f expose hex for no-std

Author: devrandom

Cargo.toml

@@ -17,6 +17,8 @@ path = "src/lib.rs"
 [features]
 default = [ "std" ]
 std = []
+# The no-std feature enables core2 and alloc.
+# You can still just disable std by disabling default features, without enabling these two.
 no-std = ["core2/alloc"]
 serde-std = ["serde/std"]
 unstable = []  # for benchmarking

src/hex.rs

@@ -15,6 +15,9 @@
 //! # Hex encoding and decoding
 //!
 
+#[cfg(feature = "no-std")]
+use alloc::{format, string::String, vec::Vec};
+
 use core::{fmt, str};
 use Hash;
 
@@ -40,7 +43,7 @@ impl fmt::Display for Error {
 }
 
 /// Trait for objects that can be serialized as hex strings
-#[cfg(any(test, feature = "std"))]
+#[cfg(any(test, feature = "std", feature = "no-std"))]
 pub trait ToHex {
     /// Hex representation of the object
     fn to_hex(&self) -> String;
@@ -60,7 +63,7 @@ pub trait FromHex: Sized {
     }
 }
 
-#[cfg(any(test, feature = "std"))]
+#[cfg(any(test, feature = "std", feature = "no-std"))]
 impl<T: fmt::LowerHex> ToHex for T {
     /// Outputs the hash in hexadecimal form
     fn to_hex(&self) -> String {
@@ -174,7 +177,7 @@ pub fn format_hex_reverse(data: &[u8], f: &mut fmt::Formatter) -> fmt::Result {
     Ok(())
 }
 
-#[cfg(any(test, feature = "std"))]
+#[cfg(any(test, feature = "std", feature = "no-std"))]
 impl ToHex for [u8] {
     fn to_hex(&self) -> String {
         use core::fmt::Write;
@@ -186,7 +189,7 @@ impl ToHex for [u8] {
     }
 }
 
-#[cfg(any(test, feature = "std"))]
+#[cfg(any(test, feature = "std", feature = "no-std"))]
 impl FromHex for Vec<u8> {
     fn from_byte_iter<I>(iter: I) -> Result<Self, Error>
         where I: Iterator<Item=Result<u8, Error>> +

src/impls.rs

@@ -19,7 +19,7 @@
 #[cfg(feature = "std")]
 use std::{error, io};
 
-#[cfg(feature = "no-std")]
+#[cfg(not(feature = "std"))]
 use core2::{error, io};
 
 use {hex, sha1, sha256, sha512, ripemd160, siphash24};

src/lib.rs

@@ -39,6 +39,7 @@
 
 #[cfg(any(test, feature="std"))] extern crate core;
 #[cfg(feature="no-std")] extern crate core2;
+#[cfg(feature="no-std")] extern crate alloc;
 #[cfg(feature="serde")] pub extern crate serde;
 #[cfg(all(test,feature="serde"))] extern crate serde_test;
 
@@ -54,6 +55,7 @@ pub mod _export {
 
 #[macro_use] mod util;
 #[macro_use] pub mod serde_macros;
+#[cfg(any(feature = "std", feature = "no-std"))]
 mod impls;
 pub mod error;
 pub mod hex;