Make alloc optional - the easy way

Author: xoac

Cargo.toml

@@ -22,7 +22,8 @@ edition = "2018"
 
 [features]
 default = ["std"]
-std = []
+std = ["alloc"]
+alloc = []
 
 [dependencies]
 serde = { version = "1.0.60", optional = true, default-features = false, features = ["alloc"] }

src/buf/buf_impl.rs

@@ -7,6 +7,7 @@ use core::{cmp, mem, ptr};
 #[cfg(feature = "std")]
 use std::io::IoSlice;
 
+#[cfg(feature = "alloc")]
 use alloc::boxed::Box;
 
 macro_rules! buf_get_impl {
@@ -813,6 +814,7 @@ pub trait Buf {
     /// let bytes = (&b"hello world"[..]).copy_to_bytes(5);
     /// assert_eq!(&bytes[..], &b"hello"[..]);
     /// ```
+    #[cfg(feature = "alloc")]
     fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
         use super::BufMut;
 
@@ -1004,6 +1006,7 @@ macro_rules! deref_forward_buf {
             (**self).get_int_le(nbytes)
         }
 
+        #[cfg(feature = "alloc")]
         fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
             (**self).copy_to_bytes(len)
         }
@@ -1014,6 +1017,7 @@ impl<T: Buf + ?Sized> Buf for &mut T {
     deref_forward_buf!();
 }
 
+#[cfg(feature = "alloc")]
 impl<T: Buf + ?Sized> Buf for Box<T> {
     deref_forward_buf!();
 }

src/buf/buf_mut.rs

@@ -4,6 +4,7 @@ use crate::buf::{writer, Writer};
 
 use core::{cmp, mem, ptr, usize};
 
+#[cfg(feature = "alloc")]
 use alloc::{boxed::Box, vec::Vec};
 
 /// A trait for values that provide sequential write access to bytes.
@@ -990,6 +991,7 @@ unsafe impl<T: BufMut + ?Sized> BufMut for &mut T {
     deref_forward_bufmut!();
 }
 
+#[cfg(feature = "alloc")]
 unsafe impl<T: BufMut + ?Sized> BufMut for Box<T> {
     deref_forward_bufmut!();
 }
@@ -1014,6 +1016,7 @@ unsafe impl BufMut for &mut [u8] {
     }
 }
 
+#[cfg(feature = "alloc")]
 unsafe impl BufMut for Vec<u8> {
     #[inline]
     fn remaining_mut(&self) -> usize {

src/lib.rs

@@ -84,11 +84,16 @@ extern crate std;
 pub mod buf;
 pub use crate::buf::{Buf, BufMut};
 
+#[cfg(feature = "alloc")]
 mod bytes;
+#[cfg(feature = "alloc")]
 mod bytes_mut;
+#[cfg(feature = "alloc")]
 mod fmt;
 mod loom;
+#[cfg(feature = "alloc")]
 pub use crate::bytes::Bytes;
+#[cfg(feature = "alloc")]
 pub use crate::bytes_mut::BytesMut;
 
 // Optional Serde support

tests/test_buf.rs

@@ -56,6 +56,7 @@ fn test_bufs_vec() {
     assert_eq!(1, buf.chunks_vectored(&mut dst[..]));
 }
 
+#[cfg(feature = "alloc")]
 #[test]
 fn test_vec_deque() {
     use std::collections::VecDeque;
@@ -98,10 +99,13 @@ fn test_deref_buf_forwards() {
     // these should all use the specialized method
     assert_eq!(Special.get_u8(), b'x');
     assert_eq!((&mut Special as &mut dyn Buf).get_u8(), b'x');
+    #[cfg(feature = "alloc")]
     assert_eq!((Box::new(Special) as Box<dyn Buf>).get_u8(), b'x');
+    #[cfg(feature = "alloc")]
     assert_eq!(Box::new(Special).get_u8(), b'x');
 }
 
+#[cfg(feature = "alloc")]
 #[test]
 fn copy_to_bytes_less() {
     let mut buf = &b"hello world"[..];
@@ -111,6 +115,7 @@ fn copy_to_bytes_less() {
     assert_eq!(buf, &b" world"[..])
 }
 
+#[cfg(feature = "alloc")]
 #[test]
 #[should_panic]
 fn copy_to_bytes_overflow() {

tests/test_buf_mut.rs

@@ -1,4 +1,5 @@
 #![warn(rust_2018_idioms)]
+#![cfg(feature = "alloc")]
 
 use bytes::buf::UninitSlice;
 use bytes::{BufMut, BytesMut};

tests/test_bytes.rs

@@ -1,4 +1,5 @@
 #![warn(rust_2018_idioms)]
+#![cfg(feature = "alloc")]
 
 use bytes::{Buf, BufMut, Bytes, BytesMut};
 

tests/test_bytes_odd_alloc.rs

@@ -2,6 +2,7 @@
 //! vectors (pointers where the LSB is set).
 
 #![cfg(not(miri))] // Miri does not support custom allocators (also, Miri is "odd" by default with 50% chance)
+#![cfg(feature = "alloc")]
 
 use std::alloc::{GlobalAlloc, Layout, System};
 use std::ptr;

tests/test_bytes_vec_alloc.rs

@@ -1,3 +1,4 @@
+#![cfg(feature = "alloc")]
 use std::alloc::{GlobalAlloc, Layout, System};
 use std::{mem, ptr};
 

tests/test_chain.rs

@@ -1,9 +1,14 @@
 #![warn(rust_2018_idioms)]
 
-use bytes::{Buf, BufMut, Bytes};
+use bytes::{Buf, BufMut};
+
+#[cfg(feature = "alloc")]
+use bytes::BytesMut;
+
 #[cfg(feature = "std")]
 use std::io::IoSlice;
 
+#[cfg(feature = "alloc")]
 #[test]
 fn collect_two_bufs() {
     let a = Bytes::from(&b"hello"[..]);
@@ -33,6 +38,7 @@ fn writing_chained() {
     }
 }
 
+#[cfg(feature = "alloc")]
 #[test]
 fn iterating_two_bufs() {
     let a = Bytes::from(&b"hello"[..]);