1    :  // Copyright 2012 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  
  15    :  #ifndef SYZYGY_MSF_MSF_STREAM_H_
  16    :  #define SYZYGY_MSF_MSF_STREAM_H_
  17    :  
  18    :  #include "base/logging.h"
  19    :  #include "base/memory/ref_counted.h"
  20    :  #include "syzygy/common/buffer_writer.h"
  21    :  #include "syzygy/msf/msf_decl.h"
  22    :  
  23    :  namespace msf {
  24    :  namespace detail {
  25    :  
  26    :  // Forward declaration.
  27    :  template <MsfFileType T>
  28    :  class WritableMsfStreamImpl;
  29    :  
  30    :  // This class represents an MSF stream. It has a stream-like interface that
  31    :  // allows invoking successive reads through the stream and seeking.
  32    :  template <MsfFileType T>
  33    :  class MsfStreamImpl : public base::RefCounted<MsfStreamImpl<T>> {
  34    :   public:
  35    :    explicit MsfStreamImpl(size_t length);
  36    :  
  37    :    // Reads @p count bytes of data starting at @p pos into the destination
  38    :    // buffer. The caller is responsible for ensuring that the destination
  39    :    // buffer has enough space to receive the data.
  40    :    //
  41    :    // @param pos the position in the stream of the first byte to read.
  42    :    // @param dest the buffer to receive the data. May be modified on failure.
  43    :    // @param count the number of bytes to read.
  44    :    // @returns true if all @p count bytes are read, false otherwise.
  45    :    virtual bool ReadBytesAt(size_t pos, size_t count, void* dest) = 0;
  46    :  
  47    :    // Returns a pointer to a WritableMsfStreamImpl if the underlying object
  48    :    // supports this interface. If this returns non-NULL, it is up to the user to
  49    :    // ensure thread safety; each writer should be used exclusively of any other
  50    :    // writer, and no reader should be used while a writer is in use. Each of the
  51    :    // reader and writer maintains its own cursor, but their view of the data (and
  52    :    // its length) will remain in sync.
  53    :    //
  54    :    // NOTE: This function should act as a factory, with each call returning a
  55    :    //     heap allocated reference counted writer. However, since each
  56    :    //     WritableMsfStreamImpl is currently implemented using a BufferWriter,
  57    :    //     and the BufferWriter maintains its own state internally rather than a
  58    :    //     shared state, its possible that one writer causing a resize could
  59    :    //     invalidate the internal data pointer held by another writer. As a
  60    :    //     workaround, there is only a single writer allowed to be allocated
  61    :    //     right now.
  62    :    //
  63    :    // TODO(chrisha): Clean this up to return an interface, which can be wrapped
  64    :    //     in some common stream-writer functionality, reusing BufferWriter.
  65    :    //
  66    :    // @returns a pointer to a WritableMsfStreamImpl.
  67  E :    virtual scoped_refptr<WritableMsfStreamImpl<T>> GetWritableStream() {
  68  E :      return scoped_refptr<WritableMsfStreamImpl<T>>();
  69  E :    }
  70    :  
  71    :    // Gets the stream's length.
  72    :    // @returns the total number of bytes in the stream.
  73  E :    size_t length() const { return length_; }
  74    :  
  75    :   protected:
  76    :    friend base::RefCounted<MsfStreamImpl>;
  77    :  
  78    :    // Protected to enforce use of ref-counted pointers at compile time.
  79    :    virtual ~MsfStreamImpl();
  80    :  
  81    :    // Sets the stream's length.
  82  E :    void set_length(size_t length) { length_ = length; }
  83    :  
  84    :   private:
  85    :    // The length of the stream.
  86    :    size_t length_;
  87    :  
  88    :    DISALLOW_COPY_AND_ASSIGN(MsfStreamImpl);
  89    :  };
  90    :  
  91    :  // Represents a writable MSF stream.
  92    :  // TODO(chrisha): For now, this inherits from common::BufferWriter, but a far
  93    :  //     cleaner approach would be to hoist a basic WritableStreamInterface, and
  94    :  //     make BufferWriter accept a pointer to said interface. The same thing
  95    :  //     could be done to the common::BufferParser/BufferReader and MsfStreamImpl
  96    :  //     hierarchy.
  97    :  template <MsfFileType T>
  98    :  class WritableMsfStreamImpl : public base::RefCounted<WritableMsfStreamImpl<T>>,
  99    :                                public common::BufferWriter {
 100    :   public:
 101    :    // Constructor.
 102  E :    WritableMsfStreamImpl() : common::BufferWriter(NULL, 0) {}
 103    :  
 104    :   protected:
 105    :    friend base::RefCounted<WritableMsfStreamImpl>;
 106    :  
 107    :    // Destructor. Protected to enforce use of ref-counted pointers at compile
 108    :    // time.
 109  E :    virtual ~WritableMsfStreamImpl() {}
 110    :  
 111    :    // Forwarded from common::BufferWriter.
 112    :    virtual uint8_t* GrowBuffer(size_t size) = 0;
 113    :  };
 114    :  
 115    :  }  // namespace detail
 116    :  
 117    :  using WritableMsfStream = detail::WritableMsfStreamImpl<kGenericMsfFileType>;
 118    :  using MsfStream = detail::MsfStreamImpl<kGenericMsfFileType>;
 119    :  
 120    :  }  // namespace msf
 121    :  
 122    :  #include "syzygy/msf/msf_stream_impl.h"
 123    :  
 124    :  #endif  // SYZYGY_MSF_MSF_STREAM_H_