Language/OS - Multiplatform Resource Library/LANGUAGE OS.iso/a_utils/yacc/flexyacc/aflex.lha/aflex/src/nfaB.a

Text File | 1991-05-16 | 19KB | 575 lines

-- Copyright (c) 1990 Regents of the University of California.
-- All rights reserved.
--
-- This software was developed by John Self of the Arcadia project
-- at the University of California, Irvine.
--
-- Redistribution and use in source and binary forms are permitted
-- provided that the above copyright notice and this paragraph are
-- duplicated in all such forms and that any documentation,
-- advertising materials, and other materials related to such
-- distribution and use acknowledge that the software was developed
-- by the University of California, Irvine.  The name of the
-- University may not be used to endorse or promote products derived
-- from this software without specific prior written permission.
-- THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
-- IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
-- WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

-- TITLE NFA construction routines
-- AUTHOR: John Self (UCI)
-- DESCRIPTION builds the NFA.
-- NOTES this file mirrors flex as closely as possible.
-- $Header: /co/ua/self/arcadia/aflex/ada/src/RCS/nfaB.a,v 1.6 90/01/12 15:20:27 self Exp Locker: self $

with MISC_DEFS, NFA, MISC, ECS;
with TSTRING, INT_IO, TEXT_IO, EXTERNAL_FILE_MANAGER; use MISC_DEFS, TSTRING,
  EXTERNAL_FILE_MANAGER;

package body NFA is

-- add_accept - add an accepting state to a machine
--
-- accepting_number becomes mach's accepting number.

  procedure ADD_ACCEPT(MACH             : in out INTEGER;
                       ACCEPTING_NUMBER : in INTEGER) is
  -- hang the accepting number off an epsilon state.  if it is associated
  -- with a state that has a non-epsilon out-transition, then the state
  -- will accept BEFORE it makes that transition, i.e., one character
  -- too soon
    ASTATE : INTEGER;
  begin
    if (TRANSCHAR(FINALST(MACH)) = SYM_EPSILON) then
      ACCPTNUM(FINALST(MACH)) := ACCEPTING_NUMBER;
    else
      ASTATE := MKSTATE(SYM_EPSILON);
      ACCPTNUM(ASTATE) := ACCEPTING_NUMBER;
      MACH := LINK_MACHINES(MACH, ASTATE);
    end if;
  end ADD_ACCEPT;


  -- copysingl - make a given number of copies of a singleton machine
  --
  --     newsng - a new singleton composed of num copies of singl
  --     singl  - a singleton machine
  --     num    - the number of copies of singl to be present in newsng

  function COPYSINGL(SINGL, NUM : in INTEGER) return INTEGER is
    COPY : INTEGER;
  begin
    COPY := MKSTATE(SYM_EPSILON);

    for I in 1 .. NUM loop
      COPY := LINK_MACHINES(COPY, DUPMACHINE(SINGL));
    end loop;

    return COPY;
  end COPYSINGL;


  -- dumpnfa - debugging routine to write out an nfa

  procedure DUMPNFA(STATE1 : in INTEGER) is
    SYM, TSP1, TSP2, ANUM : INTEGER;
    use TEXT_IO;
  begin
    TEXT_IO.NEW_LINE(STANDARD_ERROR);
    TEXT_IO.NEW_LINE(STANDARD_ERROR);
    TEXT_IO.PUT(STANDARD_ERROR,
      "********** beginning dump of nfa with start state ");
    INT_IO.PUT(STANDARD_ERROR, STATE1, 0);
    TEXT_IO.NEW_LINE(STANDARD_ERROR);

    -- we probably should loop starting at firstst[state1] and going to
    -- lastst[state1], but they're not maintained properly when we "or"
    -- all of the rules together.  So we use our knowledge that the machine
    -- starts at state 1 and ends at lastnfa.
    for NS in 1 .. LASTNFA loop
      TEXT_IO.PUT(STANDARD_ERROR, "state # ");
      INT_IO.PUT(STANDARD_ERROR, NS, 4);
      TEXT_IO.PUT(ASCII.HT);
      SYM := TRANSCHAR(NS);
      TSP1 := TRANS1(NS);
      TSP2 := TRANS2(NS);
      ANUM := ACCPTNUM(NS);

      INT_IO.PUT(STANDARD_ERROR, SYM, 5);
      TEXT_IO.PUT(STANDARD_ERROR, ":    ");
      INT_IO.PUT(STANDARD_ERROR, TSP1, 4);
      TEXT_IO.PUT(STANDARD_ERROR, ",");
      INT_IO.PUT(STANDARD_ERROR, TSP2, 4);
      if (ANUM /= NIL) then
        TEXT_IO.PUT(STANDARD_ERROR, "  [");
        INT_IO.PUT(STANDARD_ERROR, ANUM, 0);
        TEXT_IO.PUT(STANDARD_ERROR, "]");
      end if;
      TEXT_IO.NEW_LINE(STANDARD_ERROR);
    end loop;

    TEXT_IO.PUT(STANDARD_ERROR, "********** end of dump");
    TEXT_IO.NEW_LINE(STANDARD_ERROR);
  end DUMPNFA;

  -- dupmachine - make a duplicate of a given machine
  --
  --     copy - holds duplicate of mach
  --     mach - machine to be duplicated
  --
  -- note that the copy of mach is NOT an exact duplicate; rather, all the
  -- transition states values are adjusted so that the copy is self-contained,
  -- as the original should have been.
  --
  -- also note that the original MUST be contiguous, with its low and high
  -- states accessible by the arrays firstst and lastst

  function DUPMACHINE(MACH : in INTEGER) return INTEGER is
    INIT, STATE_OFFSET : INTEGER;
    STATE              : INTEGER := 0;
    LAST               : INTEGER := LASTST(MACH);
    I                  : INTEGER;
  begin
    I := FIRSTST(MACH);
    while (I <= LAST) loop
      STATE := MKSTATE(TRANSCHAR(I));

      if (TRANS1(I) /= NO_TRANSITION) then
        MKXTION(FINALST(STATE), TRANS1(I) + STATE - I);

        if ((TRANSCHAR(I) = SYM_EPSILON) and (TRANS2(I) /= NO_TRANSITION)) then
          MKXTION(FINALST(STATE), TRANS2(I) + STATE - I);
        end if;
      end if;

      ACCPTNUM(STATE) := ACCPTNUM(I);
      I := I + 1;
    end loop;

    if (STATE = 0) then
      MISC.AFLEXFATAL("empty machine in dupmachine()");
    end if;

    STATE_OFFSET := STATE - I + 1;

    INIT := MACH + STATE_OFFSET;
    FIRSTST(INIT) := FIRSTST(MACH) + STATE_OFFSET;
    FINALST(INIT) := FINALST(MACH) + STATE_OFFSET;
    LASTST(INIT) := LASTST(MACH) + STATE_OFFSET;

    return INIT;
  end DUPMACHINE;

  -- finish_rule - finish up the processing for a rule
  --
  -- An accepting number is added to the given machine.  If variable_trail_rule
  -- is true then the rule has trailing context and both the head and trail
  -- are variable size.  Otherwise if headcnt or trailcnt is non-zero then
  -- the machine recognizes a pattern with trailing context and headcnt is
  -- the number of characters in the matched part of the pattern, or zero
  -- if the matched part has variable length.  trailcnt is the number of
  -- trailing context characters in the pattern, or zero if the trailing
  -- context has variable length.

  procedure FINISH_RULE(MACH                : in INTEGER;
                        VARIABLE_TRAIL_RULE : in BOOLEAN;
                        HEADCNT, TRAILCNT   : in INTEGER) is
    P_MACH : INTEGER;
    use TEXT_IO;
  begin
    P_MACH := MACH;
    ADD_ACCEPT(P_MACH, NUM_RULES);

    -- we did this in new_rule(), but it often gets the wrong
    -- number because we do it before we start parsing the current rule
    RULE_LINENUM(NUM_RULES) := LINENUM;

    TEXT_IO.PUT(TEMP_ACTION_FILE, "when ");
    INT_IO.PUT(TEMP_ACTION_FILE, NUM_RULES, 1);
    TEXT_IO.PUT_LINE(TEMP_ACTION_FILE, " => ");

    if (VARIABLE_TRAIL_RULE) then
      RULE_TYPE(NUM_RULES) := RULE_VARIABLE;

      if (PERFORMANCE_REPORT) then
        TEXT_IO.PUT(STANDARD_ERROR, "Variable trailing context rule at line ");
        INT_IO.PUT(STANDARD_ERROR, RULE_LINENUM(NUM_RULES), 1);
        TEXT_IO.NEW_LINE(STANDARD_ERROR);
      end if;

      VARIABLE_TRAILING_CONTEXT_RULES := TRUE;
    else
      RULE_TYPE(NUM_RULES) := RULE_NORMAL;

      if ((HEADCNT > 0) or (TRAILCNT > 0)) then

        -- do trailing context magic to not match the trailing characters
        TEXT_IO.PUT_LINE(TEMP_ACTION_FILE,
          "yy_ch_buf(yy_cp) := yy_hold_char; -- undo effects of setting up yytext"
          );

        if (HEADCNT > 0) then
          TEXT_IO.PUT(TEMP_ACTION_FILE, " yy_cp := yy_bp + ");
          INT_IO.PUT(TEMP_ACTION_FILE, HEADCNT, 1);
          TEXT_IO.PUT_LINE(TEMP_ACTION_FILE, ";");
        else
          TEXT_IO.PUT(TEMP_ACTION_FILE, "yy_cp := yy_cp - ");
          INT_IO.PUT(TEMP_ACTION_FILE, TRAILCNT, 1);
          TEXT_IO.PUT_LINE(TEMP_ACTION_FILE, ";");
        end if;

        TEXT_IO.PUT_LINE(TEMP_ACTION_FILE, "yy_c_buf_p := yy_cp;");
        TEXT_IO.PUT_LINE(TEMP_ACTION_FILE,
          "YY_DO_BEFORE_ACTION; -- set up yytext again");
      end if;
    end if;

    MISC.LINE_DIRECTIVE_OUT(TEMP_ACTION_FILE);
  end FINISH_RULE;

  -- link_machines - connect two machines together
  --
  --     new    - a machine constructed by connecting first to last
  --     first  - the machine whose successor is to be last
  --     last   - the machine whose predecessor is to be first
  --
  -- note: this routine concatenates the machine first with the machine
  --  last to produce a machine new which will pattern-match first first
  --  and then last, and will fail if either of the sub-patterns fails.
  --  FIRST is set to new by the operation.  last is unmolested.

  function LINK_MACHINES(FIRST, LAST : in INTEGER) return INTEGER is
  begin
    if (FIRST = NIL) then
      return LAST;
    else
      if (LAST = NIL) then
        return FIRST;
      else
        MKXTION(FINALST(FIRST), LAST);
        FINALST(FIRST) := FINALST(LAST);
        LASTST(FIRST) := MAX(LASTST(FIRST), LASTST(LAST));
        FIRSTST(FIRST) := MIN(FIRSTST(FIRST), FIRSTST(LAST));
        return (FIRST);
      end if;
    end if;
  end LINK_MACHINES;


  -- mark_beginning_as_normal - mark each "beginning" state in a machine
--                            as being a "normal" (i.e., not trailing context-
  --                            associated) states
  --
  -- The "beginning" states are the epsilon closure of the first state

  procedure MARK_BEGINNING_AS_NORMAL(MACH : in INTEGER) is
  begin
    case (STATE_TYPE(MACH)) is
      when STATE_NORMAL =>

        -- oh, we've already visited here
        return;

      when STATE_TRAILING_CONTEXT =>
        STATE_TYPE(MACH) := STATE_NORMAL;

        if (TRANSCHAR(MACH) = SYM_EPSILON) then
          if (TRANS1(MACH) /= NO_TRANSITION) then
            MARK_BEGINNING_AS_NORMAL(TRANS1(MACH));
          end if;

          if (TRANS2(MACH) /= NO_TRANSITION) then
            MARK_BEGINNING_AS_NORMAL(TRANS2(MACH));
          end if;
        end if;
      when others =>
        MISC.AFLEXERROR("bad state type in mark_beginning_as_normal()");
    end case;
  end MARK_BEGINNING_AS_NORMAL;

  -- mkbranch - make a machine that branches to two machines
  --
  --     branch - a machine which matches either first's pattern or second's
--     first, second - machines whose patterns are to be or'ed (the | operator)
  --
  -- note that first and second are NEITHER destroyed by the operation.  Also,
  -- the resulting machine CANNOT be used with any other "mk" operation except
  -- more mkbranch's.  Compare with mkor()
  function MKBRANCH(FIRST, SECOND : in INTEGER) return INTEGER is
    EPS : INTEGER;
  begin
    if (FIRST = NO_TRANSITION) then
      return SECOND;
    else
      if (SECOND = NO_TRANSITION) then
        return FIRST;
      end if;
    end if;

    EPS := MKSTATE(SYM_EPSILON);

    MKXTION(EPS, FIRST);
    MKXTION(EPS, SECOND);

    return EPS;
  end MKBRANCH;


  -- mkclos - convert a machine into a closure
  --
  --     new - a new state which matches the closure of "state"

  function MKCLOS(STATE : in INTEGER) return INTEGER is
  begin
    return NFA.MKOPT(MKPOSCL(STATE));
  end MKCLOS;


  -- mkopt - make a machine optional
  --
  --     new  - a machine which optionally matches whatever mach matched
  --     mach - the machine to make optional
  --
  -- notes:
  --     1. mach must be the last machine created
  --     2. mach is destroyed by the call

  function MKOPT(MACH : in INTEGER) return INTEGER is
    EPS    : INTEGER;
    RESULT : INTEGER;
  begin
    RESULT := MACH;
    if (not SUPER_FREE_EPSILON(FINALST(RESULT))) then
      EPS := NFA.MKSTATE(SYM_EPSILON);
      RESULT := NFA.LINK_MACHINES(RESULT, EPS);
    end if;

    -- can't skimp on the following if FREE_EPSILON(mach) is true because
    -- some state interior to "mach" might point back to the beginning
    -- for a closure
    EPS := NFA.MKSTATE(SYM_EPSILON);
    RESULT := NFA.LINK_MACHINES(EPS, RESULT);

    NFA.MKXTION(RESULT, FINALST(RESULT));

    return RESULT;
  end MKOPT;


  -- mkor - make a machine that matches either one of two machines
  --
  --     new - a machine which matches either first's pattern or second's
--     first, second - machines whose patterns are to be or'ed (the | operator)
  --
  -- note that first and second are both destroyed by the operation
  -- the code is rather convoluted because an attempt is made to minimize
  -- the number of epsilon states needed

  function MKOR(FIRST, SECOND : in INTEGER) return INTEGER is
    EPS, OREND : INTEGER;
    P_FIRST    : INTEGER;
  begin
    P_FIRST := FIRST;
    if (P_FIRST = NIL) then
      return SECOND;
    else
      if (SECOND = NIL) then
        return P_FIRST;
      else

        -- see comment in mkopt() about why we can't use the first state
        -- of "first" or "second" if they satisfy "FREE_EPSILON"
        EPS := MKSTATE(SYM_EPSILON);

        P_FIRST := LINK_MACHINES(EPS, P_FIRST);

        MKXTION(P_FIRST, SECOND);

        if ((SUPER_FREE_EPSILON(FINALST(P_FIRST))) and (ACCPTNUM(FINALST(P_FIRST
          )) = NIL)) then
          OREND := FINALST(P_FIRST);
          MKXTION(FINALST(SECOND), OREND);
        else
          if ((SUPER_FREE_EPSILON(FINALST(SECOND))) and (ACCPTNUM(FINALST(SECOND
            )) = NIL)) then
            OREND := FINALST(SECOND);
            MKXTION(FINALST(P_FIRST), OREND);
          else
            EPS := MKSTATE(SYM_EPSILON);
            P_FIRST := LINK_MACHINES(P_FIRST, EPS);
            OREND := FINALST(P_FIRST);

            MKXTION(FINALST(SECOND), OREND);
          end if;
        end if;
      end if;
    end if;

    FINALST(P_FIRST) := OREND;
    return P_FIRST;
  end MKOR;


  -- mkposcl - convert a machine into a positive closure
  --
  --    new - a machine matching the positive closure of "state"

  function MKPOSCL(STATE : in INTEGER) return INTEGER is
    EPS : INTEGER;
  begin
    if (SUPER_FREE_EPSILON(FINALST(STATE))) then
      MKXTION(FINALST(STATE), STATE);
      return (STATE);
    else
      EPS := MKSTATE(SYM_EPSILON);
      MKXTION(EPS, STATE);
      return (LINK_MACHINES(STATE, EPS));
    end if;
  end MKPOSCL;

  -- mkrep - make a replicated machine
  --
  --    new - a machine that matches whatever "mach" matched from "lb"
  --          number of times to "ub" number of times
  --
  -- note
--   if "ub" is INFINITY then "new" matches "lb" or more occurrences of "mach"

  function MKREP(MACH, LB, UB : in INTEGER) return INTEGER is
    BASE_MACH, TAIL, COPY : INTEGER;
    P_MACH                : INTEGER;
  begin
    P_MACH := MACH;
    BASE_MACH := COPYSINGL(P_MACH, LB - 1);

    if (UB = INFINITY) then
      COPY := DUPMACHINE(P_MACH);
      P_MACH := LINK_MACHINES(P_MACH, LINK_MACHINES(BASE_MACH, MKCLOS(COPY)));
    else
      TAIL := MKSTATE(SYM_EPSILON);

      for I in LB .. UB - 1 loop
        COPY := DUPMACHINE(P_MACH);
        TAIL := MKOPT(LINK_MACHINES(COPY, TAIL));
      end loop;

      P_MACH := LINK_MACHINES(P_MACH, LINK_MACHINES(BASE_MACH, TAIL));
    end if;

    return P_MACH;
  end MKREP;

  -- mkstate - create a state with a transition on a given symbol
  --
  --     state - a new state matching sym
  --     sym   - the symbol the new state is to have an out-transition on
  --
  -- note that this routine makes new states in ascending order through the
  -- state array (and increments LASTNFA accordingly).  The routine DUPMACHINE
  -- relies on machines being made in ascending order and that they are
  -- CONTIGUOUS.  Change it and you will have to rewrite DUPMACHINE (kludge
  -- that it admittedly is)

  function MKSTATE(SYM : in INTEGER) return INTEGER is
  begin
    LASTNFA := LASTNFA + 1;
    if (LASTNFA >= CURRENT_MNS) then
      CURRENT_MNS := CURRENT_MNS + MNS_INCREMENT;
      if (CURRENT_MNS >= MAXIMUM_MNS) then
        MISC.AFLEXERROR("input rules are too complicated (>= " & INTEGER'IMAGE(
          CURRENT_MNS) & " NFA states) )");
      end if;

      NUM_REALLOCS := NUM_REALLOCS + 1;

      REALLOCATE_INTEGER_ARRAY(FIRSTST, CURRENT_MNS);
      REALLOCATE_INTEGER_ARRAY(LASTST, CURRENT_MNS);
      REALLOCATE_INTEGER_ARRAY(FINALST, CURRENT_MNS);
      REALLOCATE_INTEGER_ARRAY(TRANSCHAR, CURRENT_MNS);
      REALLOCATE_INTEGER_ARRAY(TRANS1, CURRENT_MNS);
      REALLOCATE_INTEGER_ARRAY(TRANS2, CURRENT_MNS);
      REALLOCATE_INTEGER_ARRAY(ACCPTNUM, CURRENT_MNS);
      REALLOCATE_INTEGER_ARRAY(ASSOC_RULE, CURRENT_MNS);
      REALLOCATE_STATE_ENUM_ARRAY(STATE_TYPE, CURRENT_MNS);
    end if;

    FIRSTST(LASTNFA) := LASTNFA;
    FINALST(LASTNFA) := LASTNFA;
    LASTST(LASTNFA) := LASTNFA;
    TRANSCHAR(LASTNFA) := SYM;
    TRANS1(LASTNFA) := NO_TRANSITION;
    TRANS2(LASTNFA) := NO_TRANSITION;
    ACCPTNUM(LASTNFA) := NIL;
    ASSOC_RULE(LASTNFA) := NUM_RULES;
    STATE_TYPE(LASTNFA) := CURRENT_STATE_ENUM;

    -- fix up equivalence classes base on this transition.  Note that any
    -- character which has its own transition gets its own equivalence class.
    -- Thus only characters which are only in character classes have a chance
    -- at being in the same equivalence class.  E.g. "a|b" puts 'a' and 'b'
    -- into two different equivalence classes.  "[ab]" puts them in the same
    -- equivalence class (barring other differences elsewhere in the input).
    if (SYM < 0) then

      -- we don't have to update the equivalence classes since that was
      -- already done when the ccl was created for the first time
      null;
    else
      if (SYM = SYM_EPSILON) then
        NUMEPS := NUMEPS + 1;
      else
        if (USEECS) then
          ECS.MKECHAR(SYM, NEXTECM, ECGROUP);
        end if;
      end if;
    end if;

    return LASTNFA;
  end MKSTATE;

  -- mkxtion - make a transition from one state to another
  --
  --     statefrom - the state from which the transition is to be made
  --     stateto   - the state to which the transition is to be made

  procedure MKXTION(STATEFROM, STATETO : in INTEGER) is
  begin
    if (TRANS1(STATEFROM) = NO_TRANSITION) then
      TRANS1(STATEFROM) := STATETO;
    else
      if ((TRANSCHAR(STATEFROM) /= SYM_EPSILON) or (TRANS2(STATEFROM) /=
        NO_TRANSITION)) then
        MISC.AFLEXFATAL("found too many transitions in mkxtion()");
      else

        -- second out-transition for an epsilon state
        EPS2 := EPS2 + 1;
        TRANS2(STATEFROM) := STATETO;
      end if;
    end if;
  end MKXTION;

  -- new_rule - initialize for a new rule
  --
  -- the global num_rules is incremented and the any corresponding dynamic
  -- arrays (such as rule_type()) are grown as needed.

  procedure NEW_RULE is
  begin
    NUM_RULES := NUM_RULES + 1;
    if (NUM_RULES >= CURRENT_MAX_RULES) then
      NUM_REALLOCS := NUM_REALLOCS + 1;
      CURRENT_MAX_RULES := CURRENT_MAX_RULES + MAX_RULES_INCREMENT;
      REALLOCATE_RULE_ENUM_ARRAY(RULE_TYPE, CURRENT_MAX_RULES);
      REALLOCATE_INTEGER_ARRAY(RULE_LINENUM, CURRENT_MAX_RULES);
    end if;

    if (NUM_RULES > MAX_RULE) then
      MISC.AFLEXERROR("too many rules  (> " & INTEGER'IMAGE(MAX_RULE) & ")!");
    end if;

    RULE_LINENUM(NUM_RULES) := LINENUM;
  end NEW_RULE;

end NFA;