.0.1
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CALL sbfsFind
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BNQ noSystem
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BNQ tryMissing
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; ---- The image, read whole into somewhere nothing else is using ----
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SETD.2 StageAt
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@@ -205,33 +270,59 @@ vectorsDone:
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unreadable:
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SETD.0 UnreadableText
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RCAL say
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HALT
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RCAL sayName
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RRET
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notAnImage:
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SETD.0 NotImageText
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RCAL say
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HALT
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RCAL sayName
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RRET
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wrongVersion:
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SETD.0 VersionText
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RCAL say
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HALT
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RCAL sayName
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RRET
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wantsMore:
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SETD.0 FeatureText
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RCAL say
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HALT
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RCAL sayName
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RRET
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noFilesystem:
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SETD.0 NoDiskText
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RCAL say
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HALT
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noSystem:
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tryMissing:
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SETD.0 NoSystemText
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RCAL say
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SETD.0 SystemName
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RCAL sayName
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RRET
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; Whichever image was being tried, said after the reason it did not work.
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sayName:
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SETD.0 TryName
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LDD.0.0
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RCAL say
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RCAL newLine
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RRET
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noSystem:
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SETD.0 NothingText
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RCAL say
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HALT
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; DP0 names a string and DP1 where to put it, terminator and all.
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copyString:
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LDA.0
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STA.1
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BRA copyDone
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INCD.0
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INCD.1
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BRI copyString
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copyDone:
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RRET
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; ---- Comparing a marker and stepping past it ----
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;
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; DP0 is in the image, DP2 names what it should say, A is how many bytes. DP0 is left past
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@@ -398,8 +489,38 @@ NoSystemText:
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; What to start. A name for now; the plan is for this to be read out of a file so that any
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; number of systems can sit on one disk and the choice is an ordinary safe write.
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; Where the configuration lives, and what to start when it does not say.
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ConfigPath:
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"/System/Boot/boot.cfg"
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SystemName:
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"/System/cosmos.bin"
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"/System/Boot/cosmos.bin"
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KeySystem:
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"system"
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KeyFallback:
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"fallback"
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; The keys this knows. Anything else in the file is a setting nothing asked for, and
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; cfgCheck says so rather than letting it look as though it worked.
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KnownKeys:
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"system"
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"fallback"
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""
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FallbackText:
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"trying the fallback
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"
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NothingText:
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"nothing to start
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"
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BootName:
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#Reserve 0d128
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FallbackName:
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#Reserve 0d128
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HaveFallback:
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0x00
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TryName:
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0x00 0x00
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UnreadableText:
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"could not read it
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@@ -449,6 +570,8 @@ StageAt:
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0x20 0x00
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#Include sbfs.asm
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#Include text.asm
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#Include config.asm
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; ---- The end of everything ----
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;
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Block a user