switch from the core prelude to the std prelude

in preparation for no-std support

Author: japaric

rust_crypto_provider/src/aead.rs

@@ -1,3 +1,5 @@
+use alloc::{format, vec::Vec};
+
 use aes_gcm::{Aes128Gcm as RC_Aes128Gcm, Aes256Gcm as RC_Aes256Gcm};
 use chacha20poly1305::{
     aead::{Aead, KeyInit, Payload},

rust_crypto_provider/src/hkdf.rs

@@ -1,3 +1,5 @@
+use alloc::{vec, vec::Vec};
+
 use hkdf::Hkdf;
 use hpke_rs_crypto::error::Error;
 use sha2::{Sha256, Sha384, Sha512};

rust_crypto_provider/src/lib.rs

@@ -1,5 +1,9 @@
 #![doc = include_str!("../Readme.md")]
+#![cfg_attr(not(test), no_std)]
 
+extern crate alloc;
+
+use alloc::{string::String, vec::Vec};
 use core::fmt::Display;
 
 use hpke_rs_crypto::{
@@ -161,7 +165,7 @@ impl HpkeCrypto for HpkeRustCrypto {
     fn prng() -> Self::HpkePrng {
         #[cfg(feature = "deterministic-prng")]
         {
-            let mut fake_rng = vec![0u8; 256];
+            let mut fake_rng = alloc::vec![0u8; 256];
             rand_chacha::ChaCha20Rng::from_entropy().fill_bytes(&mut fake_rng);
             HpkeRustCryptoPrng {
                 fake_rng,