Enable no_std

Cargo.toml

@@ -17,10 +17,12 @@ panic = "unwind"
 strip=true
 
 [features]
+default = ["std"]
+std = ["serde/std"]
 # TODO: maybe add an FFI feature, to allow C projects to use it? idk if that's worth it really...
 
 [dependencies]
-serde = {version = "1.0.116", features = ["derive"], optional = true}
+serde = {version = "1.0.116", features = ["derive", "alloc"], optional = true}
 # TODO: optional smallvec feature: instead of heap-allocating the first page, it can be placed on the stack.
 
 

src/entry.rs

@@ -33,7 +33,7 @@ where K: Collapse
     /// Replace the held value with another, yielding the old one
     pub fn insert(&mut self, value: V) -> V
     {
-	std::mem::replace(&mut self.0.as_mut().unwrap().1, value)
+	core::mem::replace(&mut self.0.as_mut().unwrap().1, value)
     }
     /// Remove this entry from the `Map`, yielding the removed value
     pub fn remove(self) -> V

src/iter.rs

@@ -2,7 +2,7 @@
 use super::*;
 
 /// An iterator over `Page`s
-pub struct Pages<'a, K, V>(pub(crate) std::slice::Iter<'a, Page<K,V>>);
+pub struct Pages<'a, K, V>(pub(crate) core::slice::Iter<'a, Page<K,V>>);
 
 impl<'a, K, V> Iterator for Pages<'a,K,V>
 {
@@ -18,7 +18,7 @@ impl<'a, K, V> Iterator for Pages<'a,K,V>
 }
 
 /// A mutable iterator over `Page`s
-pub struct PagesMut<'a, K, V>(pub(crate) std::slice::IterMut<'a, Page<K,V>>);
+pub struct PagesMut<'a, K, V>(pub(crate) core::slice::IterMut<'a, Page<K,V>>);
 
 impl<'a, K, V> Iterator for PagesMut<'a,K,V>
 {
@@ -34,10 +34,10 @@ impl<'a, K, V> Iterator for PagesMut<'a,K,V>
 }
 
 impl<'a, K, V> ExactSizeIterator for PagesMut<'a,K,V>{}
-impl<'a, K, V> std::iter::FusedIterator for PagesMut<'a,K,V>{}
+impl<'a, K, V> core::iter::FusedIterator for PagesMut<'a,K,V>{}
 
 /// An iterator over elements in a `Page`.
-pub struct PageElements<'a, K, V>(pub(crate) std::slice::Iter<'a, Option<(K,V)>>);
+pub struct PageElements<'a, K, V>(pub(crate) core::slice::Iter<'a, Option<(K,V)>>);
 
 impl<'a, K, V> Iterator for PageElements<'a,K,V>
 {
@@ -57,10 +57,10 @@ impl<'a, K, V> Iterator for PageElements<'a,K,V>
 	(0, self.0.size_hint().1)
     }
 }
-impl<'a, K, V> std::iter::FusedIterator for PageElements<'a,K,V>{}
+impl<'a, K, V> core::iter::FusedIterator for PageElements<'a,K,V>{}
 
 /// A mutable iterator over elements in a `Page`.
-pub struct PageElementsMut<'a, K, V>(pub(crate) std::slice::IterMut<'a, Option<(K,V)>>);
+pub struct PageElementsMut<'a, K, V>(pub(crate) core::slice::IterMut<'a, Option<(K,V)>>);
 
 impl<'a, K, V> Iterator for PageElementsMut<'a,K,V>
 {
@@ -79,7 +79,7 @@ impl<'a, K, V> Iterator for PageElementsMut<'a,K,V>
 	(0, self.0.size_hint().1)
     }
 }
-impl<'a, K, V> std::iter::FusedIterator for PageElementsMut<'a,K,V>{}
+impl<'a, K, V> core::iter::FusedIterator for PageElementsMut<'a,K,V>{}
 
 /// A consuming iterator over elements in a `Page`.
 pub struct IntoPageElements<K,V>(pub(crate) [Option<(K,V)>; MAX], pub(crate) usize);
@@ -104,7 +104,7 @@ impl<K,V> Iterator for IntoPageElements<K,V>
 	(0, Some(self.0.len()))
     }
 }
-impl<K, V> std::iter::FusedIterator for IntoPageElements<K,V>{}
+impl<K, V> core::iter::FusedIterator for IntoPageElements<K,V>{}
 
 /// An iterator over entries in a `Map`.
 pub struct Iter<'a, K, V>(pub(crate) Option<PageElements<'a,K,V>>, pub(crate) Pages<'a, K,V>);
@@ -131,7 +131,7 @@ where K: Collapse
 	(0, self.1.size_hint().1.map(|x| x * MAX))
     }
 }
-impl<'a, K: Collapse, V> std::iter::FusedIterator for Iter<'a, K,V>{}
+impl<'a, K: Collapse, V> core::iter::FusedIterator for Iter<'a, K,V>{}
 
 /// A mutable iterator over entries in a `Map`.
 pub struct IterMut<'a, K, V>(pub(crate) Option<PageElementsMut<'a,K,V>>, pub(crate) PagesMut<'a, K,V>);
@@ -158,10 +158,10 @@ where K: Collapse
 	(0, self.1.size_hint().1.map(|x| x * MAX))
     }
 }
-impl<'a, K: Collapse, V> std::iter::FusedIterator for IterMut<'a, K,V>{}
+impl<'a, K: Collapse, V> core::iter::FusedIterator for IterMut<'a, K,V>{}
 
 /// A consuming iterator over entries in a `Map`.
-pub struct IntoIter<K, V>(pub(crate) Option<IntoPageElements<K,V>>,  pub(crate) std::vec::IntoIter<Page<K,V>>);
+pub struct IntoIter<K, V>(pub(crate) Option<IntoPageElements<K,V>>,  pub(crate) vec::IntoIter<Page<K,V>>);
 
 impl<K, V> Iterator for IntoIter<K,V>
 where K: Collapse
@@ -187,7 +187,7 @@ where K: Collapse
     }
 }
 
-impl<K: Collapse, V> std::iter::FusedIterator for IntoIter<K,V>{}
+impl<K: Collapse, V> core::iter::FusedIterator for IntoIter<K,V>{}
 
 #[cfg(test)]
 mod tests

src/lib.rs

@@ -26,16 +26,19 @@
 //!
 //! ###  When not to use
 //! Generally don't use this if your key would have a lot of collisions being represents in 8 bits, otherwise it might be a faster alternative to hash-based maps. You should check yourself before sticking with this crate instead of `std`'s vectorised map implementations.
-
+#![cfg_attr(not(test), no_std)]
 #![cfg_attr(nightly, feature(test))] 
 #![cfg_attr(nightly, feature(drain_filter))] 
 #![cfg_attr(nightly, feature(never_type))] 
 
 #[cfg(nightly)] extern crate test;
+extern crate alloc;
 
 const MAX: usize = 256;
 
-use std::borrow::Borrow;
+use alloc::vec;
+use alloc::vec::Vec;
+use core::borrow::Borrow;
 
 pub mod iter;
 use iter::*;
@@ -138,7 +141,7 @@ where K: Collapse
     /// This is a count that iterates over all slots, if possible store it in a temporary instead of re-calling it many times.
     pub fn len(&self) -> usize
     {
-	self.0.iter().map(Option::as_ref).filter_map(std::convert::identity).count()
+	self.0.iter().map(Option::as_ref).filter_map(core::convert::identity).count()
     }
 
     /// An iterator over all entries currently in this page
@@ -166,11 +169,11 @@ where K: Collapse
 
     fn replace(&mut self, k: K, v: V) -> Option<(K,V)>
     {
-	std::mem::replace(&mut self.0[usize::from(k.collapse())], Some((k,v)))
+	core::mem::replace(&mut self.0[usize::from(k.collapse())], Some((k,v)))
     }
 }
 
-impl<K: Collapse, V> std::iter::FromIterator<(K, V)> for Map<K,V>
+impl<K: Collapse, V> core::iter::FromIterator<(K, V)> for Map<K,V>
 {
     fn from_iter<I: IntoIterator<Item=(K, V)>>(iter: I) -> Self
     {
@@ -221,8 +224,8 @@ impl<K,V> Map<K,V>
     #[allow(dead_code)] // Used in test cases, but compiler still warns about it
     pub(crate) fn internal_size_bytes(&self) -> usize
     {
-	self.0.capacity() * std::mem::size_of::<Page<K,V>>()
+	self.0.capacity() * core::mem::size_of::<Page<K,V>>()
-	//self.0.iter().map(std::mem::size_of_val).sum::<usize>()
+	//self.0.iter().map(core::mem::size_of_val).sum::<usize>()
     }
 }
 
@@ -432,7 +435,7 @@ where K: Collapse
 	{
 	    match page.search_mut(&key) {
 		Some((ref ok, ov)) if ok.eq(&key) => {
-		    return Some(std::mem::replace(ov, value));
+		    return Some(core::mem::replace(ov, value));
 		},
 		empty @ None => {
 		    return empty.replace((key, value))
@@ -484,7 +487,7 @@ impl<K: Collapse, V> IntoIterator for Map<K,V>
     }
 }
 
-impl<K: Collapse, V> std::iter::Extend<(K,V)> for Map<K,V>
+impl<K: Collapse, V> core::iter::Extend<(K,V)> for Map<K,V>
 {
     fn extend<T: IntoIterator<Item = (K,V)>>(&mut self, iter: T) {
 	// we can probably optimise this better, right?
@@ -495,8 +498,8 @@ impl<K: Collapse, V> std::iter::Extend<(K,V)> for Map<K,V>
     }
 }
 
-use std::hash::{Hash, Hasher,};
+use core::hash::{Hash, Hasher,};
-use std::ops::{Index, IndexMut};
+use core::ops::{Index, IndexMut};
 
 impl<T: ?Sized + Hash + Eq> Collapse for T
 {

src/page_impls.rs

@@ -1,6 +1,6 @@
 //! Because we can't #derive big arrays on stable smh
 use super::*;
-use std::{
+use core::{
     fmt::{self, Debug,},
     hash,
 };

src/primitive.rs

@@ -6,7 +6,7 @@
 //!
 //! If/when Rust gets specialisation, this will be unneeded.
 use super::*;
-use std::num::*;
+use core::num::*;
 
 /// Sealed trait allowing for wrapping primitive types with a more efficient implemntation for the `Collapse` trait.
 /// This should not be used for much directly, instead use the newtype shim `Primitive<T>`.

src/space.rs

@@ -12,12 +12,12 @@ use super::*;
 /// A set of only non-zero bytes.
 ///
 /// This type is entirely space efficient and will only ever allocate `256` bytes of memory.
-pub type NonZeroByteSet = Set<std::num::NonZeroU8>;
+pub type NonZeroByteSet = Set<core::num::NonZeroU8>;
 
 /// A set of non-zero signed 8-bit integers.
 ///
 /// This type is entirely space efficient and will only ever allocate `256` bytes of memory.
-pub type NonZeroI8Set = Set<std::num::NonZeroI8>;
+pub type NonZeroI8Set = Set<core::num::NonZeroI8>;
 
 /// A set of non-zero unsigned 8-bit integers.
 ///