From 15a00898af8639ddf738e13aa147d5c8c1962eac Mon Sep 17 00:00:00 2001
From: Brian Quinlan <bquinlan@google.com>
Date: Thu, 10 Jul 2025 18:28:01 -0700
Subject: [PATCH] Add the ability to copy pipes using File.Copy

Bug:https://github.com/dart-lang/sdk/issues/60999
Change-Id: I2e20ad5c051b43582483d5275d6d2b65b6f3395a
Tested: unit
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/439823
Commit-Queue: Brian Quinlan <bquinlan@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
---
 runtime/bin/file_linux.cc               |  5 ++++-
 runtime/bin/file_macos.cc               |  2 ++
 tests/standalone/io/file_copy_test.dart | 27 +++++++++++++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/runtime/bin/file_linux.cc b/runtime/bin/file_linux.cc
index 471ed13bafc..9f7cbaf96df 100644
--- a/runtime/bin/file_linux.cc
+++ b/runtime/bin/file_linux.cc
@@ -494,7 +494,10 @@ bool File::Copy(Namespace* namespc,
   // From sendfile man pages:
   //   Applications may wish to fall back to read(2)/write(2) in the case
   //   where sendfile() fails with EINVAL or ENOSYS.
-  if ((result < 0) && ((errno == EINVAL) || (errno == ENOSYS))) {
+  //
+  // Also, fallback on ESPIPE (returned when the input file is not seekable).
+  if ((result < 0) &&
+      ((errno == EINVAL) || (errno == ENOSYS) || (errno == ESPIPE))) {
     const intptr_t kBufferSize = 8 * KB;
     uint8_t* buffer = reinterpret_cast<uint8_t*>(malloc(kBufferSize));
     while ((result = TEMP_FAILURE_RETRY(read(old_fd, buffer, kBufferSize))) >
diff --git a/runtime/bin/file_macos.cc b/runtime/bin/file_macos.cc
index 00849f2452a..456bf24deab 100644
--- a/runtime/bin/file_macos.cc
+++ b/runtime/bin/file_macos.cc
@@ -489,6 +489,8 @@ bool File::Copy(Namespace* namespc,
                 const char* new_path) {
   File::Type type = File::GetType(namespc, old_path, true);
   if (type == kIsFile || type == kIsSock || type == kIsPipe) {
+    // `copyfile` will complete with [ENOTSUP] if the source file is:
+    // "...not a directory, symbolic link, or regular file."
     return (copyfile(old_path, new_path, nullptr, COPYFILE_ALL) == 0);
   }
   SetErrno(type);
diff --git a/tests/standalone/io/file_copy_test.dart b/tests/standalone/io/file_copy_test.dart
index 605a6182022..fe8b595acce 100644
--- a/tests/standalone/io/file_copy_test.dart
+++ b/tests/standalone/io/file_copy_test.dart
@@ -5,13 +5,39 @@
 // Dart test program for testing File.copy*
 
 import 'dart:io';
+import 'dart:ffi' as ffi;
 
 import "package:expect/async_helper.dart";
 import "package:expect/expect.dart";
+import 'package:ffi/ffi.dart';
 
 const FILE_CONTENT1 = 'some string';
 const FILE_CONTENT2 = 'some other string';
 
+@ffi.Native<ffi.Int Function(ffi.Pointer<ffi.Char>, ffi.Int)>()
+external int mkfifo(ffi.Pointer<ffi.Char> pathname, int mode);
+
+void testFifo() async {
+  var tmp = Directory.systemTemp.createTempSync('copy-fifo');
+  if (!Platform.isLinux) {
+    return;
+  }
+
+  using((arena) {
+    // 432 => rw-rw----
+    if (mkfifo("${tmp.path}/fifo".toNativeUtf8(allocator: arena).cast(), 432) ==
+        -1) {
+      throw FileSystemException('error creating FIFO');
+    }
+  });
+
+  final write = File("${tmp.path}/fifo").writeAsString("Hello World!");
+  final copy = File("${tmp.path}/fifo").copy("${tmp.path}/copy");
+  await Future.wait([write, copy]);
+  Expect.equals("Hello World!", File("${tmp.path}/copy").readAsStringSync());
+  tmp.deleteSync(recursive: true);
+}
+
 void testCopySync() {
   var tmp = Directory.systemTemp.createTempSync('dart-file-copy');
 
@@ -115,6 +141,7 @@ void testCopy() {
 main() {
   testCopySync();
   testCopy();
+  testFifo();
   // This is Windows only test.
   testWithForwardSlashes();
 }