Add fallback-implementation for sendfile on linux and android.

runtime/bin/file_android.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_ANDROID)
 
 #include "bin/file.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 220 matching lines @@
     if (old_fd < 0) {
       return false;
     }
     int new_fd = TEMP_FAILURE_RETRY(
         open(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) {
+    int result = 1;
+    while (result > 0) {
       // Loop to ensure we copy everything, and not only up to 2GB.
-      bytes = TEMP_FAILURE_RETRY(
+      result = TEMP_FAILURE_RETRY(
           sendfile(new_fd, old_fd, &offset, kMaxUint32));
     }

[Søren Gjesse, 2013/12/16 08:01:52]

Please add a comment to this "feature testing". Is it supported on some Android
versions?

[Anders Johnsen, 2013/12/16 08:52:56]

Done.

-    if (bytes < 0) {
+    if (result < 0 && (errno == EINVAL || errno == ENOSYS)) {
+      const intptr_t kBufferSize = 8 * 1024;

[Søren Gjesse, 2013/12/16 08:01:52]

We actually have the constant KB in platform/globals.h.

[Anders Johnsen, 2013/12/16 08:52:56]

Done.

+      uint8_t buffer[kBufferSize];
+      while ((result = TEMP_FAILURE_RETRY(
+          read(old_fd, buffer, kBufferSize))) > 0) {
+        int wrote = TEMP_FAILURE_RETRY(write(new_fd, buffer, result));
+        if (wrote != result) {
+          result = -1;
+          break;
+        }
+      }
+    }
+    if (result < 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;
@@ skipping 142 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_ANDROID)