implement access_file/2 in C

C/iopreds.c

@@ -2332,6 +2332,75 @@ p_access(void)
   }
 }
 
+static Int
+p_access2(void)
+{
+  Term tname = Deref(ARG1);
+  Term tmode = Deref(ARG2);
+  char ares[YAP_FILENAME_MAX];
+  Atom atmode;
+
+  if (IsVarTerm(tmode)) {
+    Yap_Error(INSTANTIATION_ERROR, tmode, "access");
+    return FALSE;
+  } else if (!IsAtomTerm (tmode)) {
+    Yap_Error(TYPE_ERROR_ATOM, tname, "access");
+    return FALSE;
+  }
+  atmode = AtomOfTerm(tmode);
+  if (IsVarTerm(tname)) {
+    Yap_Error(INSTANTIATION_ERROR, tname, "access");
+    return FALSE;
+  } else if (!IsAtomTerm (tname)) {
+    Yap_Error(TYPE_ERROR_ATOM, tname, "access");
+    return FALSE;
+  } else {
+    if (atmode == AtomNone)
+      return TRUE;
+    if (!Yap_TrueFileName (RepAtom(AtomOfTerm(tname))->StrOfAE, ares, (atmode == AtomCsult)))
+      return FALSE;
+  }
+#if HAVE_ACCESS
+  {
+    int mode;
+
+    if (atmode == AtomExist)
+      mode = F_OK;
+    else if (atmode == AtomWrite)
+      mode = W_OK;
+    else if (atmode == AtomRead)
+      mode = R_OK;
+    else if (atmode == AtomAppend)
+      mode = W_OK;
+    else if (atmode == AtomCsult)
+      mode = R_OK;
+    else if (atmode == AtomExecute)
+      mode = X_OK;
+    else {
+      Yap_Error(DOMAIN_ERROR_IO_MODE, tmode, "access_file/2");
+      return FALSE;   
+    }
+    if (access(ares, mode) != 0) {
+      /* ignore errors while checking a file */
+      return FALSE;
+    }
+    return TRUE;
+  }
+#elif HAVE_STAT
+  {
+    struct SYSTEM_STAT ss;
+
+    if (SYSTEM_STAT(ares, &ss) != 0) {
+    /* ignore errors while checking a file */
+      return FALSE;
+    }
+    return TRUE;
+  }
+#else
+  return FALSE;
+#endif
+}
+
 static Int
 p_exists_directory(void)
 {
@@ -6455,6 +6524,7 @@ Yap_InitIOPreds(void)
   Yap_InitCPred ("get0", 2, p_get0, SafePredFlag|SyncPredFlag|HiddenPredFlag);
   Yap_InitCPred ("$get0_line_codes", 2, p_get0_line_codes, SafePredFlag|SyncPredFlag|HiddenPredFlag);
   Yap_InitCPred ("$get_byte", 2, p_get_byte, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred ("access_file", 2, p_access2, SafePredFlag|HiddenPredFlag);
   Yap_InitCPred ("$access", 1, p_access, SafePredFlag|SyncPredFlag|HiddenPredFlag);
   Yap_InitCPred ("exists_directory", 1, p_exists_directory, SafePredFlag|SyncPredFlag);
   Yap_InitCPred ("$open", 6, p_open, SafePredFlag|SyncPredFlag|HiddenPredFlag);

H/iatoms.h

@@ -90,10 +90,12 @@
   AtomError = Yap_LookupAtom("error");
   AtomEvaluable = Yap_LookupAtom("evaluable");
   AtomEvaluationError = Yap_LookupAtom("evaluation_error");
+  AtomExecute = Yap_LookupAtom("execute");
   AtomExecAnswers = Yap_LookupAtom("exec_answers");
   AtomExecuteInMod = Yap_FullLookupAtom("$execute_in_mod");
   AtomExecuteWithin = Yap_FullLookupAtom("$execute_within");
   AtomExecuteWoMod = Yap_FullLookupAtom("$execute_wo_mod");
+  AtomExist = Yap_LookupAtom("exist");
   AtomExistenceError = Yap_LookupAtom("existence_error");
   AtomExpectedNumber = Yap_LookupAtom("expected_number_syntax");
   AtomExtendFileSearchPath = Yap_FullLookupAtom("$extend_file_search_path");
@@ -172,6 +174,7 @@
   AtomNbTerm = Yap_LookupAtom("nb_term");
   AtomNew = Yap_LookupAtom("new");
   AtomNoMemory = Yap_LookupAtom("no_memory");
+  AtomNone = Yap_LookupAtom("none");
   AtomNonEmptyList = Yap_LookupAtom("non_empty_list");
   AtomNot = Yap_LookupAtom("\\+");
   AtomNotImplemented = Yap_LookupAtom("not_implemented");

H/ratoms.h

@@ -90,10 +90,12 @@
   AtomError = AtomAdjust(AtomError);
   AtomEvaluable = AtomAdjust(AtomEvaluable);
   AtomEvaluationError = AtomAdjust(AtomEvaluationError);
+  AtomExecute = AtomAdjust(AtomExecute);
   AtomExecAnswers = AtomAdjust(AtomExecAnswers);
   AtomExecuteInMod = AtomAdjust(AtomExecuteInMod);
   AtomExecuteWithin = AtomAdjust(AtomExecuteWithin);
   AtomExecuteWoMod = AtomAdjust(AtomExecuteWoMod);
+  AtomExist = AtomAdjust(AtomExist);
   AtomExistenceError = AtomAdjust(AtomExistenceError);
   AtomExpectedNumber = AtomAdjust(AtomExpectedNumber);
   AtomExtendFileSearchPath = AtomAdjust(AtomExtendFileSearchPath);
@@ -172,6 +174,7 @@
   AtomNbTerm = AtomAdjust(AtomNbTerm);
   AtomNew = AtomAdjust(AtomNew);
   AtomNoMemory = AtomAdjust(AtomNoMemory);
+  AtomNone = AtomAdjust(AtomNone);
   AtomNonEmptyList = AtomAdjust(AtomNonEmptyList);
   AtomNot = AtomAdjust(AtomNot);
   AtomNotImplemented = AtomAdjust(AtomNotImplemented);

H/tatoms.h

@@ -178,6 +178,8 @@
 #define AtomEvaluable Yap_heap_regs->AtomEvaluable_
   Atom AtomEvaluationError_;
 #define AtomEvaluationError Yap_heap_regs->AtomEvaluationError_
+  Atom AtomExecute_;
+#define AtomExecute Yap_heap_regs->AtomExecute_
   Atom AtomExecAnswers_;
 #define AtomExecAnswers Yap_heap_regs->AtomExecAnswers_
   Atom AtomExecuteInMod_;
@@ -186,6 +188,8 @@
 #define AtomExecuteWithin Yap_heap_regs->AtomExecuteWithin_
   Atom AtomExecuteWoMod_;
 #define AtomExecuteWoMod Yap_heap_regs->AtomExecuteWoMod_
+  Atom AtomExist_;
+#define AtomExist Yap_heap_regs->AtomExist_
   Atom AtomExistenceError_;
 #define AtomExistenceError Yap_heap_regs->AtomExistenceError_
   Atom AtomExpectedNumber_;
@@ -342,6 +346,8 @@
 #define AtomNew Yap_heap_regs->AtomNew_
   Atom AtomNoMemory_;
 #define AtomNoMemory Yap_heap_regs->AtomNoMemory_
+  Atom AtomNone_;
+#define AtomNone Yap_heap_regs->AtomNone_
   Atom AtomNonEmptyList_;
 #define AtomNonEmptyList Yap_heap_regs->AtomNonEmptyList_
   Atom AtomNot_;

misc/ATOMS

@@ -95,10 +95,12 @@ A	Eq			N	"="
 A	Error			N	"error"
 A	Evaluable		N	"evaluable"
 A	EvaluationError		N	"evaluation_error"
+A	Execute			N	"execute"
 A	ExecAnswers		N	"exec_answers"
 A	ExecuteInMod		F	"$execute_in_mod"
 A	ExecuteWithin		F	"$execute_within"
 A	ExecuteWoMod		F	"$execute_wo_mod"
+A	Exist			N	"exist"
 A	ExistenceError		N	"existence_error"
 A	ExpectedNumber		N	"expected_number_syntax"
 A	ExtendFileSearchPath	F	"$extend_file_search_path"
@@ -177,6 +179,7 @@ A	Nb			N	"nb"
 A	NbTerm			N	"nb_term"
 A	New			N	"new"
 A	NoMemory		N	"no_memory"
+A	None			N	"none"
 A	NonEmptyList		N	"non_empty_list"
 A	Not			N	"\\+"
 A	NotImplemented		N	"not_implemented"

pl/boot.yap

@@ -1120,29 +1120,6 @@ bootstrap(F) :-
 	'$do_error'(type_error(callable,H),P).
 '$check_head'(_,_).
 
-% Path predicates
-
-access_file(F,Mode) :-
-	'$exists'(F,Mode).
-
-'$exists'(_,none) :- !.
-'$exists'(F,exist) :- !,
-	'$access'(F).
-'$exists'(F,Mode) :-
-	get_value(fileerrors,V),
-	set_value(fileerrors,0),
-	operating_system_support:true_file_name(F, F1),
-	(
-	 '$open'(F1, Mode, S, 0, 1, F)
-	->
-	 '$close'(S),
-	 set_value(fileerrors,V)
-	;
-	 set_value(fileerrors,V),
-	 fail
-	).
-
-
 % term expansion
 %
 % return two arguments: Expanded0 is the term after "USER" expansion.