From 261395beaf8a2dba8970a893691ab081687f65f1 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Wed, 19 Jan 2022 14:25:52 +0100
Subject: [PATCH] `rec!` macro; access to `io::Write` inside `Writer`s

---
 .../rust/preserves/src/value/packed/writer.rs | 10 +++++++++
 .../rust/preserves/src/value/repr.rs          | 21 +++++++++++++++++++
 .../rust/preserves/src/value/text/writer.rs   |  8 +++++++
 .../rust/preserves/src/value/writer.rs        |  2 ++
 4 files changed, 41 insertions(+)

diff --git a/implementations/rust/preserves/src/value/packed/writer.rs b/implementations/rust/preserves/src/value/packed/writer.rs
index 4dfecbb..126516d 100644
--- a/implementations/rust/preserves/src/value/packed/writer.rs
+++ b/implementations/rust/preserves/src/value/packed/writer.rs
@@ -268,6 +268,11 @@ impl Writer for BinaryOrderWriter {
         self.push(ptr);
         Ok(())
     }
+
+    #[inline(always)]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
 }
 
 macro_rules! fits_in_bytes {
@@ -522,4 +527,9 @@ impl<W: io::Write> Writer for PackedWriter<W>
         self.resume(ann);
         Ok(())
     }
+
+    #[inline(always)]
+    fn flush(&mut self) -> io::Result<()> {
+        self.0.flush()
+    }
 }
diff --git a/implementations/rust/preserves/src/value/repr.rs b/implementations/rust/preserves/src/value/repr.rs
index b72aa71..9bdbe67 100644
--- a/implementations/rust/preserves/src/value/repr.rs
+++ b/implementations/rust/preserves/src/value/repr.rs
@@ -1533,3 +1533,24 @@ impl<D: Embeddable> NestedValue for DummyValue<D> {
         self.0.1
     }
 }
+
+//---------------------------------------------------------------------------
+
+// https://stackoverflow.com/questions/34304593/counting-length-of-repetition-in-macro/34324856
+#[macro_export]
+//#[allow(unused_macros)]
+macro_rules! count__ {
+    () => (0usize);
+    ( $x:tt $($xs:tt)* ) => (1usize + $crate::count__!($($xs)*));
+}
+
+#[macro_export]
+macro_rules! rec {
+    ( $label:expr $(, $item:expr)* ) => {
+        {
+            let mut r__ = $crate::value::Value::record($label, $crate::count__!($($item)*));
+            $(r__.fields_vec_mut().push($item);)*
+            r__.finish().wrap()
+        }
+    }
+}
diff --git a/implementations/rust/preserves/src/value/text/writer.rs b/implementations/rust/preserves/src/value/text/writer.rs
index a1d2217..71acfc8 100644
--- a/implementations/rust/preserves/src/value/text/writer.rs
+++ b/implementations/rust/preserves/src/value/text/writer.rs
@@ -121,6 +121,10 @@ impl<W: io::Write> TextWriter<W> {
             write!(self.w, " ")
         }
     }
+
+    pub fn borrow_write(&mut self) -> &mut W {
+        &mut self.w
+    }
 }
 
 impl<W: io::Write> CompoundWriter for TextWriter<W> {
@@ -313,4 +317,8 @@ impl<W: io::Write> Writer for TextWriter<W> {
         self.resume(ptr);
         Ok(())
     }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.w.flush()
+    }
 }
diff --git a/implementations/rust/preserves/src/value/writer.rs b/implementations/rust/preserves/src/value/writer.rs
index bbd222e..8cc5fd8 100644
--- a/implementations/rust/preserves/src/value/writer.rs
+++ b/implementations/rust/preserves/src/value/writer.rs
@@ -56,6 +56,8 @@ pub trait Writer: Sized {
     fn start_embedded(&mut self) -> io::Result<Self::EmbeddedWriter>;
     fn end_embedded(&mut self, ptr: Self::EmbeddedWriter) -> io::Result<()>;
 
+    fn flush(&mut self) -> io::Result<()>;
+
     //---------------------------------------------------------------------------
 
     fn write<N: NestedValue, Enc: DomainEncode<N::Embedded>>(