yap-6.3/os/readterm.c

/*************************************************************************
*									 *
*	 YAP Prolog							 *
*									 *
*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
*									 *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997	 *
*									 *
**************************************************************************
*									 *
* File:		iopreds.c *
* Last rev:	5/2/88							 *
* mods: *
* comments:	Input/Output C implemented predicates			 *
*									 *
*************************************************************************/
#ifdef SCCS
static char SccsId[] = "%W% %G%";
#endif

/*
 * This file includes the definition of a miscellania of standard predicates
 * for yap refering to: Files and GLOBAL_Streams, Simple Input/Output,
 *
 */

#include "Yap.h"
#include "YapEval.h"
#include "YapFlags.h"
#include "YapHeap.h"
#include "YapText.h"
#include "Yatom.h"
#include "yapio.h"
#include <stdlib.h>
#if HAVE_STDARG_H
#include <stdarg.h>
#endif
#if HAVE_CTYPE_H
#include <ctype.h>
#endif
#if HAVE_WCTYPE_H
#include <wctype.h>
#endif
#if HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_SELECT_H && !_MSC_VER && !defined(__MINGW32__)
#include <sys/select.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_STRING_H
#include <string.h>
#endif
#if HAVE_SIGNAL_H
#include <signal.h>
#endif
#if HAVE_FCNTL_H
/* for O_BINARY and O_TEXT in WIN32 */
#include <fcntl.h>
#endif
#ifdef _WIN32
#if HAVE_IO_H
/* priows */
#include <io.h>
#endif
#endif
#if !HAVE_STRNCAT
#define strncat(X, Y, Z) strcat(X, Y)
#endif
#if !HAVE_STRNCPY
#define strncpy(X, Y, Z) strcpy(X, Y)
#endif
#if _MSC_VER || defined(__MINGW32__)
#if HAVE_SOCKET
#include <winsock2.h>
#endif
#include <windows.h>
#ifndef S_ISDIR
#define S_ISDIR(x) (((x) & _S_IFDIR) == _S_IFDIR)
#endif
#endif
#include "iopreds.h"

#if _MSC_VER || defined(__MINGW32__)
#define SYSTEM_STAT _stat
#else
#define SYSTEM_STAT stat
#endif

static Term syntax_error(TokEntry *errtok, int sno, Term cmod, Int start, bool code, const char *msg);

static void clean_vars(VarEntry *p)
{
  if (p == NULL)
    return;
  p->VarAdr = TermNil;
  clean_vars(p->VarLeft);
  clean_vars(p->VarRight);
}

#undef PAR

#ifdef O_QUASIQUOTATIONS
/** '$qq_open'(+QQRange, -Stream) is det.

    Opens a quasi-quoted memory range.

    @arg QQRange is a term '$quasi_quotation'(ReadData, Start, Length)
    @arg Stream  is a UTF-8 encoded string, whose position indication
    reflects the location in the real file.
 */

static Int qq_open(USES_REGS1)
{
  PRED_LD

  Term t = Deref(ARG1);

  if (!IsVarTerm(t) && IsApplTerm(t) && FunctorOfTerm(t) =
        FunctorDQuasiQuotation)
    {
      void *ptr;
      char *start;
      size_t l int s;
      Term t0, t1, t2;

      if (IsPointerTerm((t0 = ArgOfTerm(1, t))) &&
          IsPointerTerm((t1 = ArgOfTerm(2, t))) &&
          IsIntegerTerm((t2 = ArgOfTerm(3, t))))
        {
          ptr = PointerOfTerm(t0);
          start = PointerOfTerm(t1);
          len = IntegerOfTerm(t2);
          if ((s = Yap_open_buf_read_stream(start, len, ENC_UTF8, MEM_BUF_USER)) <
              0)
            return false;
          return Yap_unify(ARG2, Yap_MkStream(s));
        }
      else
        {
          Yap_Error(TYPE_ERROR_READ_CONTEXT, t);
        }

      return FALSE;
    }
}

static int parse_quasi_quotations(ReadData _PL_rd ARG_LD)
{
  if (_PL_rd->qq_tail)
    {
      term_t av;
      int rc;

      if (!PL_unify_nil(_PL_rd->qq_tail))
        return FALSE;

      if (!_PL_rd->quasi_quotations)
        {
          if ((av = PL_new_term_refs(2)) && PL_put_term(av + 0, _PL_rd->qq) &&
#if __YAP_PROLOG__
              PL_put_atom(av + 1, YAP_SWIAtomFromAtom(_PL_rd->module->AtomOfME)) &&
#else
              PL_put_atom(av + 1, _PL_rd->module->name) &&
#endif
              PL_cons_functor_v(av, FUNCTOR_dparse_quasi_quotations2, av))
            {
              term_t ex;
              rc = callProlog(MODULE_system, av + 0, PL_Q_CATCH_EXCEPTION, &ex);
              if (rc)
                return TRUE;
              _PL_rd->exception = ex;
              _PL_rd->has_exception = TRUE;
            }
          return FALSE;
        }
      else
        return TRUE;
    }
  else if (_PL_rd->quasi_quotations)   /* user option, but no quotes */
    {
      return PL_unify_nil(_PL_rd->quasi_quotations);
    }
  else
    return TRUE;
}

#endif /*O_QUASIQUOTATIONS*/

#define READ_DEFS()                                                     \
  PAR("comments", list_filler, READ_COMMENTS)                           \
  , PAR("module", isatom, READ_MODULE), PAR("priority", nat, READ_PRIORITY), \
  PAR("output", filler, READ_OUTPUT),                                 \
  PAR("quasi_quotations", filler, READ_QUASI_QUOTATIONS),             \
  PAR("term_position", filler, READ_TERM_POSITION),                   \
  PAR("syntax_errors", isatom, READ_SYNTAX_ERRORS),                   \
  PAR("singletons", filler, READ_SINGLETONS),                         \
  PAR("variables", filler, READ_VARIABLES),                           \
  PAR("variable_names", filler, READ_VARIABLE_NAMES),                 \
  PAR("character_escapes", booleanFlag, READ_CHARACTER_ESCAPES),      \
  PAR("backquoted_string", isatom, READ_BACKQUOTED_STRING),           \
  PAR("cycles", ok, READ_CYCLES), PAR(NULL, ok, READ_END)

#define PAR(x, y, z) z

typedef enum open_enum_choices { READ_DEFS() } read_choices_t;

#undef PAR

#define PAR(x, y, z)                            \
  { x, y, z }

static const param_t read_defs[] = { READ_DEFS() };
#undef PAR

static Term add_output(Term t, Term tail)
{
  Term topt = Yap_MkNewApplTerm(Yap_MkFunctor(AtomOutput, 1), 1);

  tail = Deref(tail);
  if (IsVarTerm(tail))
    {
      Yap_ThrowError(INSTANTIATION_ERROR, tail, "unbound list of options");
    }
  Yap_unify(t, ArgOfTerm(1, topt));
  if (IsVarTerm(tail))
    {
      Yap_ThrowError(INSTANTIATION_ERROR, tail, "unbound list of options");
    }
  else if (IsPairTerm(tail) || tail == TermNil)
    {
      return MkPairTerm(topt, tail);
    }
  else
    {
      return MkPairTerm(topt, MkPairTerm(tail, TermNil));
    }
}

static Term add_names(Term t, Term tail)
{
  Term topt = Yap_MkNewApplTerm(Yap_MkFunctor(AtomVariableNames, 1), 1);

  Yap_unify(t, ArgOfTerm(1, topt));
  if (IsVarTerm(tail))
    {
      Yap_ThrowError(INSTANTIATION_ERROR, tail, "unbound list of options");
    }
  else if (IsPairTerm(tail) || tail == TermNil)
    {
      return MkPairTerm(topt, tail);
    }
  else
    {
      return MkPairTerm(topt, MkPairTerm(tail, TermNil));
    }
}

static Term add_priority(Term t, Term tail)
{
  Term topt = Yap_MkNewApplTerm(Yap_MkFunctor(AtomPriority, 1), 1);

  Yap_unify(t, ArgOfTerm(1, topt));
  if (IsVarTerm(tail))
    {
      Yap_ThrowError(INSTANTIATION_ERROR, tail, "unbound list of options");
    }
  else if (IsPairTerm(tail) || tail == TermNil)
    {
      return MkPairTerm(topt, tail);
    }
  else
    {
      return MkPairTerm(topt, MkPairTerm(tail, TermNil));
    }
}

static Term scanToList(TokEntry *tok, TokEntry *errtok)
{
  TokEntry *tok0 = tok;
  CELL *Hi = HR;
  Term ts[1];

  ts[0] = TermNil;
  Term *tailp = ts;

  while (tok)
    {
      if (HR > ASP - 1024)
        {
          Int used = HR - Hi;
          /* for some reason moving this earlier confuses gcc on solaris */
          HR = Hi;
          tok = tok0;
          if (!Yap_gcl(used, 1, ENV, CP))
            {
              return 0;
            }
          continue;
        }
      if (tok == errtok && tok->Tok != Error_tok)
        {
          *tailp = MkPairTerm(MkAtomTerm(AtomError), TermNil);
          tailp = RepPair(*tailp) + 1;
        }
      Term rep = Yap_tokRep(tok);
      *tailp = MkPairTerm(rep, TermNil);
      tailp = RepPair(*tailp) + 1;
      if (tok->TokNext == NULL)
        {
          break;
        }
      tok = tok->TokNext;
    }
  return ts[0];
}

/**
   @pred scan_to_list( +Stream, -Tokens )
   Generate a list of tokens from a scan of the (input) stream, Tokens are of
   the form:

 + `atom`(Atom)
 + `<QQ>`(Text)
 + `number`(Number)
 + `var`(VarName)
 + `string`(String)
 + 'EOF''
 + symbols, including `(`, `)`, `,`, `;`

 */
static Int scan_to_list(USES_REGS1)
{
  int inp_stream;
  Term tpos, tout;

  /* needs to change LOCAL_output_stream for write */
  inp_stream = Yap_CheckTextStream(ARG1, Input_Stream_f, "read/3");
  if (inp_stream == -1)
    {
      return false;
    }
  TokEntry *tok = LOCAL_tokptr = LOCAL_toktide =
                                   Yap_tokenizer(GLOBAL_Stream + inp_stream, false, &tpos);
  UNLOCK(GLOBAL_Stream[inp_stream].streamlock);
  tout = scanToList(tok, NULL);
  if (tout == 0)
    return false;
  Yap_clean_tokenizer(tok, LOCAL_VarTable, LOCAL_AnonVarTable);

  return Yap_unify(ARG2, tout);
}

/**
 * Syntax Error Handler
 *
 * @par tokptr: the sequence of tokens
 * @par sno: the stream numbet
 *
 * Implicit arguments:
 *    +
 */
static Term syntax_error(TokEntry *errtok, int sno, Term cmod, Int newpos, bool code, const char *msg)
{
  CACHE_REGS
  Yap_MkErrorRecord(LOCAL_ActiveError, __FILE__, __FUNCTION__, __LINE__, SYNTAX_ERROR, 0, NULL);
  TokEntry *tok = LOCAL_tokptr;
  Int start_line = tok->TokLine;
  Int err_line = errtok->TokLine;
  Int end_line = GetCurInpLine(GLOBAL_Stream + sno);
  Int startpos = tok->TokPos;
  Int errpos = errtok->TokPos;
  Int endpos = GetCurInpPos(GLOBAL_Stream + sno);

  Yap_local.ActiveError->errorNo = SYNTAX_ERROR;
  Yap_local.ActiveError->parserFirstLine = start_line;
  Yap_local.ActiveError->parserLastLine = end_line;
  Yap_local.ActiveError->parserFirstPos = startpos;
  Yap_local.ActiveError->parserLastPos = endpos;
  Yap_local.ActiveError->parserFile =
    RepAtom(AtomOfTerm((GLOBAL_Stream + sno)->user_name))->StrOfAE;
  Yap_local.ActiveError->parserReadingCode = code;
  int lvl = push_text_stack();
  if (GLOBAL_Stream[sno].status & Seekable_Stream_f)
    {
      char *o, *o2;
      if (startpos)
	startpos--;
#if HAVE_FTELLO
      fseeko(GLOBAL_Stream[sno].file, startpos, SEEK_SET);
#else
      fseek(GLOBAL_Stream[sno].file, startpos, SEEK_SET);
#endif
      if (GLOBAL_Stream[sno].status & Seekable_Stream_f)
        {
          while (tok && tok->Tok != Error_tok && tok != errtok)
                {
		  if (tok->TokNext)
		    tok = tok->TokNext;
		  else
		    break;
                }
          err_line = tok->TokLine;
          errpos = tok->TokPos -1;
          if (errpos <= startpos)
            {
              o = malloc(1);
              o[0] = '\0';
            }
          else
            {
              Int sza = (errpos - startpos) + 1, tot = sza;
              o = malloc(sza);
              char *p = o;
                {
                  size_t siz = fread(p, tot - 1, 1, GLOBAL_Stream[sno].file);
                  if (siz < 0)
                    Yap_Error(EVALUATION_ERROR_READ_STREAM, GLOBAL_Stream[sno].user_name, "%s", strerror(errno));
              o[sza - 1] = '\0';
            }
          Yap_local.ActiveError->parserTextA = o;
          if (endpos <= errpos)
            {
              o2 = malloc(1);
              o2[0] = '\0';
            }
          else
            {
              Int sza = (endpos - errpos) + 1, tot = sza;
              o2 = malloc(sza);
              char *p = o2;
                {
                  size_t siz = fread(p, tot - 1, 1, GLOBAL_Stream[sno].file);
                  if (siz < 0)
                    Yap_Error(EVALUATION_ERROR_READ_STREAM, GLOBAL_Stream[sno].user_name, "%s", strerror(errno));
                 
              o2[sza - 1] = '\0';
            }
          Yap_local.ActiveError->parserTextB = o2;
	    }
	    }
	}
      else
        {
          size_t sz = 1024, e;
          char *o = malloc(1024);
          char *s = o;
          o[0] = '\0';
          while (tok)
            {
              if (tok->Tok == Error_tok)
                {
                  o = realloc(o, strlen(o) + 1);
                  Yap_local.ActiveError->parserTextA = o;
                  o = malloc(1024);
                  sz = 1024;
                  err_line = tok->TokLine;
                  errpos = tok->TokPos;
                  tok = tok->TokNext;
                  continue;
                }
              const char *ns = Yap_tokText(tok);
              e = strlen(ns);
              if (ns && ns[0] && e + 1 > sz - 256)
                {
                  strcat(s, ns);
                  o += e;
                  sz -= e;
                }
              if (tok->TokNext && tok->TokNext->TokLine > tok->TokLine)
                {
                  strcat(s, "\n")
                  ; sz--;
                }
              tok = tok->TokNext;
            }
          o = realloc(o, strlen(o) + 1);
          Yap_local.ActiveError->parserTextB = o;
        }
    }
  Yap_local.ActiveError->parserPos = errpos;
      Yap_local.ActiveError->parserLine = err_line;
      /* 0:  strat, error, end line */
      /*2 msg */
      /* 1: file */
      if (!msg)
        msg = "unspecified";
      Yap_local.ActiveError->culprit =
        Yap_local.ActiveError->errorMsg = (char*)msg;
      Yap_local.ActiveError->errorMsgLen = strlen(msg);
      clean_vars(LOCAL_VarTable);
      clean_vars(LOCAL_AnonVarTable);
      if (Yap_ExecutionMode == YAP_BOOT_MODE)
        {
          fprintf(stderr, "SYNTAX ERROR while booting: ");
        }
      pop_text_stack(lvl);
      return Yap_MkFullError();
    }

  Term Yap_syntax_error(TokEntry *errtok, int sno, const char *msg)
  {
    return syntax_error(errtok, sno, CurrentModule, -1, false, msg);
  }

  typedef struct FEnv {
    Term qq, tp, sp, np, vp, ce;
    Term tpos;         /// initial position of the term to be read.
    Term t, t0;        /// the output term
    TokEntry *tokstart; /// the token list
    TokEntry *toklast; /// the last token
    CELL *old_H;       /// initial H, will be reset on stack overflow.
    tr_fr_ptr old_TR;  /// initial TR
    xarg *args;        /// input args
    bool reading_clause; /// read_clause
    size_t nargs;      /// arity of current procedure
    encoding_t enc;    /// encoding of the stream being read
    Term tcomms;       /// Access to comments
    Term cmod;         /// Access to comments
    char *msg;         /// Error  Messagge
  } FEnv;

  typedef struct renv {
    Term bq;
    bool ce, sw;
    Term sy;
    UInt cpos;
    int prio;
    int ungetc_oldc;
    int had_ungetc;
    bool seekable;
  } REnv;

  static xarg *setClauseReadEnv(Term opts, FEnv *fe, struct renv *re,
                                int inp_stream);
  static xarg *setReadEnv(Term opts, FEnv *fe, struct renv *re, int inp_stream)
  {
    CACHE_REGS
      LOCAL_VarTable = NULL;

    LOCAL_AnonVarTable = NULL;
    fe->enc = GLOBAL_Stream[inp_stream].encoding;
    xarg *args =
      Yap_ArgListToVector(opts, read_defs, READ_END, DOMAIN_ERROR_READ_OPTION);
    if (args == NULL)
      {
        return NULL;
      }

    re->bq = getReadTermBackQuotesFlag();
    if (args[READ_OUTPUT].used)
      {
        fe->t0 = args[READ_OUTPUT].tvalue;
      }
    else
      {
        fe->t0 = 0;
      }
    if (args[READ_MODULE].used)
      {
        fe->cmod = args[READ_MODULE].tvalue;
      }
    else
      {
        fe->cmod = CurrentModule;
        if (fe->cmod == TermProlog)
          fe->cmod = PROLOG_MODULE;
      }
    if (args[READ_BACKQUOTED_STRING].used)
      {
        if (!setReadTermBackQuotesFlag(args[READ_BACKQUOTED_STRING].tvalue))
          {
            return false;
          }
      }
    if (args[READ_QUASI_QUOTATIONS].used)
      {
        fe->qq = args[READ_QUASI_QUOTATIONS].tvalue;
      }
    else
      {
        fe->qq = 0;
      }
    if (args[READ_COMMENTS].used)
      {
        fe->tcomms = args[READ_COMMENTS].tvalue;
      }
    else
      {
        fe->tcomms = 0;
      }
    if (args[READ_TERM_POSITION].used)
      {
        fe->tp = args[READ_TERM_POSITION].tvalue;
      }
    else
      {
        fe->tp = 0;
      }
    if (args[READ_SINGLETONS].used)
      {
        fe->sp = args[READ_SINGLETONS].tvalue;
      }
    else
      {
        fe->sp = 0;
      }
    if (args[READ_SYNTAX_ERRORS].used)
      {
        re->sy = args[READ_SYNTAX_ERRORS].tvalue;
      }
    else
      {
        re->sy = TermError; // getYapFlag( MkAtomTerm(AtomSyntaxErrors) );
      }
    if (args[READ_VARIABLES].used)
      {
        fe->vp = args[READ_VARIABLES].tvalue;
      }
    else
      {
        fe->vp = 0;
      }
    if (args[READ_VARIABLE_NAMES].used)
      {
        fe->np = args[READ_VARIABLE_NAMES].tvalue;
      }
    else
      {
        fe->np = 0;
      }
    if (args[READ_CHARACTER_ESCAPES].used || Yap_CharacterEscapes(fe->cmod))
      {
        fe->ce = true;
      }
    else
      {
        fe->ce = false;
      }
    re->seekable = (GLOBAL_Stream[inp_stream].status & Seekable_Stream_f) != 0;
    if (re->seekable)
      {
        re->cpos = GLOBAL_Stream[inp_stream].charcount;
      }
    if (args[READ_PRIORITY].used)
      {
        re->prio = IntegerOfTerm(args[READ_PRIORITY].tvalue);
        if (re->prio > GLOBAL_MaxPriority)
          {
            Yap_ThrowError(DOMAIN_ERROR_OPERATOR_PRIORITY, opts,
                           "max priority in Prolog is %d, not %ld",
                           GLOBAL_MaxPriority, re->prio);
          }
      }
    else
      {
        re->prio = LOCAL_default_priority;
      }
    fe->msg = NULL;
    return args;
  }

  typedef enum {
    YAP_START_PARSING, /// initialization
    YAP_SCANNING,     /// input to list of tokens
    YAP_SCANNING_ERROR, /// serious error (eg oom); trying error handling, followd
    /// by either restart or failure
    YAP_PARSING,       /// list of tokens to term
    YAP_PARSING_ERROR, /// oom or syntax error
    YAP_PARSING_FINISHED /// exit parser
  } parser_state_t;

  Int Yap_FirstLineInParse(void)
  {
    CACHE_REGS
    return LOCAL_StartLineCount;
  }

#define PUSHFET(X) *HR++ = fe->X
#define POPFET(X) fe->X = *--HR

  static void reset_regs(TokEntry *tokstart, FEnv *fe)
  {
    CACHE_REGS

    restore_machine_regs();

    /* restart global */
    PUSHFET(qq);
    PUSHFET(tp);
    PUSHFET(sp);
    PUSHFET(np);
    PUSHFET(vp);
    PUSHFET(tpos);
    PUSHFET(t);
    HR = fe->old_H;
    TR = (tr_fr_ptr)LOCAL_ScannerStack;
    LOCAL_Error_TYPE = YAP_NO_ERROR;
    Yap_growstack_in_parser(&fe->old_TR, &tokstart, &LOCAL_VarTable);
    LOCAL_ScannerStack = (char*)TR;
    TR = fe->old_TR;
    POPFET(t);
    POPFET(tpos);
    POPFET(vp);
    POPFET(np);
    POPFET(sp);
    POPFET(tp);
    POPFET(qq);
  }

  static Term get_variables(FEnv *fe, TokEntry *tokstart)
  {
    CACHE_REGS
    Term v;

    if (fe->vp)
      {
        while (true)
          {
            fe->old_H = HR;
            if (setjmp(LOCAL_IOBotch) == 0)
              {
                if ((v = Yap_Variables(LOCAL_VarTable, TermNil)))
                  {
                    fe->old_H = HR;
                    return v;
                  }
              }
            else
              {
                reset_regs(tokstart, fe);
              }
          }
      }
    return 0;
  }

  static Term get_varnames(FEnv *fe, TokEntry *tokstart)
  {
    CACHE_REGS
    Term v;

    if (fe->np)
      {
        while (true)
          {
            fe->old_H = HR;

            if (setjmp(LOCAL_IOBotch) == 0)
              {
                if ((v = Yap_VarNames(LOCAL_VarTable, TermNil)))
                  {
                    fe->old_H = HR;
                    return v;
                  }
              }
            else
              {
                reset_regs(tokstart, fe);
              }
          }
      }
    return 0;
  }

  static Term get_singletons(FEnv *fe, TokEntry *tokstart)
  {
    CACHE_REGS
    Term v;

    if (fe->sp)
      {
        while (TRUE)
          {
            fe->old_H = HR;

            if (setjmp(LOCAL_IOBotch) == 0)
              {
                if ((v = Yap_Singletons(LOCAL_VarTable, TermNil)))
                  {
                    return v;
                  }
              }
            else
              {
                reset_regs(tokstart, fe);
              }
          }
      }
    return 0;
  }

  static void warn_singletons(FEnv *fe, TokEntry *tokstart)
  {
    CACHE_REGS
    Term v;

    fe->sp = TermNil;
    v = get_singletons(fe, tokstart);
    if (v && v != TermNil)
      {
        Term singls[4];
        singls[0] = Yap_MkApplTerm(Yap_MkFunctor(AtomSingleton, 1), 1, &v);
        singls[1] = MkIntegerTerm(LOCAL_SourceFileLineno);
        singls[2] = MkAtomTerm(LOCAL_SourceFileName);
        if (fe->t)
          singls[3] = fe->t;
        else
          singls[1] = TermTrue;
        Term t = Yap_MkApplTerm(Yap_MkFunctor(AtomStyleCheck, 4), 4, singls);
        Yap_PrintWarning(t);
      }
  }

  static Term get_stream_position(FEnv *fe, TokEntry *tokstart)
  {
    CACHE_REGS
    Term v;

    if (fe->tp)
      {
        while (true)
          {
            fe->old_H = HR;

            if (setjmp(LOCAL_IOBotch) == 0)
              {
                if ((v = CurrentPositionToTerm()))
                  {
                    return v;
                  }
              }
            else
              {
                reset_regs(tokstart, fe);
              }
          }
      }
    return 0;
  }

  static bool complete_processing(FEnv *fe, TokEntry *tokstart)
  {
    CACHE_REGS
    Term v1, v2, v3, vc, tp;

    if (fe->t0 && fe->t && !(Yap_unify(fe->t, fe->t0)))
      return false;

    if (fe->t && fe->vp)
      v1 = get_variables(fe, tokstart);
    else
      v1 = 0L;
    if (fe->t && fe->np)
      v2 = get_varnames(fe, tokstart);
    else
      v2 = 0L;
    if (fe->t && fe->sp)
      v3 = get_singletons(fe, tokstart);
    else
      v3 = 0L;
    if (fe->t && fe->tcomms)
      vc = LOCAL_Comments;
    else
      vc = 0L;
    if (fe->t && fe->tp)
      tp = get_stream_position(fe, tokstart);
    else
      tp = 0L;
    Yap_clean_tokenizer(tokstart, LOCAL_VarTable, LOCAL_AnonVarTable);
    free(fe->args);

    // trail must be ok by now.]
    if (fe->t)
      {
        return (!v1 || Yap_unify(v1, fe->vp)) && (!v2 || Yap_unify(v2, fe->np)) &&
               (!v3 || Yap_unify(v3, fe->sp)) && (!tp || Yap_unify(tp, fe->tp)) &&
               (!vc || Yap_unify(vc, fe->tcomms));
      }
    return true;
  }

  static bool complete_clause_processing(FEnv *fe, TokEntry *tokstart)
  {
    CACHE_REGS
    Term v_vp, v_vnames, v_comments, v_pos;

    if (fe->t0 && fe->t && !Yap_unify(fe->t, fe->t0))
      return false;
    if (fe->t && fe->vp)
      v_vp = get_variables(fe, tokstart);
    else
      v_vp = 0L;
    if (fe->t && fe->np)
      v_vnames = get_varnames(fe, tokstart);
    else
      v_vnames = 0L;
    if (fe->t && trueGlobalPrologFlag(SINGLE_VAR_WARNINGS_FLAG))
      {
        warn_singletons(fe, tokstart);
      }
    if (fe->t && fe->tcomms)
      v_comments = LOCAL_Comments;
    else
      v_comments = 0L;
    if (fe->t && fe->tp)
      v_pos = get_stream_position(fe, tokstart);
    else
      v_pos = 0L;
    Yap_clean_tokenizer(tokstart, LOCAL_VarTable, LOCAL_AnonVarTable);
    free(fe->args);
    // trail must be ok by now.]
    if (fe->t)
      {
        return (!v_vp || Yap_unify(v_vp, fe->vp)) &&
               (!v_vnames || Yap_unify(v_vnames, fe->np)) &&
               (!v_pos || Yap_unify(v_pos, fe->tp)) &&
               (!v_comments || Yap_unify(v_comments, fe->tcomms));
      }
    return true;
  }

  static parser_state_t initParser(Term opts, FEnv *fe, REnv *re, int inp_stream,
                                   bool clause);

  static parser_state_t parse(REnv *re, FEnv *fe, int inp_stream);

  static parser_state_t scanError(REnv *re, FEnv *fe, int inp_stream);

  static parser_state_t scanEOF(FEnv *fe, int inp_stream);

  static parser_state_t scan(REnv *re, FEnv *fe, int inp_stream);

  static parser_state_t scanEOF(FEnv *fe, int inp_stream)
  {
    CACHE_REGS
    // bool store_comments = false;
    TokEntry *tokstart = LOCAL_tokptr;

    // check for an user abort
    if (tokstart != NULL && tokstart->Tok != Ord(eot_tok))
      {
        /* we got the end of file from an abort */
        if (fe->msg && !strcmp(fe->msg, "Abort"))
          {
            fe->t = 0L;
            Yap_clean_tokenizer(tokstart, LOCAL_VarTable, LOCAL_AnonVarTable);
            return YAP_PARSING_FINISHED;
          }
        // a :- <eof>
        if (GLOBAL_Stream[inp_stream].status & Past_Eof_Stream_f)
          {
            fe->msg = "parsing stopped at a end-of-file";
            return YAP_PARSING_ERROR;
          }
        /* we need to force the next read to also give end of file.*/
        GLOBAL_Stream[inp_stream].status |= Push_Eof_Stream_f;
        fe->msg = "end of file found before end of term";
        return YAP_PARSING;
      }
    else
      {
        // <eof>
        // return end_of_file
        TR = (tr_fr_ptr)tokstart;
        Yap_clean_tokenizer(tokstart, LOCAL_VarTable, LOCAL_AnonVarTable);
        fe->t = MkAtomTerm(AtomEof);
        if (fe->np && !Yap_unify(TermNil, fe->np))
          fe->t = 0;
        if (fe->sp && !Yap_unify(TermNil, fe->sp))
          fe->t = 0;
        if (fe->vp && !Yap_unify(TermNil, fe->vp))
          fe->t = 0;
        if (fe->tp && !Yap_unify(fe->tp, fe->tpos))
          fe->t = 0;
#if DEBUG
        if (GLOBAL_Option['p' - 'a' + 1])
          {
            fprintf(stderr, "[ end_of_file %p ]\n", GLOBAL_Stream[inp_stream].name);
          }
#endif
        return YAP_PARSING_FINISHED;
      }
  }

  static parser_state_t initParser(Term opts, FEnv *fe, REnv *re, int inp_stream,
                                   bool clause)
  {
    LOCAL_ErrorMessage = NULL;
    fe->old_TR = TR;
    LOCAL_Error_TYPE = YAP_NO_ERROR;
    LOCAL_SourceFileName = GLOBAL_Stream[inp_stream].name;
    LOCAL_eot_before_eof = false;
    fe->tpos = StreamPosition(inp_stream);
    fe->reading_clause = clause;
    if (clause)
      {
        fe->args = setClauseReadEnv(opts, fe, re, inp_stream);
      }
    else
      {
        fe->args = setReadEnv(opts, fe, re, inp_stream);
      }
    if (fe->args == NULL)
      {
        if (LOCAL_Error_TYPE == DOMAIN_ERROR_OUT_OF_RANGE)
          LOCAL_Error_TYPE = DOMAIN_ERROR_READ_OPTION;
        if (LOCAL_Error_TYPE)
          Yap_Error(LOCAL_Error_TYPE, opts, NULL);
        fe->t = 0;
        return YAP_PARSING_FINISHED;
        ;
      }
    if (GLOBAL_Stream[inp_stream].status & Push_Eof_Stream_f)
      {
        fe->t = MkAtomTerm(AtomEof);
        GLOBAL_Stream[inp_stream].status &= ~Push_Eof_Stream_f;
        return YAP_PARSING_FINISHED;
      }
    if (!fe->args)
      {
        return YAP_PARSING_FINISHED;
      }
    return YAP_SCANNING;
  }

  static parser_state_t scan(REnv *re, FEnv *fe, int sno)
  {
    CACHE_REGS
    /* preserve   value of H after scanning: otherwise we may lose strings
       and floats */
      LOCAL_tokptr = LOCAL_toktide =

                       Yap_tokenizer(GLOBAL_Stream + sno, false, &fe->tpos);

#if DEBUG
    if (GLOBAL_Option[2])
      {
        TokEntry *t = LOCAL_tokptr;
        int n = 0;
        while (t)
          {
            fprintf(stderr, "[Token %d %s %d]", Ord(t->Tok), Yap_tokText(t), n++);
            t = t->TokNext;
          }
        fprintf(stderr, "\n");
      }
#endif
    if (LOCAL_ErrorMessage)
      return YAP_SCANNING_ERROR;
    if (LOCAL_tokptr->Tok != Ord(eot_tok))
      {
        // next step
        return YAP_PARSING;
      }
    if (LOCAL_tokptr->Tok == eot_tok && LOCAL_tokptr->TokInfo == TermNl)
      {
        LOCAL_ErrorMessage = ". is end-of-term?";
        return YAP_PARSING_ERROR;
      }
    return scanEOF(fe, sno);
  }

  static parser_state_t scanError(REnv *re, FEnv *fe, int inp_stream)
  {
    CACHE_REGS
    fe->t = 0;

    // running out of memory
    if (LOCAL_Error_TYPE == RESOURCE_ERROR_TRAIL)
      {
        LOCAL_Error_TYPE = YAP_NO_ERROR;
        if (!Yap_growtrail(sizeof(CELL) * K16, FALSE))
          {
            return YAP_PARSING_FINISHED;
          }
      }
    else if (LOCAL_Error_TYPE == RESOURCE_ERROR_AUXILIARY_STACK)
      {
        LOCAL_Error_TYPE = YAP_NO_ERROR;
        if (!Yap_ExpandPreAllocCodeSpace(0, NULL, TRUE))
          {
            return YAP_PARSING_FINISHED;
          }
      }
    else if (LOCAL_Error_TYPE == RESOURCE_ERROR_HEAP)
      {
        LOCAL_Error_TYPE = YAP_NO_ERROR;
        if (!Yap_growheap(FALSE, 0, NULL))
          {
            return YAP_PARSING_FINISHED;
          }
      }
    else if (LOCAL_Error_TYPE == RESOURCE_ERROR_STACK)
      {
        LOCAL_Error_TYPE = YAP_NO_ERROR;
        if (!Yap_gcl(LOCAL_Error_Size, fe->nargs, ENV, CP))
          {
            return YAP_PARSING_FINISHED;
          }
      }
    // go back to the start
    if (LOCAL_Error_TYPE == SYNTAX_ERROR)
      {
        return YAP_PARSING_ERROR;
      }
    if (re->seekable)
      {
        if (GLOBAL_Stream[inp_stream].status & InMemory_Stream_f)
          {
            GLOBAL_Stream[inp_stream].u.mem_string.pos = re->cpos;
          }
        else if (GLOBAL_Stream[inp_stream].status)
          {
#if HAVE_FTELLO
            fseeko(GLOBAL_Stream[inp_stream].file, re->cpos, 0L);
#else
            fseek(GLOBAL_Stream[inp_stream].file, re->cpos, 0L);
#endif
          }
      }
    return YAP_SCANNING;
  }

  static parser_state_t parseError(REnv *re, FEnv *fe, int inp_stream)
  {
    CACHE_REGS
    fe->t = 0;

    if (LOCAL_Error_TYPE != SYNTAX_ERROR && LOCAL_Error_TYPE != YAP_NO_ERROR)
      {
        return YAP_SCANNING_ERROR;
      }
    Term ParserErrorStyle = re->sy;
    if (ParserErrorStyle == TermQuiet || LOCAL_Error_TYPE == YAP_NO_ERROR)
      {
        /* just fail */
        LOCAL_Error_TYPE = YAP_NO_ERROR;
        return YAP_PARSING_FINISHED;
      }
    Term t = syntax_error(fe->toklast, inp_stream, fe->cmod, re->cpos, fe->reading_clause, fe->msg);
    if (ParserErrorStyle == TermException)
      {
        if (LOCAL_RestartEnv && !LOCAL_delay)
          {
            Yap_RestartYap(5);
          }
        Yap_exit(5);
      }
    if (re->seekable)
      {
        re->cpos = GLOBAL_Stream[inp_stream].charcount;
      }
    LOCAL_Error_TYPE = WARNING_SYNTAX_ERROR;
    t = Yap_MkFullError();
    Yap_PrintWarning(t);
    LOCAL_Error_TYPE = YAP_NO_ERROR;
    if (ParserErrorStyle == TermDec10)
      {
        return YAP_SCANNING;
      }
    return YAP_PARSING_FINISHED;
  }

  static parser_state_t parse(REnv *re, FEnv *fe, int inp_stream)
  {
    CACHE_REGS
    TokEntry *tokstart = LOCAL_tokptr;

    fe->t = Yap_Parse(re->prio, fe->enc, fe->cmod);
    fe->toklast = LOCAL_tokptr;
    LOCAL_tokptr = tokstart;
    TR = (tr_fr_ptr)tokstart;
#if EMACS
    first_char = tokstart->TokPos;
#endif /* EMACS */
    if (LOCAL_Error_TYPE != YAP_NO_ERROR || fe->t == 0)
      return YAP_PARSING_ERROR;
    return YAP_PARSING_FINISHED;
  }

/**
 * @brief generic routine to read terms from a stream
 *
 *
 * @arg inp_stream: where we read from
 * @arg: opts, a list with options
 * @arg: if called from read_term, arity
 *  called from read_clause, -arity
 *
 * @return the term or 0 in case of error.
 *
 * Implementation uses a state machine: default is init, scan, parse, complete.
 *
 *
 */
  Term Yap_read_term(int sno, Term opts, bool clause)
  {
    FEnv fe;
    REnv re;

#if EMACS
    int emacs_cares = FALSE;
#endif

    yap_error_descriptor_t *new = malloc(sizeof *new);
    bool err = Yap_pushErrorContext(true, new);
    int lvl = push_text_stack();
    parser_state_t state = YAP_START_PARSING;
    while (true)
      {
        switch (state)
          {
          case YAP_START_PARSING:
            state = initParser(opts, &fe, &re, sno, clause);
            if (state == YAP_PARSING_FINISHED)
              {
                pop_text_stack(lvl);
                Yap_popErrorContext(err, true);
                return 0;
              }
            break;

          case YAP_SCANNING:
            state = scan(&re, &fe, sno);
            break;

          case YAP_SCANNING_ERROR:
            state = scanError(&re, &fe, sno);
            break;

          case YAP_PARSING:
            state = parse(&re, &fe, sno);
            break;

          case YAP_PARSING_ERROR:
            state = parseError(&re, &fe, sno);
            break;

          case YAP_PARSING_FINISHED: {
            CACHE_REGS
            bool done;
            if (fe.reading_clause)
              done = complete_clause_processing(&fe, LOCAL_tokptr);
            else
              done = complete_processing(&fe, LOCAL_tokptr);
            if (!done)
              {
                state = YAP_PARSING_ERROR;
                fe.t = 0;
                break;
              }
#if EMACS
            first_char = tokstart->TokPos;
#endif /* EMACS */
            pop_text_stack(lvl);
            Yap_popErrorContext(err, true);
            return fe.t;
          }
          }
      }
    Yap_popErrorContext(err, true);
    pop_text_stack(lvl);
    return 0;
  }

  static Int
  read_term2(USES_REGS1) /* '$read'(+Flag,?Term,?Module,?Vars,-Pos,-Err) */
  {
    return Yap_read_term(LOCAL_c_input_stream, add_output(ARG1, ARG2), false) !=
           0;
  }

  static Int read_term(
    USES_REGS1)                    /* '$read2'(+Flag,?Term,?Module,?Vars,-Pos,-Err,+Stream)  */
  {
    int sno;
    Term out;

    /* needs to change LOCAL_output_stream for write */

    sno = Yap_CheckTextStream(ARG1, Input_Stream_f, "read/3");
    if (sno == -1)
      {
        return(FALSE);
      }
    out = Yap_read_term(sno, add_output(ARG2, ARG3), false);
    UNLOCK(GLOBAL_Stream[sno].streamlock);
    return out != 0L;
  }

#define READ_CLAUSE_DEFS()                                              \
  PAR("comments", list_filler, READ_CLAUSE_COMMENTS)                    \
  , PAR("module", isatom, READ_CLAUSE_MODULE),                          \
  PAR("variable_names", filler, READ_CLAUSE_VARIABLE_NAMES),          \
  PAR("variables", filler, READ_CLAUSE_VARIABLES),                    \
  PAR("term_position", filler, READ_CLAUSE_TERM_POSITION),            \
  PAR("syntax_errors", isatom, READ_CLAUSE_SYNTAX_ERRORS),            \
  PAR("output", isatom, READ_CLAUSE_OUTPUT),                          \
  PAR(NULL, ok, READ_CLAUSE_END)

#define PAR(x, y, z) z

  typedef enum read_clause_enum_choices {
    READ_CLAUSE_DEFS()
  } read_clause_choices_t;

#undef PAR

#define PAR(x, y, z)                            \
  { x, y, z }

  static const param_t read_clause_defs[] = { READ_CLAUSE_DEFS() };
#undef PAR

  static xarg *setClauseReadEnv(Term opts, FEnv *fe, struct renv *re, int sno)
  {
    CACHE_REGS

    xarg *args = Yap_ArgListToVector(opts, read_clause_defs, READ_CLAUSE_END,
                                     DOMAIN_ERROR_READ_OPTION);

    if (args == NULL)
      {
        return NULL;
      }
    if (args[READ_CLAUSE_OUTPUT].used)
      {
        fe->t0 = args[READ_CLAUSE_OUTPUT].tvalue;
      }
    else
      {
        fe->t0 = 0;
      }
    if (args[READ_CLAUSE_MODULE].used)
      {
        fe->cmod = args[READ_CLAUSE_MODULE].tvalue;
      }
    else
      {
        fe->cmod = LOCAL_SourceModule;
        if (fe->cmod == TermProlog)
          fe->cmod = PROLOG_MODULE;
      }
    re->bq = getReadTermBackQuotesFlag();
    fe->enc = GLOBAL_Stream[sno].encoding;
    fe->sp = 0;
    fe->qq = 0;
    if (args[READ_CLAUSE_OUTPUT].used)
      {
        fe->t0 = args[READ_CLAUSE_OUTPUT].tvalue;
      }
    else
      {
        fe->t0 = 0;
      }
    if (args[READ_CLAUSE_TERM_POSITION].used)
      {
        fe->tp = args[READ_CLAUSE_TERM_POSITION].tvalue;
      }
    else
      {
        fe->tp = 0;
      }
    fe->sp = 0;
    if (args[READ_CLAUSE_COMMENTS].used)
      {
        fe->tcomms = args[READ_CLAUSE_COMMENTS].tvalue;
      }
    else
      {
        fe->tcomms = 0L;
      }
    if (args[READ_CLAUSE_SYNTAX_ERRORS].used)
      {
        re->sy = args[READ_CLAUSE_SYNTAX_ERRORS].tvalue;
      }
    else
      {
        re->sy = TermDec10;
      }
    fe->vp = 0;
    if (args[READ_CLAUSE_VARIABLE_NAMES].used)
      {
        fe->np = args[READ_CLAUSE_VARIABLE_NAMES].tvalue;
      }
    else
      {
        fe->np = 0;
      }
    if (args[READ_CLAUSE_VARIABLES].used)
      {
        fe->vp = args[READ_CLAUSE_VARIABLES].tvalue;
      }
    else
      {
        fe->vp = 0;
      }
    fe->ce = Yap_CharacterEscapes(fe->cmod);
    re->seekable = (GLOBAL_Stream[sno].status & Seekable_Stream_f) != 0;
    if (re->seekable)
      {
        re->cpos = GLOBAL_Stream[sno].charcount;
      }
    re->prio = LOCAL_default_priority;
    fe->msg = NULL;
    return args;
  }

/**
 * @pred read_clause( +Stream, -Clause, ?Opts) is det
 *
 * Same as read_clause/3, but from the standard input stream.
 *
 */
  static Int read_clause2(USES_REGS1)
  {
    Term ctl = add_output(ARG1, ARG2);

    return Yap_read_term(LOCAL_c_input_stream, ctl, true);
  }

/**
 * @pred read_clause( +Stream, -Clause, ?Opts) is det
 *
 * This predicate receives a set of options _OPts_ based on read_term/3, but
 * specific
 * to readin clauses. The following options are considered:
 *
 *   + The `comments` option unifies its argument with the comments in the
 * term,
 *     represented as strings
 *   + The `process_comments` option calls a hook, it is current ignored by
 * YAP.
 *   + The `term_position` unifies its argument with a term describing the
 *     position of the term.
 *   + The `syntax_errors` flag controls response to syntactic errors, the
 * default is `dec10`.
 *
 * The next two options are called implicitly:
 *
 *   + The `module` option is initialized to the current source module, by
 * default.
 *   + The `singletons` option is set from the single var flag
 */
  static Int read_clause(
    USES_REGS1)                      /* '$read2'(+Flag,?Term,?Module,?Vars,-Pos,-Err,+Stream)  */
  {
    int sno;
    Term out;

    /* needs to change LOCAL_output_stream for write */
    sno = Yap_CheckTextStream(ARG1, Input_Stream_f, "read/3");
    if (sno < 0)
      return false;
    out = Yap_read_term(sno, add_output(ARG2, ARG3), true);
    UNLOCK(GLOBAL_Stream[sno].streamlock);
    return out != 0;
  }

/**
 * start input for a meta-clause. Should obtain:
 *   - predicate name
 *   - predicate arity
 *   - address for 256 cluses.
 *
 * @param  ARG1 input stream
 * @param  ARG2 Adress of predicate.
 * @param  ARG3 Term read.
 * @return            [description]
 */
#if 0
  static Int start_mega(USES_REGS1)
  {
    int sno;
    Term out;
    Term t3 = Deref(ARG3);
    yhandle_t h = Yap_InitSlot(ARG2);
    TokENtry *tok;
    arity_t srity = 0;

    /* needs to change LOCAL_output_stream for write */
    sno = Yap_CheckTextStream(ARG1, Input_Stream_f, "read_exo/3");
    if (sno < 0)
      return false;
    /* preserve   value of H after scanning: otherwise we may lose strings
       and floats */
    LOCAL_tokptr = LOCAL_toktide =
                     x Yap_tokenizer(GLOBAL_Stream + sno, false, &tpos);
    if (tokptr->Tok == Name_tok && (next = tokptr->TokNext) != NULL &&
        next->Tok == Ponctuation_tok && next->TokInfo == TermOpenBracket)
      {
        bool start = true;
        while ((tokptr = next->TokNext))
          {
            if (IsAtomOrIntTerm(t = *tp))
              {
                ip->opc = Yap_opcode(get_atom);
                ip->y_u.x_c.c = t.
                                ip->y_u.x_c.x = tp++; / ()c * /
              }
            else if (IsAtomOrIntTerm(t = *tp))
              {
                (IsAtom(tok->Tokt) || IsIntTerm(XREGS + (i + 1)))extra[arity]
                ]
              }
#endif
  /**
   * @pred source_location( - _File_ , _Line_ )
   *
   * unify  _File_ and  _Line_ wuth the position of the last term read, if the
   * term
   * comes from a stream created by opening a file-system path with open/3 and
   * friends.>position
   * It ignores user_input or
   * sockets.
   *
   * @param - _File_
   * @param - _Line_
   *
   *
   *
   * @note SWI-Prolog built-in.
   */
  static Int source_location(USES_REGS1)
  {
    return Yap_unify(ARG1, MkAtomTerm(LOCAL_SourceFileName)) &&
           Yap_unify(ARG2, MkIntegerTerm(LOCAL_SourceFileLineno));
  }

  /**
   * @pred read(+ Stream, -Term ) is iso
   *
   * Reads term  _T_ from the stream  _S_ instead of from the current input
   * stream.
   *
   * @param - _Stream_
   * @param - _Term_
   *
   */
  static Int read2(
    USES_REGS1)                    /* '$read2'(+Flag,?Term,?Module,?Vars,-Pos,-Err,+Stream)  */
  {
    int sno;
    Int out;

    /* needs to change LOCAL_output_stream for write */
    sno = Yap_CheckTextStream(ARG1, Input_Stream_f, "read/3");
    if (sno == -1)
      {
        return(FALSE);
      }
    out = Yap_read_term(sno, add_output(ARG2, TermNil), false);
    UNLOCK(GLOBAL_Stream[sno].streamlock);
    return out;
  }

  /** @pred  read(- T) is iso

      Reads the next term from the current input stream, and unifies it with
      _T_. The term must be followed by a dot (`.`) and any blank-character
      as previously defined. The syntax of the term must match the current
      declarations for operators (see op). If the end-of-stream is reached,
      _T_ is unified with the atom `end_of_file`. Further reads from of
      the same stream may cause an error failure (see open/3).

   */
  static Int read1(
    USES_REGS1)                    /* '$read2'(+Flag,?Term,?Module,?Vars,-Pos,-Err,+Stream)  */
  {
    Term out = Yap_read_term(LOCAL_c_input_stream, add_output(ARG1, TermNil), 1);

    return out;
  }

  /**  @pred fileerrors

       Switches on the file_errors flag so that in certain error conditions
       Input/Output predicates will produce an appropriated message and abort.

   */
  static Int fileerrors(USES_REGS1)
  {
    return setYapFlag(TermFileErrors, TermTrue);
  }

  /**
     @pred  nofileerrors

     Switches off the `file_errors` flag, so that the predicates see/1,
     tell/1, open/3 and close/1 just fail, instead of producing
     an error message and aborting whenever the specified file cannot be
     opened or closed.

   */
  static Int nofileerrors(
    USES_REGS1)                           /* '$read2'(+Flag,?Term,?Module,?Vars,-Pos,-Err,+Stream)  */
  {
    return setYapFlag(TermFileerrors, TermFalse);
  }

  static Int style_checker(USES_REGS1)
  {
    Term t = Deref(ARG1);

    if (IsVarTerm(t))
      {
        Term t = TermNil;
        if (getYapFlag(MkAtomTerm(AtomSingleVarWarnings)) == TermTrue)
          {
            t = MkPairTerm(MkAtomTerm(AtomSingleVarWarnings), t);
          }
        if (getYapFlag(MkAtomTerm(AtomDiscontiguousWarnings)) == TermTrue)
          {
            t = MkPairTerm(MkAtomTerm(AtomDiscontiguousWarnings), t);
          }
        if (getYapFlag(MkAtomTerm(AtomRedefineWarnings)) == TermTrue)
          {
            t = MkPairTerm(MkAtomTerm(AtomRedefineWarnings), t);
          }
      }
    else
      {
        while (IsPairTerm(t))
          {
            Term h = HeadOfTerm(t);
            t = TailOfTerm(t);

            if (IsVarTerm(h))
              {
                Yap_Error(INSTANTIATION_ERROR, t, "style_check/1");
                return(FALSE);
              }
            else if (IsAtomTerm(h))
              {
                Atom at = AtomOfTerm(h);
                if (at == AtomSingleVarWarnings)
                  setYapFlag(MkAtomTerm(AtomSingleVarWarnings), TermTrue);
                else if (at == AtomDiscontiguousWarnings)
                  setYapFlag(MkAtomTerm(AtomDiscontiguousWarnings), TermTrue);
                else if (at == AtomRedefineWarnings)
                  setYapFlag(MkAtomTerm(AtomRedefineWarnings), TermTrue);
              }
            else
              {
                Atom at = AtomOfTerm(ArgOfTerm(1, h));
                if (at == AtomSingleVarWarnings)
                  setYapFlag(MkAtomTerm(AtomSingleVarWarnings), TermFalse);
                else if (at == AtomDiscontiguousWarnings)
                  setYapFlag(MkAtomTerm(AtomDiscontiguousWarnings), TermFalse);
                else if (at == AtomRedefineWarnings)
                  setYapFlag(MkAtomTerm(AtomRedefineWarnings), TermFalse);
              }
          }
      }
    return TRUE;
  }

  Term Yap_BufferToTerm(const char *s, Term opts)
  {
    Term rval;
    int sno;
    encoding_t l = ENC_ISO_UTF8;

    sno =
      Yap_open_buf_read_stream((char*)s, strlen(s) + 1, &l, MEM_BUF_USER,
                               Yap_LookupAtom(Yap_StrPrefix(s, 16)), TermNone);

    GLOBAL_Stream[sno].status |= CloseOnException_Stream_f;
    rval = Yap_read_term(sno, opts, false);
    Yap_CloseStream(sno);
    return rval;
  }

  Term Yap_UBufferToTerm(const unsigned char *s, Term opts)
  {
    Term rval;
    int sno;
    encoding_t l = ENC_ISO_UTF8;

    sno = Yap_open_buf_read_stream(
      (char*)s, strlen((const char*)s), &l, MEM_BUF_USER,
      Yap_LookupAtom(Yap_StrPrefix((char*)s, 16)), TermNone);
    GLOBAL_Stream[sno].status |= CloseOnException_Stream_f;
    rval = Yap_read_term(sno, opts, false);
    Yap_CloseStream(sno);
    return rval;
  }

  X_API Term Yap_BufferToTermWithPrioBindings(const char *s, Term opts,
                                              Term bindings, size_t len,
                                              int prio)
  {
    CACHE_REGS
    Term ctl;

    ctl = opts;
    if (bindings)
      {
        ctl = add_names(bindings, TermNil);
      }
    if (prio != 1200)
      {
        ctl = add_priority(bindings, ctl);
      }
    return Yap_BufferToTerm(s, ctl);
  }

  /**
   * @pred read_term_from_atom( +Atom , -T , +Options )
   *
   * read a term _T_ stored in constant _Atom_ according to  _Options_
   *
   * @param _Atom_ the source _Atom_
   * @param _T_ the output term _T_, may be any term
   * @param _Options_ read_term/3 options.
   *
   * @note Originally from SWI-Prolog, in YAP only works with internalised
   * atoms
   * Check  read_term_from_atomic/3 for the general version. Also, the built-in
   * is
   * supposed to
   * use YAP's internal encoding, so please avoid the encoding/1 option.
   */
  static Int read_term_from_atom(USES_REGS1)
  {
    Term t1 = Deref(ARG1);
    Atom at;
    const unsigned char *s;

    if (IsVarTerm(t1))
      {
        Yap_Error(INSTANTIATION_ERROR, t1, "style_check/1");
        return false;
      }
    else if (!IsAtomTerm(t1))
      {
        Yap_Error(TYPE_ERROR_ATOM, t1, "style_check/1");
        return false;
      }
    else
      {
        at = AtomOfTerm(t1);
        s = at->UStrOfAE;
      }
    Term ctl = add_output(ARG2, ARG3);

    return Yap_UBufferToTerm(s, ctl);
  }

  /**
   *  @pred read_term_from_atomic( +Atomic , - T , +Options )
   *
   * read a term _T_ stored in text _Atomic_ according to  _Options_
   *
   * @param _Atomic_ the source may be an atom, string, list of codes, or list
   * of
   * chars.
   * @param _T_ the output term _T_, may be any term
   * @param _Options_ read_term/3 options.
   *
   * @notes Idea originally from SWI-Prolog, but in YAP we separate atomic and
   * atom.
   * Encoding is fixed in atoms and strings.
   */
  static Int read_term_from_atomic(USES_REGS1)
  {
    Term t1 = Deref(ARG1);
    const unsigned char *s;

    if (IsVarTerm(t1))
      {
        Yap_Error(INSTANTIATION_ERROR, t1, "read_term_from_atomic/3");
        return(FALSE);
      }
    else if (!IsAtomicTerm(t1))
      {
        Yap_Error(TYPE_ERROR_ATOMIC, t1, "read_term_from_atomic/3");
        return(FALSE);
      }
    else
      {
        Term t = Yap_AtomicToString(t1 PASS_REGS);
        s = UStringOfTerm(t);
      }
    Term ctl = add_output(ARG2, ARG3);

    return Yap_UBufferToTerm(s, ctl);
  }

  /**
   * @pred read_term_from_string( +String , - T , + Options )
   *
   * read a term _T_ stored in constant _String_ according to  _Options_
   *
   * @param _String_ the source _String_
   * @param _T_ the output term _T_, may be any term
   * @param _Options_ read_term/3 options.
   *
   *  Idea from SWI-Prolog, in YAP only works with strings
   * Check  read_term_from_atomic/3 for the general version.
   */
  static Int read_term_from_string(USES_REGS1)
  {
    Term t1 = Deref(ARG1), rc;
    const unsigned char *s;
    size_t len;

    BACKUP_H()
    if (IsVarTerm(t1))
      {
        Yap_Error(INSTANTIATION_ERROR, t1, "read_term_from_string/3");
        return(FALSE);
      }
    else if (!IsStringTerm(t1))
      {
        Yap_Error(TYPE_ERROR_STRING, t1, "read_term_from_string/3");
        return(FALSE);
      }
    else
      {
        s = UStringOfTerm(t1);
        len = strlen_utf8(s);
      }
    char *ss = (char*)s;
    encoding_t enc = ENC_ISO_UTF8;
    int sno = Yap_open_buf_read_stream(ss, len, &enc, MEM_BUF_USER,
                                       Yap_LookupAtom(Yap_StrPrefix(ss, 16)),
                                       TermString);
    GLOBAL_Stream[sno].status |= CloseOnException_Stream_f;
    rc = Yap_read_term(sno, Deref(ARG3), 3);
    Yap_CloseStream(sno);
    RECOVER_H();
    if (!rc)
      return false;
    return Yap_unify(rc, ARG2);
  }

  static Int atomic_to_term(USES_REGS1)
  {
    Term t1 = Deref(ARG1);
    int l = push_text_stack();
    const unsigned char *s = Yap_TextToUTF8Buffer(t1 PASS_REGS);
    Int rc = Yap_UBufferToTerm(s, add_output(ARG2, add_names(ARG3, TermNil)));

    pop_text_stack(l);
    return rc;
  }

  static Int atom_to_term(USES_REGS1)
  {
    Term t1 = Deref(ARG1);

    if (IsVarTerm(t1))
      {
        Yap_Error(INSTANTIATION_ERROR, t1, "read_term_from_string/3");
        return(FALSE);
      }
    else if (!IsAtomTerm(t1))
      {
        Yap_Error(TYPE_ERROR_ATOM, t1, "read_term_from_atomic/3");
        return(FALSE);
      }
    else
      {
        Term t = Yap_AtomicToString(t1 PASS_REGS);
        const unsigned char *us = UStringOfTerm(t);
        return Yap_UBufferToTerm(us, add_output(ARG2, add_names(ARG3, TermNil)));
      }
  }

  static Int string_to_term(USES_REGS1)
  {
    Term t1 = Deref(ARG1);

    if (IsVarTerm(t1))
      {
        Yap_Error(INSTANTIATION_ERROR, t1, "read_term_from_string/3");
        return(FALSE);
      }
    else if (!IsStringTerm(t1))
      {
        Yap_Error(TYPE_ERROR_STRING, t1, "read_term_from_string/3");
        return(FALSE);
      }
    else
      {
        const unsigned char *us = UStringOfTerm(t1);
        return Yap_UBufferToTerm(us, add_output(ARG2, add_names(ARG3, TermNil)));
      }
  }

  void Yap_InitReadTPreds(void)
  {
    Yap_InitCPred("read_term", 2, read_term2, SyncPredFlag);
    Yap_InitCPred("read_term", 3, read_term, SyncPredFlag);

    Yap_InitCPred("scan_to_list", 2, scan_to_list, SyncPredFlag);
    Yap_InitCPred("read", 1, read1, SyncPredFlag);
    Yap_InitCPred("read", 2, read2, SyncPredFlag);
    Yap_InitCPred("read_clause", 2, read_clause2, SyncPredFlag);
    Yap_InitCPred("read_clause", 3, read_clause, 0);
    Yap_InitCPred("read_term_from_atom", 3, read_term_from_atom, 0);
    Yap_InitCPred("read_term_from_atomic", 3, read_term_from_atomic, 0);
    Yap_InitCPred("read_term_from_string", 3, read_term_from_string, 0);
    Yap_InitCPred("atom_to_term", 3, atom_to_term, 0);
    Yap_InitCPred("atomic_to_term", 3, atomic_to_term, 0);
    Yap_InitCPred("string_to_term", 3, string_to_term, 0);

    Yap_InitCPred("fileerrors", 0, fileerrors, SyncPredFlag);
    Yap_InitCPred("nofileeleerrors", 0, nofileerrors, SyncPredFlag);
    Yap_InitCPred("source_location", 2, source_location, SyncPredFlag);
    Yap_InitCPred("$style_checker", 1, style_checker,
                  SyncPredFlag | HiddenPredFlag);
  }