---- Pseudocode for Macro Processor
COP 3601: Introduction to Systems Software

Handles nested definitions?
Handles nested invocations?

Macro Processor Pseudocode

BEGIN
  initialize Scnt, Indx, and Level to 0
  Expanding <-- FALSE
  WHILE Opcode <> "END"
    BEGIN
      Getline
      Processline
    END {While}
END {Main Program}


Getline:
BEGIN
  IF Expanding
    Nextline <-- Mactab[Indx]
    substitute arguments from Argtab for positional notation
    increment Indx
  ELSE
    Nextline <-- Sourcecode[Scnt]
    increment Scnt
  ENDIF
END {Getline}


Processline:
BEGIN
  Breakup Nextline
  Xsearch Macnames for Opcode
  IF found
    Expand
  ELSE
    IF Level > 0
      add Nextline to Mactab
    ELSE
      IF Opcode = "MACRO" 
        Define
      ELSE
        append Nextline to expanded source file
      ENDIF
    ENDIF
  ENDIF
END {Processline}


Expand:
BEGIN
  Expanding <-- TRUE
  get the macro prototype statement from Mactab
    Note: Indx (retrieved under xsearch) points into Mactab
  set up Argtab from the prototype argument list
  append Nextline as a comment to expanded source file
  WHILE Indx <> end of Macro body
    BEGIN
      Getline
      Processline
    END {While}
  Expanding <-- FALSE
END {Expand}


Define:
BEGIN
  Insert Opcode,Indx into Macnames 
    {components of a Macnames entry are macro-name, starting-index, ending-index (TBD)}
  add Nextline to Mactab
  Level <-- 1
    WHILE Level > 0
      BEGIN
        Getline
        IF Nextline is not a comment
          substitute positional notation for parameters
          Processline
          IF Opcode = "MACRO"
            Level <-- Level + 1
          ELSE
            IF Opcode = "MEND"
              Level <-- Level - 1
            ENDIF
          ENDIF
        ENDIF
      END {While}
  update Macnames entry by inserting Indx {ending-index} 
END {Define}