Feature: add support for no_std environments

Cargo.toml

@@ -1,22 +1,34 @@
 [package]
 name = "bigdecimal"
-version = "0.3.0"
+version = "0.4.0"
 authors = ["Andrew Kubera"]
 description = "Arbitrary precision decimal numbers"
 documentation = "https://docs.rs/bigdecimal"
 homepage = "https://github.com/akubera/bigdecimal-rs"
 repository = "https://github.com/akubera/bigdecimal-rs"
-keywords = ["mathematics", "numerics", "decimal", "arbitrary-precision", "floating-point"]
+keywords = [
+    "mathematics",
+    "numerics",
+    "decimal",
+    "arbitrary-precision",
+    "floating-point",
+    "no-std",
+]
 license = "MIT/Apache-2.0"
 
 [dependencies]
-num-bigint = "0.4"
-num-integer = "0.1"
-num-traits = "0.2"
-serde = { version = "1.0", optional = true }
+libm = "0.2.6"
+num-bigint = { version = "0.4", default-features = false }
+num-integer = { version = "0.1", default-features = false }
+num-traits = { version = "0.2", default-features = false }
+serde = { version = "1.0", optional = true, default-features = false }
 
-[dev-dependencies.serde_json]
-version = "1.0"
+[dev-dependencies]
+serde_json = "1.0"
+siphasher = { version = "0.3.10", default-features = false }
 
 [features]
+default = ["std"]
+alloc = []
 string-only = []
+std = ["num-bigint/std", "num-integer/std", "num-traits/std", "serde/std"]

src/lib.rs

@@ -39,6 +39,7 @@
 //!
 //! println!("Input ({}) with 10 decimals: {} vs {})", input, dec, float);
 //! ```
+#![cfg_attr(not(feature = "std"), no_std)]
 #![allow(clippy::unreadable_literal)]
 #![allow(clippy::needless_return)]
 #![allow(clippy::suspicious_arithmetic_impl)]
@@ -52,16 +53,24 @@ extern crate num_integer;
 #[cfg(feature = "serde")]
 extern crate serde;
 
-use std::cmp::Ordering;
-use std::convert::TryFrom;
-use std::default::Default;
-use std::error::Error;
-use std::fmt;
-use std::hash::{Hash, Hasher};
-use std::num::{ParseFloatError, ParseIntError};
-use std::ops::{Add, AddAssign, Div, Mul, MulAssign, Neg, Rem, Sub, SubAssign};
-use std::iter::Sum;
-use std::str::{self, FromStr};
+#[cfg(feature = "std")]
+include!("./with_std.rs");
+
+#[cfg(not(feature = "std"))]
+include!("./without_std.rs");
+
+#[cfg(all(not(feature = "std"), feature = "alloc"))]
+include!("./with_alloc.rs");
+
+use crate::cmp::Ordering;
+use crate::convert::TryFrom;
+use crate::default::Default;
+use crate::hash::{Hash, Hasher};
+use crate::num::{ParseFloatError, ParseIntError};
+use crate::ops::{Add, AddAssign, Div, Mul, MulAssign, Neg, Rem, Sub, SubAssign};
+use crate::iter::Sum;
+use crate::str::FromStr;
+use crate::string::{String, ToString};
 
 use num_bigint::{BigInt, ParseBigIntError, Sign, ToBigInt};
 use num_integer::Integer as IntegerTrait;
@@ -151,6 +160,17 @@ pub struct BigDecimal {
     scale: i64,
 }
 
+#[cfg(not(feature = "std"))]
+// f64::exp2 is only available in std, we have to use an external crate like libm
+fn exp2(x: f64) -> f64 {
+    libm::exp2(x)
+}
+
+#[cfg(feature = "std")]
+fn exp2(x: f64) -> f64 {
+    x.exp2()
+}
+
 impl BigDecimal {
     /// Creates and initializes a `BigDecimal`.
     ///
@@ -399,7 +419,8 @@ impl BigDecimal {
         let guess = {
             let magic_guess_scale = 1.1951678538495576_f64;
             let initial_guess = (self.int_val.bits() as f64 - self.scale as f64 * LOG2_10) / 2.0;
-            let res = magic_guess_scale * initial_guess.exp2();
+            let res = magic_guess_scale * exp2(initial_guess);
+
             if res.is_normal() {
                 BigDecimal::try_from(res).unwrap()
             } else {
@@ -471,7 +492,8 @@ impl BigDecimal {
         let guess = {
             let magic_guess_scale = 1.124960491619939_f64;
             let initial_guess = (self.int_val.bits() as f64 - self.scale as f64 * LOG2_10) / 3.0;
-            let res = magic_guess_scale * initial_guess.exp2();
+            let res = magic_guess_scale * exp2(initial_guess);
+
             if res.is_normal() {
                 BigDecimal::try_from(res).unwrap()
             } else {
@@ -538,7 +560,7 @@ impl BigDecimal {
 
             let magic_factor = 0.721507597259061_f64;
             let initial_guess = scale * LOG2_10 - bits;
-            let res = magic_factor * initial_guess.exp2();
+            let res = magic_factor * exp2(initial_guess);
 
             if res.is_normal() {
                 BigDecimal::try_from(res).unwrap()
@@ -689,7 +711,8 @@ impl fmt::Display for ParseBigDecimalError {
     }
 }
 
-impl Error for ParseBigDecimalError {
+#[cfg(feature = "std")]
+impl std::error::Error for ParseBigDecimalError {
     fn description(&self) -> &str {
         "failed to parse bigint/biguint"
     }
@@ -1012,7 +1035,7 @@ impl Sub<BigDecimal> for BigDecimal {
     #[inline]
     fn sub(self, rhs: BigDecimal) -> BigDecimal {
         let mut lhs = self;
-        let scale = std::cmp::max(lhs.scale, rhs.scale);
+        let scale = cmp::max(lhs.scale, rhs.scale);
 
         match lhs.scale.cmp(&rhs.scale) {
             Ordering::Equal => {
@@ -1031,7 +1054,7 @@ impl<'a> Sub<&'a BigDecimal> for BigDecimal {
     #[inline]
     fn sub(self, rhs: &BigDecimal) -> BigDecimal {
         let mut lhs = self;
-        let scale = std::cmp::max(lhs.scale, rhs.scale);
+        let scale = cmp::max(lhs.scale, rhs.scale);
 
         match lhs.scale.cmp(&rhs.scale) {
             Ordering::Equal => {
@@ -1407,7 +1430,7 @@ impl Rem<BigDecimal> for BigDecimal {
 
     #[inline]
     fn rem(self, other: BigDecimal) -> BigDecimal {
-        let scale = std::cmp::max(self.scale, other.scale);
+        let scale = cmp::max(self.scale, other.scale);
 
         let num = self.take_and_scale(scale).int_val;
         let den = other.take_and_scale(scale).int_val;
@@ -1421,7 +1444,7 @@ impl<'a> Rem<&'a BigDecimal> for BigDecimal {
 
     #[inline]
     fn rem(self, other: &BigDecimal) -> BigDecimal {
-        let scale = std::cmp::max(self.scale, other.scale);
+        let scale = cmp::max(self.scale, other.scale);
         let num = self.take_and_scale(scale).int_val;
         let den = &other.int_val;
 
@@ -1438,7 +1461,7 @@ impl<'a> Rem<BigDecimal> for &'a BigDecimal {
 
     #[inline]
     fn rem(self, other: BigDecimal) -> BigDecimal {
-        let scale = std::cmp::max(self.scale, other.scale);
+        let scale = cmp::max(self.scale, other.scale);
         let num = &self.int_val;
         let den = other.take_and_scale(scale).int_val;
 
@@ -1458,7 +1481,7 @@ impl<'a, 'b> Rem<&'b BigDecimal> for &'a BigDecimal {
 
     #[inline]
     fn rem(self, other: &BigDecimal) -> BigDecimal {
-        let scale = std::cmp::max(self.scale, other.scale);
+        let scale = cmp::max(self.scale, other.scale);
         let num = &self.int_val;
         let den = &other.int_val;
 
@@ -1765,7 +1788,7 @@ impl TryFrom<f32> for BigDecimal {
 
     #[inline]
     fn try_from(n: f32) -> Result<Self, Self::Error> {
-        BigDecimal::from_str(&format!("{:.PRECISION$e}", n, PRECISION = ::std::f32::DIGITS as usize))
+        BigDecimal::from_str(&format!("{:.PRECISION$e}", n, PRECISION = f32::DIGITS as usize))
     }
 }
 
@@ -1774,7 +1797,7 @@ impl TryFrom<f64> for BigDecimal {
 
     #[inline]
     fn try_from(n: f64) -> Result<Self, Self::Error> {
-        BigDecimal::from_str(&format!("{:.PRECISION$e}", n, PRECISION = ::std::f64::DIGITS as usize))
+        BigDecimal::from_str(&format!("{:.PRECISION$e}", n, PRECISION = f64::DIGITS as usize))
     }
 }
 
@@ -1809,11 +1832,11 @@ impl ToBigInt for BigDecimal {
 /// Tools to help serializing/deserializing `BigDecimal`s
 #[cfg(feature = "serde")]
 mod bigdecimal_serde {
+    use crate::{fmt, TryFrom, FromStr};
+
     use super::BigDecimal;
     use serde::{de, ser};
-    use std::convert::TryFrom;
-    use std::fmt;
-    use std::str::FromStr;
+
     #[allow(unused_imports)]
     use num_traits::FromPrimitive;
 
@@ -1964,9 +1987,9 @@ mod bigdecimal_serde {
             0.001,
             12.34,
             5.0 * 0.03125,
-            ::std::f64::consts::PI,
-            ::std::f64::consts::PI * 10000.0,
-            ::std::f64::consts::PI * 30000.0,
+            crate::f64::consts::PI,
+            crate::f64::consts::PI * 10000.0,
+            crate::f64::consts::PI * 30000.0,
         ];
         for n in vals {
             let expected = BigDecimal::from_f64(n).unwrap();
@@ -1979,12 +2002,13 @@ mod bigdecimal_serde {
 #[rustfmt::skip]
 #[cfg(test)]
 mod bigdecimal_tests {
-    use BigDecimal;
+    use crate::{BigDecimal, FromStr, TryFrom};
     use num_traits::{ToPrimitive, FromPrimitive, Signed, Zero, One};
-    use std::convert::TryFrom;
-    use std::str::FromStr;
     use num_bigint;
 
+    #[cfg(all(not(feature = "std"), feature = "alloc"))]
+    use crate::{vec, format, ToString};
+
     #[test]
     fn test_sum() {
         let vals = vec![
@@ -2056,8 +2080,8 @@ mod bigdecimal_tests {
             ("12", 12),
             ("-13", -13),
             ("111", 111),
-            ("-128", ::std::i8::MIN),
-            ("127", ::std::i8::MAX),
+            ("-128", i8::MIN),
+            ("127", i8::MAX),
         ];
         for (s, n) in vals {
             let expected = BigDecimal::from_str(s).unwrap();
@@ -2077,10 +2101,10 @@ mod bigdecimal_tests {
             ("0.001", 0.001),
             ("12.34", 12.34),
             ("0.15625", 5.0 * 0.03125),
-            ("3.141593", ::std::f32::consts::PI),
-            ("31415.93", ::std::f32::consts::PI * 10000.0),
-            ("94247.78", ::std::f32::consts::PI * 30000.0),
-            // ("3.14159265358979323846264338327950288f32", ::std::f32::consts::PI),
+            ("3.141593", crate::f32::consts::PI),
+            ("31415.93", crate::f32::consts::PI * 10000.0),
+            ("94247.78", crate::f32::consts::PI * 30000.0),
+            // ("3.14159265358979323846264338327950288f32", crate::f32::consts::PI),
 
         ];
         for (s, n) in vals {
@@ -2104,9 +2128,9 @@ mod bigdecimal_tests {
             // ("12.3399999999999999", 12.34), // <- Precision 16 decimal points
             ("0.15625", 5.0 * 0.03125),
             ("0.3333333333333333", 1.0 / 3.0),
-            ("3.141592653589793", ::std::f64::consts::PI),
-            ("31415.92653589793", ::std::f64::consts::PI * 10000.0f64),
-            ("94247.77960769380", ::std::f64::consts::PI * 30000.0f64),
+            ("3.141592653589793", crate::f64::consts::PI),
+            ("31415.92653589793", crate::f64::consts::PI * 10000.0f64),
+            ("94247.77960769380", crate::f64::consts::PI * 30000.0f64),
         ];
         for (s, n) in vals {
             let expected = BigDecimal::from_str(s).unwrap();
@@ -2118,8 +2142,8 @@ mod bigdecimal_tests {
 
     #[test]
     fn test_nan_float() {
-        assert!(BigDecimal::try_from(std::f32::NAN).is_err());
-        assert!(BigDecimal::try_from(std::f64::NAN).is_err());
+        assert!(BigDecimal::try_from(f32::NAN).is_err());
+        assert!(BigDecimal::try_from(f64::NAN).is_err());
     }
 
     #[test]
@@ -2349,8 +2373,7 @@ mod bigdecimal_tests {
 
     #[test]
     fn test_hash_equal() {
-        use std::hash::{Hash, Hasher};
-        use std::collections::hash_map::DefaultHasher;
+        use crate::{Hash, Hasher, DefaultHasher};
 
         fn hash<T>(obj: &T) -> u64
             where T: Hash
@@ -2386,8 +2409,7 @@ mod bigdecimal_tests {
 
     #[test]
     fn test_hash_not_equal() {
-        use std::hash::{Hash, Hasher};
-        use std::collections::hash_map::DefaultHasher;
+        use crate::{Hash, Hasher, DefaultHasher};
 
         fn hash<T>(obj: &T) -> u64
             where T: Hash
@@ -2413,8 +2435,7 @@ mod bigdecimal_tests {
 
     #[test]
     fn test_hash_equal_scale() {
-        use std::hash::{Hash, Hasher};
-        use std::collections::hash_map::DefaultHasher;
+        use crate::{Hash, Hasher, DefaultHasher};
 
         fn hash<T>(obj: &T) -> u64
             where T: Hash

src/with_alloc.rs

@@ -0,0 +1,3 @@
+extern crate alloc;
+
+use alloc::{format, string, vec};

src/with_std.rs

@@ -0,0 +1,4 @@
+use std::{cmp, convert, default, fmt, hash, num, ops, iter, str, string, i8, f32, f64};
+
+#[cfg(test)]
+use std::collections::hash_map::DefaultHasher;

src/without_std.rs

@@ -0,0 +1,11 @@
+use core::{cmp, convert, default, fmt, hash, num, ops, iter, str, i8, f32, f64};
+
+#[cfg(test)]
+extern crate siphasher;
+
+#[cfg(test)]
+use siphasher::sip::SipHasher as DefaultHasher;
+
+// Without this import we get the following error:
+// error[E0599]: no method named `powi` found for type `f64` in the current scope
+use num_traits::float::FloatCore;