decouple ToBytes into a separate crate

crates/to-bytes/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "it-to-bytes"
+version = "0.1.0"
+authors = ["Fluence Labs"]
+description = "Defines trait ToBytes used for IT serialization"
+edition = "2018"
+license = "Apache-2.0"

crates/to-bytes/src/lib.rs

@@ -0,0 +1,104 @@
+use std::io;
+use std::io::Write;
+
+/// A trait for converting a value to bytes.
+pub trait ToBytes<W>
+where
+    W: Write,
+{
+    /// Converts the given value into `&[u8]` in the given `writer`.
+    fn to_bytes(&self, writer: &mut W) -> io::Result<()>;
+}
+
+/// Encode a `u8` into a byte (well, it's already a byte!).
+impl<W> ToBytes<W> for u8
+where
+    W: Write,
+{
+    fn to_bytes(&self, writer: &mut W) -> io::Result<()> {
+        writer.write_all(&[*self])
+    }
+}
+
+/// Encode a `u64` into bytes with a LEB128 representation.
+///
+/// Decoder is `decoders::binary::uleb`.
+impl<W> ToBytes<W> for u64
+where
+    W: Write,
+{
+    fn to_bytes(&self, writer: &mut W) -> io::Result<()> {
+        let mut value = *self;
+
+        // Code adapted from the Rust' `serialize` library.
+        loop {
+            if value < 0x80 {
+                writer.write_all(&[value as u8])?;
+
+                break;
+            }
+
+            writer.write_all(&[((value & 0x7f) | 0x80) as u8])?;
+            value >>= 7;
+        }
+
+        Ok(())
+    }
+}
+
+/// Encode a `str` into bytes.
+///
+/// Decoder is `decoders::binary::string`.
+impl<W> ToBytes<W> for &str
+where
+    W: Write,
+{
+    fn to_bytes(&self, writer: &mut W) -> io::Result<()> {
+        // Size first.
+        writer.write_all(&[self.len() as u8])?;
+
+        // Then the string.
+        writer.write_all(self.as_bytes())?;
+
+        Ok(())
+    }
+}
+
+/// Encode a String into bytes.
+///
+/// Decoder is `decoders::binary::string`.
+impl<W> ToBytes<W> for String
+where
+    W: Write,
+{
+    fn to_bytes(&self, writer: &mut W) -> io::Result<()> {
+        // Size first.
+        writer.write_all(&[self.len() as u8])?;
+
+        // Then the string.
+        writer.write_all(self.as_bytes())?;
+
+        Ok(())
+    }
+}
+
+/// Encode a vector into bytes.
+///
+/// Decoder is `decoders::binary::list`.
+impl<W, I> ToBytes<W> for Vec<I>
+where
+    W: Write,
+    I: ToBytes<W>,
+{
+    fn to_bytes(&self, writer: &mut W) -> io::Result<()> {
+        // Size first.
+        (self.len() as u64).to_bytes(writer)?;
+
+        // Then the items.
+        for item in self {
+            item.to_bytes(writer)?;
+        }
+
+        Ok(())
+    }
+}