Move UntrustedString and PrintableString to lightning-types

`lightning-invoice` currently has a dependency on the entire
`lightning` crate just because it wants to use some of the useful
types from it. This is obviously backwards and leads to some
awkwardness like the BOLT 11 invoice signing API in the `lightning`
crate taking a `[u5]` rather than a `Bolt11Invoice`.

This takes one more step, moving the `UntrustedString` and
`PrintableString` types to `lightning-types`.

Author: TheBlueMatt

lightning-types/src/lib.rs

@@ -26,3 +26,4 @@ extern crate core;
 pub mod features;
 pub mod payment;
 pub mod routing;
+pub mod string;

lightning/src/util/string.rs renamed to lightning-types/src/string.rs

@@ -9,31 +9,13 @@
 
 //! Utilities for strings.
 
+use alloc::string::String;
 use core::fmt;
-use crate::io::{self, Read};
-use crate::ln::msgs;
-use crate::util::ser::{Writeable, Writer, Readable};
-
-#[allow(unused_imports)]
-use crate::prelude::*;
 
 /// Struct to `Display` fields in a safe way using `PrintableString`
 #[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, Default)]
 pub struct UntrustedString(pub String);
 
-impl Writeable for UntrustedString {
-	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
-		self.0.write(w)
-	}
-}
-
-impl Readable for UntrustedString {
-	fn read<R: Read>(r: &mut R) -> Result<Self, msgs::DecodeError> {
-		let s: String = Readable::read(r)?;
-		Ok(Self(s))
-	}
-}
-
 impl fmt::Display for UntrustedString {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		PrintableString(&self.0).fmt(f)

lightning/src/util/mod.rs

@@ -21,7 +21,6 @@ pub mod message_signing;
 pub mod invoice;
 pub mod persist;
 pub mod scid_utils;
-pub mod string;
 pub mod sweep;
 pub mod wakers;
 #[cfg(fuzzing)]
@@ -54,3 +53,7 @@ pub mod test_utils;
 #[cfg(any(test, feature = "_test_utils"))]
 pub mod test_channel_signer;
 
+pub mod string {
+	//! Utilities to wrap untrusted strings and handle them (more) safely
+	pub use lightning_types::string::{PrintableString, UntrustedString};
+}

lightning/src/util/ser.rs

@@ -627,6 +627,18 @@ impl<'a> From<&'a String> for WithoutLength<&'a String> {
 	fn from(s: &'a String) -> Self { Self(s) }
 }
 
+impl Writeable for UntrustedString {
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		self.0.write(w)
+	}
+}
+
+impl Readable for UntrustedString {
+	fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
+		let s: String = Readable::read(r)?;
+		Ok(Self(s))
+	}
+}
 
 impl Writeable for WithoutLength<&UntrustedString> {
 	#[inline]