Use alloc instead of std when possible.

STYLE.md

@@ -88,7 +88,7 @@ The C code generally uses the C `int` type as a return value, where 1 indicates
 success and 0 indicates failure. The module [ring::bssl](src/bssl.rs) contains
 a [transparent] `Result` type which should be used as the return type when
 declaring foreign functions which follow this convention. A
-`ring::bssl::Result` should be converted to a `std::result::Result` using the
+`ring::bssl::Result` should be converted to a `core::result::Result` using the
 pattern in the following example (note the placement of `unsafe`):
 
 [transparent]: https://doc.rust-lang.org/nightly/reference/type-layout.html#the-transparent-representation

src/aead/chacha.rs

@@ -142,8 +142,8 @@ pub const KEY_LEN: usize = KEY_BLOCKS * BLOCK_LEN;
 mod tests {
     use super::*;
     use crate::test;
+    use alloc::vec;
     use core::convert::TryInto;
-    use std::vec;
 
     // This verifies the encryption functionality provided by ChaCha20_ctr32
     // is successful when either computed on disjoint input/output buffers,

src/arithmetic.rs

@@ -14,5 +14,8 @@
 
 #[macro_use]
 pub mod constant;
+
+#[cfg(feature = "use_heap")]
 pub mod bigint;
+
 pub mod montgomery;

src/arithmetic/bigint.rs

@@ -43,11 +43,11 @@ use crate::{
     bits, bssl, c, error,
     limb::{self, Limb, LimbMask, LIMB_BITS, LIMB_BYTES},
 };
+use alloc::{borrow::ToOwned as _, boxed::Box, vec, vec::Vec};
 use core::{
     marker::PhantomData,
     ops::{Deref, DerefMut},
 };
-use std::{borrow::ToOwned as _, boxed::Box, vec, vec::Vec};
 use untrusted;
 
 pub unsafe trait Prime {}
@@ -1292,7 +1292,7 @@ extern "C" {
 mod tests {
     use super::*;
     use crate::test;
-    use std::format;
+    use alloc::format;
     use untrusted;
 
     // Type-level representation of an arbitrary modulus.

src/digest.rs

@@ -489,7 +489,7 @@ mod tests {
     mod max_input {
         use super::super::super::digest;
         use crate::polyfill;
-        use std::vec;
+        use alloc::vec;
 
         macro_rules! max_input_tests {
             ( $algorithm_name:ident ) => {

src/ec/suite_b/ops.rs

@@ -440,7 +440,8 @@ extern "C" {
 mod tests {
     use super::*;
     use crate::test;
-    use std::{format, print, vec, vec::Vec};
+    use alloc::{format, vec, vec::Vec};
+    use std::print;
     use untrusted;
 
     const ZERO_SCALAR: Scalar = Scalar {

src/error.rs

@@ -196,7 +196,7 @@ impl KeyRejected {
     }
 }
 
-#[cfg(feature = "use_heap")]
+#[cfg(feature = "use_std")]
 impl std::error::Error for KeyRejected {
     fn cause(&self) -> Option<&dyn std::error::Error> {
         None

src/io/der_writer.rs

@@ -13,7 +13,7 @@
 // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 use super::{der::*, writer::*, *};
-use std::boxed::Box;
+use alloc::boxed::Box;
 
 pub(crate) fn write_positive_integer(output: &mut dyn Accumulator, value: &Positive) {
     let first_byte = value.first_byte();

src/io/writer.rs

@@ -12,7 +12,7 @@
 // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
-use std::{boxed::Box, vec::Vec};
+use alloc::{boxed::Box, vec::Vec};
 
 pub trait Accumulator {
     fn write_byte(&mut self, value: u8);

src/lib.rs

@@ -62,6 +62,9 @@
 #![no_std]
 #![cfg_attr(feature = "internal_benches", allow(unstable_features), feature(test))]
 
+#[cfg(any(test, feature = "use_heap"))]
+extern crate alloc;
+
 #[cfg(any(test, feature = "use_heap"))]
 extern crate std;
 

src/rsa/padding.rs

@@ -521,7 +521,7 @@ rsa_pss_padding!(
 mod test {
     use super::*;
     use crate::{digest, error, test};
-    use std::vec;
+    use alloc::vec;
     use untrusted;
 
     #[test]

src/rsa/signing.rs

@@ -24,7 +24,7 @@ use crate::{
     io::{self, der, der_writer},
     pkcs8, rand, signature,
 };
-use std::boxed::Box;
+use alloc::boxed::Box;
 use untrusted;
 
 /// An RSA key pair, used for signing.

src/test.rs

@@ -122,8 +122,8 @@ use crate::bits;
 
 use crate::{digest, error};
 
-use std::{format, string::String, vec::Vec};
+use alloc::{format, string::String, vec::Vec};
-use std::{panic, println};
+use std::println;
 
 /// `compile_time_assert_clone::<T>();` fails to compile if `T` doesn't
 /// implement `Clone`.
@@ -311,7 +311,7 @@ where
 
     #[allow(box_pointers)]
     while let Some(mut test_case) = parse_test_case(&mut current_section, lines) {
-        let result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        let result = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
             f(&current_section, &mut test_case)
         }));
         let result = match result {

tests/ecdsa_tests.rs

@@ -45,8 +45,6 @@ fn ecdsa_from_pkcs8_test() {
     test::run(
         test_file!("ecdsa_from_pkcs8_tests.txt"),
         |section, test_case| {
-            use std::error::Error;
-
             assert_eq!(section, "");
 
             let curve_name = test_case.consume_string("Curve");
@@ -85,7 +83,7 @@ fn ecdsa_from_pkcs8_test() {
                 (Ok(_), None) => (),
                 (Err(e), None) => panic!("Failed with error \"{}\", but expected to succeed", e),
                 (Ok(_), Some(e)) => panic!("Succeeded, but expected error \"{}\"", e),
-                (Err(actual), Some(expected)) => assert_eq!(actual.description(), expected),
+                (Err(actual), Some(expected)) => assert_eq!(format!("{}", actual), expected),
             };
 
             match (
@@ -95,7 +93,7 @@ fn ecdsa_from_pkcs8_test() {
                 (Ok(_), None) => (),
                 (Err(e), None) => panic!("Failed with error \"{}\", but expected to succeed", e),
                 (Ok(_), Some(e)) => panic!("Succeeded, but expected error \"{}\"", e),
-                (Err(actual), Some(expected)) => assert_eq!(actual.description(), expected),
+                (Err(actual), Some(expected)) => assert_eq!(format!("{}", actual), expected),
             };
 
             assert!(signature::EcdsaKeyPair::from_pkcs8(other_fixed, &input).is_err());

tests/pbkdf2_tests.rs

@@ -32,7 +32,7 @@
 )]
 
 use ring::{digest, error, pbkdf2, test, test_file};
-use std::num::NonZeroU32;
+use core::num::NonZeroU32;
 
 #[test]
 pub fn pbkdf2_tests() {

tests/rsa_tests.rs

@@ -46,8 +46,6 @@ fn rsa_from_pkcs8_test() {
     test::run(
         test_file!("rsa_from_pkcs8_tests.txt"),
         |section, test_case| {
-            use std::error::Error;
-
             assert_eq!(section, "");
 
             let input = test_case.consume_bytes("Input");
@@ -57,7 +55,7 @@ fn rsa_from_pkcs8_test() {
                 (Ok(_), None) => (),
                 (Err(e), None) => panic!("Failed with error \"{}\", but expected to succeed", e),
                 (Ok(_), Some(e)) => panic!("Succeeded, but expected error \"{}\"", e),
-                (Err(actual), Some(expected)) => assert_eq!(actual.description(), expected),
+                (Err(actual), Some(expected)) => assert_eq!(format!("{}", actual), expected),
             };
 
             Ok(())
@@ -93,7 +91,6 @@ fn test_signature_rsa_pkcs1_sign() {
                 return Ok(());
             }
             let key_pair = key_pair.unwrap();
-            let key_pair = std::sync::Arc::new(key_pair);
 
             // XXX: This test is too slow on Android ARM Travis CI builds.
             // TODO: re-enable these tests on Android ARM.