Spoke too soon, we can still implement read_buf normally

Author: slightlyoutofphase

src/trait_impls.rs

@@ -19,14 +19,17 @@ use crate::StaticVec;
 #[cfg(feature = "std")]
 use core::str;
 
+#[cfg(feature = "std")]
+use crate::utils::const_min;
+
 #[cfg(feature = "std")]
 use alloc::string::String;
 
 #[cfg(feature = "std")]
 use alloc::vec::Vec;
 
 #[cfg(feature = "std")]
-use std::io::{self, BufRead, IoSlice, IoSliceMut, Read};
+use std::io::{self, BorrowedCursor, BufRead, IoSlice, IoSliceMut, Read};
 
 #[cfg(feature = "serde")]
 use core::marker::PhantomData;
@@ -884,6 +887,16 @@ impl<const N: usize> Read for StaticVec<u8, N> {
     }
     Ok(total_read)
   }
+
+  #[inline]
+  fn read_buf(&mut self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> {
+    // Here we directly adapt the implementation from &[u8].
+    let amount = const_min(cursor.capacity(), self.len());
+    let b = self.split_off(amount);
+    cursor.append(&self);
+    *self = b;
+    Ok(())
+  }
 }
 
 impl<const N: usize> fmt::Write for StaticVec<u8, N> {

test/test_staticvec.rs

@@ -2083,7 +2083,7 @@ fn quicksort_unstable() {
 mod read_tests {
   use core::mem::MaybeUninit;
   use staticvec::*;
-  use std::io::{self, BufRead, Read};
+  use std::io::{self, BorrowedBuf, BufRead, Read};
 
   // We provide custom implementations of most `Read` methods; test those impls
   #[test]
@@ -2174,6 +2174,38 @@ mod read_tests {
     assert_eq!(ints2, [10, 11, 12]);
   }
 
+  #[test]
+  fn read_buf() {
+    let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4];
+    let mut reader = StaticVec::<u8, 8>::from(inner);
+    let buf: &mut [_] = &mut [MaybeUninit::uninit(); 3];
+    let mut buf: BorrowedBuf<'_> = buf.into();
+    reader.read_buf(buf.unfilled()).unwrap();
+    assert_eq!(buf.filled(), [5, 6, 7]);
+    assert_eq!(reader, [0, 1, 2, 3, 4]);
+    let buf: &mut [_] = &mut [MaybeUninit::uninit(); 2];
+    let mut buf: BorrowedBuf<'_> = buf.into();
+    reader.read_buf(buf.unfilled()).unwrap();
+    assert_eq!(buf.filled(), [0, 1]);
+    assert_eq!(reader, [2, 3, 4]);
+    let buf: &mut [_] = &mut [MaybeUninit::uninit(); 1];
+    let mut buf: BorrowedBuf<'_> = buf.into();
+    reader.read_buf(buf.unfilled()).unwrap();
+    assert_eq!(buf.filled(), [2]);
+    assert_eq!(reader, [3, 4]);
+    let buf: &mut [_] = &mut [MaybeUninit::uninit(); 3];
+    let mut buf: BorrowedBuf<'_> = buf.into();
+    reader.read_buf(buf.unfilled()).unwrap();
+    assert_eq!(buf.filled(), [3, 4]);
+    assert_eq!(reader, []);
+    reader.read_buf(buf.unfilled()).unwrap();
+    assert_eq!(buf.filled(), [3, 4]);
+    assert_eq!(reader, []);
+    buf.clear();
+    reader.read_buf(buf.unfilled()).unwrap();
+    assert!(buf.filled().is_empty());
+  }
+
   #[test]
   fn bufread() {
     let mut cursor = StaticVec::<u8, 7>::from("foo\nbar".as_bytes());