lparser.c

Lua 语言解释器源码

static void closelistfield (FuncState *fs, struct ConsControl *cc) {
  if (cc->v.k == VVOID) return;  /* there is no list item */
  luaK_exp2nextreg(fs, &cc->v);
  cc->v.k = VVOID;
  if (cc->tostore == LFIELDS_PER_FLUSH) {
    luaK_codeABx(fs, OP_SETLIST, cc->t->info, cc->na-1);  /* flush */
    cc->tostore = 0;  /* no more items pending */
    fs->freereg = cc->t->info + 1;  /* free registers */
  }
}


static void lastlistfield (FuncState *fs, struct ConsControl *cc) {
  if (cc->tostore == 0) return;
  if (cc->v.k == VCALL) {
    luaK_setcallreturns(fs, &cc->v, LUA_MULTRET);
    luaK_codeABx(fs, OP_SETLISTO, cc->t->info, cc->na-1);
  }
  else {
    if (cc->v.k != VVOID)
      luaK_exp2nextreg(fs, &cc->v);
    luaK_codeABx(fs, OP_SETLIST, cc->t->info, cc->na-1);
  }
  fs->freereg = cc->t->info + 1;  /* free registers */
}


static void listfield (LexState *ls, struct ConsControl *cc) {
  expr(ls, &cc->v);
  luaX_checklimit(ls, cc->na, MAXARG_Bx, "items in a constructor");
  cc->na++;
  cc->tostore++;
}


static void constructor (LexState *ls, expdesc *t) {
  /* constructor -> ?? */
  FuncState *fs = ls->fs;
  int line = ls->linenumber;
  int pc = luaK_codeABC(fs, OP_NEWTABLE, 0, 0, 0);
  struct ConsControl cc;
  cc.na = cc.nh = cc.tostore = 0;
  cc.t = t;
  init_exp(t, VRELOCABLE, pc);
  init_exp(&cc.v, VVOID, 0);  /* no value (yet) */
  luaK_exp2nextreg(ls->fs, t);  /* fix it at stack top (for gc) */
  check(ls, '{');
  do {
    lua_assert(cc.v.k == VVOID || cc.tostore > 0);
    testnext(ls, ';');  /* compatibility only */
    if (ls->t.token == '}') break;
    closelistfield(fs, &cc);
    switch(ls->t.token) {
      case TK_NAME: {  /* may be listfields or recfields */
        lookahead(ls);
        if (ls->lookahead.token != '=')  /* expression? */
          listfield(ls, &cc);
        else
          recfield(ls, &cc);
        break;
      }
      case '[': {  /* constructor_item -> recfield */
        recfield(ls, &cc);
        break;
      }
      default: {  /* constructor_part -> listfield */
        listfield(ls, &cc);
        break;
      }
    }
  } while (testnext(ls, ',') || testnext(ls, ';'));
  check_match(ls, '}', '{', line);
  lastlistfield(fs, &cc);
  SETARG_B(fs->f->code[pc], luaO_int2fb(cc.na)); /* set initial array size */
  SETARG_C(fs->f->code[pc], luaO_log2(cc.nh)+1);  /* set initial table size */
}

/* }====================================================================== */



static void parlist (LexState *ls) {
  /* parlist -> [ param { `,' param } ] */
  int nparams = 0;
  int dots = 0;
  if (ls->t.token != ')') {  /* is `parlist' not empty? */
    do {
      switch (ls->t.token) {
        case TK_DOTS: dots = 1; next(ls); break;
        case TK_NAME: new_localvar(ls, str_checkname(ls), nparams++); break;
        default: luaX_syntaxerror(ls, "<name> or `...' expected");
      }
    } while (!dots && testnext(ls, ','));
  }
  code_params(ls, nparams, dots);
}


static void body (LexState *ls, expdesc *e, int needself, int line) {
  /* body ->  `(' parlist `)' chunk END */
  FuncState new_fs;
  open_func(ls, &new_fs);
  new_fs.f->lineDefined = line;
  check(ls, '(');
  if (needself)
    create_local(ls, "self");
  parlist(ls);
  check(ls, ')');
  chunk(ls);
  check_match(ls, TK_END, TK_FUNCTION, line);
  close_func(ls);
  pushclosure(ls, &new_fs, e);
}


static int explist1 (LexState *ls, expdesc *v) {
  /* explist1 -> expr { `,' expr } */
  int n = 1;  /* at least one expression */
  expr(ls, v);
  while (testnext(ls, ',')) {
    luaK_exp2nextreg(ls->fs, v);
    expr(ls, v);
    n++;
  }
  return n;
}


static void funcargs (LexState *ls, expdesc *f) {
  FuncState *fs = ls->fs;
  expdesc args;
  int base, nparams;
  int line = ls->linenumber;
  switch (ls->t.token) {
    case '(': {  /* funcargs -> `(' [ explist1 ] `)' */
      if (line != ls->lastline)
        luaX_syntaxerror(ls,"ambiguous syntax (function call x new statement)");
      next(ls);
      if (ls->t.token == ')')  /* arg list is empty? */
        args.k = VVOID;
      else {
        explist1(ls, &args);
        luaK_setcallreturns(fs, &args, LUA_MULTRET);
      }
      check_match(ls, ')', '(', line);
      break;
    }
    case '{': {  /* funcargs -> constructor */
      constructor(ls, &args);
      break;
    }
    case TK_STRING: {  /* funcargs -> STRING */
      codestring(ls, &args, ls->t.seminfo.ts);
      next(ls);  /* must use `seminfo' before `next' */
      break;
    }
    default: {
      luaX_syntaxerror(ls, "function arguments expected");
      return;
    }
  }
  lua_assert(f->k == VNONRELOC);
  base = f->info;  /* base register for call */
  if (args.k == VCALL)
    nparams = LUA_MULTRET;  /* open call */
  else {
    if (args.k != VVOID)
      luaK_exp2nextreg(fs, &args);  /* close last argument */
    nparams = fs->freereg - (base+1);
  }
  init_exp(f, VCALL, luaK_codeABC(fs, OP_CALL, base, nparams+1, 2));
  luaK_fixline(fs, line);
  fs->freereg = base+1;  /* call remove function and arguments and leaves
                            (unless changed) one result */
}




/*
** {======================================================================
** Expression parsing
** =======================================================================
*/


static void prefixexp (LexState *ls, expdesc *v) {
  /* prefixexp -> NAME | '(' expr ')' */
  switch (ls->t.token) {
    case '(': {
      int line = ls->linenumber;
      next(ls);
      expr(ls, v);
      check_match(ls, ')', '(', line);
      luaK_dischargevars(ls->fs, v);
      return;
    }
    case TK_NAME: {
      singlevar(ls, v, 1);
      return;
    }
#ifdef LUA_COMPATUPSYNTAX
    case '%': {  /* for compatibility only */
      TString *varname;
      int line = ls->linenumber;
      next(ls);  /* skip `%' */
      varname = singlevar(ls, v, 1);
      if (v->k != VUPVAL)
        luaX_errorline(ls, "global upvalues are obsolete",
                           getstr(varname), line);
      return;
    }
#endif
    default: {
      luaX_syntaxerror(ls, "unexpected symbol");
      return;
    }
  }
}


static void primaryexp (LexState *ls, expdesc *v) {
  /* primaryexp ->
        prefixexp { `.' NAME | `[' exp `]' | `:' NAME funcargs | funcargs } */
  FuncState *fs = ls->fs;
  prefixexp(ls, v);
  for (;;) {
    switch (ls->t.token) {
      case '.': {  /* field */
        luaY_field(ls, v);
        break;
      }
      case '[': {  /* `[' exp1 `]' */
        expdesc key;
        luaK_exp2anyreg(fs, v);
        luaY_index(ls, &key);
        luaK_indexed(fs, v, &key);
        break;
      }
      case ':': {  /* `:' NAME funcargs */
        expdesc key;
        next(ls);
        checkname(ls, &key);
        luaK_self(fs, v, &key);
        funcargs(ls, v);
        break;
      }
      case '(': case TK_STRING: case '{': {  /* funcargs */
        luaK_exp2nextreg(fs, v);
        funcargs(ls, v);
        break;
      }
      default: return;
    }
  }
}


static void simpleexp (LexState *ls, expdesc *v) {
  /* simpleexp -> NUMBER | STRING | NIL | constructor | FUNCTION body
               | primaryexp */
  switch (ls->t.token) {
    case TK_NUMBER: {
      init_exp(v, VK, luaK_numberK(ls->fs, ls->t.seminfo.r));
      next(ls);  /* must use `seminfo' before `next' */
      break;
    }
    case TK_STRING: {
      codestring(ls, v, ls->t.seminfo.ts);
      next(ls);  /* must use `seminfo' before `next' */
      break;
    }
    case TK_NIL: {
      init_exp(v, VNIL, 0);
      next(ls);
      break;
    }
    case TK_TRUE: {
      init_exp(v, VTRUE, 0);
      next(ls);
      break;
    }
    case TK_FALSE: {
      init_exp(v, VFALSE, 0);
      next(ls);
      break;
    }
    case '{': {  /* constructor */
      constructor(ls, v);
      break;
    }
    case TK_FUNCTION: {
      next(ls);
      body(ls, v, 0, ls->linenumber);
      break;
    }
    default: {
      primaryexp(ls, v);
      break;
    }
  }
}


static UnOpr getunopr (int op) {
  switch (op) {
    case TK_NOT: return OPR_NOT;
    case '-': return OPR_MINUS;
    default: return OPR_NOUNOPR;
  }
}


static BinOpr getbinopr (int op) {
  switch (op) {
    case '+': return OPR_ADD;
    case '-': return OPR_SUB;
    case '*': return OPR_MULT;
    case '/': return OPR_DIV;
    case '^': return OPR_POW;
    case TK_CONCAT: return OPR_CONCAT;
    case TK_NE: return OPR_NE;
    case TK_EQ: return OPR_EQ;
    case '<': return OPR_LT;
    case TK_LE: return OPR_LE;
    case '>': return OPR_GT;
    case TK_GE: return OPR_GE;
    case TK_AND: return OPR_AND;
    case TK_OR: return OPR_OR;
    default: return OPR_NOBINOPR;
  }
}


static const struct {
  lu_byte left;  /* left priority for each binary operator */
  lu_byte right; /* right priority */
} priority[] = {  /* ORDER OPR */
   {6, 6}, {6, 6}, {7, 7}, {7, 7},  /* arithmetic */
   {10, 9}, {5, 4},                 /* power and concat (right associative) */
   {3, 3}, {3, 3},                  /* equality */
   {3, 3}, {3, 3}, {3, 3}, {3, 3},  /* order */
   {2, 2}, {1, 1}                   /* logical (and/or) */
};

#define UNARY_PRIORITY	8  /* priority for unary operators */


/*
** subexpr -> (simplexep | unop subexpr) { binop subexpr }
** where `binop' is any binary operator with a priority higher than `limit'
*/
static BinOpr subexpr (LexState *ls, expdesc *v, int limit) {
  BinOpr op;
  UnOpr uop;
  enterlevel(ls);
  uop = getunopr(ls->t.token);
  if (uop != OPR_NOUNOPR) {
    next(ls);
    subexpr(ls, v, UNARY_PRIORITY);
    luaK_prefix(ls->fs, uop, v);
  }
  else simpleexp(ls, v);
  /* expand while operators have priorities higher than `limit' */
  op = getbinopr(ls->t.token);
  while (op != OPR_NOBINOPR && cast(int, priority[op].left) > limit) {
    expdesc v2;
    BinOpr nextop;
    next(ls);
    luaK_infix(ls->fs, op, v);
    /* read sub-expression with higher priority */
    nextop = subexpr(ls, &v2, cast(int, priority[op].right));
    luaK_posfix(ls->fs, op, v, &v2);
    op = nextop;
  }
  leavelevel(ls);
  return op;  /* return first untreated operator */
}


static void expr (LexState *ls, expdesc *v) {
  subexpr(ls, v, -1);
}

/* }==================================================================== */



/*
** {======================================================================
** Rules for Statements
** =======================================================================
*/


static int block_follow (int token) {
  switch (token) {
    case TK_ELSE: case TK_ELSEIF: case TK_END:
    case TK_UNTIL: case TK_EOS:
      return 1;
    default: return 0;
  }
}


static void block (LexState *ls) {
  /* block -> chunk */
  FuncState *fs = ls->fs;
  BlockCnt bl;
  enterblock(fs, &bl, 0);
  chunk(ls);
  lua_assert(bl.breaklist == NO_JUMP);
  leaveblock(fs);
}


/*
** structure to chain all variables in the left-hand side of an
** assignment
*/
struct LHS_assign {
  struct LHS_assign *prev;
  expdesc v;  /* variable (global, local, upvalue, or indexed) */
};


/*
** check whether, in an assignment to a local variable, the local variable
** is needed in a previous assignment (to a table). If so, save original
** local value in a safe place and use this safe copy in the previous
** assignment.
*/
static void check_conflict (LexState *ls, struct LHS_assign *lh, expdesc *v) {
  FuncState *fs = ls->fs;
  int extra = fs->freereg;  /* eventual position to save local variable */
  int conflict = 0;
  for (; lh; lh = lh->prev) {
    if (lh->v.k == VINDEXED) {
      if (lh->v.info == v->info) {  /* conflict? */
        conflict = 1;
        lh->v.info = extra;  /* previous assignment will use safe copy */
      }
      if (lh->v.aux == v->info) {  /* conflict? */
        conflict = 1;