Depend on our new io crate

Remove the optional dependency on `core2` and add an optional dependency
on the new `bitcoin-io` crate.

Note we never need to enable the "std" or "alloc" features in `io`.

Cargo.toml

@@ -27,10 +27,9 @@ alloc = []
 [dependencies]
 arrayvec = { version = "0.7", default-features = false }
 
-core2 = { version = "0.3.2", default-features = false, optional = true }
+io = { package = "bitcoin-io", version = "0.1.0", default-features = false, optional = true }
 serde = { version = "1.0", default-features = false, optional = true }
 
-
 [dev-dependencies]
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
@@ -50,3 +49,6 @@ name = "wrap_array_fmt_traits"
 [[example]]
 name = "serde"
 required-features = ["std", "serde"]
+
+[patch.crates-io.bitcoin-io]
+path = "../../rust-bitcoin/master/io"

contrib/test.sh

@@ -2,7 +2,7 @@
 
 set -ex
 
-FEATURES="std alloc core2 serde"
+FEATURES="std alloc io serde"
 MSRV="1\.48\.0"
 
 cargo --version

src/iter.rs

@@ -4,11 +4,6 @@
 
 use core::iter::FusedIterator;
 use core::str;
-#[cfg(feature = "std")]
-use std::io;
-
-#[cfg(all(feature = "core2", not(feature = "std")))]
-use core2::io;
 
 use crate::error::{InvalidCharError, OddLengthStringError};
 
@@ -76,7 +71,7 @@ impl<'a> ExactSizeIterator for HexToBytesIter<'a> {
 
 impl<'a> FusedIterator for HexToBytesIter<'a> {}
 
-#[cfg(any(feature = "std", feature = "core2"))]
+#[cfg(feature = "io")]
 impl<'a> io::Read for HexToBytesIter<'a> {
     #[inline]
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {