Detect EOF when reading stdio from terminal on Mac OS

runtime/bin/socket.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/io_buffer.h"
 #include "bin/socket.h"
 #include "bin/dartutils.h"
 #include "bin/thread.h"
 #include "bin/utils.h"
 
@@ skipping 131 matching lines @@
       if (length == -1 || available < length) {
         length = available;
       }
       uint8_t* buffer = NULL;
       Dart_Handle result = IOBuffer::Allocate(length, &buffer);
       if (Dart_IsError(result)) Dart_PropagateError(result);
       ASSERT(buffer != NULL);
       intptr_t bytes_read = Socket::Read(socket, buffer, length);
       if (bytes_read == length) {
         Dart_SetReturnValue(args, result);
-      } else if (bytes_read == 0) {
-        // On MacOS when reading from a tty Ctrl-D will result in one
-        // byte reported as available. Attempting to read it out will
-        // result in zero bytes read. When that happens there is no
-        // data which is indicated by a null return value.
-        Dart_SetReturnValue(args, Dart_Null());
+      } else if (bytes_read < length) {
+        // On MacOS when reading from a tty Ctrl-D will result in reading one
+        // less byte then reported as available.
+        if (bytes_read == 0) {
+          Dart_SetReturnValue(args, Dart_Null());
+        } else {
+          uint8_t* new_buffer = NULL;
+          Dart_Handle new_result = IOBuffer::Allocate(bytes_read, &new_buffer);
+          if (Dart_IsError(new_result)) Dart_PropagateError(new_result);
+          ASSERT(new_buffer != NULL);
+          memmove(new_buffer, buffer, bytes_read);
+          Dart_SetReturnValue(args, new_result);
+        }
       } else {
         ASSERT(bytes_read == -1);
         Dart_SetReturnValue(args, DartUtils::NewDartOSError());
       }
     } else {
       OSError os_error(-1, "Invalid argument", OSError::kUnknown);
       Dart_Handle err = DartUtils::NewDartOSError(&os_error);
       if (Dart_IsError(err)) Dart_PropagateError(err);
       Dart_SetReturnValue(args, err);
     }
@@ skipping 463 matching lines @@
   return Dart_SetNativeInstanceField(socket, kSocketIdNativeField, id);
 }
 
 
 Dart_Handle Socket::GetSocketIdNativeField(Dart_Handle socket, intptr_t* id) {
   return Dart_GetNativeInstanceField(socket, kSocketIdNativeField, id);
 }
 
 }  // namespace bin
 }  // namespace dart