/*  Lzlib - A compression library for lzip files
    Copyright (C) 2009, 2010, 2011 Antonio Diaz Diaz.

    This library is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this library.  If not, see <http://www.gnu.org/licenses/>.

    As a special exception, you may use this file as part of a free
    software library without restriction.  Specifically, if other files
    instantiate templates or use macros or inline functions from this
    file, or you compile this file and link it with other files to
    produce an executable, this file does not by itself cause the
    resulting executable to be covered by the GNU General Public
    License.  This exception does not however invalidate any other
    reasons why the executable file might be covered by the GNU General
    Public License.
*/

namespace Lzlib {

class State
  {
  unsigned char st;

public:
  enum { states = 12 };
  State() throw() : st( 0 ) {}
  unsigned char operator()() const throw() { return st; }
  bool is_char() const throw() { return st < 7; }

  void set_char() throw()
    {
    static const unsigned char next[states] =
      { 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 4, 5 };
    st = next[st];
    }

  void set_match() throw()
    {
    static const unsigned char next[states] =
      { 7, 7, 7, 7, 7, 7, 7, 10, 10, 10, 10, 10 };
    st = next[st];
    }

  void set_rep() throw()
    {
    static const unsigned char next[states] =
      { 8, 8, 8, 8, 8, 8, 8, 11, 11, 11, 11, 11 };
    st = next[st];
    }

  void set_short_rep() throw()
    {
    static const unsigned char next[states] =
      { 9, 9, 9, 9, 9, 9, 9, 11, 11, 11, 11, 11 };
    st = next[st];
    }
  };


enum {
  min_dictionary_bits = 12,
  min_dictionary_size = 1 << min_dictionary_bits,
  max_dictionary_bits = 29,
  max_dictionary_size = 1 << max_dictionary_bits,
  literal_context_bits = 3,
  pos_state_bits = 2,
  pos_states = 1 << pos_state_bits,
  pos_state_mask = pos_states - 1,

  dis_slot_bits = 6,
  start_dis_model = 4,
  end_dis_model = 14,
  modeled_distances = 1 << (end_dis_model / 2),
  dis_align_bits = 4,
  dis_align_size = 1 << dis_align_bits,

  len_low_bits = 3,
  len_mid_bits = 3,
  len_high_bits = 8,
  len_low_symbols = 1 << len_low_bits,
  len_mid_symbols = 1 << len_mid_bits,
  len_high_symbols = 1 << len_high_bits,
  max_len_symbols = len_low_symbols + len_mid_symbols + len_high_symbols,

  min_match_len = 2,		// must be 2
  max_match_len = min_match_len + max_len_symbols - 1,	// 273
  min_match_len_limit = 5,

  max_dis_states = 4 };

inline int get_dis_state( int len ) throw()
  {
  len -= min_match_len;
  if( len >= max_dis_states ) len = max_dis_states - 1;
  return len;
  }


enum { bit_model_move_bits = 5,
       bit_model_total_bits = 11,
       bit_model_total = 1 << bit_model_total_bits };

struct Bit_model
  {
  unsigned int probability;
  Bit_model() throw() : probability( bit_model_total / 2 ) {}
  };


class CRC32
  {
  uint32_t data[256];		// Table of CRCs of all 8-bit messages.

public:
  CRC32()
    {
    for( unsigned int n = 0; n < 256; ++n )
      {
      unsigned int c = n;
      for( int k = 0; k < 8; ++k )
        { if( c & 1 ) c = 0xEDB88320U ^ ( c >> 1 ); else c >>= 1; }
      data[n] = c;
      }
    }

  uint32_t operator[]( const uint8_t byte ) const throw() { return data[byte]; }
  void update( uint32_t & crc, const uint8_t byte ) const throw()
    { crc = data[(crc^byte)&0xFF] ^ ( crc >> 8 ); }
  void update( uint32_t & crc, const uint8_t * const buffer, const int size ) const throw()
    {
    for( int i = 0; i < size; ++i )
      crc = data[(crc^buffer[i])&0xFF] ^ ( crc >> 8 );
    }
  };

extern const CRC32 crc32;


inline int real_bits( const int value ) throw()
  {
  int bits = 0;
  for( int i = 1, mask = 1; mask > 0; ++i, mask <<= 1 )
    if( value & mask ) bits = i;
  return bits;
  }

const uint8_t magic_string[4] = { 'L', 'Z', 'I', 'P' };

struct File_header
  {
  uint8_t data[6];			// 0-3 magic bytes
					//   4 version
					//   5 coded_dict_size
  enum { size = 6 };

  void set_magic() throw()
    { std::memcpy( data, magic_string, 4 ); data[4] = 1; }

  bool verify_magic() const throw()
    { return ( std::memcmp( data, magic_string, 4 ) == 0 ); }

  uint8_t version() const throw() { return data[4]; }
  bool verify_version() const throw() { return ( data[4] <= 1 ); }

  bool verify() const throw()
    {
    return ( verify_magic() && verify_version() &&
             dictionary_size() >= min_dictionary_size &&
             dictionary_size() <= max_dictionary_size );
    }

  int dictionary_size() const throw()
    {
    int sz = ( 1 << ( data[5] & 0x1F ) );
    if( sz > min_dictionary_size && sz <= max_dictionary_size )
      sz -= ( sz / 16 ) * ( ( data[5] >> 5 ) & 0x07 );
    return sz;
    }

  bool dictionary_size( const int sz ) throw()
    {
    if( sz >= min_dictionary_size && sz <= max_dictionary_size )
      {
      data[5] = real_bits( sz - 1 );
      if( sz > min_dictionary_size )
        {
        const int base_size = 1 << data[5];
        const int wedge = base_size / 16;
        for( int i = 7; i >= 1; --i )
          if( base_size - ( i * wedge ) >= sz )
            { data[5] |= ( i << 5 ); break; }
        }
      return true;
      }
    return false;
    }
  };


struct File_trailer
  {
  uint8_t data[20];	//  0-3  CRC32 of the uncompressed data
			//  4-11 size of the uncompressed data
			// 12-19 member size including header and trailer

  static int size( const int version = 1 )
    { return ( ( version >= 1 ) ? 20 : 12 ); }

  uint32_t data_crc() const throw()
    {
    uint32_t tmp = 0;
    for( int i = 3; i >= 0; --i ) { tmp <<= 8; tmp += data[i]; }
    return tmp;
    }

  void data_crc( uint32_t crc ) throw()
    { for( int i = 0; i <= 3; ++i ) { data[i] = (uint8_t)crc; crc >>= 8; } }

  long long data_size() const throw()
    {
    long long tmp = 0;
    for( int i = 11; i >= 4; --i ) { tmp <<= 8; tmp += data[i]; }
    return tmp;
    }

  void data_size( long long sz ) throw()
    {
    for( int i = 4; i <= 11; ++i ) { data[i] = (uint8_t)sz; sz >>= 8; }
    }

  long long member_size() const throw()
    {
    long long tmp = 0;
    for( int i = 19; i >= 12; --i ) { tmp <<= 8; tmp += data[i]; }
    return tmp;
    }

  void member_size( long long sz ) throw()
    {
    for( int i = 12; i <= 19; ++i ) { data[i] = (uint8_t)sz; sz >>= 8; }
    }
  };


class Circular_buffer
  {
protected:
  const int buffer_size;	// capacity == buffer_size - 1
  uint8_t * const buffer;
  int get;			// buffer is empty when get == put
  int put;

  void reset() throw() { get = 0; put = 0; }

public:
  Circular_buffer( const int buf_size )
    :
    buffer_size( buf_size + 1 ),
    buffer( new uint8_t[buffer_size] ),
    get( 0 ),
    put( 0 ) {}

  ~Circular_buffer() { delete[] buffer; }

  int used_bytes() const throw()
    { return ( (get <= put) ? 0 : buffer_size ) + put - get; }
  int free_bytes() const throw()
    { return ( (get <= put) ? buffer_size : 0 ) - put + get - 1; }

  uint8_t get_byte() throw()
    {
    const uint8_t b = buffer[get];
    if( ++get >= buffer_size ) get = 0;
    return b;
    }

  void put_byte( const uint8_t b ) throw()
    {
    buffer[put] = b;
    if( ++put >= buffer_size ) put = 0;
    }

  int read_data( uint8_t * const out_buffer, const int out_size ) throw();
  int write_data( const uint8_t * const in_buffer, const int in_size ) throw();
  };

} // end namespace Lzlib