/*
 * 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