Reorganize and refactor, adding integration test for common library stuff

common/src/io.rs

@@ -0,0 +1,36 @@
+use std::io::{Error, ErrorKind, Read, Write};
+
+/// The saslauthd protocol transmits strings as
+/// 16-bit unsigned network-byte-order lengths followed
+/// by the string itself.
+///
+pub fn read_string(stream: &mut impl Read) -> Result<String, Error> {
+    let mut length_buffer = [0u8, 0u8];
+
+    stream.read_exact(&mut length_buffer)?;
+    let length = u16::from_be_bytes(length_buffer);
+
+    let mut string_buffer = vec![0u8; length as usize];
+
+    stream.read_exact(&mut string_buffer)?;
+
+    match String::from_utf8(string_buffer) {
+        Ok(str) => Ok(str),
+        Err(_err) => Err(Error::new(ErrorKind::Other, "Invalid UTF-8 sent")),
+    }
+}
+
+pub fn write_string(stream: &mut impl Write, s: &str) -> Result<(), Error> {
+    let length = s.len();
+
+    if length > 0xffff {
+        return Err(Error::new(ErrorKind::Other, "String too long to write"));
+    }
+
+    let length_buffer = [(length >> 8) as u8, (length & 0xff) as u8];
+
+    stream.write_all(&length_buffer)?;
+    stream.write_all(s.as_bytes())?;
+
+    Ok(())
+}