From c1df7ead1a7001615cf82d0db1cd87425516e0eb Mon Sep 17 00:00:00 2001
From: Mark Thom <markjordanthom@gmail.com>
Date: Sun, 10 May 2020 14:50:17 -0600
Subject: [PATCH] set past end of stream, set Byte to -1, Char and Code to
 end_of_file, at end of stream (#479)

---
 src/prolog/machine/streams.rs      |  8 +++-
 src/prolog/machine/system_calls.rs | 60 ++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/src/prolog/machine/streams.rs b/src/prolog/machine/streams.rs
index 7542bec9..1eefe581 100644
--- a/src/prolog/machine/streams.rs
+++ b/src/prolog/machine/streams.rs
@@ -59,7 +59,7 @@ pub enum EOFAction {
     Reset,
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub enum AtEndOfStream {
     Not,
     At,
@@ -328,6 +328,12 @@ impl Stream {
         self.stream_inst.0.borrow_mut().0
     }
 
+    #[inline]
+    pub(crate)
+    fn at_end_of_stream(&mut self) -> bool {
+        self.position_relative_to_end() == AtEndOfStream::At
+    }
+
     #[inline]
     pub(crate)
     fn set_past_end_of_stream(&mut self) {
diff --git a/src/prolog/machine/system_calls.rs b/src/prolog/machine/system_calls.rs
index 0f02d141..b1abfdd2 100644
--- a/src/prolog/machine/system_calls.rs
+++ b/src/prolog/machine/system_calls.rs
@@ -1190,6 +1190,12 @@ impl MachineState {
                     }
                 }
 
+                if stream.at_end_of_stream() {
+                    stream.set_past_end_of_stream();
+                    self.unify(self[temp_v!(2)], Addr::Fixnum(-1));
+                    return return_from_clause!(self.last_call, self);
+                }
+
                 let addr =
                     match self.store(self.deref(self[temp_v!(2)])) {
                         addr if addr.is_ref() => {
@@ -1287,6 +1293,18 @@ impl MachineState {
                     }
                 }
 
+                if stream.at_end_of_stream() {
+                    let end_of_file = clause_name!("end_of_file");
+                    let end_of_file = self.heap.to_unifiable(
+                        HeapCellValue::Atom(end_of_file, None),
+                    );
+
+                    stream.set_past_end_of_stream();
+
+                    self.unify(self[temp_v!(2)], end_of_file);
+                    return return_from_clause!(self.last_call, self);
+                }
+
                 let addr =
                     match self.store(self.deref(self[temp_v!(2)])) {
                         addr if addr.is_ref() => {
@@ -1385,6 +1403,18 @@ impl MachineState {
                     }
                 }
 
+                if stream.at_end_of_stream() {
+                    let end_of_file = clause_name!("end_of_file");
+                    let end_of_file = self.heap.to_unifiable(
+                        HeapCellValue::Atom(end_of_file, None),
+                    );
+
+                    stream.set_past_end_of_stream();
+
+                    self.unify(self[temp_v!(2)], end_of_file);
+                    return return_from_clause!(self.last_call, self);
+                }
+
                 let addr =
                     match self.store(self.deref(self[temp_v!(2)])) {
                         addr if addr.is_ref() => {
@@ -2076,6 +2106,12 @@ impl MachineState {
                     }
                 }
 
+                if stream.at_end_of_stream() {
+                    stream.set_past_end_of_stream();
+                    self.unify(self[temp_v!(2)], Addr::Fixnum(-1));
+                    return return_from_clause!(self.last_call, self);
+                }
+
                 let addr =
                     match self.store(self.deref(self[temp_v!(2)])) {
                         addr if addr.is_ref() => {
@@ -2171,6 +2207,18 @@ impl MachineState {
                     }
                 }
 
+                if stream.at_end_of_stream() {
+                    let end_of_file = clause_name!("end_of_file");
+                    let end_of_file = self.heap.to_unifiable(
+                        HeapCellValue::Atom(end_of_file, None),
+                    );
+
+                    stream.set_past_end_of_stream();
+
+                    self.unify(self[temp_v!(2)], end_of_file);
+                    return return_from_clause!(self.last_call, self);
+                }
+
                 let mut iter = self.open_parsing_stream(
                     stream.clone(),
                     "get_char",
@@ -2273,6 +2321,18 @@ impl MachineState {
                     }
                 }
 
+                if stream.at_end_of_stream() {
+                    let end_of_file = clause_name!("end_of_file");
+                    let end_of_file = self.heap.to_unifiable(
+                        HeapCellValue::Atom(end_of_file, None),
+                    );
+
+                    stream.set_past_end_of_stream();
+
+                    self.unify(self[temp_v!(2)], end_of_file);
+                    return return_from_clause!(self.last_call, self);
+                }
+
                 let addr =
                     match self.store(self.deref(self[temp_v!(2)])) {
                         addr if addr.is_ref() => {
-- 
2.54.0