Rollup merge of rust-lang#143470 - Ayush1325:uefi-tcp4-recv, r=joshtriplett

std: sys: net: uefi: tcp4: Implement read

- A blocking implementation of tcp4 read.
- Basically a copy of [write](rust-lang#141532)

Author: matthiaskrgr

library/std/src/sys/net/connection/uefi/mod.rs

@@ -38,16 +38,17 @@ impl TcpStream {
         unsupported()
     }
 
-    pub fn read(&self, _: &mut [u8]) -> io::Result<usize> {
-        unsupported()
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.0.read(buf)
     }
 
-    pub fn read_buf(&self, _buf: BorrowedCursor<'_>) -> io::Result<()> {
-        unsupported()
+    pub fn read_buf(&self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
+        crate::io::default_read_buf(|buf| self.read(buf), cursor)
     }
 
-    pub fn read_vectored(&self, _: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
-        unsupported()
+    pub fn read_vectored(&self, buf: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        // FIXME: UEFI does support vectored read, so implement that.
+        crate::io::default_read_vectored(|b| self.read(b), buf)
     }
 
     pub fn is_read_vectored(&self) -> bool {

library/std/src/sys/net/connection/uefi/tcp.rs

@@ -24,4 +24,10 @@ impl Tcp {
             Self::V4(client) => client.write(buf),
         }
     }
+
+    pub(crate) fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        match self {
+            Self::V4(client) => client.read(buf),
+        }
+    }
 }

library/std/src/sys/net/connection/uefi/tcp4.rs

@@ -128,6 +128,45 @@ impl Tcp4 {
         }
     }
 
+    pub(crate) fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        let evt = unsafe { self.create_evt() }?;
+        let completion_token =
+            tcp4::CompletionToken { event: evt.as_ptr(), status: Status::SUCCESS };
+        let data_len = u32::try_from(buf.len()).unwrap_or(u32::MAX);
+
+        let fragment = tcp4::FragmentData {
+            fragment_length: data_len,
+            fragment_buffer: buf.as_mut_ptr().cast::<crate::ffi::c_void>(),
+        };
+        let mut tx_data = tcp4::ReceiveData {
+            urgent_flag: r_efi::efi::Boolean::FALSE,
+            data_length: data_len,
+            fragment_count: 1,
+            fragment_table: [fragment],
+        };
+
+        let protocol = self.protocol.as_ptr();
+        let mut token = tcp4::IoToken {
+            completion_token,
+            packet: tcp4::IoTokenPacket {
+                rx_data: (&raw mut tx_data).cast::<tcp4::ReceiveData<0>>(),
+            },
+        };
+
+        let r = unsafe { ((*protocol).receive)(protocol, &mut token) };
+        if r.is_error() {
+            return Err(io::Error::from_raw_os_error(r.as_usize()));
+        }
+
+        self.wait_for_flag();
+
+        if completion_token.status.is_error() {
+            Err(io::Error::from_raw_os_error(completion_token.status.as_usize()))
+        } else {
+            Ok(data_len as usize)
+        }
+    }
+
     unsafe fn create_evt(&self) -> io::Result<helpers::OwnedEvent> {
         self.flag.store(false, Ordering::Relaxed);
         helpers::OwnedEvent::new(