; A program that says what is on the disk.
;
; Which no program could do until now. Everything the system offered took a name a program
; already knew - read it, save it, rename it, delete it, ask how big it is - and there was no
; way to ask what names there are. dir could list only because it lives in the shell and calls
; the filesystem directly. So a file manager, a backup, and the package manager still to come
; were all unwritable for want of two services.
;
; This is those two, used as simply as they can be: walk, say what each thing is, and ask
; about it.
;
;   > Walk
;   f Say.sbx 1
;   d Apps 0
;   u halfsaved.txt 3
;
; ---- And it asks about each one AS IT GOES, which is the point ----
;
; Where a walk has got to is the system's, and so is where the last file it was asked about
; lives - the same eight bytes of filesystem state. A program that walks a directory and asks
; osFileInfo about each entry is using both at once, which is the obvious thing to write and
; the thing that would quietly go wrong if the two shared a position.
;
; Calling osFileInfo between two steps of the walk is therefore not decoration here. It is the
; check, and a walk that came back wrong afterwards would show up as a short listing or a
; repeated name rather than as an error.

#Include services.asm

#Program

  #Base 0x5000

start:
  SETD.0 Name
  INIB 0d24
  SWI osDirFirst
  BRI walkCheck

walkStep:
  SETD.0 Name
  INIB 0d24
  SWI osDirNext

walkCheck:
  ; The kind is written down before anything else wants the registers: the comparison below
  ; is an ALU operation and Q is where its answer goes.
  MVQA
  SETD.0 Kind
  STA.0
  INIB 0xFF
  CCF
  SUB
  BRQ walkDone

  ; f, d or u. A chain rather than a table, because three is not enough to index - and A is
  ; still the kind, since SUB writes Q and leaves it alone.
  BRA walkFile
  INIB 0d1
  CCF
  SUB
  BRQ walkDirectory
  SETD.0 Unfinished
  BRI walkSay
walkDirectory:
  SETD.0 Directory
  BRI walkSay
walkFile:
  SETD.0 File

walkSay:
  SWI osPrintString
  SETD.0 Name
  SWI osPrintString
  SETD.0 Space
  SWI osPrintString

  ; ---- And how big it is, asked BETWEEN two steps of the walk ----
  ;
  ; The name is the only thing the walk hands over, which is what keeps it from being a record
  ; both sides have to agree the shape of. A program that wants more asks about the name, the
  ; same way anything else does.
  ;
  ; A directory is not asked about. osFileInfo answers for one perfectly well and says nought
  ; blocks, which is true and reads as a size - and nought is a size a file can genuinely
  ; have, so the two would be indistinguishable in the listing.
  SETD.0 Kind
  LDA.0
  INIB 0d1
  CCF
  SUB
  BRQ walkNoSize

  SETD.0 Name
  SWI osFileInfo
  BNQ walkNoSize

  PSHD.3
  POPB
  POPA
  SWI osPrintNumber
  BRI walkEnded

walkNoSize:
  SETD.0 NoSize
  SWI osPrintString

walkEnded:
  SETD.0 NewLine
  SWI osPrintString
  BRI walkStep

walkDone:
  RSTA
  SWI osExit

#Data

  #Base 0x3000

File:
"f "
Directory:
"d "
Unfinished:
"u "
Space:
" "
NoSize:
"-"
NewLine:
  0x0A 0x00

Kind:
  0x00
Name:
  #Reserve 0d24