Add FileReaderInterface::ReadExactly() and FileSeekerInterface::SeekSet()

util/file/file_reader.h

 // Copyright 2015 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 #ifndef CRASHPAD_UTIL_FILE_FILE_READER_H_
 #define CRASHPAD_UTIL_FILE_FILE_READER_H_
 
 #include <sys/types.h>
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
 #include "util/file/file_io.h"
 #include "util/file/file_seeker.h"
 
 namespace crashpad {
 
 //! \brief An interface to read to files and other file-like objects with
 //!     semantics matching the underlying platform (POSIX or Windows).
-class FileReaderInterface : public FileSeekerInterface {
+class FileReaderInterface : public virtual FileSeekerInterface {
  public:
   //! \brief Wraps ReadFile(), or provides an implementation with identical
   //!     semantics.
   //!
   //! \return The number of bytes actually read if the operation succeeded,
   //!     which may be `0` or any positive value less than or equal to \a size.
   //!     `-1` if the operation failed, with an error message logged.
   virtual ssize_t Read(void* data, size_t size) = 0;
 
+  //! \brief Wraps Read(), ensuring that the read succeeded and exactly \a size
+  //!     bytes were read.
+  //!
+  //! Semantically, this behaves as LoggingReadFile().
+  //!
+  //! \return `true` if the operation succeeded, `false` if it failed, with an
+  //!     error message logged. Short reads are treated as failures.
+  bool ReadExactly(void* data, size_t size);
+
  protected:
   ~FileReaderInterface() {}
 };
 
 //! \brief A file reader backed by a FileHandle.
 //!
 //! FileReader requires users to provide a FilePath to open, but this class
 //! accepts an already-open FileHandle instead. Like FileReader, this class may
 //! read from a filesystem-based file, but unlike FileReader, this class is not
 //! responsible for opening or closing the file. Users of this class must ensure
@@ skipping 82 matching lines @@
  private:
   ScopedFileHandle file_;
   WeakFileHandleFileReader weak_file_handle_file_reader_;
 
   DISALLOW_COPY_AND_ASSIGN(FileReader);
 };
 
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_FILE_FILE_READER_H_