avoid arena allocation of stream in read_term_from_chars (#1266)

src/arena.rs

@@ -698,9 +698,9 @@ unsafe fn drop_slab_in_place(value: &mut AllocSlab) {
         ArenaHeaderTag::HttpReadStream => {
             ptr::drop_in_place(value.payload_offset::<StreamLayout<CharReader<HttpReadStream>>>());
         }
-	ArenaHeaderTag::HttpWriteStream => {
-	    ptr::drop_in_place(value.payload_offset::<StreamLayout<CharReader<HttpWriteStream>>>());
-	}
+	    ArenaHeaderTag::HttpWriteStream => {
+	        ptr::drop_in_place(value.payload_offset::<StreamLayout<CharReader<HttpWriteStream>>>());
+	    }
         ArenaHeaderTag::ReadlineStream => {
             ptr::drop_in_place(value.payload_offset::<StreamLayout<ReadlineStream>>());
         }
@@ -721,12 +721,12 @@ unsafe fn drop_slab_in_place(value: &mut AllocSlab) {
         ArenaHeaderTag::TcpListener => {
             ptr::drop_in_place(value.payload_offset::<TcpListener>());
         }
-	ArenaHeaderTag::HttpListener => {
-	    ptr::drop_in_place(value.payload_offset::<HttpListener>());
-	}
-	ArenaHeaderTag::HttpResponse => {
-	    ptr::drop_in_place(value.payload_offset::<HttpResponse>());
-	}
+	    ArenaHeaderTag::HttpListener => {
+	        ptr::drop_in_place(value.payload_offset::<HttpListener>());
+	    }
+	    ArenaHeaderTag::HttpResponse => {
+	        ptr::drop_in_place(value.payload_offset::<HttpResponse>());
+	    }
         ArenaHeaderTag::StandardOutputStream => {
             ptr::drop_in_place(value.payload_offset::<StreamLayout<StandardOutputStream>>());
         }

src/machine/streams.rs

@@ -102,6 +102,13 @@ impl EOFAction {
 #[derive(Debug)]
 pub struct ByteStream(Cursor<Vec<u8>>);
 
+impl ByteStream {
+    #[inline(always)]
+    pub fn from_string(string: String) -> Self {
+        ByteStream(Cursor::new(string.into()))
+    }
+}
+
 impl Read for ByteStream {
     #[inline]
     fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
@@ -1132,14 +1139,14 @@ impl Stream {
 
                 Ok(())
             }
-	    Stream::HttpWrite(ref mut http_stream) => {
+	        Stream::HttpWrite(ref mut http_stream) => {
                 unsafe {
                     http_stream.set_tag(ArenaHeaderTag::Dropped);
                     std::ptr::drop_in_place(&mut http_stream.inner_mut().body_writer as *mut _);
                 }
 
                 Ok(())
-	    }
+	        }
             Stream::InputFile(mut file_stream) => {
                 // close the stream by dropping the inner File.
                 unsafe {

src/machine/system_calls.rs

@@ -5138,10 +5138,20 @@ impl Machine {
     #[inline(always)]
     pub(crate) fn read_term_from_chars(&mut self) -> CallResult {
         if let Some(atom_or_string) = self.machine_st.value_to_str_like(self.machine_st.registers[1]) {
-            let chars = atom_or_string.to_string();
-            let stream = Stream::from_owned_string(chars, &mut self.machine_st.arena);
+            let chars = CharReader::new(ByteStream::from_string(atom_or_string.to_string()));
+            let mut parser = Parser::new(chars, &mut self.machine_st);
 
-            let term_write_result = match self.machine_st.read(stream, &self.indices.op_dir) {
+            let term_write_result = parser.read_term(&CompositeOpDir::new(&self.indices.op_dir, None))
+                .map_err(CompilationError::from)
+                .and_then(|term| {
+                    write_term_to_heap(
+                        &term,
+                        &mut self.machine_st.heap,
+                        &mut self.machine_st.atom_tbl,
+                    )
+                });
+
+            let term_write_result = match term_write_result {
                 Ok(term_write_result) => term_write_result,
                 Err(e) => {
                     let stub = functor_stub(atom!("read_term_from_chars"), 2);