Add support for no alloc.

.github/workflows/ci.yml

@@ -26,8 +26,11 @@ jobs:
     - name: Run tests
       run: cargo test
 
-    - name: Run tests (no_std)
-      run: cargo test --no-default-features
+    - name: Check (no_std)
+      run: cargo check --no-default-features
+
+    - name: Check (no_std, alloc)
+      run: cargo check --no-default-features --features alloc
 
     - name: Run clippy
       run: cargo clippy

Cargo.toml

@@ -11,9 +11,14 @@ repository = "https://github.com/tuffy/bitstream-io"
 edition = "2018"
 rust-version = "1.83"
 
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
 [dependencies]
-core2 = "0.4"
+core2 = { version = "0.4", default-features = false }
 
 [features]
-std = []
+std = ["core2/std", "alloc"]
+alloc = ["core2/alloc"]
 default = ["std"]

src/lib.rs

@@ -141,10 +141,12 @@
 //! of bit reader or bit writer, regardless of the underlying
 //! stream byte source or endianness.
 
+#![cfg_attr(docsrs, feature(doc_cfg))]
 #![warn(missing_docs)]
 #![forbid(unsafe_code)]
 #![no_std]
 
+#[cfg(feature = "alloc")]
 extern crate alloc;
 #[cfg(feature = "std")]
 extern crate std;
@@ -168,8 +170,11 @@ pub use read::{
     BitRead, BitRead2, BitReader, ByteRead, ByteReader, FromBitStream, FromBitStreamUsing,
     FromBitStreamWith, FromByteStream, FromByteStreamUsing, FromByteStreamWith,
 };
+#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
+#[cfg(feature = "alloc")]
+pub use write::BitRecorder;
 pub use write::{
-    BitRecorder, BitWrite, BitWrite2, BitWriter, BitsWritten, ByteWrite, ByteWriter, ToBitStream,
+    BitWrite, BitWrite2, BitWriter, BitsWritten, ByteWrite, ByteWriter, ToBitStream,
     ToBitStreamUsing, ToBitStreamWith, ToByteStream, ToByteStreamUsing, ToByteStreamWith,
 };
 
@@ -2251,10 +2256,7 @@ impl<const BITS: u32, U: UnsignedInteger> private::Checkable for CheckedUnsigned
 impl<const BITS: u32, U: UnsignedInteger> CheckablePrimitive for CheckedUnsignedFixed<BITS, U> {
     type CountType = FixedBitCount<BITS>;
 
-    fn read<R: BitRead + ?Sized>(
-        reader: &mut R,
-        count: FixedBitCount<BITS>,
-    ) -> std::io::Result<Self> {
+    fn read<R: BitRead + ?Sized>(reader: &mut R, count: FixedBitCount<BITS>) -> io::Result<Self> {
         Ok(Self {
             value: reader.read_unsigned::<BITS, _>()?,
             count,
@@ -2545,7 +2547,7 @@ impl<const BITS: u32, S: SignedInteger> CheckablePrimitive for CheckedSignedFixe
     fn read<R: BitRead + ?Sized>(
         reader: &mut R,
         count: FixedSignedBitCount<BITS>,
-    ) -> std::io::Result<Self> {
+    ) -> io::Result<Self> {
         Ok(Self {
             value: reader.read_signed::<BITS, _>()?,
             count,

src/read.rs

@@ -13,6 +13,7 @@
 #[cfg(not(feature = "std"))]
 use core2::io;
 
+#[cfg(feature = "alloc")]
 use alloc::{vec, vec::Vec};
 #[cfg(feature = "std")]
 use std::io;
@@ -683,6 +684,8 @@ pub trait BitRead {
     /// assert_eq!(r.read_to_vec(3).unwrap().as_slice(), &[0x01, 0x02, 0x03]);
     /// assert_eq!(r.read::<8, u8>().unwrap(), 0x04);
     /// ```
+    #[cfg(feature = "alloc")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
     fn read_to_vec(&mut self, bytes: usize) -> io::Result<Vec<u8>> {
         read_to_vec(|buf| self.read_bytes(buf), bytes)
     }
@@ -1011,6 +1014,7 @@ impl<R: BitRead + ?Sized> BitRead for &mut R {
     }
 
     #[inline]
+    #[cfg(feature = "alloc")]
     fn read_to_vec(&mut self, bytes: usize) -> io::Result<Vec<u8>> {
         (**self).read_to_vec(bytes)
     }
@@ -1209,6 +1213,8 @@ pub trait BitRead2 {
     /// # Errors
     ///
     /// Passes along any I/O error from the underlying stream.
+    #[cfg(feature = "alloc")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
     fn read_to_vec(&mut self, bytes: usize) -> io::Result<Vec<u8>> {
         read_to_vec(|buf| self.read_bytes(buf), bytes)
     }
@@ -1704,8 +1710,10 @@ where
     /// assert_eq!(reader.position_in_bits().unwrap(), 6);
     /// ```
     #[inline]
+    #[allow(clippy::seek_from_current)]
     pub fn position_in_bits(&mut self) -> io::Result<u64> {
-        let bytes = self.reader.stream_position()?;
+        // core2 doesn't have `seek_from_current`
+        let bytes = self.reader.seek(io::SeekFrom::Current(0))?;
         Ok(bytes * 8 - (self.bits as u64))
     }
 }
@@ -1818,6 +1826,8 @@ pub trait ByteRead {
     /// # Errors
     ///
     /// Passes along any I/O error from the underlying stream.
+    #[cfg(feature = "alloc")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
     fn read_to_vec(&mut self, bytes: usize) -> io::Result<Vec<u8>> {
         read_to_vec(|buf| self.read_bytes(buf), bytes)
     }
@@ -2322,6 +2332,7 @@ pub trait FromByteStreamUsing {
         Self: Sized;
 }
 
+#[cfg(feature = "alloc")]
 fn read_to_vec(
     mut read: impl FnMut(&mut [u8]) -> io::Result<()>,
     bytes: usize,