Add File.copy(Sync) to dart:io.

runtime/bin/file_linux.cc

 // Copyright (c) 2012, 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 "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/file.h"
 
 #include <errno.h>  // NOLINT
 #include <fcntl.h>  // NOLINT
 #include <sys/stat.h>  // NOLINT
 #include <sys/types.h>  // NOLINT
+#include <sys/sendfile.h>  // NOLINT
 #include <unistd.h>  // NOLINT
 #include <libgen.h>  // NOLINT
 
 #include "bin/builtin.h"
 #include "bin/log.h"
 
 
 namespace dart {
 namespace bin {
 
@@ skipping 189 matching lines @@
     return TEMP_FAILURE_RETRY(rename(old_path, new_path)) == 0;
   } else if (type == kIsDirectory) {
     errno = EISDIR;
   } else {
     errno = EINVAL;
   }
   return false;
 }
 
 
+bool File::Copy(const char* old_path, const char* new_path) {
+  File::Type type = File::GetType(old_path, true);
+  if (type == kIsFile) {
+    struct stat64 st;
+    if (TEMP_FAILURE_RETRY(stat64(old_path, &st)) != 0) {
+      return false;
+    }
+    int old_fd = TEMP_FAILURE_RETRY(open64(old_path, O_RDONLY | O_CLOEXEC));
+    if (old_fd < 0) {
+      return false;
+    }
+    int new_fd = TEMP_FAILURE_RETRY(
+        open64(new_path, O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, st.st_mode));
+    if (new_fd < 0) {
+      VOID_TEMP_FAILURE_RETRY(close(old_fd));
+      return false;
+    }
+    off64_t offset = 0;
+    int bytes = 1;
+    while (bytes > 0) {
+      // Loop to ensure we copy everything, and not only up to 2GB.
+      bytes = TEMP_FAILURE_RETRY(sendfile64(new_fd, old_fd, &offset, -1));
+    }
+    if (bytes < 0) {
+      int e = errno;
+      VOID_TEMP_FAILURE_RETRY(close(old_fd));
+      VOID_TEMP_FAILURE_RETRY(close(new_fd));
+      VOID_TEMP_FAILURE_RETRY(unlink(new_path));
+      errno = e;
+      return false;
+    }
+    return true;
+  } else if (type == kIsDirectory) {
+    errno = EISDIR;
+  } else {
+    errno = ENOENT;
+  }
+  return false;
+}
+
+
 off64_t File::LengthFromPath(const char* name) {
   struct stat64 st;
   if (TEMP_FAILURE_RETRY(stat64(name, &st)) == 0) {
     return st.st_size;
   }
   return -1;
 }
 
 
 void File::Stat(const char* name, int64_t* data) {
@@ skipping 118 matching lines @@
   return (file_1_info.st_ino == file_2_info.st_ino &&
           file_1_info.st_dev == file_2_info.st_dev) ?
       File::kIdentical :
       File::kDifferent;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)