correct peek_byte/2 bugs (#1882)

src/machine/streams.rs

@@ -1268,12 +1268,9 @@ impl Stream {
                 }
             }
             Stream::InputFile(ref mut file) => {
-                let mut b = [0u8; 1];
-
-                match file.read(&mut b)? {
-                    1 => {
-                        file.stream.get_mut().file.seek(SeekFrom::Current(-1))?;
-                        Ok(b[0])
+                match file.peek_byte() {
+                    Some(result) => {
+                        Ok(result?)
                     }
                     _ => Err(std::io::Error::new(
                         ErrorKind::UnexpectedEof,

src/machine/system_calls.rs

@@ -2444,7 +2444,11 @@ impl Machine {
                 addr,
             );
 
-            return Ok(());
+            if !self.machine_st.fail {
+                return Ok(());
+            } else {
+                self.machine_st.fail = false;
+            }
         }
 
         let addr = match addr {

src/parser/char_reader.rs

@@ -128,6 +128,19 @@ impl<R: Read> CharReader<R> {
 
         Ok(&self.buf[self.pos..])
     }
+
+    pub fn peek_byte(&mut self) -> Option<io::Result<u8>> {
+        match self.refresh_buffer() {
+            Ok(_buf) => {}
+            Err(e) => return Some(Err(e)),
+        }
+
+        return if let Some(b) = self.buf.get(0).cloned() {
+            Some(Ok(b))
+        } else {
+            None
+        };
+    }
 }
 
 impl<R: Read> CharRead for CharReader<R> {