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/*

 * A C++ I/O streams interface to the zlib gz* functions

 *

 * by Ludwig Schwardt <schwardt@sun.ac.za>

 * original version by Kevin Ruland <kevin@rodin.wustl.edu>

 *

 * This version is standard-compliant and compatible with gcc 3.x.

 */

#ifndef ZFSTREAM_H

#define ZFSTREAM_H

#include <istream>  // not iostream, since we don't need cin/cout

#include <ostream>

#include "zlib.h"

/*****************************************************************************/

/**

 *  @brief  Gzipped file stream buffer class.

 *

 *  This class implements basic_filebuf for gzipped files. It doesn't yet support

 *  seeking (allowed by zlib but slow/limited), putback and read/write access

 *  (tricky). Otherwise, it attempts to be a drop-in replacement for the standard

 *  file streambuf.

*/

class gzfilebuf : public std::streambuf

{

public:

  //  Default constructor.

  gzfilebuf();

  //  Destructor.

  virtual

  ~gzfilebuf();

  /**

   *  @brief  Set compression level and strategy on the fly.

   *  @param  comp_level  Compression level (see zlib.h for allowed values)

   *  @param  comp_strategy  Compression strategy (see zlib.h for allowed values)

   *  @return  Z_OK on success, Z_STREAM_ERROR otherwise.

   *

   *  Unfortunately, these parameters cannot be modified separately, as the

   *  previous zfstream version assumed. Since the strategy is seldom changed,

   *  it can default and setcompression(level) then becomes like the old

   *  setcompressionlevel(level).

  */

  int

  setcompression(int comp_level,

                 int comp_strategy = Z_DEFAULT_STRATEGY);

  /**

   *  @brief  Check if file is open.

   *  @return  True if file is open.

  */

  bool

  is_open() const { return (file != NULL); }

  /**

   *  @brief  Open gzipped file.

   *  @param  name  File name.

   *  @param  mode  Open mode flags.

   *  @return  @c this on success, NULL on failure.

  */

  gzfilebuf*

  open(const char* name,

       std::ios_base::openmode mode);

  /**

   *  @brief  Attach to already open gzipped file.

   *  @param  fd  File descriptor.

   *  @param  mode  Open mode flags.

   *  @return  @c this on success, NULL on failure.

  */

  gzfilebuf*

  attach(int fd,

         std::ios_base::openmode mode);

  /**

   *  @brief  Close gzipped file.

   *  @return  @c this on success, NULL on failure.

  */

  gzfilebuf*

  close();

protected:

  /**

   *  @brief  Convert ios open mode int to mode string used by zlib.

   *  @return  True if valid mode flag combination.

  */

  bool

  open_mode(std::ios_base::openmode mode,

            char* c_mode) const;

  /**

   *  @brief  Number of characters available in stream buffer.

   *  @return  Number of characters.

   *

   *  This indicates number of characters in get area of stream buffer.

   *  These characters can be read without accessing the gzipped file.

  */

  virtual std::streamsize

  showmanyc();

  /**

   *  @brief  Fill get area from gzipped file.

   *  @return  First character in get area on success, EOF on error.

   *

   *  This actually reads characters from gzipped file to stream

   *  buffer. Always buffered.

  */

  virtual int_type

  underflow();

  /**

   *  @brief  Write put area to gzipped file.

   *  @param  c  Extra character to add to buffer contents.

   *  @return  Non-EOF on success, EOF on error.

   *

   *  This actually writes characters in stream buffer to

   *  gzipped file. With unbuffered output this is done one

   *  character at a time.

  */

  virtual int_type

  overflow(int_type c = traits_type::eof());

  /**

   *  @brief  Installs external stream buffer.

   *  @param  p  Pointer to char buffer.

   *  @param  n  Size of external buffer.

   *  @return  @c this on success, NULL on failure.

   *

   *  Call setbuf(0,0) to enable unbuffered output.

  */

  virtual std::streambuf*

  setbuf(char_type* p,

         std::streamsize n);

  /**

   *  @brief  Flush stream buffer to file.

   *  @return  0 on success, -1 on error.

   *

   *  This calls underflow(EOF) to do the job.

  */

  virtual int

  sync();

//

// Some future enhancements

//

//  virtual int_type uflow();

//  virtual int_type pbackfail(int_type c = traits_type::eof());

//  virtual pos_type

//  seekoff(off_type off,

//          std::ios_base::seekdir way,

//          std::ios_base::openmode mode = std::ios_base::in|std::ios_base::out);

//  virtual pos_type

//  seekpos(pos_type sp,

//          std::ios_base::openmode mode = std::ios_base::in|std::ios_base::out);

private:

  /**

   *  @brief  Allocate internal buffer.

   *

   *  This function is safe to call multiple times. It will ensure

   *  that a proper internal buffer exists if it is required. If the

   *  buffer already exists or is external, the buffer pointers will be

   *  reset to their original state.

  */

  void

  enable_buffer();

  /**

   *  @brief  Destroy internal buffer.

   *

   *  This function is safe to call multiple times. It will ensure

   *  that the internal buffer is deallocated if it exists. In any

   *  case, it will also reset the buffer pointers.

  */

  void

  disable_buffer();

  /**

   *  Underlying file pointer.

  */

  gzFile file;

  /**

   *  Mode in which file was opened.

  */

  std::ios_base::openmode io_mode;

  /**

   *  @brief  True if this object owns file descriptor.

   *

   *  This makes the class responsible for closing the file

   *  upon destruction.

  */

  bool own_fd;

  /**

   *  @brief  Stream buffer.

   *

   *  For simplicity this remains allocated on the free store for the

   *  entire life span of the gzfilebuf object, unless replaced by setbuf.

  */

  char_type* buffer;

  /**

   *  @brief  Stream buffer size.

   *

   *  Defaults to system default buffer size (typically 8192 bytes).

   *  Modified by setbuf.

  */

  std::streamsize buffer_size;

  /**

   *  @brief  True if this object owns stream buffer.

   *

   *  This makes the class responsible for deleting the buffer

   *  upon destruction.

  */

  bool own_buffer;

};

/*****************************************************************************/

/**

 *  @brief  Gzipped file input stream class.

 *

 *  This class implements ifstream for gzipped files. Seeking and putback

 *  is not supported yet.

*/

class gzifstream : public std::istream

{

public:

  //  Default constructor

  gzifstream();

  /**

   *  @brief  Construct stream on gzipped file to be opened.

   *  @param  name  File name.

   *  @param  mode  Open mode flags (forced to contain ios::in).

  */

  explicit

  gzifstream(const char* name,

             std::ios_base::openmode mode = std::ios_base::in);

  /**

   *  @brief  Construct stream on already open gzipped file.

   *  @param  fd    File descriptor.

   *  @param  mode  Open mode flags (forced to contain ios::in).

  */

  explicit

  gzifstream(int fd,

             std::ios_base::openmode mode = std::ios_base::in);

  /**

   *  Obtain underlying stream buffer.

  */

  gzfilebuf*

  rdbuf() const

  { return const_cast<gzfilebuf*>(&sb); }

  /**

   *  @brief  Check if file is open.

   *  @return  True if file is open.

  */

  bool

  is_open() { return sb.is_open(); }

  /**

   *  @brief  Open gzipped file.

   *  @param  name  File name.

   *  @param  mode  Open mode flags (forced to contain ios::in).

   *

   *  Stream will be in state good() if file opens successfully;

   *  otherwise in state fail(). This differs from the behavior of

   *  ifstream, which never sets the state to good() and therefore

   *  won't allow you to reuse the stream for a second file unless

   *  you manually clear() the state. The choice is a matter of

   *  convenience.

  */

  void

  open(const char* name,

       std::ios_base::openmode mode = std::ios_base::in);

  /**

   *  @brief  Attach to already open gzipped file.

   *  @param  fd  File descriptor.

   *  @param  mode  Open mode flags (forced to contain ios::in).

   *

   *  Stream will be in state good() if attach succeeded; otherwise

   *  in state fail().

  */

  void

  attach(int fd,

         std::ios_base::openmode mode = std::ios_base::in);

  /**

   *  @brief  Close gzipped file.

   *

   *  Stream will be in state fail() if close failed.

  */

  void

  close();

private:

  /**

   *  Underlying stream buffer.

  */

  gzfilebuf sb;

};

/*****************************************************************************/

/**

 *  @brief  Gzipped file output stream class.

 *

 *  This class implements ofstream for gzipped files. Seeking and putback

 *  is not supported yet.

*/

class gzofstream : public std::ostream

{

public:

  //  Default constructor

  gzofstream();

  /**

   *  @brief  Construct stream on gzipped file to be opened.

   *  @param  name  File name.

   *  @param  mode  Open mode flags (forced to contain ios::out).

  */

  explicit

  gzofstream(const char* name,

             std::ios_base::openmode mode = std::ios_base::out);

  /**

   *  @brief  Construct stream on already open gzipped file.

   *  @param  fd    File descriptor.

   *  @param  mode  Open mode flags (forced to contain ios::out).

  */

  explicit

  gzofstream(int fd,

             std::ios_base::openmode mode = std::ios_base::out);

  /**

   *  Obtain underlying stream buffer.

  */

  gzfilebuf*

  rdbuf() const

  { return const_cast<gzfilebuf*>(&sb); }

  /**

   *  @brief  Check if file is open.

   *  @return  True if file is open.

  */

  bool

  is_open() { return sb.is_open(); }

  /**

   *  @brief  Open gzipped file.

   *  @param  name  File name.

   *  @param  mode  Open mode flags (forced to contain ios::out).

   *

   *  Stream will be in state good() if file opens successfully;

   *  otherwise in state fail(). This differs from the behavior of

   *  ofstream, which never sets the state to good() and therefore

   *  won't allow you to reuse the stream for a second file unless

   *  you manually clear() the state. The choice is a matter of

   *  convenience.

  */

  void

  open(const char* name,

       std::ios_base::openmode mode = std::ios_base::out);

  /**

   *  @brief  Attach to already open gzipped file.

   *  @param  fd  File descriptor.

   *  @param  mode  Open mode flags (forced to contain ios::out).

   *

   *  Stream will be in state good() if attach succeeded; otherwise

   *  in state fail().

  */

  void

  attach(int fd,

         std::ios_base::openmode mode = std::ios_base::out);

  /**

   *  @brief  Close gzipped file.

   *

   *  Stream will be in state fail() if close failed.

  */

  void

  close();

private:

  /**

   *  Underlying stream buffer.

  */

  gzfilebuf sb;

};

/*****************************************************************************/

/**

 *  @brief  Gzipped file output stream manipulator class.

 *

 *  This class defines a two-argument manipulator for gzofstream. It is used

 *  as base for the setcompression(int,int) manipulator.

*/

template<typename T1, typename T2>

  class gzomanip2

  {

  public:

    // Allows insertor to peek at internals

    template <typename Ta, typename Tb>

      friend gzofstream&

      operator<<(gzofstream&,

                 const gzomanip2<Ta,Tb>&);

    // Constructor

    gzomanip2(gzofstream& (*f)(gzofstream&, T1, T2),

              T1 v1,

              T2 v2);

  private:

    // Underlying manipulator function

    gzofstream&

    (*func)(gzofstream&, T1, T2);

    // Arguments for manipulator function

    T1 val1;

    T2 val2;

  };

/*****************************************************************************/

// Manipulator function thunks through to stream buffer

inline gzofstream&

setcompression(gzofstream &gzs, int l, int s = Z_DEFAULT_STRATEGY)

{

  (gzs.rdbuf())->setcompression(l, s);

  return gzs;

}

// Manipulator constructor stores arguments

template<typename T1, typename T2>

  inline

  gzomanip2<T1,T2>::gzomanip2(gzofstream &(*f)(gzofstream &, T1, T2),

                              T1 v1,

                              T2 v2)

  : func(f), val1(v1), val2(v2)

  { }

// Insertor applies underlying manipulator function to stream

template<typename T1, typename T2>

  inline gzofstream&

  operator<<(gzofstream& s, const gzomanip2<T1,T2>& m)

  { return (*m.func)(s, m.val1, m.val2); }

// Insert this onto stream to simplify setting of compression level

inline gzomanip2<int,int>

setcompression(int l, int s = Z_DEFAULT_STRATEGY)

{ return gzomanip2<int,int>(&setcompression, l, s); }

#endif // ZFSTREAM_H