#![no_std] as an optional feature

Cargo.toml

@@ -33,6 +33,7 @@ name = "bench"
 harness = false
 
 [features]
+no-std = ["primal-check/no-std", "primal-estimate/no-std", "primal-sieve/no-std"]
 unstable = ["primal-sieve/unstable"]
 
 [workspace]

README.md

@@ -25,3 +25,6 @@ count the exact number of primes below 10<sup>10</sup> (455052511)
 on the author's laptop (i7-3517U).
 
 [**Documentation**](http://docs.rs/primal/)
+
+### no_std
+This crate can be built for no_std environments by enabling the no-std feature.

primal-bit/Cargo.toml

@@ -16,7 +16,9 @@ Bit-vector specialised to the prime-number-related needs of `primal`.
 """
 
 [dependencies]
-hamming = "0.1"
+# last update to crates.io was 8 years ago and the crate did not support no-std then
+hamming = { git = "https://github.com/huonw/hamming.git", rev = "4b528d75cfa2e102b6edc6c60b629cd986215437" }
 
 [features]
+no-std = []
 unstable = []

primal-bit/src/inner.rs

@@ -2,6 +2,9 @@
 //! encapsulated in a module to reduce scope.
 #![allow(unsafe_code)]
 
+#[cfg(feature = "no-std")]
+use alloc::{vec, vec::Vec};
+
 use crate::BITS;
 
 /// The bitvector type.

primal-bit/src/iter.rs

@@ -1,8 +1,12 @@
-use std::iter;
-use std::mem;
-use std::ops::Range;
-use std::slice;
+use core::iter;
+use core::mem;
+use core::ops::Range;
+use core::slice;
+
+#[cfg(not(feature = "no-std"))]
 use std::vec;
+#[cfg(feature = "no-std")]
+use alloc::vec;
 
 use crate::BitVec;
 use crate::BITS;

primal-bit/src/lib.rs

@@ -10,11 +10,15 @@
 
 //! A very simple bit-vector that serves the needs of `primal`.
 
+#![cfg_attr(feature = "no-std", no_std)]
 #![deny(unsafe_code)]
 
-use std::fmt;
-use std::hash;
-use std::ops::Index;
+#[cfg(feature = "no-std")]
+extern crate alloc;
+
+use core::fmt;
+use core::hash;
+use core::ops::Index;
 
 mod inner;
 mod iter;

primal-check/Cargo.toml

@@ -15,10 +15,12 @@ Fast standalone primality testing.
 """
 
 [dependencies]
-num-integer = "0.1"
+libm = { version = "0.2.8", optional = true }
+num-integer = { version = "0.1", default_features = false }
 
 [dev-dependencies]
 primal = { path = "..", version = "0.3" }
 
 [features]
+no-std = ["libm"]
 unstable = []

primal-check/src/is_prime.rs

@@ -74,7 +74,7 @@ pub fn miller_rabin(n: u64) -> bool {
         (3_474_749_660_382, &[2, 3, 5, 7, 11, 13]),
         (341_550_071_728_320, &[2, 3, 5, 7, 11, 13, 17]),
         (3_825_123_056_546_413_050, &[2, 3, 5, 7, 11, 13, 17, 19, 23]),
-        (std::u64::MAX, &[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37]),
+        (core::u64::MAX, &[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37]),
     ];
 
     if n % 2 == 0 { return n == 2 }

primal-check/src/lib.rs

@@ -2,6 +2,8 @@
 //!
 //! This crate is designed to be used via `primal`.
 
+#![cfg_attr(feature = "no-std", no_std)]
+
 pub use crate::is_prime::miller_rabin;
 pub use crate::perfect_power::{as_perfect_power, as_prime_power};
 

primal-check/src/perfect_power.rs

@@ -43,7 +43,10 @@ pub fn as_perfect_power(x: u64) -> (u64, u8) {
     let mut expn: u32 = 2;
     let mut step = 1;
     while expn <= floor_log_2 {
+        #[cfg(not(feature = "no-std"))]
         let factor = x_.powf(1.0/expn as f64).round() as u64;
+        #[cfg(feature = "no-std")]
+        let factor = libm::round(libm::pow(x_, 1.0/expn as f64)) as u64;
         // the only case this will wrap is if x is close to 2^64 and
         // the round() rounds up, pushing this calculation over the
         // edge, however, the overflow will be well away from x, so we

primal-estimate/Cargo.toml

@@ -14,8 +14,12 @@ State-of-the-art estimation of upper and lower bounds for π(n)
 (the number of primes below n) and p_k (the k-th prime).
 """
 
+[dependencies]
+libm = { version = "0.2.8", optional = true }
+
 [dev-dependencies]
 primal = { path = "..", version = "0.3" }
 
 [features]
+no-std = ["libm"]
 unstable = []

primal-estimate/src/lib.rs

@@ -3,6 +3,8 @@
 //!
 //! This is designed to be used via the `primal` crate.
 
+#![cfg_attr(feature = "no-std", no_std)]
+
 #[allow(dead_code)]
 mod tables;
 
@@ -43,7 +45,10 @@ pub fn prime_pi(n: u64) -> (u64, u64) {
         (x, x)
     } else {
         let n_ = n as f64;
+        #[cfg(not(feature = "no-std"))]
         let lg = n_.ln();
+        #[cfg(feature = "no-std")]
+        let lg = libm::log(n_);
         let inv_lg = 1.0 / lg;
         let n_inv_lg = n_ * inv_lg;
 
@@ -124,9 +129,17 @@ pub fn nth_prime(n: u64) -> (u64, u64) {
         (x, x)
     } else {
         let n_ = n as f64;
+
+        #[cfg(not(feature = "no-std"))]
         let lg = n_.ln();
+        #[cfg(not(feature = "no-std"))]
         let lglg = lg.ln();
 
+        #[cfg(feature = "no-std")]
+        let lg = libm::log(n_);
+        #[cfg(feature = "no-std")]
+        let lglg = libm::log(lg);
+
         let lo = match () {
             // [2] Theorem 1.6
             _ if n >= 3520_u64 => n_ * (lg + lglg - 1.0 + (lglg - 2.1) / lg),

primal-sieve/Cargo.toml

@@ -15,6 +15,7 @@ A high performance prime sieve.
 """
 
 [dependencies]
+libm = { version = "0.2.8", optional = true }
 primal-bit = { path = "../primal-bit", version = "0.3" }
 primal-estimate = { path = "../primal-estimate", version = "0.3" }
 smallvec = "1"
@@ -29,6 +30,7 @@ name = "bench"
 harness = false
 
 [features]
+no-std = ["libm", "primal-bit/no-std", "primal-estimate/no-std"]
 unstable = []
 safe = []
 slow_tests = []

primal-sieve/src/lib.rs

@@ -2,6 +2,11 @@
 //!
 //! This is designed to be used via the `primal` crate.
 
+#![cfg_attr(feature = "no-std", no_std)]
+
+#[cfg(feature = "no-std")]
+extern crate alloc;
+
 // black boxes for pointers; LLVM isn't so happy without
 // them. Unfortunately only usable with 1.59+ asm!, but the code isn't
 // *too* much slower without them.

primal-sieve/src/sieve.rs

@@ -2,8 +2,11 @@ use primal_bit::BitVec;
 use crate::wheel;
 use crate::streaming::StreamingSieve;
 
-use std::cmp;
-use std::slice;
+use core::cmp;
+use core::slice;
+
+#[cfg(feature = "no-std")]
+use alloc::{vec, vec::Vec};
 
 type SmallVec1<T> = ::smallvec::SmallVec<[T; 1]>;
 
@@ -777,7 +780,7 @@ mod tests {
         const LAST: usize = 4_294_967_291; // last 32-bit prime
         const SUM: u64 = 425_649_736_193_687_430; // sum of 32-bit primes
 
-        let sieve = Sieve::new(::std::u32::MAX as usize);
+        let sieve = Sieve::new(core::u32::MAX as usize);
         assert!(sieve.upper_bound() >= LAST);
         assert_eq!(sieve.primes_from(LAST - 100).last(), Some(LAST));
 

primal-sieve/src/streaming/mod.rs

@@ -1,5 +1,8 @@
 use primal_bit::BitVec;
-use std::cmp;
+use core::cmp;
+
+#[cfg(feature = "no-std")]
+use alloc::{vec, vec::Vec};
 
 use crate::wheel;
 
@@ -46,7 +49,11 @@ const SEG_ELEMS: usize = 8 * CACHE;
 const SEG_LEN: usize = SEG_ELEMS * wheel::BYTE_MODULO / wheel::BYTE_SIZE;
 
 fn isqrt(x: usize) -> usize {
-    (x as f64).sqrt() as usize
+    #[cfg(not(feature = "no-std"))]
+    let ret = (x as f64).sqrt() as usize;
+    #[cfg(feature = "no-std")]
+    let ret = libm::sqrt(x as f64) as usize;
+    ret
 }
 
 impl StreamingSieve {

primal-sieve/src/streaming/presieve.rs

@@ -1,5 +1,8 @@
 use primal_bit::BitVec;
-use std::cmp;
+use core::cmp;
+
+#[cfg(feature = "no-std")]
+use alloc::vec;
 
 use crate::wheel;
 use super::StreamingSieve;

primal-sieve/src/streaming/primes.rs

@@ -1,3 +1,6 @@
+#[cfg(feature = "no-std")]
+use alloc::boxed::Box;
+
 use crate::wheel;
 use crate::streaming::{self, StreamingSieve};
 
@@ -206,7 +209,7 @@ mod tests {
     fn equality_huge() {
         let limit = if cfg!(feature = "slow_tests") {
             // This takes a minute or so in debug mode, but it does work!
-            ::std::u32::MAX as usize
+            core::u32::MAX as usize
         } else {
             100_000_000
         };

primal-sieve/src/wheel/mod.rs

@@ -1,6 +1,9 @@
-use std::cmp;
+use core::cmp;
 use primal_bit::BitVec;
 
+#[cfg(feature = "no-std")]
+use alloc::borrow::ToOwned;
+
 pub const BYTE_SIZE: usize = 8;
 pub const BYTE_MODULO: usize = 30;
 

primal-sieve/src/wheel/wheel210.rs

@@ -679,7 +679,7 @@ pub unsafe fn hardcoded_sieve(bytes: &mut [u8], si_: &mut usize, wi_: &mut usize
     let bytes = bytes;
     let start = bytes.as_mut_ptr();
     let len = bytes.len() as isize;
-    let largest_step = ::std::cmp::min(len, 210 * (prime as isize + 1) - 1);
+    let largest_step = core::cmp::min(len, 210 * (prime as isize + 1) - 1);
     let loop_len = len - largest_step;
     let loop_end = start.offset(loop_len);
     let end = start.offset(len);

primal-sieve/src/wheel/wheel30.rs

@@ -185,7 +185,7 @@ pub unsafe fn hardcoded_sieve(bytes: &mut [u8], si_: &mut usize, wi_: &mut usize
     let bytes = bytes;
     let start = bytes.as_mut_ptr();
     let len = bytes.len() as isize;
-    let largest_step = ::std::cmp::min(len, 30 * (prime as isize + 1) - 1);
+    let largest_step = core::cmp::min(len, 30 * (prime as isize + 1) - 1);
     let loop_len = len - largest_step;
     let loop_end = start.offset(loop_len);
     let end = start.offset(len);

primal-slowsieve/Cargo.toml

@@ -16,6 +16,7 @@ probably want `primal-sieve`, or even just `primal` itself.
 """
 
 [dependencies]
+libm = { version = "0.2.8", optional = true }
 primal-bit = { path = "../primal-bit", version = "0.3" }
 primal-estimate = { path = "../primal-estimate", version = "0.3" }
 
@@ -27,5 +28,6 @@ name = "bench"
 harness = false
 
 [features]
+no-std = ["libm", "primal-bit/no-std", "primal-estimate/no-std"]
 unstable = []
 slow_tests = []

primal-slowsieve/src/lib.rs

@@ -2,8 +2,16 @@
 //!
 //! This is designed to be used via the `primal` crate.
 
+#![cfg_attr(feature = "no-std", no_std)]
+
+#[cfg(feature = "no-std")]
+extern crate alloc;
+
 use primal_bit::BitVec;
-use std::{iter, cmp};
+use core::{iter, cmp};
+
+#[cfg(feature = "no-std")]
+use alloc::{vec, vec::Vec};
 
 /// Stores information about primes up to some limit.
 ///
@@ -55,7 +63,10 @@ impl Primes {
         // the ticking works properly)
         filter(&mut is_prime, limit, 3);
 
+        #[cfg(not(feature = "no-std"))]
         let bound = (limit as f64).sqrt() as usize + 1;
+        #[cfg(feature = "no-std")]
+        let bound = libm::sqrt(limit as f64) as usize + 1;
         // skip 2.
         let mut check = 2;
         let mut tick = if check % 3 == 1 {2} else {1};

src/lib.rs

@@ -249,6 +249,8 @@
 //! This takes 6 <em>micro</em>seconds: more than 500,000&times;
 //! faster than the iterator!
 
+#![cfg_attr(feature = "no-std", no_std)]
+
 pub use primal_estimate::prime_pi as estimate_prime_pi;
 pub use primal_estimate::nth_prime as estimate_nth_prime;
 pub use primal_check::miller_rabin as is_prime;