Support length operation without opening file.

runtime/bin/file_impl.dart

 // 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.
 
 class _FileInputStream extends _BaseDataInputStream implements InputStream {
   _FileInputStream(String name) {
     _file = new File(name);
     _data = [];
     _position = 0;
     _file.onError = (e) {
@@ skipping 199 matching lines @@
   static final kCreateRequest = 1;
   static final kDeleteRequest = 2;
   static final kOpenRequest = 3;
   static final kFullPathRequest = 4;
   static final kDirectoryRequest = 5;
   static final kCloseRequest = 6;
   static final kPositionRequest = 7;
   static final kSetPositionRequest = 8;
   static final kTruncateRequest = 9;
   static final kLengthRequest = 10;
-  static final kFlushRequest = 11;
-  static final kReadByteRequest = 12;
-  static final kWriteByteRequest = 13;
-  static final kReadListRequest = 14;
-  static final kWriteListRequest = 15;
-  static final kWriteStringRequest = 16;
+  static final kLengthFromNameRequest = 11;
+  static final kFlushRequest = 12;
+  static final kReadByteRequest = 13;
+  static final kWriteByteRequest = 14;
+  static final kReadListRequest = 15;
+  static final kWriteListRequest = 16;
+  static final kWriteStringRequest = 17;
 
   static final kSuccessResponse = 0;
   static final kIllegalArgumentResponse = 1;
   static final kOSErrorResponse = 2;
   static final kFileClosedResponse = 3;
 
   static final kErrorResponseErrorType = 0;
   static final kOSErrorResponseErrorCode = 1;
   static final kOSErrorResponseMessage = 2;
 
@@ skipping 22 matching lines @@
     }
     return [outBuffer, outOffset];
   }
 
   static exists(String name) native "File_Exists";
   static open(String name, int mode) native "File_Open";
   static create(String name) native "File_Create";
   static delete(String name) native "File_Delete";
   static fullPath(String name) native "File_FullPath";
   static directory(String name) native "File_Directory";
+  static lengthFromName(String name) native "File_LengthFromName";
   static int close(int id) native "File_Close";
   static readByte(int id) native "File_ReadByte";
   static readList(int id, List<int> buffer, int offset, int bytes)
       native "File_ReadList";
   static writeByte(int id, int value) native "File_WriteByte";
   static writeList(int id, List<int> buffer, int offset, int bytes) {
     List result =
         _FileUtils.ensureFastAndSerializableBuffer(buffer, offset, bytes);
     List outBuffer = result[0];
     int outOffset = result[1];
@@ skipping 69 matching lines @@
     if (name is !String) {
       throw new IllegalArgumentException();
     }
     var result = directory(name);
     if (result is OSError) {
       throw new FileIOException("Cannot retrieve directory for file", result);
     }
     return result;
   }
 
+  static int checkedLengthFromName(String name) {
+    if (name is !String) {
+      throw new IllegalArgumentException();
+    }
+    var result = lengthFromName(name);
+    if (result is OSError) {
+      throw new FileIOException("Cannot retrieve length for file", result);
+    }
+    return result;
+  }
+
   static int checkReadWriteListArguments(int length, int offset, int bytes) {
     if (offset < 0) return offset;
     if (bytes < 0) return bytes;
     if ((offset + bytes) > length) return offset + bytes;
     return 0;
   }
 
   static int checkedWriteString(int id, String string) {
     if (string is !String) return -1;
     return writeString(id, string);
@@ skipping 133 matching lines @@
     request[2] = mode._mode;  // Direct int value for serialization.
     _fileService.call(request).then((response) {
       if (_isErrorResponse(response)) {
         _reportError(response, "Cannot open file");
       } else {
         callback(new _RandomAccessFile(response, _name));
       }
     });
   }
 
+  void length(void callback(int length)) {
+    _ensureFileService();
+    List request = new List(2);
+    request[0] = _FileUtils.kLengthFromNameRequest;
+    request[1] = _name;
+    _fileService.call(request).then((response) {
+      if (_isErrorResponse(response)) {
+        _reportError(response, "Cannot retrieve length for file");
+      } else {
+        callback(response);
+      }
+    });
+  }
+
+  int lengthSync() {
+    var result = _FileUtils.checkedLengthFromName(_name);
+    if (result is OSError) {
+      throw new FileIOException("Cannot retrieve lenght for file", result);

[Søren Gjesse, 2012/04/12 11:41:44]

lenght -> length
for -> of

[Mads Ager (google), 2012/04/13 12:24:11]

Done.

+    }
+    return result;
+  }
+
   RandomAccessFile openSync([FileMode mode = FileMode.READ]) {
     if (mode != FileMode.READ &&
         mode != FileMode.WRITE &&
         mode != FileMode.APPEND) {
       throw new FileIOException("Unknown file mode. Use FileMode.READ, "
                                 "FileMode.WRITE or FileMode.APPEND.");
     }
     var id = _FileUtils.checkedOpen(_name, mode._mode);
     assert(id != 0);
     return new _RandomAccessFile(id, _name);
@@ skipping 499 matching lines @@
   String _name;
   int _id;
   int _pendingWrites = 0;
 
   SendPort _fileService;
 
   Timer _noPendingWriteTimer;
 
   Function _onNoPendingWrites;
 }