no_std support

.travis.yml

@@ -8,20 +8,28 @@ matrix:
         # (we only use it in benchmarks anyway...)
         - cargo generate-lockfile
         - cargo update -p lazy_static --precise 1.0.2
+      env:
+       - FEATURES='force_std'
     - rust: stable
       env:
        - FEATURES='serde-1'
+       - TEST_FEATURES='force_std'
     - rust: beta
+      env:
+       - TEST_FEATURES='force_std'
     - rust: nightly
+      env:
+       - TEST_FEATURES='force_std'
     - rust: nightly
       env:
        - FEATURES='test_low_transition_point'
+       - TEST_FEATURES='force_std'
 branches:
   only:
     - master
 script:
   - |
       cargo build --verbose --features "$FEATURES" &&
-      cargo test --verbose --features "$FEATURES" &&
-      cargo test --release --verbose --features "$FEATURES" &&
+      cargo test --verbose --features "$FEATURES $TEST_FEATURES" &&
+      cargo test --release --verbose --features "$FEATURES $TEST_FEATURES" &&
       cargo doc --verbose --features "$FEATURES"

Cargo.toml

@@ -24,14 +24,20 @@ indexmap.
 keywords = ["hashmap"]
 categories = ["data-structures"]
 
+[package.metadata.release]
+no-dev-version = true
+
+[package.metadata.docs.rs]
+features = ["serde-1"]
+
 [lib]
 bench = false
 
 [dependencies]
 serde = { version = "1.0", optional = true }
 
 [dev-dependencies]
-itertools = "0.7.0" # 0.8 not compiles on Rust 1.18
+itertools = "0.7.0"
 rand = "0.4"
 quickcheck = { version = "0.6", default-features = false }
 fnv = "1.0"
@@ -46,11 +52,34 @@ serde-1 = ["serde"]
 test_low_transition_point = []
 test_debug = []
 
+force_std = []
+
 [profile.bench]
 debug = true
 
-[package.metadata.release]
-no-dev-version = true
+[build-dependencies]
+autocfg = "0.1.5"
 
-[package.metadata.docs.rs]
-features = ["serde-1"]
+[[test]]
+name = "tests"
+required-features = [ "force_std" ]
+
+[[test]]
+name = "serde"
+required-features = [ "force_std" ]
+
+[[test]]
+name = "quick"
+required-features = [ "force_std" ]
+
+[[test]]
+name = "equivalent_trait"
+required-features = [ "force_std" ]
+
+[[bench]]
+name = "bench"
+required-features = [ "force_std" ]
+
+[[bench]]
+name = "faststring"
+required-features = [ "force_std" ]

benches/bench.rs

@@ -580,7 +580,7 @@ fn remove_ordermap_100_000(b: &mut Bencher) {
     b.iter(|| {
         let mut map = map.clone();
         for key in &keys {
-            map.remove(key).is_some();
+            let _ = map.remove(key).is_some();
         }
         assert_eq!(map.len(), 0);
         map

build.rs

@@ -0,0 +1,9 @@
+extern crate autocfg;
+
+fn main() {
+    //let ac = autocfg::new();
+    //ac.emit_sysroot_crate("std");
+    //ac.emit_sysroot_crate("alloc");
+    autocfg::emit("std");
+    //autocfg::emit("alloc");
+}

src/equivalent.rs

@@ -1,5 +1,5 @@
 
-use std::borrow::Borrow;
+use core::borrow::Borrow;
 
 /// Key equivalence trait.
 ///

src/lib.rs

@@ -20,6 +20,19 @@
 //! upgrade policy, where in a later 1.x version, we will raise the minimum
 //! required Rust version.
 
+#![cfg_attr(all(not(test), has_alloc, not(feature = "force_std")), no_std)]
+
+extern crate core;
+
+#[cfg(all(has_alloc, not(feature = "force_std")))]
+extern crate alloc;
+
+#[cfg(all(has_alloc, has_std))]
+extern crate std;
+
+#[cfg(any(not(has_alloc), feature = "force_std"))]
+extern crate std as alloc;
+
 #[macro_use]
 mod macros;
 #[cfg(feature = "serde-1")]

src/macros.rs

@@ -1,10 +1,10 @@
-
 #[macro_export]
-/// Create an `IndexMap` from a list of key-value pairs
+/// Create an `IndexMap` from a list of key-value pairs. Requires `std` to be available.
 ///
 /// ## Example
 ///
 /// ```
+/// 
 /// #[macro_use] extern crate indexmap;
 /// # fn main() {
 ///
@@ -20,6 +20,7 @@
 /// assert_eq!(map.keys().next(), Some(&"a"));
 /// # }
 /// ```
+#[cfg(any(has_std, feature = "force_std", test))]
 macro_rules! indexmap {
     (@single $($x:tt)*) => (());
     (@count $($rest:expr),*) => (<[()]>::len(&[$(indexmap!(@single $rest)),*]));
@@ -58,6 +59,7 @@ macro_rules! indexmap {
 /// assert_eq!(set.iter().next(), Some(&"a"));
 /// # }
 /// ```
+#[cfg(any(has_std, feature = "force_std", test))]
 macro_rules! indexset {
     (@single $($x:tt)*) => (());
     (@count $($rest:expr),*) => (<[()]>::len(&[$(indexset!(@single $rest)),*]));

src/map.rs

@@ -3,17 +3,20 @@
 
 pub use mutable_keys::MutableKeys;
 
-use std::hash::Hash;
-use std::hash::BuildHasher;
-use std::hash::Hasher;
-use std::iter::FromIterator;
-use std::collections::hash_map::RandomState;
-use std::ops::RangeFull;
-
-use std::cmp::{max, Ordering};
-use std::fmt;
-use std::mem::{replace};
-use std::marker::PhantomData;
+use core::hash::Hash;
+use core::hash::BuildHasher;
+use core::hash::Hasher;
+use core::iter::FromIterator;
+use core::ops::RangeFull;
+
+use core::cmp::{max, Ordering};
+use core::fmt;
+use core::mem::{replace};
+use core::marker::PhantomData;
+
+use alloc::vec::Vec;
+use alloc::boxed::Box;
+use alloc::vec;
 
 use util::{third, ptrdistance, enumerate};
 use equivalent::Equivalent;
@@ -246,6 +249,7 @@ impl<Sz> ShortHashProxy<Sz>
 /// # Examples
 ///
 /// ```
+/// # extern crate indexmap;
 /// use indexmap::IndexMap;
 ///
 /// // count the frequency of each letter in a sentence.
@@ -260,7 +264,15 @@ impl<Sz> ShortHashProxy<Sz>
 /// assert_eq!(letters.get(&'y'), None);
 /// ```
 #[derive(Clone)]
-pub struct IndexMap<K, V, S = RandomState> {
+#[cfg(any(has_std, feature = "force_std", test))]
+pub struct IndexMap<K, V, S = ::std::collections::hash_map::RandomState> {
+    core: OrderMapCore<K, V>,
+    hash_builder: S,
+}
+
+#[derive(Clone)]
+#[cfg(not(any(has_std, feature = "force_std", test)))]
+pub struct IndexMap<K, V, S> {
     core: OrderMapCore<K, V>,
     hash_builder: S,
 }
@@ -351,7 +363,8 @@ macro_rules! probe_loop {
     }
 }
 
-impl<K, V> IndexMap<K, V> {
+#[cfg(any(has_std, feature = "force_std", test))]
+impl<K, V> IndexMap<K, V, ::std::collections::hash_map::RandomState> {
     /// Create a new map. (Does not allocate.)
     pub fn new() -> Self {
         Self::with_capacity(0)
@@ -1492,9 +1505,9 @@ fn find_existing_entry_at<Sz>(indices: &[Pos], hash: HashValue,
     });
 }
 
-use std::slice::Iter as SliceIter;
-use std::slice::IterMut as SliceIterMut;
-use std::vec::IntoIter as VecIntoIter;
+use core::slice::Iter as SliceIter;
+use core::slice::IterMut as SliceIterMut;
+use alloc::vec::IntoIter as VecIntoIter;
 
 /// An iterator over the keys of a `IndexMap`.
 ///
@@ -1730,7 +1743,7 @@ impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IntoIter<K, V> {
 /// [`drain`]: struct.IndexMap.html#method.drain
 /// [`IndexMap`]: struct.IndexMap.html
 pub struct Drain<'a, K, V> where K: 'a, V: 'a {
-    pub(crate) iter: ::std::vec::Drain<'a, Bucket<K, V>>
+    pub(crate) iter: ::alloc::vec::Drain<'a, Bucket<K, V>>
 }
 
 impl<'a, K, V> Iterator for Drain<'a, K, V> {
@@ -1779,7 +1792,7 @@ impl<K, V, S> IntoIterator for IndexMap<K, V, S>
     }
 }
 
-use std::ops::{Index, IndexMut};
+use core::ops::{Index, IndexMut};
 
 impl<'a, K, V, Q: ?Sized, S> Index<&'a Q> for IndexMap<K, V, S>
     where Q: Hash + Equivalent<K>,

src/mutable_keys.rs

@@ -1,6 +1,6 @@
 
-use std::hash::Hash;
-use std::hash::BuildHasher;
+use core::hash::Hash;
+use core::hash::BuildHasher;
 
 use super::{IndexMap, Equivalent};
 

src/set.rs

@@ -1,14 +1,13 @@
 //! A hash set implemented using `IndexMap`
 
-use std::cmp::Ordering;
-use std::collections::hash_map::RandomState;
-use std::fmt;
-use std::iter::{FromIterator, Chain};
-use std::hash::{Hash, BuildHasher};
-use std::ops::RangeFull;
-use std::ops::{BitAnd, BitOr, BitXor, Sub};
-use std::slice;
-use std::vec;
+use core::cmp::Ordering;
+use core::fmt;
+use core::iter::{FromIterator, Chain};
+use core::hash::{Hash, BuildHasher};
+use core::ops::RangeFull;
+use core::ops::{BitAnd, BitOr, BitXor, Sub};
+use core::slice;
+use alloc::vec;
 
 use super::{IndexMap, Equivalent};
 
@@ -45,6 +44,7 @@ type Bucket<T> = super::Bucket<T, ()>;
 /// # Examples
 ///
 /// ```
+/// # extern crate indexmap;
 /// use indexmap::IndexSet;
 ///
 /// // Collects which letters appear in a sentence.
@@ -56,7 +56,14 @@ type Bucket<T> = super::Bucket<T, ()>;
 /// assert!(!letters.contains(&'y'));
 /// ```
 #[derive(Clone)]
-pub struct IndexSet<T, S = RandomState> {
+#[cfg(any(has_std, feature = "force_std", test))]
+pub struct IndexSet<T, S = ::std::collections::hash_map::RandomState> {
+    map: IndexMap<T, (), S>,
+}
+
+#[derive(Clone)]
+#[cfg(not(any(has_std, feature = "force_std", test)))]
+pub struct IndexSet<T, S> {
     map: IndexMap<T, (), S>,
 }
 
@@ -74,6 +81,7 @@ impl<T, S> fmt::Debug for IndexSet<T, S>
     }
 }
 
+#[cfg(any(has_std, feature = "force_std", test))]
 impl<T> IndexSet<T> {
     /// Create a new set. (Does not allocate.)
     pub fn new() -> Self {

src/util.rs

@@ -1,6 +1,6 @@
 
-use std::iter::Enumerate;
-use std::mem::size_of;
+use core::iter::Enumerate;
+use core::mem::size_of;
 
 pub fn third<A, B, C>(t: (A, B, C)) -> C { t.2 }