[Oberon] Shortening Files.WriteBuf

[Andreas Pirklbauer]

When rewriting Files.Mod to allow for arbitrarily large file sizes while simultaneously maintaining a very low memory footprint in f.ext (and a new f.dbl), I bumped into some code in Files.Mod that seems unnecessary (i.e. removing it does nothing to the system)

Does anyone see any strong reason why one CANNOT shorten Files. WriteBuf

From:

  PROCEDURE WriteBuf(f: File; buf: Buffer);
    VAR i, k: INTEGER;
      secadr: DiskAdr; inx: Index;
  BEGIN
    IF buf.apos < STS THEN
      secadr := f.sec[buf.apos];
      IF secadr = 0 THEN
        Disk.AllocSector(f.sechint, secadr);
        f.modH := TRUE; f.sec[buf.apos] := secadr; f.sechint := secadr
      END ;
      IF buf.apos = 0 THEN
        UpdateHeader(f, SYSTEM.VAL(FileDir.FileHeader, buf.data)); f.modH := FALSE
      END
    ELSE i := (buf.apos - STS) DIV XS; inx := f.ext[i];
      IF inx = NIL THEN
        NEW(inx); inx.adr := 0; inx.sec[0] := 0; f.ext[i] := inx; f.modH := TRUE
      END ;
      k := (buf.apos - STS) MOD XS; secadr := inx.sec[k];
      IF secadr = 0 THEN
        Disk.AllocSector(f.sechint, secadr);
        f.modH := TRUE; inx.mod := TRUE; inx.sec[k] := secadr; f.sechint := secadr
      END
    END ;
    Disk.PutSector(secadr, buf.data); buf.mod := FALSE
  END WriteBuf;


To

  PROCEDURE WriteBuf(f: File; buf: Buffer);
    VAR i: INTEGER;
      secadr: DiskAdr; inx: Index;
  BEGIN
    IF buf.apos < STS THEN
      secadr := f.sec[buf.apos];
      IF secadr = 0 THEN
        Disk.AllocSector(f.sechint, secadr);
        f.modH := TRUE; f.sec[buf.apos] := secadr; f.sechint := secadr
      END ;
      IF buf.apos = 0 THEN
        UpdateHeader(f, SYSTEM.VAL(FileDir.FileHeader, buf.data)); f.modH := FALSE
      END
    ELSE inx := f.ext[(buf.apos - STS) DIV XS];
      i := (buf.apos - STS) MOD XS; secadr := inx.sec[i];
      IF secadr = 0 THEN
        Disk.AllocSector(f.sechint, secadr);
        inx.mod := TRUE; inx.sec[i] := secadr; f.sechint := secadr
      END
    END ;
    Disk.PutSector(secadr, buf.data); buf.mod := FALSE
  END WriteBuf;

?

Two changes were made:

1) the code IF inx = NIL THEN .. END is removed - since the in-memory data structure rooted in f.ext[i] can only ever grow in Files.NewExt)

2) the assignment f.modH in the last IF statement of Files.WriteBuf is removed - as this is handled by IF inx.mod THEN .. END in Files.Unbuffer