lparser.c

Lua 语言解释器源码

/*
** $Id: lparser.c,v 1.208a 2003/04/03 13:35:34 roberto Exp $
** Lua Parser
** See Copyright Notice in lua.h
*/


#include <string.h>

#define lparser_c

#include "lua.h"

#include "lcode.h"
#include "ldebug.h"
#include "lfunc.h"
#include "llex.h"
#include "lmem.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lparser.h"
#include "lstate.h"
#include "lstring.h"




#define getlocvar(fs, i)	((fs)->f->locvars[(fs)->actvar[i]])


#define enterlevel(ls)	if (++(ls)->nestlevel > LUA_MAXPARSERLEVEL) \
		luaX_syntaxerror(ls, "too many syntax levels");
#define leavelevel(ls)	((ls)->nestlevel--)


/*
** nodes for block list (list of active blocks)
*/
typedef struct BlockCnt {
  struct BlockCnt *previous;  /* chain */
  int breaklist;  /* list of jumps out of this loop */
  int nactvar;  /* # active local variables outside the breakable structure */
  int upval;  /* true if some variable in the block is an upvalue */
  int isbreakable;  /* true if `block' is a loop */
} BlockCnt;



/*
** prototypes for recursive non-terminal functions
*/
static void chunk (LexState *ls);
static void expr (LexState *ls, expdesc *v);



static void next (LexState *ls) {
  ls->lastline = ls->linenumber;
  if (ls->lookahead.token != TK_EOS) {  /* is there a look-ahead token? */
    ls->t = ls->lookahead;  /* use this one */
    ls->lookahead.token = TK_EOS;  /* and discharge it */
  }
  else
    ls->t.token = luaX_lex(ls, &ls->t.seminfo);  /* read next token */
}


static void lookahead (LexState *ls) {
  lua_assert(ls->lookahead.token == TK_EOS);
  ls->lookahead.token = luaX_lex(ls, &ls->lookahead.seminfo);
}


static void error_expected (LexState *ls, int token) {
  luaX_syntaxerror(ls,
         luaO_pushfstring(ls->L, "`%s' expected", luaX_token2str(ls, token)));
}


static int testnext (LexState *ls, int c) {
  if (ls->t.token == c) {
    next(ls);
    return 1;
  }
  else return 0;
}


static void check (LexState *ls, int c) {
  if (!testnext(ls, c))
    error_expected(ls, c);
}


#define check_condition(ls,c,msg)	{ if (!(c)) luaX_syntaxerror(ls, msg); }



static void check_match (LexState *ls, int what, int who, int where) {
  if (!testnext(ls, what)) {
    if (where == ls->linenumber)
      error_expected(ls, what);
    else {
      luaX_syntaxerror(ls, luaO_pushfstring(ls->L,
             "`%s' expected (to close `%s' at line %d)",
              luaX_token2str(ls, what), luaX_token2str(ls, who), where));
    }
  }
}


static TString *str_checkname (LexState *ls) {
  TString *ts;
  check_condition(ls, (ls->t.token == TK_NAME), "<name> expected");
  ts = ls->t.seminfo.ts;
  next(ls);
  return ts;
}


static void init_exp (expdesc *e, expkind k, int i) {
  e->f = e->t = NO_JUMP;
  e->k = k;
  e->info = i;
}


static void codestring (LexState *ls, expdesc *e, TString *s) {
  init_exp(e, VK, luaK_stringK(ls->fs, s));
}


static void checkname(LexState *ls, expdesc *e) {
  codestring(ls, e, str_checkname(ls));
}


static int luaI_registerlocalvar (LexState *ls, TString *varname) {
  FuncState *fs = ls->fs;
  Proto *f = fs->f;
  luaM_growvector(ls->L, f->locvars, fs->nlocvars, f->sizelocvars,
                  LocVar, MAX_INT, "");
  f->locvars[fs->nlocvars].varname = varname;
  return fs->nlocvars++;
}


static void new_localvar (LexState *ls, TString *name, int n) {
  FuncState *fs = ls->fs;
  luaX_checklimit(ls, fs->nactvar+n+1, MAXVARS, "local variables");
  fs->actvar[fs->nactvar+n] = luaI_registerlocalvar(ls, name);
}


static void adjustlocalvars (LexState *ls, int nvars) {
  FuncState *fs = ls->fs;
  fs->nactvar += nvars;
  for (; nvars; nvars--) {
    getlocvar(fs, fs->nactvar - nvars).startpc = fs->pc;
  }
}


static void removevars (LexState *ls, int tolevel) {
  FuncState *fs = ls->fs;
  while (fs->nactvar > tolevel)
    getlocvar(fs, --fs->nactvar).endpc = fs->pc;
}


static void new_localvarstr (LexState *ls, const char *name, int n) {
  new_localvar(ls, luaS_new(ls->L, name), n);
}


static void create_local (LexState *ls, const char *name) {
  new_localvarstr(ls, name, 0);
  adjustlocalvars(ls, 1);
}


static int indexupvalue (FuncState *fs, TString *name, expdesc *v) {
  int i;
  Proto *f = fs->f;
  for (i=0; i<f->nups; i++) {
    if (fs->upvalues[i].k == v->k && fs->upvalues[i].info == v->info) {
      lua_assert(fs->f->upvalues[i] == name);
      return i;
    }
  }
  /* new one */
  luaX_checklimit(fs->ls, f->nups + 1, MAXUPVALUES, "upvalues");
  luaM_growvector(fs->L, fs->f->upvalues, f->nups, fs->f->sizeupvalues,
                  TString *, MAX_INT, "");
  fs->f->upvalues[f->nups] = name;
  fs->upvalues[f->nups] = *v;
  return f->nups++;
}


static int searchvar (FuncState *fs, TString *n) {
  int i;
  for (i=fs->nactvar-1; i >= 0; i--) {
    if (n == getlocvar(fs, i).varname)
      return i;
  }
  return -1;  /* not found */
}


static void markupval (FuncState *fs, int level) {
  BlockCnt *bl = fs->bl;
  while (bl && bl->nactvar > level) bl = bl->previous;
  if (bl) bl->upval = 1;
}


static void singlevaraux (FuncState *fs, TString *n, expdesc *var, int base) {
  if (fs == NULL)  /* no more levels? */
    init_exp(var, VGLOBAL, NO_REG);  /* default is global variable */
  else {
    int v = searchvar(fs, n);  /* look up at current level */
    if (v >= 0) {
      init_exp(var, VLOCAL, v);
      if (!base)
        markupval(fs, v);  /* local will be used as an upval */
    }
    else {  /* not found at current level; try upper one */
      singlevaraux(fs->prev, n, var, 0);
      if (var->k == VGLOBAL) {
        if (base)
          var->info = luaK_stringK(fs, n);  /* info points to global name */
      }
      else {  /* LOCAL or UPVAL */
        var->info = indexupvalue(fs, n, var);
        var->k = VUPVAL;  /* upvalue in this level */
      }
    }
  }
}


static TString *singlevar (LexState *ls, expdesc *var, int base) {
  TString *varname = str_checkname(ls);
  singlevaraux(ls->fs, varname, var, base);
  return varname;
}


static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e) {
  FuncState *fs = ls->fs;
  int extra = nvars - nexps;
  if (e->k == VCALL) {
    extra++;  /* includes call itself */
    if (extra <= 0) extra = 0;
    else luaK_reserveregs(fs, extra-1);
    luaK_setcallreturns(fs, e, extra);  /* call provides the difference */
  }
  else {
    if (e->k != VVOID) luaK_exp2nextreg(fs, e);  /* close last expression */
    if (extra > 0) {
      int reg = fs->freereg;
      luaK_reserveregs(fs, extra);
      luaK_nil(fs, reg, extra);
    }
  }
}


static void code_params (LexState *ls, int nparams, int dots) {
  FuncState *fs = ls->fs;
  adjustlocalvars(ls, nparams);
  luaX_checklimit(ls, fs->nactvar, MAXPARAMS, "parameters");
  fs->f->numparams = cast(lu_byte, fs->nactvar);
  fs->f->is_vararg = cast(lu_byte, dots);
  if (dots)
    create_local(ls, "arg");
  luaK_reserveregs(fs, fs->nactvar);  /* reserve register for parameters */
}


static void enterblock (FuncState *fs, BlockCnt *bl, int isbreakable) {
  bl->breaklist = NO_JUMP;
  bl->isbreakable = isbreakable;
  bl->nactvar = fs->nactvar;
  bl->upval = 0;
  bl->previous = fs->bl;
  fs->bl = bl;
  lua_assert(fs->freereg == fs->nactvar);
}


static void leaveblock (FuncState *fs) {
  BlockCnt *bl = fs->bl;
  fs->bl = bl->previous;
  removevars(fs->ls, bl->nactvar);
  if (bl->upval)
    luaK_codeABC(fs, OP_CLOSE, bl->nactvar, 0, 0);
  lua_assert(bl->nactvar == fs->nactvar);
  fs->freereg = fs->nactvar;  /* free registers */
  luaK_patchtohere(fs, bl->breaklist);
}


static void pushclosure (LexState *ls, FuncState *func, expdesc *v) {
  FuncState *fs = ls->fs;
  Proto *f = fs->f;
  int i;
  luaM_growvector(ls->L, f->p, fs->np, f->sizep, Proto *,
                  MAXARG_Bx, "constant table overflow");
  f->p[fs->np++] = func->f;
  init_exp(v, VRELOCABLE, luaK_codeABx(fs, OP_CLOSURE, 0, fs->np-1));
  for (i=0; i<func->f->nups; i++) {
    OpCode o = (func->upvalues[i].k == VLOCAL) ? OP_MOVE : OP_GETUPVAL;
    luaK_codeABC(fs, o, 0, func->upvalues[i].info, 0);
  }
}


static void open_func (LexState *ls, FuncState *fs) {
  Proto *f = luaF_newproto(ls->L);
  fs->f = f;
  fs->prev = ls->fs;  /* linked list of funcstates */
  fs->ls = ls;
  fs->L = ls->L;
  ls->fs = fs;
  fs->pc = 0;
  fs->lasttarget = 0;
  fs->jpc = NO_JUMP;
  fs->freereg = 0;
  fs->nk = 0;
  fs->h = luaH_new(ls->L, 0, 0);
  fs->np = 0;
  fs->nlocvars = 0;
  fs->nactvar = 0;
  fs->bl = NULL;
  f->source = ls->source;
  f->maxstacksize = 2;  /* registers 0/1 are always valid */
}


static void close_func (LexState *ls) {
  lua_State *L = ls->L;
  FuncState *fs = ls->fs;
  Proto *f = fs->f;
  removevars(ls, 0);
  luaK_codeABC(fs, OP_RETURN, 0, 1, 0);  /* final return */
  luaM_reallocvector(L, f->code, f->sizecode, fs->pc, Instruction);
  f->sizecode = fs->pc;
  luaM_reallocvector(L, f->lineinfo, f->sizelineinfo, fs->pc, int);
  f->sizelineinfo = fs->pc;
  luaM_reallocvector(L, f->k, f->sizek, fs->nk, TObject);
  f->sizek = fs->nk;
  luaM_reallocvector(L, f->p, f->sizep, fs->np, Proto *);
  f->sizep = fs->np;
  luaM_reallocvector(L, f->locvars, f->sizelocvars, fs->nlocvars, LocVar);
  f->sizelocvars = fs->nlocvars;
  luaM_reallocvector(L, f->upvalues, f->sizeupvalues, f->nups, TString *);
  f->sizeupvalues = f->nups;
  lua_assert(luaG_checkcode(f));
  lua_assert(fs->bl == NULL);
  ls->fs = fs->prev;
}


Proto *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff) {
  struct LexState lexstate;
  struct FuncState funcstate;
  lexstate.buff = buff;
  lexstate.nestlevel = 0;
  luaX_setinput(L, &lexstate, z, luaS_new(L, zname(z)));
  open_func(&lexstate, &funcstate);
  next(&lexstate);  /* read first token */
  chunk(&lexstate);
  check_condition(&lexstate, (lexstate.t.token == TK_EOS), "<eof> expected");
  close_func(&lexstate);
  lua_assert(funcstate.prev == NULL);
  lua_assert(funcstate.f->nups == 0);
  lua_assert(lexstate.nestlevel == 0);
  return funcstate.f;
}



/*============================================================*/
/* GRAMMAR RULES */
/*============================================================*/


static void luaY_field (LexState *ls, expdesc *v) {
  /* field -> ['.' | ':'] NAME */
  FuncState *fs = ls->fs;
  expdesc key;
  luaK_exp2anyreg(fs, v);
  next(ls);  /* skip the dot or colon */
  checkname(ls, &key);
  luaK_indexed(fs, v, &key);
}


static void luaY_index (LexState *ls, expdesc *v) {
  /* index -> '[' expr ']' */
  next(ls);  /* skip the '[' */
  expr(ls, v);
  luaK_exp2val(ls->fs, v);
  check(ls, ']');
}


/*
** {======================================================================
** Rules for Constructors
** =======================================================================
*/


struct ConsControl {
  expdesc v;  /* last list item read */
  expdesc *t;  /* table descriptor */
  int nh;  /* total number of `record' elements */
  int na;  /* total number of array elements */
  int tostore;  /* number of array elements pending to be stored */
};


static void recfield (LexState *ls, struct ConsControl *cc) {
  /* recfield -> (NAME | `['exp1`]') = exp1 */
  FuncState *fs = ls->fs;
  int reg = ls->fs->freereg;
  expdesc key, val;
  if (ls->t.token == TK_NAME) {
    luaX_checklimit(ls, cc->nh, MAX_INT, "items in a constructor");
    cc->nh++;
    checkname(ls, &key);
  }
  else  /* ls->t.token == '[' */
    luaY_index(ls, &key);
  check(ls, '=');
  luaK_exp2RK(fs, &key);
  expr(ls, &val);
  luaK_codeABC(fs, OP_SETTABLE, cc->t->info, luaK_exp2RK(fs, &key),
                                             luaK_exp2RK(fs, &val));
  fs->freereg = reg;  /* free registers */
}