stream.h

//----------------------------------------------------------------------------//
//                                                                            //
// ozz-animation is hosted at http://github.com/guillaumeblanc/ozz-animation  //
// and distributed under the MIT License (MIT).                               //
//                                                                            //
// Copyright (c) Guillaume Blanc                                              //
//                                                                            //
// Permission is hereby granted, free of charge, to any person obtaining a    //
// copy of this software and associated documentation files (the "Software"), //
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//----------------------------------------------------------------------------//
 
#ifndef OZZ_OZZ_BASE_IO_STREAM_H_
#define OZZ_OZZ_BASE_IO_STREAM_H_
 
// Provides Stream interface used to read/write a memory buffer or a file with
// Crt fread/fwrite/fseek/ftell like functions.
 
#include <cstddef>
 
#include "ozz/base/platform.h"
 
namespace ozz {
namespace io {
 
// Declares a stream access interface that conforms with CRT FILE API.
// This interface should be used to remap io operations.
class OZZ_BASE_DLL Stream {
 public:
  // Tests whether a file is opened.
  virtual bool opened() const = 0;
 
  // Reads _size bytes of data to _buffer from the stream. _buffer must be big
  // enough to store _size bytes. The position indicator of the stream is
  // advanced by the total amount of bytes read.
  // Returns the number of bytes actually read, which may be less than _size.
  virtual size_t Read(void* _buffer, size_t _size) = 0;
 
  // Writes _size bytes of data from _buffer to the stream. The position
  // indicator of the stream is advanced by the total number of bytes written.
  // Returns the number of bytes actually written, which may be less than _size.
  virtual size_t Write(const void* _buffer, size_t _size) = 0;
 
  // Declares seeking origin enumeration.
  enum Origin {
    kCurrent,  // Current position of the stream pointer.
    kEnd,      // End of stream.
    kSet,      // Beginning of stream.
  };
  // Sets the position indicator associated with the stream to a new position
  // defined by adding _offset to a reference position specified by _origin.
  // Returns a zero value if successful, otherwise returns a non-zero value.
  virtual int Seek(int _offset, Origin _origin) = 0;
 
  // Returns the current value of the position indicator of the stream.
  // Returns -1 if an error occurs.
  virtual int Tell() const = 0;
 
  // Returns the current size of the stream.
  virtual size_t Size() const = 0;
 
 protected:
  Stream() {}
 
  // Required virtual destructor.
  virtual ~Stream() {}
 
 private:
  Stream(const Stream&);
  void operator=(const Stream&);
};
 
// Implements Stream of type File.
class OZZ_BASE_DLL File : public Stream {
 public:
  // Test if a file at path _filename exists.
  // Note that this function is costly. If you aim to open the file right after,
  // then open it and use File::opened() to test if it's actually existing.
  static bool Exist(const char* _filename);
 
  // Open a file at path _filename with mode * _mode, in conformance with fopen
  // specifications.
  // Use opened() function to test opening result.
  File(const char* _filename, const char* _mode);
 
  // Gives _file ownership to the FileStream, which will be in charge of closing
  // it. _file must be nullptr or a valid std::FILE pointer.
  explicit File(void* _file);
 
  // Close the file if it is opened.
  virtual ~File();
 
  // Close the file if it is opened.
  void Close();
 
  // See Stream::opened for details.
  virtual bool opened() const;
 
  // See Stream::Read for details.
  virtual size_t Read(void* _buffer, size_t _size);
 
  // See Stream::Write for details.
  virtual size_t Write(const void* _buffer, size_t _size);
 
  // See Stream::Seek for details.
  virtual int Seek(int _offset, Origin _origin);
 
  // See Stream::Tell for details.
  virtual int Tell() const;
 
  // See Stream::Tell for details.
  virtual size_t Size() const;
 
 private:
  // The CRT file pointer.
  void* file_;
};
 
// Implements an in-memory Stream. Allows to use a memory buffer as a Stream.
// The opening mode is equivalent to fopen w+b (binary read/write).
class OZZ_BASE_DLL MemoryStream : public Stream {
 public:
  // Construct an empty memory stream opened in w+b mode.
  MemoryStream();
 
  // Closes the stream and deallocates memory buffer.
  virtual ~MemoryStream();
 
  // See Stream::opened for details.
  virtual bool opened() const;
 
  // See Stream::Read for details.
  virtual size_t Read(void* _buffer, size_t _size);
 
  // See Stream::Write for details.
  virtual size_t Write(const void* _buffer, size_t _size);
 
  // See Stream::Seek for details.
  virtual int Seek(int _offset, Origin _origin);
 
  // See Stream::Tell for details.
  virtual int Tell() const;
 
  // See Stream::Tell for details.
  virtual size_t Size() const;
 
 private:
  // Resizes buffers size to _size bytes. If _size is less than the actual
  // buffer size, then it remains unchanged.
  // Returns true if the buffer can contains _size bytes.
  bool Resize(size_t _size);
 
  // Size of the buffer increment.
  static const size_t kBufferSizeIncrement;
 
  // Maximum stream size.
  static const size_t kMaxSize;
 
  // Buffer of data.
  byte* buffer_;
 
  // The size of the buffer, which is greater or equal to the size of the data
  // it contains (end_).
  size_t alloc_size_;
 
  // The effective size of the data in the buffer.
  int end_;
 
  // The cursor position in the buffer of data.
  int tell_;
};
}  // namespace io
}  // namespace ozz
#endif  // OZZ_OZZ_BASE_IO_STREAM_H_