Rollup merge of #110173 - solid-rs:patch/kmc-solid/socket-read-buf, r=cuviper

kmc-solid: Implement `Socket::read_buf`

Follow-up to #108326. Implements `Socket::read_buf` for the [`*-kmc-solid_*`](https://doc.rust-lang.org/nightly/rustc/platform-support/kmc-solid.html) Tier 3 targets.

library/std/src/sys/solid/net.rs

@@ -2,7 +2,7 @@
 use crate::{
     cmp,
     ffi::CStr,
-    io::{self, ErrorKind, IoSlice, IoSliceMut},
+    io::{self, BorrowedBuf, BorrowedCursor, ErrorKind, IoSlice, IoSliceMut},
     mem,
     net::{Shutdown, SocketAddr},
     ptr, str,
@@ -294,19 +294,30 @@ pub fn duplicate(&self) -> io::Result<Socket> {
         self.0.duplicate().map(Socket)
     }
 
-    fn recv_with_flags(&self, buf: &mut [u8], flags: c_int) -> io::Result<usize> {
+    fn recv_with_flags(&self, mut buf: BorrowedCursor<'_>, flags: c_int) -> io::Result<()> {
         let ret = cvt(unsafe {
-            netc::recv(self.0.raw(), buf.as_mut_ptr() as *mut c_void, buf.len(), flags)
+            netc::recv(self.0.raw(), buf.as_mut().as_mut_ptr().cast(), buf.capacity(), flags)
         })?;
-        Ok(ret as usize)
+        unsafe {
+            buf.advance(ret as usize);
+        }
+        Ok(())
     }
 
     pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
-        self.recv_with_flags(buf, 0)
+        let mut buf = BorrowedBuf::from(buf);
+        self.recv_with_flags(buf.unfilled(), 0)?;
+        Ok(buf.len())
     }
 
     pub fn peek(&self, buf: &mut [u8]) -> io::Result<usize> {
-        self.recv_with_flags(buf, MSG_PEEK)
+        let mut buf = BorrowedBuf::from(buf);
+        self.recv_with_flags(buf.unfilled(), MSG_PEEK)?;
+        Ok(buf.len())
+    }
+
+    pub fn read_buf(&self, buf: BorrowedCursor<'_>) -> io::Result<()> {
+        self.recv_with_flags(buf, 0)
     }
 
     pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {