fix features

Author: Darksonn

src/buf/buf_impl.rs

@@ -1,7 +1,9 @@
 #[cfg(feature = "std")]
 use crate::buf::{reader, Reader};
 use crate::buf::{take, Chain, Take};
-use crate::{min_u64_usize, panic_advance, panic_does_not_fit, saturating_sub_usize_u64};
+#[cfg(feature = "std")]
+use crate::{min_u64_usize, saturating_sub_usize_u64};
+use crate::{panic_advance, panic_does_not_fit};
 
 #[cfg(feature = "std")]
 use std::io::IoSlice;

src/lib.rs

@@ -117,6 +117,7 @@ fn abort() -> ! {
 }
 
 #[inline(always)]
+#[cfg(feature = "std")]
 fn saturating_sub_usize_u64(a: usize, b: u64) -> usize {
     use core::convert::TryFrom;
     match usize::try_from(b) {
@@ -126,6 +127,7 @@ fn saturating_sub_usize_u64(a: usize, b: u64) -> usize {
 }
 
 #[inline(always)]
+#[cfg(feature = "std")]
 fn min_u64_usize(a: u64, b: usize) -> usize {
     use core::convert::TryFrom;
     match usize::try_from(a) {