feat: no std (#78)

Author: robjtede

.github/workflows/ci.yml

@@ -47,6 +47,7 @@ jobs:
         uses: actions-rust-lang/[email protected]
         with:
           toolchain: ${{ matrix.toolchain.version }}
+          target: thumbv6m-none-eabi
 
       - name: Install just, nextest
         uses: taiki-e/[email protected]
@@ -55,3 +56,7 @@ jobs:
 
       - name: Test
         run: just test
+
+      - name: Build (no-std)
+        if: matrix.toolchain.name == 'stable'
+        run: just build-no-std

Cargo.toml

@@ -8,14 +8,15 @@ authors = [
     "Rob Ede <[email protected]>",
 ]
 keywords = ["byte", "byte-size", "utility", "human-readable", "format"]
-categories = ["development-tools", "filesystem"]
+categories = ["development-tools", "filesystem", "no-std"]
 repository = "https://github.com/bytesize-rs/bytesize"
 license = "Apache-2.0"
 edition = "2021"
 rust-version = "1.70"
 
 [features]
-default = []
+default = ["std"]
+std = []
 arbitrary = ["dep:arbitrary"]
 serde = ["dep:serde"]
 

ensure-no-std/Cargo.lock

@@ -0,0 +1,14 @@
+[package]
+name = "ensure-no-std"
+version = "0.1.0"
+publish = false
+edition = "2018"
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+
+[dependencies]
+bytesize = { path = "..", default-features = false }

ensure-no-std/Cargo.toml

@@ -0,0 +1,7 @@
+use alloc::string::ToString as _;
+
+use bytesize::ByteSize;
+
+pub fn create_byte_size() {
+    ByteSize::kib(44).to_string();
+}

ensure-no-std/src/compat_test.rs

@@ -0,0 +1,36 @@
+#![no_std]
+#![no_main]
+#![allow(dead_code, clippy::from_over_into)]
+
+extern crate alloc;
+
+use alloc::alloc::{GlobalAlloc, Layout};
+
+struct NoopAllocator;
+
+#[global_allocator]
+static ALLOCATOR: NoopAllocator = NoopAllocator;
+
+unsafe impl Sync for NoopAllocator {}
+
+unsafe impl GlobalAlloc for NoopAllocator {
+    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
+        unimplemented!()
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        unimplemented!()
+    }
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    loop {}
+}
+
+mod compat_test;

ensure-no-std/src/main.rs

@@ -66,6 +66,10 @@ test-coverage-codecov toolchain="":
 test-coverage-lcov toolchain="":
     cargo {{ toolchain }} llvm-cov --workspace --all-features --lcov --output-path lcov.info
 
+# Build crate for a no-std target.
+build-no-std:
+    cargo build --target=thumbv6m-none-eabi --manifest-path=./ensure-no-std/Cargo.toml
+
 # Document crates in workspace.
 [group("docs")]
 doc *args:

justfile

@@ -122,6 +122,7 @@ impl fmt::Display for Display {
         let bytes = self.byte_size.as_u64();
 
         let unit = self.format.unit();
+        #[allow(unused_variables)] // used in std contexts
         let unit_base = self.format.unit_base();
 
         let unit_prefixes = self.format.unit_prefixes();
@@ -132,10 +133,12 @@ impl fmt::Display for Display {
             write!(f, "{bytes}{unit_separator}B")?;
         } else {
             let size = bytes as f64;
-            let exp = match (size.ln() / unit_base) as usize {
-                0 => 1,
-                e => e,
-            };
+
+            #[cfg(feature = "std")]
+            let exp = ideal_unit_std(size, unit_base);
+
+            #[cfg(not(feature = "std"))]
+            let exp = ideal_unit_no_std(size, unit);
 
             let unit_prefix = unit_prefixes[exp - 1] as char;
 
@@ -150,10 +153,67 @@ impl fmt::Display for Display {
     }
 }
 
+#[allow(dead_code)] // used in no-std contexts
+fn ideal_unit_no_std(size: f64, unit: u64) -> usize {
+    assert!(size >= unit as f64, "only called when bytes >= unit");
+
+    let mut ideal_prefix = 0;
+    let mut ideal_size = size;
+
+    loop {
+        ideal_prefix += 1;
+        ideal_size /= unit as f64;
+
+        if ideal_size < unit as f64 {
+            break;
+        }
+    }
+
+    ideal_prefix
+}
+
+#[cfg(feature = "std")]
+#[allow(dead_code)] // used in std contexts
+fn ideal_unit_std(size: f64, unit_base: f64) -> usize {
+    assert!(size.ln() >= unit_base, "only called when bytes >= unit");
+
+    match (size.ln() / unit_base) as usize {
+        0 => unreachable!(),
+        e => e,
+    }
+}
+
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString as _;
+
     use super::*;
 
+    #[cfg(feature = "std")]
+    quickcheck::quickcheck! {
+        #[test]
+        fn ideal_unit_selection_std_no_std_iec(bytes: ByteSize) -> bool {
+            if bytes.0 < 1025 {
+                return true;
+            }
+
+            let size = bytes.0 as f64;
+
+            ideal_unit_std(size, crate::LN_KIB) == ideal_unit_no_std(size, crate::KIB)
+        }
+
+        #[test]
+        fn ideal_unit_selection_std_no_std_si(bytes: ByteSize) -> bool {
+            if bytes.0 < 1025 {
+                return true;
+            }
+
+            let size = bytes.0 as f64;
+
+            ideal_unit_std(size, crate::LN_KB) == ideal_unit_no_std(size, crate::KB)
+        }
+    }
+
     #[test]
     fn to_string_iec() {
         let display = Display {

src/display.rs

@@ -41,10 +41,12 @@
 //! assert_eq!(ByteSize::gb(996), minus);
 //! ```
 
-use std::{
-    fmt,
-    ops::{Add, AddAssign, Mul, MulAssign, Sub, SubAssign},
-};
+#![cfg_attr(not(feature = "std"), no_std)]
+
+extern crate alloc;
+
+use alloc::string::ToString as _;
+use core::{fmt, ops};
 
 #[cfg(feature = "arbitrary")]
 mod arbitrary;
@@ -251,15 +253,15 @@ impl fmt::Debug for ByteSize {
 
 macro_rules! commutative_op {
     ($t:ty) => {
-        impl Add<ByteSize> for $t {
+        impl ops::Add<ByteSize> for $t {
             type Output = ByteSize;
             #[inline(always)]
             fn add(self, rhs: ByteSize) -> ByteSize {
                 ByteSize(rhs.0 + (self as u64))
             }
         }
 
-        impl Mul<ByteSize> for $t {
+        impl ops::Mul<ByteSize> for $t {
             type Output = ByteSize;
             #[inline(always)]
             fn mul(self, rhs: ByteSize) -> ByteSize {
@@ -274,7 +276,7 @@ commutative_op!(u32);
 commutative_op!(u16);
 commutative_op!(u8);
 
-impl Add<ByteSize> for ByteSize {
+impl ops::Add<ByteSize> for ByteSize {
     type Output = ByteSize;
 
     #[inline(always)]
@@ -283,14 +285,14 @@ impl Add<ByteSize> for ByteSize {
     }
 }
 
-impl AddAssign<ByteSize> for ByteSize {
+impl ops::AddAssign<ByteSize> for ByteSize {
     #[inline(always)]
     fn add_assign(&mut self, rhs: ByteSize) {
         self.0 += rhs.0
     }
 }
 
-impl<T> Add<T> for ByteSize
+impl<T> ops::Add<T> for ByteSize
 where
     T: Into<u64>,
 {
@@ -301,7 +303,7 @@ where
     }
 }
 
-impl<T> AddAssign<T> for ByteSize
+impl<T> ops::AddAssign<T> for ByteSize
 where
     T: Into<u64>,
 {
@@ -311,7 +313,7 @@ where
     }
 }
 
-impl Sub<ByteSize> for ByteSize {
+impl ops::Sub<ByteSize> for ByteSize {
     type Output = ByteSize;
 
     #[inline(always)]
@@ -320,14 +322,14 @@ impl Sub<ByteSize> for ByteSize {
     }
 }
 
-impl SubAssign<ByteSize> for ByteSize {
+impl ops::SubAssign<ByteSize> for ByteSize {
     #[inline(always)]
     fn sub_assign(&mut self, rhs: ByteSize) {
         self.0 -= rhs.0
     }
 }
 
-impl<T> Sub<T> for ByteSize
+impl<T> ops::Sub<T> for ByteSize
 where
     T: Into<u64>,
 {
@@ -338,7 +340,7 @@ where
     }
 }
 
-impl<T> SubAssign<T> for ByteSize
+impl<T> ops::SubAssign<T> for ByteSize
 where
     T: Into<u64>,
 {
@@ -348,7 +350,7 @@ where
     }
 }
 
-impl<T> Mul<T> for ByteSize
+impl<T> ops::Mul<T> for ByteSize
 where
     T: Into<u64>,
 {
@@ -359,7 +361,7 @@ where
     }
 }
 
-impl<T> MulAssign<T> for ByteSize
+impl<T> ops::MulAssign<T> for ByteSize
 where
     T: Into<u64>,
 {
@@ -371,6 +373,8 @@ where
 
 #[cfg(test)]
 mod property_tests {
+    use alloc::string::{String, ToString as _};
+
     use super::*;
 
     impl quickcheck::Arbitrary for ByteSize {
@@ -393,15 +397,21 @@ mod property_tests {
             size.to_string().len() < 11
         }
 
-        // // currently fails on input like "14.0 EiB"
-        // fn string_round_trip(size: ByteSize) -> bool {
-        //     size.to_string().parse::<ByteSize>().unwrap() == size
-        // }
+        fn string_round_trip(size: ByteSize) -> bool {
+            // currently fails on many inputs above the pebibyte level
+            if size > ByteSize::pib(1) {
+                return true;
+            }
+
+            size.to_string().parse::<ByteSize>().unwrap() == size
+        }
     }
 }
 
 #[cfg(test)]
 mod tests {
+    use alloc::format;
+
     use super::*;
 
     #[test]