Add socket sendfile function

vm/src/stdlib/socket.rs

@@ -21,6 +21,7 @@ use crate::pyobject::{
     BorrowValue, Either, IntoPyObject, PyClassImpl, PyObjectRef, PyRef, PyResult, PyValue,
     StaticType, TryFromObject,
 };
+use crate::stdlib::os::rust_file;
 use crate::vm::VirtualMachine;
 
 #[cfg(unix)]
@@ -220,6 +221,31 @@ impl PySocket {
         Ok(())
     }
 
+    #[pymethod]
+    fn sendfile(&self, fd: i64, offset: OptionalArg<u64>, count: OptionalArg<u64>, vm: &VirtualMachine) -> PyResult<usize> {
+        let mut file = rust_file(fd);
+        let mut bufsize: u64 = 0;
+
+        if let Ok(metadata) = file.metadata() {
+            bufsize = metadata.len();
+        }
+
+        if let OptionalArg::Present(c) = count {
+            bufsize = c;
+        }
+
+        let mut buffer = vec![0u8; bufsize as usize];
+
+        let n = file
+            .read(&mut buffer)
+            .map_err(|err| err.into_pyexception(vm))?;
+
+        buffer.truncate(n);
+
+        let bytes = PyBytesLike::try_from_object(vm, vm.ctx.new_bytes(buffer))?;
+        self.send(bytes, vm)
+    }
+
     #[pymethod]
     fn close(&self) {
         *self.sock_mut() = invalid_sock();