no std support

Author: fredszaq

tests/hash.rs

@@ -1,13 +1,10 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
-fn do_hash<T: derive_more::core::hash::Hash>(t: &T) -> u64 {
-    use std::hash::{DefaultHasher, Hasher};
-    let mut hasher = DefaultHasher::default();
-    t.hash(&mut hasher);
-    hasher.finish()
-}
-mod utils {
-    pub fn alternate_u32_hash_function<H: derive_more::core::hash::Hasher>(
+mod hash_utils;
+use hash_utils::do_hash;
+
+pub mod utils {
+    pub fn alternate_u32_hash_function<H: core::hash::Hasher>(
         value: &u32,
         state: &mut H,
     ) {
@@ -51,6 +48,7 @@ mod structs {
     }
 
     mod multi_field {
+        use super::super::utils;
         use crate::do_hash;
         use derive_more::Hash;
 
@@ -66,7 +64,7 @@ mod structs {
 
         #[derive(Hash)]
         struct StructWithAlternateHashFunction {
-            #[hash(with(crate::utils::alternate_u32_hash_function))]
+            #[hash(with(utils::alternate_u32_hash_function))]
             a: u32,
             b: &'static str,
             c: bool,
@@ -144,6 +142,7 @@ mod structs {
 }
 
 mod enums {
+    use super::utils;
     use crate::do_hash;
     use derive_more::Hash;
 
@@ -176,7 +175,7 @@ mod enums {
             _skipped: &'static str,
         },
         B(
-            #[hash(with(crate::utils::alternate_u32_hash_function))] u32,
+            #[hash(with(utils::alternate_u32_hash_function))] u32,
             #[hash(skip)]
             #[allow(unused)]
             &'static str,

tests/hash_and_eq.rs

@@ -1,12 +1,7 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use core::hash::{DefaultHasher, Hash, Hasher};
-
-fn do_hash<T: Hash>(t: &T) -> u64 {
-    let mut hasher = DefaultHasher::default();
-    t.hash(&mut hasher);
-    hasher.finish()
-}
+mod hash_utils;
+use hash_utils::do_hash;
 
 mod hash_respects_eq_skip {
     use super::*;

tests/hash_utils.rs

@@ -0,0 +1,30 @@
+#[cfg(feature = "std")]
+pub fn do_hash<T: core::hash::Hash>(t: &T) -> u64 {
+    use std::hash::{DefaultHasher, Hasher};
+    let mut hasher = DefaultHasher::default();
+    t.hash(&mut hasher);
+    hasher.finish()
+}
+
+#[cfg(not(feature = "std"))]
+pub fn do_hash<T: core::hash::Hash>(t: &T) -> u64 {
+    use core::hash::Hasher;
+    // Simple FNV-1a hasher for no_std, for testing purposes only.
+    struct FnvHasher(u64);
+
+    impl core::hash::Hasher for FnvHasher {
+        fn write(&mut self, bytes: &[u8]) {
+            for byte in bytes {
+                self.0 ^= *byte as u64;
+                self.0 = self.0.wrapping_mul(0x100000001b3);
+            }
+        }
+        fn finish(&self) -> u64 {
+            self.0
+        }
+    }
+
+    let mut hasher = FnvHasher(0xcbf29ce484222325);
+    t.hash(&mut hasher);
+    hasher.finish()
+}