Revert "Upgrade fastrand to 2.0.1"emu-34-3-release

This reverts commit f00a459d95e87096a8366dc67f5fbfdf33a4e205.

Reason for revert: Breaks netsim + emulator due to tempfile's dependency issue.

Change-Id: I48b80276c0754d052bcf270d62df7a375340f099

11 files changed, 237 insertions, 530 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
deleted file mode 100644
index 9bdc3d0..0000000
--- a/.cargo_vcs_info.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "git": {
-    "sha1": "387e3baead884a504d98e89bb4316db98f5c15ce"
-  },
-  "path_in_vcs": ""
-}
\ No newline at end of file
diff --git a/Android.bp b/Android.bp
index 5543b15..6c3c500 100644
--- a/Android.bp
+++ b/Android.bp
@@ -42,14 +42,9 @@ rust_library {
     host_supported: true,
     crate_name: "fastrand",
     cargo_env_compat: true,
-    cargo_pkg_version: "2.0.1",
+    cargo_pkg_version: "1.9.0",
     srcs: ["src/lib.rs"],
     edition: "2018",
-    features: [
-        "alloc",
-        "default",
-        "std",
-    ],
     apex_available: [
         "//apex_available:platform",
         "com.android.virt",
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b744e31..869f314 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,17 +1,3 @@
-# Version 2.0.1
-
-- Clarify documentation for the `fork()` method. (#62)
-- Mention `fastrand-contrib` in documentation. (#70)
-
-# Version 2.0.0
-
-- **Breaking:** Remove interior mutability from `Rng`. (#47)
-- Add a `fork()` method. (#49)
-- Add a `no_std` mode. (#50)
-- Add an iterator selection function. (#51)
-- Add a `choose_multiple()` function for sampling several elements from an iterator. (#55)
-- Use the `getrandom` crate for seeding on WebAssembly targets if the `js` feature is enabled. (#60)
-
 # Version 1.9.0
 
 - Add `Rng::fill()` (#35, #43)
diff --git a/Cargo.toml b/Cargo.toml
index a618bff..7cc602f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,9 +11,9 @@
 
 [package]
 edition = "2018"
-rust-version = "1.36"
+rust-version = "1.34"
 name = "fastrand"
-version = "2.0.1"
+version = "1.9.0"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 exclude = ["/.*"]
 description = "A simple and fast random number generator"
@@ -29,13 +29,6 @@ categories = ["algorithms"]
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/fastrand"
 
-[package.metadata.docs.rs]
-all-features = true
-rustdoc-args = [
-    "--cfg",
-    "docsrs",
-]
-
 [dev-dependencies.getrandom]
 version = "0.2"
 
@@ -45,23 +38,16 @@ version = "0.8"
 [dev-dependencies.wyhash]
 version = "0.5"
 
-[features]
-alloc = []
-default = ["std"]
-js = [
-    "std",
-    "getrandom",
-]
-std = ["alloc"]
+[target."cfg(all(target_arch = \"wasm32\", not(target_os = \"wasi\")))".dependencies.instant]
+version = "0.1"
 
-[target."cfg(all(any(target_arch = \"wasm32\", target_arch = \"wasm64\"), target_os = \"unknown\"))".dependencies.getrandom]
+[target."cfg(all(target_arch = \"wasm32\", not(target_os = \"wasi\")))".dev-dependencies.getrandom]
 version = "0.2"
 features = ["js"]
-optional = true
 
-[target."cfg(all(any(target_arch = \"wasm32\", target_arch = \"wasm64\"), target_os = \"unknown\"))".dev-dependencies.getrandom]
-version = "0.2"
-features = ["js"]
+[target."cfg(all(target_arch = \"wasm32\", not(target_os = \"wasi\")))".dev-dependencies.instant]
+version = "0.1"
+features = ["wasm-bindgen"]
 
-[target."cfg(all(any(target_arch = \"wasm32\", target_arch = \"wasm64\"), target_os = \"unknown\"))".dev-dependencies.wasm-bindgen-test]
+[target."cfg(all(target_arch = \"wasm32\", not(target_os = \"wasi\")))".dev-dependencies.wasm-bindgen-test]
 version = "0.3"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
index c5e85ad..8c80502 100644
--- a/Cargo.toml.orig
+++ b/Cargo.toml.orig
@@ -2,11 +2,11 @@
 name = "fastrand"
 # When publishing a new version:
 # - Update CHANGELOG.md
-# - Create "v2.x.y" git tag
-version = "2.0.1"
+# - Create "v1.x.y" git tag
+version = "1.9.0"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 edition = "2018"
-rust-version = "1.36"
+rust-version = "1.34"
 description = "A simple and fast random number generator"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/fastrand"
@@ -14,16 +14,11 @@ keywords = ["simple", "fast", "rand", "random", "wyrand"]
 categories = ["algorithms"]
 exclude = ["/.*"]
 
-[features]
-default = ["std"]
-alloc = []
-std = ["alloc"]
-js = ["std", "getrandom"]
+[target.'cfg(all(target_arch = "wasm32", not(target_os = "wasi")))'.dependencies]
+instant = "0.1"
 
-[target.'cfg(all(any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown"))'.dependencies]
-getrandom = { version = "0.2", features = ["js"], optional = true }
-
-[target.'cfg(all(any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown"))'.dev-dependencies]
+[target.'cfg(all(target_arch = "wasm32", not(target_os = "wasi")))'.dev-dependencies]
+instant = { version = "0.1", features = ["wasm-bindgen"] }
 wasm-bindgen-test = "0.3"
 getrandom = { version = "0.2", features = ["js"] }
 
@@ -31,7 +26,3 @@ getrandom = { version = "0.2", features = ["js"] }
 rand = "0.8"
 wyhash = "0.5"
 getrandom = "0.2"
-
-[package.metadata.docs.rs]
-all-features = true
-rustdoc-args = ["--cfg", "docsrs"]
diff --git a/METADATA b/METADATA
index 16729af..5ec32de 100644
--- a/METADATA
+++ b/METADATA
@@ -1,20 +1,20 @@
-# This project was upgraded with external_updater.
-# Usage: tools/external_updater/updater.sh update external/rust/crates/fastrand
-# For more info, check https://cs.android.com/android/platform/superproject/+/main:tools/external_updater/README.md
-
 name: "fastrand"
 description: "A simple and fast random number generator"
 third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/fastrand"
+  }
+  url {
+    type: ARCHIVE
+    value: "https://static.crates.io/crates/fastrand/fastrand-1.9.0.crate"
+  }
+  version: "1.9.0"
+  # Dual-licensed, using the least restrictive per go/thirdpartylicenses#same.
   license_type: NOTICE
   last_upgrade_date {
-    year: 2024
+    year: 2023
     month: 2
-    day: 8
-  }
-  homepage: "https://crates.io/crates/fastrand"
-  identifier {
-    type: "Archive"
-    value: "https://static.crates.io/crates/fastrand/fastrand-2.0.1.crate"
-    version: "2.0.1"
+    day: 17
   }
 }
diff --git a/README.md b/README.md
index 46ea830..0da0612 100644
--- a/README.md
+++ b/README.md
@@ -40,13 +40,6 @@ let i = fastrand::usize(..v.len());
 let elem = v[i];
 ```
 
-Sample values from an array with `O(n)` complexity (`n` is the length of array):
-
-```rust
-fastrand::choose_multiple(vec![1, 4, 5].iter(), 2);
-fastrand::choose_multiple(0..20, 12);
-```
-
 Shuffle an array:
 
 ```rust
@@ -83,17 +76,6 @@ let rng = fastrand::Rng::new();
 let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect();
 ```
 
-This crate aims to expose a core set of useful randomness primitives. For more niche algorithms, consider using the [`fastrand-contrib`] crate alongside this one.
-
-# Features
-
-- `std` (enabled by default): Enables the `std` library. This is required for the global
-  generator and global entropy. Without this feature, [`Rng`] can only be instantiated using
-  the [`with_seed`](https://docs.rs/fastrand/latest/fastrand/struct.Rng.html#method.with_seed) method.
-- `js`: Assumes that WebAssembly targets are being run in a JavaScript environment.
-
-[`fastrand-contrib`]: https://crates.io/crates/fastrand-contrib
-
 ## License
 
 Licensed under either of
diff --git a/benches/bench.rs b/benches/bench.rs
index a940aac..4b882b7 100644
--- a/benches/bench.rs
+++ b/benches/bench.rs
@@ -18,7 +18,7 @@ fn shuffle_wyhash(b: &mut Bencher) {
 
 #[bench]
 fn shuffle_fastrand(b: &mut Bencher) {
-    let mut rng = fastrand::Rng::new();
+    let rng = fastrand::Rng::new();
     let mut x = (0..100).collect::<Vec<usize>>();
     b.iter(|| {
         rng.shuffle(&mut x);
@@ -40,7 +40,7 @@ fn u8_wyhash(b: &mut Bencher) {
 
 #[bench]
 fn u8_fastrand(b: &mut Bencher) {
-    let mut rng = fastrand::Rng::new();
+    let rng = fastrand::Rng::new();
     b.iter(|| {
         let mut sum = 0u8;
         for _ in 0..10_000 {
@@ -64,7 +64,7 @@ fn u32_wyhash(b: &mut Bencher) {
 
 #[bench]
 fn u32_fastrand(b: &mut Bencher) {
-    let mut rng = fastrand::Rng::new();
+    let rng = fastrand::Rng::new();
     b.iter(|| {
         let mut sum = 0u32;
         for _ in 0..10_000 {
@@ -76,7 +76,7 @@ fn u32_fastrand(b: &mut Bencher) {
 
 #[bench]
 fn fill(b: &mut Bencher) {
-    let mut rng = fastrand::Rng::new();
+    let rng = fastrand::Rng::new();
     b.iter(|| {
         // Pick a size that isn't divisble by 8.
         let mut bytes = [0u8; 367];
@@ -87,7 +87,7 @@ fn fill(b: &mut Bencher) {
 
 #[bench]
 fn fill_naive(b: &mut Bencher) {
-    let mut rng = fastrand::Rng::new();
+    let rng = fastrand::Rng::new();
     b.iter(|| {
         let mut bytes = [0u8; 367];
         for item in &mut bytes {
diff --git a/src/global_rng.rs b/src/global_rng.rs
deleted file mode 100644
index f994902..0000000
--- a/src/global_rng.rs
+++ /dev/null
@@ -1,218 +0,0 @@
-//! A global, thread-local random number generator.
-
-use crate::Rng;
-
-use std::cell::Cell;
-use std::ops::RangeBounds;
-
-// Chosen by fair roll of the dice.
-const DEFAULT_RNG_SEED: u64 = 0xef6f79ed30ba75a;
-
-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(random_seed().unwrap_or(DEFAULT_RNG_SEED)));
-}
-
-/// 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())
-}
-
-/// Choose an item from an iterator at random.
-///
-/// This function may have an unexpected result if the `len()` property of the
-/// iterator does not match the actual number of items in the iterator. If
-/// the iterator is empty, this returns `None`.
-#[inline]
-pub fn choice<I>(iter: I) -> Option<I::Item>
-where
-    I: IntoIterator,
-    I::IntoIter: ExactSizeIterator,
-{
-    with_rng(|r| r.choice(iter))
-}
-
-/// 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())
-}
-
-/// Collects `amount` values at random from the iterator into a vector.
-pub fn choose_multiple<T: Iterator>(source: T, amount: usize) -> Vec<T::Item> {
-    with_rng(|rng| rng.choose_multiple(source, amount))
-}
-
-#[cfg(not(all(
-    any(target_arch = "wasm32", target_arch = "wasm64"),
-    target_os = "unknown"
-)))]
-fn random_seed() -> Option<u64> {
-    use std::collections::hash_map::DefaultHasher;
-    use std::hash::{Hash, Hasher};
-    use std::thread;
-    use std::time::Instant;
-
-    let mut hasher = DefaultHasher::new();
-    Instant::now().hash(&mut hasher);
-    thread::current().id().hash(&mut hasher);
-    let hash = hasher.finish();
-    Some((hash << 1) | 1)
-}
-
-#[cfg(all(
-    any(target_arch = "wasm32", target_arch = "wasm64"),
-    target_os = "unknown",
-    feature = "js"
-))]
-fn random_seed() -> Option<u64> {
-    // TODO(notgull): Failures should be logged somewhere.
-    let mut seed = [0u8; 8];
-    getrandom::getrandom(&mut seed).ok()?;
-    Some(u64::from_ne_bytes(seed))
-}
-
-#[cfg(all(
-    any(target_arch = "wasm32", target_arch = "wasm64"),
-    target_os = "unknown",
-    not(feature = "js")
-))]
-fn random_seed() -> Option<u64> {
-    None
-}
diff --git a/src/lib.rs b/src/lib.rs
index 24de8dd..3f3ec3d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29,14 +29,6 @@
 //! let elem = v[i];
 //! ```
 //!
-//! Sample values from an array with `O(n)` complexity (`n` is the length of array):
-//!
-//! ```
-//! fastrand::choose_multiple(vec![1, 4, 5].iter(), 2);
-//! fastrand::choose_multiple(0..20, 12);
-//! ```
-//!
-//!
 //! Shuffle an array:
 //!
 //! ```
@@ -69,98 +61,87 @@
 //! ```
 //! use std::iter::repeat_with;
 //!
-//! let mut rng = fastrand::Rng::new();
+//! let rng = fastrand::Rng::new();
 //! let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect();
 //! ```
-//!
-//! This crate aims to expose a core set of useful randomness primitives. For more niche algorithms,
-//! consider using the [`fastrand-contrib`] crate alongside this one.
-//!
-//! # Features
-//!
-//! - `std` (enabled by default): Enables the `std` library. This is required for the global
-//!   generator and global entropy. Without this feature, [`Rng`] can only be instantiated using
-//!   the [`with_seed`](Rng::with_seed) method.
-//! - `js`: Assumes that WebAssembly targets are being run in a JavaScript environment. See the
-//!   [WebAssembly Notes](#webassembly-notes) section for more information.
-//!
-//! # WebAssembly Notes
-//!
-//! For non-WASI WASM targets, there is additional sublety to consider when utilizing the global RNG.
-//! By default, `std` targets will use entropy sources in the standard library to seed the global RNG.
-//! However, these sources are not available by default on WASM targets outside of WASI.
-//!
-//! If the `js` feature is enabled, this crate will assume that it is running in a JavaScript
-//! environment. At this point, the [`getrandom`] crate will be used in order to access the available
-//! entropy sources and seed the global RNG. If the `js` feature is not enabled, the global RNG will
-//! use a predefined seed.
-//!
-//! [`fastrand-contrib`]: https://crates.io/crates/fastrand-contrib
-//! [`getrandom`]: https://crates.io/crates/getrandom
 
-#![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(docsrs, feature(doc_cfg))]
 #![forbid(unsafe_code)]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
-#![doc(
-    html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
-)]
-#![doc(
-    html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
-)]
-
-#[cfg(feature = "alloc")]
-extern crate alloc;
-
-use core::convert::{TryFrom, TryInto};
-use core::ops::{Bound, RangeBounds};
 
-#[cfg(feature = "alloc")]
-use alloc::vec::Vec;
+use std::cell::Cell;
+use std::collections::hash_map::DefaultHasher;
+use std::convert::TryInto;
+use std::hash::{Hash, Hasher};
+use std::ops::{Bound, RangeBounds};
+use std::thread;
 
-#[cfg(feature = "std")]
-#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
-mod global_rng;
-
-#[cfg(feature = "std")]
-pub use global_rng::*;
+#[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;
 
 /// A random number generator.
 #[derive(Debug, PartialEq, Eq)]
-pub struct Rng(u64);
+pub struct Rng(Cell<u64>);
+
+impl Default for Rng {
+    #[inline]
+    fn default() -> Rng {
+        Rng::new()
+    }
+}
 
 impl Clone for Rng {
-    /// Clones the generator by creating a new generator with the same seed.
+    /// Clones the generator by deterministically deriving a new generator based on the initial
+    /// seed.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// // Seed two generators equally, and clone both of them.
+    /// let base1 = fastrand::Rng::new();
+    /// base1.seed(0x4d595df4d0f33173);
+    /// base1.bool(); // Use the generator once.
+    ///
+    /// let base2 = fastrand::Rng::new();
+    /// base2.seed(0x4d595df4d0f33173);
+    /// base2.bool(); // Use the generator once.
+    ///
+    /// let rng1 = base1.clone();
+    /// let rng2 = base2.clone();
+    ///
+    /// assert_eq!(rng1.u64(..), rng2.u64(..), "the cloned generators are identical");
+    /// ```
     fn clone(&self) -> Rng {
-        Rng::with_seed(self.0)
+        Rng::with_seed(self.gen_u64())
     }
 }
 
 impl Rng {
     /// Generates a random `u32`.
     #[inline]
-    fn gen_u32(&mut self) -> u32 {
+    fn gen_u32(&self) -> u32 {
         self.gen_u64() as u32
     }
 
     /// Generates a random `u64`.
     #[inline]
-    fn gen_u64(&mut self) -> u64 {
-        let s = self.0.wrapping_add(0xA0761D6478BD642F);
-        self.0 = s;
+    fn gen_u64(&self) -> u64 {
+        let s = self.0.get().wrapping_add(0xA0761D6478BD642F);
+        self.0.set(s);
         let t = u128::from(s) * u128::from(s ^ 0xE7037ED1A0B428DB);
         (t as u64) ^ (t >> 64) as u64
     }
 
     /// Generates a random `u128`.
     #[inline]
-    fn gen_u128(&mut self) -> u128 {
+    fn gen_u128(&self) -> u128 {
         (u128::from(self.gen_u64()) << 64) | u128::from(self.gen_u64())
     }
 
     /// Generates a random `u32` in `0..n`.
     #[inline]
-    fn gen_mod_u32(&mut self, n: u32) -> u32 {
+    fn gen_mod_u32(&self, n: u32) -> u32 {
         // Adapted from: https://lemire.me/blog/2016/06/30/fast-random-shuffling/
         let mut r = self.gen_u32();
         let mut hi = mul_high_u32(r, n);
@@ -178,7 +159,7 @@ impl Rng {
 
     /// Generates a random `u64` in `0..n`.
     #[inline]
-    fn gen_mod_u64(&mut self, n: u64) -> u64 {
+    fn gen_mod_u64(&self, n: u64) -> u64 {
         // Adapted from: https://lemire.me/blog/2016/06/30/fast-random-shuffling/
         let mut r = self.gen_u64();
         let mut hi = mul_high_u64(r, n);
@@ -196,7 +177,7 @@ impl Rng {
 
     /// Generates a random `u128` in `0..n`.
     #[inline]
-    fn gen_mod_u128(&mut self, n: u128) -> u128 {
+    fn gen_mod_u128(&self, n: u128) -> u128 {
         // Adapted from: https://lemire.me/blog/2016/06/30/fast-random-shuffling/
         let mut r = self.gen_u128();
         let mut hi = mul_high_u128(r, n);
@@ -213,6 +194,16 @@ impl Rng {
     }
 }
 
+thread_local! {
+    static RNG: Rng = Rng(Cell::new({
+        let mut hasher = DefaultHasher::new();
+        Instant::now().hash(&mut hasher);
+        thread::current().id().hash(&mut hasher);
+        let hash = hasher.finish();
+        (hash << 1) | 1
+    }));
+}
+
 /// Computes `(a * b) >> 32`.
 #[inline]
 fn mul_high_u32(a: u32, b: u32) -> u32 {
@@ -244,7 +235,7 @@ macro_rules! rng_integer {
         ///
         /// Panics if the range is empty.
         #[inline]
-        pub fn $t(&mut self, range: impl RangeBounds<$t>) -> $t {
+        pub fn $t(&self, range: impl RangeBounds<$t>) -> $t {
             let panic_empty_range = || {
                 panic!(
                     "empty range: {:?}..{:?}",
@@ -254,13 +245,13 @@ macro_rules! rng_integer {
             };
 
             let low = match range.start_bound() {
-                Bound::Unbounded => core::$t::MIN,
+                Bound::Unbounded => std::$t::MIN,
                 Bound::Included(&x) => x,
                 Bound::Excluded(&x) => x.checked_add(1).unwrap_or_else(panic_empty_range),
             };
 
             let high = match range.end_bound() {
-                Bound::Unbounded => core::$t::MAX,
+                Bound::Unbounded => std::$t::MAX,
                 Bound::Included(&x) => x,
                 Bound::Excluded(&x) => x.checked_sub(1).unwrap_or_else(panic_empty_range),
             };
@@ -269,7 +260,7 @@ macro_rules! rng_integer {
                 panic_empty_range();
             }
 
-            if low == core::$t::MIN && high == core::$t::MAX {
+            if low == std::$t::MIN && high == std::$t::MAX {
                 self.$gen() as $t
             } else {
                 let len = high.wrapping_sub(low).wrapping_add(1);
@@ -280,62 +271,46 @@ macro_rules! rng_integer {
 }
 
 impl Rng {
+    /// Creates a new random number generator.
+    #[inline]
+    pub fn new() -> Rng {
+        Rng::with_seed(
+            RNG.try_with(|rng| rng.u64(..))
+                .unwrap_or(0x4d595df4d0f33173),
+        )
+    }
+
     /// Creates a new random number generator with the initial seed.
     #[inline]
     #[must_use = "this creates a new instance of `Rng`; if you want to initialize the thread-local generator, use `fastrand::seed()` instead"]
     pub fn with_seed(seed: u64) -> Self {
-        let mut rng = Rng(0);
+        let rng = Rng(Cell::new(0));
 
         rng.seed(seed);
         rng
     }
 
-    /// Clones the generator by deterministically deriving a new generator based on the initial
-    /// seed.
-    ///
-    /// This function can be used to create a new generator that is a "spinoff" of the old
-    /// generator. The new generator will not produce the same sequence of values as the
-    /// old generator.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// // Seed two generators equally, and clone both of them.
-    /// let mut base1 = fastrand::Rng::with_seed(0x4d595df4d0f33173);
-    /// base1.bool(); // Use the generator once.
-    ///
-    /// let mut base2 = fastrand::Rng::with_seed(0x4d595df4d0f33173);
-    /// base2.bool(); // Use the generator once.
-    ///
-    /// let mut rng1 = base1.fork();
-    /// let mut rng2 = base2.fork();
-    ///
-    /// println!("rng1 returns {}", rng1.u32(..));
-    /// println!("rng2 returns {}", rng2.u32(..));
-    /// ```
-    #[inline]
-    #[must_use = "this creates a new instance of `Rng`"]
-    pub fn fork(&mut self) -> Self {
-        Rng::with_seed(self.gen_u64())
-    }
-
     /// Generates a random `char` in ranges a-z and A-Z.
     #[inline]
-    pub fn alphabetic(&mut self) -> char {
+    pub fn alphabetic(&self) -> char {
         const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
-        *self.choice(CHARS).unwrap() as char
+        let len = CHARS.len() as u8;
+        let i = self.u8(..len);
+        CHARS[i as usize] as char
     }
 
     /// Generates a random `char` in ranges a-z, A-Z and 0-9.
     #[inline]
-    pub fn alphanumeric(&mut self) -> char {
+    pub fn alphanumeric(&self) -> char {
         const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
-        *self.choice(CHARS).unwrap() as char
+        let len = CHARS.len() as u8;
+        let i = self.u8(..len);
+        CHARS[i as usize] as char
     }
 
     /// Generates a random `bool`.
     #[inline]
-    pub fn bool(&mut self) -> bool {
+    pub fn bool(&self) -> bool {
         self.u8(..) % 2 == 0
     }
 
@@ -345,7 +320,7 @@ impl Rng {
     ///
     /// Panics if the base is zero or greater than 36.
     #[inline]
-    pub fn digit(&mut self, base: u32) -> char {
+    pub fn digit(&self, base: u32) -> char {
         if base == 0 {
             panic!("base cannot be zero");
         }
@@ -361,57 +336,19 @@ impl Rng {
     }
 
     /// Generates a random `f32` in range `0..1`.
-    pub fn f32(&mut self) -> f32 {
+    pub fn f32(&self) -> f32 {
         let b = 32;
-        let f = core::f32::MANTISSA_DIGITS - 1;
+        let f = std::f32::MANTISSA_DIGITS - 1;
         f32::from_bits((1 << (b - 2)) - (1 << f) + (self.u32(..) >> (b - f))) - 1.0
     }
 
     /// Generates a random `f64` in range `0..1`.
-    pub fn f64(&mut self) -> f64 {
+    pub fn f64(&self) -> f64 {
         let b = 64;
-        let f = core::f64::MANTISSA_DIGITS - 1;
+        let f = std::f64::MANTISSA_DIGITS - 1;
         f64::from_bits((1 << (b - 2)) - (1 << f) + (self.u64(..) >> (b - f))) - 1.0
     }
 
-    /// Collects `amount` values at random from the iterator into a vector.
-    ///
-    /// The length of the returned vector equals `amount` unless the iterator
-    /// contains insufficient elements, in which case it equals the number of
-    /// elements available.
-    ///
-    /// Complexity is `O(n)` where `n` is the length of the iterator.
-    #[cfg(feature = "alloc")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
-    pub fn choose_multiple<T: Iterator>(&mut self, mut source: T, amount: usize) -> Vec<T::Item> {
-        // Adapted from: https://docs.rs/rand/latest/rand/seq/trait.IteratorRandom.html#method.choose_multiple
-        let mut reservoir = Vec::with_capacity(amount);
-
-        reservoir.extend(source.by_ref().take(amount));
-
-        // Continue unless the iterator was exhausted
-        //
-        // note: this prevents iterators that "restart" from causing problems.
-        // If the iterator stops once, then so do we.
-        if reservoir.len() == amount {
-            for (i, elem) in source.enumerate() {
-                let end = i + 1 + amount;
-                let k = self.usize(0..end);
-                if let Some(slot) = reservoir.get_mut(k) {
-                    *slot = elem;
-                }
-            }
-        } else {
-            // If less than one third of the `Vec` was used, reallocate
-            // so that the unused space is not wasted. There is a corner
-            // case where `amount` was much less than `self.len()`.
-            if reservoir.capacity() > 3 * reservoir.len() {
-                reservoir.shrink_to_fit();
-            }
-        }
-        reservoir
-    }
-
     rng_integer!(
         i8,
         u8,
@@ -479,49 +416,28 @@ impl Rng {
 
     /// Generates a random `char` in range a-z.
     #[inline]
-    pub fn lowercase(&mut self) -> char {
+    pub fn lowercase(&self) -> char {
         const CHARS: &[u8] = b"abcdefghijklmnopqrstuvwxyz";
-        *self.choice(CHARS).unwrap() as char
+        let len = CHARS.len() as u8;
+        let i = self.u8(..len);
+        CHARS[i as usize] as char
     }
 
     /// Initializes this generator with the given seed.
     #[inline]
-    pub fn seed(&mut self, seed: u64) {
-        self.0 = seed;
+    pub fn seed(&self, seed: u64) {
+        self.0.set(seed);
     }
 
     /// Gives back **current** seed that is being held by this generator.
     #[inline]
     pub fn get_seed(&self) -> u64 {
-        self.0
-    }
-
-    /// Choose an item from an iterator at random.
-    ///
-    /// This function may have an unexpected result if the `len()` property of the
-    /// iterator does not match the actual number of items in the iterator. If
-    /// the iterator is empty, this returns `None`.
-    #[inline]
-    pub fn choice<I>(&mut self, iter: I) -> Option<I::Item>
-    where
-        I: IntoIterator,
-        I::IntoIter: ExactSizeIterator,
-    {
-        let mut iter = iter.into_iter();
-
-        // Get the item at a random index.
-        let len = iter.len();
-        if len == 0 {
-            return None;
-        }
-        let index = self.usize(0..len);
-
-        iter.nth(index)
+        self.0.get()
     }
 
     /// Shuffles a slice randomly.
     #[inline]
-    pub fn shuffle<T>(&mut self, slice: &mut [T]) {
+    pub fn shuffle<T>(&self, slice: &mut [T]) {
         for i in 1..slice.len() {
             slice.swap(i, self.usize(..=i));
         }
@@ -529,7 +445,7 @@ impl Rng {
 
     /// Fill a byte slice with random data.
     #[inline]
-    pub fn fill(&mut self, slice: &mut [u8]) {
+    pub fn fill(&self, slice: &mut [u8]) {
         // We fill the slice by chunks of 8 bytes, or one block of
         // WyRand output per new state.
         let mut chunks = slice.chunks_exact_mut(core::mem::size_of::<u64>());
@@ -626,16 +542,20 @@ impl Rng {
 
     /// Generates a random `char` in range A-Z.
     #[inline]
-    pub fn uppercase(&mut self) -> char {
+    pub fn uppercase(&self) -> char {
         const CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
-        *self.choice(CHARS).unwrap() as char
+        let len = CHARS.len() as u8;
+        let i = self.u8(..len);
+        CHARS[i as usize] as char
     }
 
     /// Generates a random `char` in the given range.
     ///
     /// Panics if the range is empty.
     #[inline]
-    pub fn char(&mut self, range: impl RangeBounds<char>) -> char {
+    pub fn char(&self, range: impl RangeBounds<char>) -> char {
+        use std::convert::TryFrom;
+
         let panic_empty_range = || {
             panic!(
                 "empty range: {:?}..{:?}",
@@ -661,7 +581,7 @@ impl Rng {
         };
 
         let high = match range.end_bound() {
-            Bound::Unbounded => core::char::MAX,
+            Bound::Unbounded => std::char::MAX,
             Bound::Included(&x) => x,
             Bound::Excluded(&x) => {
                 let scalar = if x as u32 == surrogate_start + surrogate_len {
@@ -690,3 +610,97 @@ impl Rng {
         val.try_into().unwrap()
     }
 }
+
+/// Initializes the thread-local generator with the given seed.
+#[inline]
+pub fn seed(seed: u64) {
+    RNG.with(|rng| rng.seed(seed))
+}
+
+/// Gives back **current** seed that is being held by the thread-local generator.
+#[inline]
+pub fn get_seed() -> u64 {
+    RNG.with(|rng| rng.get_seed())
+}
+
+/// Generates a random `bool`.
+#[inline]
+pub fn bool() -> bool {
+    RNG.with(|rng| rng.bool())
+}
+
+/// Generates a random `char` in ranges a-z and A-Z.
+#[inline]
+pub fn alphabetic() -> char {
+    RNG.with(|rng| rng.alphabetic())
+}
+
+/// Generates a random `char` in ranges a-z, A-Z and 0-9.
+#[inline]
+pub fn alphanumeric() -> char {
+    RNG.with(|rng| rng.alphanumeric())
+}
+
+/// Generates a random `char` in range a-z.
+#[inline]
+pub fn lowercase() -> char {
+    RNG.with(|rng| rng.lowercase())
+}
+
+/// Generates a random `char` in range A-Z.
+#[inline]
+pub fn uppercase() -> char {
+    RNG.with(|rng| rng.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 {
+    RNG.with(|rng| rng.digit(base))
+}
+
+/// Shuffles a slice randomly.
+#[inline]
+pub fn shuffle<T>(slice: &mut [T]) {
+    RNG.with(|rng| rng.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>) -> $t {
+            RNG.with(|rng| rng.$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 {
+    RNG.with(|rng| rng.f32())
+}
+
+/// Generates a random `f64` in range `0..1`.
+pub fn f64() -> f64 {
+    RNG.with(|rng| rng.f64())
+}
diff --git a/tests/smoke.rs b/tests/smoke.rs
index 7c92ee5..ff3cea6 100644
--- a/tests/smoke.rs
+++ b/tests/smoke.rs
@@ -77,7 +77,7 @@ fn u128() {
 
 #[test]
 fn fill() {
-    let mut r = fastrand::Rng::new();
+    let r = fastrand::Rng::new();
     let mut a = [0u8; 64];
     let mut b = [0u8; 64];
 
@@ -89,7 +89,7 @@ fn fill() {
 
 #[test]
 fn rng() {
-    let mut r = fastrand::Rng::new();
+    let r = fastrand::Rng::new();
 
     assert_ne!(r.u64(..), r.u64(..));
 
@@ -102,8 +102,8 @@ fn rng() {
 
 #[test]
 fn rng_init() {
-    let mut a = fastrand::Rng::new();
-    let mut b = fastrand::Rng::new();
+    let a = fastrand::Rng::new();
+    let b = fastrand::Rng::new();
     assert_ne!(a.u64(..), b.u64(..));
 
     a.seed(7);
@@ -113,31 +113,8 @@ fn rng_init() {
 
 #[test]
 fn with_seed() {
-    let mut a = fastrand::Rng::with_seed(7);
-    let mut b = fastrand::Rng::new();
+    let a = fastrand::Rng::with_seed(7);
+    let b = fastrand::Rng::new();
     b.seed(7);
     assert_eq!(a.u64(..), b.u64(..));
 }
-
-#[test]
-fn choose_multiple() {
-    let mut a = fastrand::Rng::new();
-    let mut elements = (0..20).collect::<Vec<_>>();
-
-    while !elements.is_empty() {
-        let chosen = a.choose_multiple(0..20, 5);
-        for &x in &chosen {
-            elements.retain(|&y| y != x);
-        }
-    }
-}
-
-#[test]
-fn choice() {
-    let items = [1, 4, 9, 5, 2, 3, 6, 7, 8, 0];
-    let mut r = fastrand::Rng::new();
-
-    for item in &items {
-        while r.choice(&items).unwrap() != item {}
-    }
-}