Add size_hint in ser and call size_hint in all message serializers

[rust-lightning] / src / util / ser.rs

diff --git a/src/util/ser.rs b/src/util/ser.rs
index 6c40820905adf7291fb31e60debbbe22278a42f7..fe92332dfe93571636284687d345b6cb4f83f230 100644 (file)
--- a/src/util/ser.rs
+++ b/src/util/ser.rs
@@ -14,17 +14,25 @@ use util::byte_utils::{be64_to_array, be32_to_array, be16_to_array, slice_to_be1
 
 const MAX_BUF_SIZE: usize = 64 * 1024;
 
-/// A trait that is similar to std::io::Write.
-/// An impl is provided for any type that also impls std::io::Write.
+/// A trait that is similar to std::io::Write but has one extra function which can be used to size
+/// buffers being written into.
+/// An impl is provided for any type that also impls std::io::Write which simply ignores size
+/// hints.
 pub trait Writer {
        /// Writes the given buf out. See std::io::Write::write_all for more
        fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error>;
+       /// Hints that data of the given size is about the be written. This may not always be called
+       /// prior to data being written and may be safely ignored.
+       fn size_hint(&mut self, size: usize);
 }
 
 impl<W: ::std::io::Write> Writer for W {
+       #[inline]
        fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
                <Self as ::std::io::Write>::write_all(self, buf)
        }
+       #[inline]
+       fn size_hint(&mut self, _size: usize) { }
 }
 
 /// A trait that various rust-lightning types implement allowing them to be written out to a Writer