feat: Add no_std mode

.github/workflows/ci.yml

@@ -48,6 +48,8 @@ jobs:
         if: startsWith(matrix.rust, 'nightly')
         run: cargo check -Z features=dev_dep
       - run: cargo test
+      - name: Build with no default features
+        run: cargo build --no-default-features
       - name: Test wasm
         run: wasm-pack test --headless --chrome
         if: startsWith(matrix.os, 'ubuntu')

Cargo.toml

@@ -14,6 +14,10 @@ keywords = ["simple", "fast", "rand", "random", "wyrand"]
 categories = ["algorithms"]
 exclude = ["/.*"]
 
+[features]
+default = ["std"]
+std = []
+
 [target.'cfg(all(target_arch = "wasm32", not(target_os = "wasi")))'.dependencies]
 instant = "0.1"
 

src/global_rng.rs

@@ -0,0 +1,173 @@
+//! A global, thread-local random number generator.
+
+use crate::Rng;
+
+use std::cell::Cell;
+use std::ops::RangeBounds;
+
+#[cfg(all(target_arch = "wasm32", not(target_os = "wasi")))]
+use instant::Instant;
+#[cfg(not(all(target_arch = "wasm32", not(target_os = "wasi"))))]
+use std::time::Instant;
+
+impl Default for Rng {
+    /// Initialize the `Rng` from the system's random number generator.
+    ///
+    /// This is equivalent to [`Rng::new()`].
+    #[inline]
+    fn default() -> Rng {
+        Rng::new()
+    }
+}
+
+impl Rng {
+    /// Creates a new random number generator.
+    #[inline]
+    pub fn new() -> Rng {
+        try_with_rng(Rng::fork).unwrap_or_else(|_| Rng::with_seed(0x4d595df4d0f33173))
+    }
+}
+
+thread_local! {
+    static RNG: Cell<Rng> = Cell::new(Rng({
+        use std::collections::hash_map::DefaultHasher;
+        use std::hash::{Hash, Hasher};
+        use std::thread;
+
+        let mut hasher = DefaultHasher::new();
+        Instant::now().hash(&mut hasher);
+        thread::current().id().hash(&mut hasher);
+        let hash = hasher.finish();
+        (hash << 1) | 1
+    }));
+}
+
+/// Run an operation with the current thread-local generator.
+#[inline]
+fn with_rng<R>(f: impl FnOnce(&mut Rng) -> R) -> R {
+    RNG.with(|rng| {
+        let current = rng.replace(Rng(0));
+
+        let mut restore = RestoreOnDrop { rng, current };
+
+        f(&mut restore.current)
+    })
+}
+
+/// Try to run an operation with the current thread-local generator.
+#[inline]
+fn try_with_rng<R>(f: impl FnOnce(&mut Rng) -> R) -> Result<R, std::thread::AccessError> {
+    RNG.try_with(|rng| {
+        let current = rng.replace(Rng(0));
+
+        let mut restore = RestoreOnDrop { rng, current };
+
+        f(&mut restore.current)
+    })
+}
+
+/// Make sure the original RNG is restored even on panic.
+struct RestoreOnDrop<'a> {
+    rng: &'a Cell<Rng>,
+    current: Rng,
+}
+
+impl Drop for RestoreOnDrop<'_> {
+    fn drop(&mut self) {
+        self.rng.set(Rng(self.current.0));
+    }
+}
+
+/// Initializes the thread-local generator with the given seed.
+#[inline]
+pub fn seed(seed: u64) {
+    with_rng(|r| r.seed(seed));
+}
+
+/// Gives back **current** seed that is being held by the thread-local generator.
+#[inline]
+pub fn get_seed() -> u64 {
+    with_rng(|r| r.get_seed())
+}
+
+/// Generates a random `bool`.
+#[inline]
+pub fn bool() -> bool {
+    with_rng(|r| r.bool())
+}
+
+/// Generates a random `char` in ranges a-z and A-Z.
+#[inline]
+pub fn alphabetic() -> char {
+    with_rng(|r| r.alphabetic())
+}
+
+/// Generates a random `char` in ranges a-z, A-Z and 0-9.
+#[inline]
+pub fn alphanumeric() -> char {
+    with_rng(|r| r.alphanumeric())
+}
+
+/// Generates a random `char` in range a-z.
+#[inline]
+pub fn lowercase() -> char {
+    with_rng(|r| r.lowercase())
+}
+
+/// Generates a random `char` in range A-Z.
+#[inline]
+pub fn uppercase() -> char {
+    with_rng(|r| r.uppercase())
+}
+
+/// Generates a random digit in the given `base`.
+///
+/// Digits are represented by `char`s in ranges 0-9 and a-z.
+///
+/// Panics if the base is zero or greater than 36.
+#[inline]
+pub fn digit(base: u32) -> char {
+    with_rng(|r| r.digit(base))
+}
+
+/// Shuffles a slice randomly.
+#[inline]
+pub fn shuffle<T>(slice: &mut [T]) {
+    with_rng(|r| r.shuffle(slice))
+}
+
+macro_rules! integer {
+    ($t:tt, $doc:tt) => {
+        #[doc = $doc]
+        ///
+        /// Panics if the range is empty.
+        #[inline]
+        pub fn $t(range: impl RangeBounds<$t>) -> $t {
+            with_rng(|r| r.$t(range))
+        }
+    };
+}
+
+integer!(u8, "Generates a random `u8` in the given range.");
+integer!(i8, "Generates a random `i8` in the given range.");
+integer!(u16, "Generates a random `u16` in the given range.");
+integer!(i16, "Generates a random `i16` in the given range.");
+integer!(u32, "Generates a random `u32` in the given range.");
+integer!(i32, "Generates a random `i32` in the given range.");
+integer!(u64, "Generates a random `u64` in the given range.");
+integer!(i64, "Generates a random `i64` in the given range.");
+integer!(u128, "Generates a random `u128` in the given range.");
+integer!(i128, "Generates a random `i128` in the given range.");
+integer!(usize, "Generates a random `usize` in the given range.");
+integer!(isize, "Generates a random `isize` in the given range.");
+integer!(char, "Generates a random `char` in the given range.");
+
+/// Generates a random `f32` in range `0..1`.
+pub fn f32() -> f32 {
+    with_rng(|r| r.f32())
+}
+
+/// Generates a random `f64` in range `0..1`.
+pub fn f64() -> f64 {
+    with_rng(|r| r.f64())
+}