Adding upstream version 0.1.upstream/0.1

Signed-off-by: Daniel Baumann <mail@daniel-baumann.ch>

1 files changed, 363 insertions, 0 deletions

diff --git a/decoder.cc b/decoder.cc
new file mode 100644
index 0000000..fbfcdb3
--- /dev/null
+++ b/decoder.cc
@@ -0,0 +1,363 @@
+/*  Lzd - Educational decompressor for lzip files
+    Copyright (C) 2013 Antonio Diaz Diaz.
+
+    This program is free software: you have unlimited permission
+    to copy, distribute and modify it.
+
+    This program 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.
+*/
+
+class State
+  {
+  int st;
+
+public:
+  enum { states = 12 };
+  State() : st( 0 ) {}
+  int operator()() const { return st; }
+  bool is_char() const { return st < 7; }
+
+  void set_char()
+    {
+    static const int next[states] = { 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 4, 5 };
+    st = next[st];
+    }
+
+  void set_match()     { st = ( ( st < 7 ) ? 7 : 10 ); }
+  void set_rep()       { st = ( ( st < 7 ) ? 8 : 11 ); }
+  void set_short_rep() { st = ( ( st < 7 ) ? 9 : 11 ); }
+  };
+
+
+enum {
+  literal_context_bits = 3,
+  pos_state_bits = 2,
+  pos_states = 1 << pos_state_bits,
+  pos_state_mask = pos_states - 1,
+
+  max_dis_states = 4,
+  dis_slot_bits = 6,
+  start_dis_model = 4,
+  end_dis_model = 14,
+  modeled_distances = 1 << (end_dis_model / 2),		// 128
+  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
+
+  bit_model_move_bits = 5,
+  bit_model_total_bits = 11,
+  bit_model_total = 1 << bit_model_total_bits };
+
+
+struct Bit_model
+  {
+  int probability;
+  Bit_model() : probability( bit_model_total / 2 ) {}
+  };
+
+struct Len_model
+  {
+  Bit_model choice1;
+  Bit_model choice2;
+  Bit_model bm_low[pos_states][len_low_symbols];
+  Bit_model bm_mid[pos_states][len_mid_symbols];
+  Bit_model bm_high[len_high_symbols];
+  };
+
+
+class Range_decoder
+  {
+  uint32_t code;
+  uint32_t range;
+
+public:
+  Range_decoder() : code( 0 ), range( 0xFFFFFFFFU )
+    {
+    for( int i = 0; i < 5; ++i ) code = (code << 8) | std::getc( stdin );
+    }
+
+  int decode( const int num_bits )
+    {
+    int symbol = 0;
+    for( int i = 0; i < num_bits; ++i )
+      {
+      range >>= 1;
+      symbol <<= 1;
+      if( code >= range ) { code -= range; symbol |= 1; }
+      if( range <= 0x00FFFFFFU )			// normalize
+        { range <<= 8; code = (code << 8) | std::getc( stdin ); }
+      }
+    return symbol;
+    }
+
+  int decode_bit( Bit_model & bm )
+    {
+    int symbol;
+    const uint32_t bound = ( range >> bit_model_total_bits ) * bm.probability;
+    if( code < bound )
+      {
+      range = bound;
+      bm.probability += (bit_model_total - bm.probability) >> bit_model_move_bits;
+      symbol = 0;
+      }
+    else
+      {
+      range -= bound;
+      code -= bound;
+      bm.probability -= bm.probability >> bit_model_move_bits;
+      symbol = 1;
+      }
+    if( range <= 0x00FFFFFFU )				// normalize
+      { range <<= 8; code = (code << 8) | std::getc( stdin ); }
+    return symbol;
+    }
+
+  int decode_tree( Bit_model bm[], const int num_bits )
+    {
+    int symbol = 1;
+    for( int i = 0; i < num_bits; ++i )
+      symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+    return symbol - (1 << num_bits);
+    }
+
+  int decode_tree_reversed( Bit_model bm[], const int num_bits )
+    {
+    int symbol = decode_tree( bm, num_bits );
+    int reversed_symbol = 0;
+    for( int i = 0; i < num_bits; ++i )
+      {
+      reversed_symbol = ( reversed_symbol << 1 ) | ( symbol & 1 );
+      symbol >>= 1;
+      }
+    return reversed_symbol;
+    }
+
+  int decode_matched( Bit_model bm[], const int match_byte )
+    {
+    Bit_model * const bm1 = bm + 0x100;
+    int symbol = 1;
+    for( int i = 7; i >= 0; --i )
+      {
+      const int match_bit = ( match_byte >> i ) & 1;
+      const int bit = decode_bit( bm1[(match_bit<<8)+symbol] );
+      symbol = ( symbol << 1 ) | bit;
+      if( match_bit != bit )
+        {
+        while( symbol < 0x100 )
+          symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+        break;
+        }
+      }
+    return symbol - 0x100;
+    }
+
+  int decode_len( Len_model & lm, const int pos_state )
+    {
+    if( decode_bit( lm.choice1 ) == 0 )
+      return min_match_len +
+             decode_tree( lm.bm_low[pos_state], len_low_bits );
+    if( decode_bit( lm.choice2 ) == 0 )
+      return min_match_len + len_low_symbols +
+             decode_tree( lm.bm_mid[pos_state], len_mid_bits );
+    return min_match_len + len_low_symbols + len_mid_symbols +
+           decode_tree( lm.bm_high, len_high_bits );
+    }
+  };
+
+
+class LZ_decoder
+  {
+  unsigned long long partial_data_pos;
+  Range_decoder rdec;
+  const unsigned dictionary_size;
+  uint8_t * const buffer;	// output buffer
+  unsigned pos;			// current pos in buffer
+  unsigned stream_pos;		// first byte not yet written to stdout
+  uint32_t crc_;
+
+  void flush_data();
+
+  uint8_t get_byte( const unsigned distance ) const
+    {
+    int i = pos - distance - 1;
+    if( i < 0 ) i += dictionary_size;
+    return buffer[i];
+    }
+
+  void put_byte( const uint8_t b )
+    {
+    buffer[pos] = b;
+    if( ++pos >= dictionary_size ) flush_data();
+    }
+
+public:
+  LZ_decoder( const unsigned dict_size )
+    :
+    partial_data_pos( 0 ),
+    dictionary_size( dict_size ),
+    buffer( new uint8_t[dictionary_size] ),
+    pos( 0 ),
+    stream_pos( 0 ),
+    crc_( 0xFFFFFFFFU )
+    { buffer[dictionary_size-1] = 0; }		// prev_byte of first_byte
+
+  ~LZ_decoder() { delete[] buffer; }
+
+  unsigned crc() const { return crc_ ^ 0xFFFFFFFFU; }
+  unsigned long long data_position() const { return partial_data_pos + pos; }
+
+  bool decode_member();
+  };
+
+
+class CRC32
+  {
+  uint32_t data[256];		// Table of CRCs of all 8-bit messages.
+
+public:
+  CRC32()
+    {
+    for( unsigned n = 0; n < 256; ++n )
+      {
+      unsigned c = n;
+      for( int k = 0; k < 8; ++k )
+        { if( c & 1 ) c = 0xEDB88320U ^ ( c >> 1 ); else c >>= 1; }
+      data[n] = c;
+      }
+    }
+
+  void update( uint32_t & crc, const uint8_t * buffer, const int size ) const
+    {
+    for( int i = 0; i < size; ++i )
+      crc = data[(crc^buffer[i])&0xFF] ^ ( crc >> 8 );
+    }
+  };
+
+const CRC32 crc32;
+
+
+void LZ_decoder::flush_data()
+  {
+  if( pos > stream_pos )
+    {
+    const unsigned size = pos - stream_pos;
+    crc32.update( crc_, buffer + stream_pos, size );
+    errno = 0;
+    if( std::fwrite( buffer + stream_pos, 1, size, stdout ) != size )
+      { std::fprintf( stderr, "Write error: %s\n", std::strerror( errno ) );
+        std::exit( 1 ); }
+    if( pos >= dictionary_size ) { partial_data_pos += pos; pos = 0; }
+    stream_pos = pos;
+    }
+  }
+
+
+bool LZ_decoder::decode_member()		// Returns false if error
+  {
+  Bit_model bm_literal[1<<literal_context_bits][0x300];
+  Bit_model bm_match[State::states][pos_states];
+  Bit_model bm_rep[State::states];
+  Bit_model bm_rep0[State::states];
+  Bit_model bm_rep1[State::states];
+  Bit_model bm_rep2[State::states];
+  Bit_model bm_len[State::states][pos_states];
+  Bit_model bm_dis_slot[max_dis_states][1<<dis_slot_bits];
+  Bit_model bm_dis[modeled_distances-end_dis_model];
+  Bit_model bm_align[dis_align_size];
+  Len_model match_len_model;
+  Len_model rep_len_model;
+  unsigned rep0 = 0;			// rep[0-3] latest four distances
+  unsigned rep1 = 0;			// used for efficient coding of
+  unsigned rep2 = 0;			// repeated distances
+  unsigned rep3 = 0;
+  State state;
+
+  while( !std::feof( stdin ) && !std::ferror( stdin ) )
+    {
+    const int pos_state = data_position() & pos_state_mask;
+    if( rdec.decode_bit( bm_match[state()][pos_state] ) == 0 )	// 1st bit
+      {
+      const uint8_t prev_byte = get_byte( 0 );
+      const int literal_state = prev_byte >> ( 8 - literal_context_bits );
+      Bit_model * const bm = bm_literal[literal_state];
+      if( state.is_char() )
+        put_byte( rdec.decode_tree( bm, 8 ) );
+      else
+        put_byte( rdec.decode_matched( bm, get_byte( rep0 ) ) );
+      state.set_char();
+      }
+    else
+      {
+      int len;
+      if( rdec.decode_bit( bm_rep[state()] ) == 1 )		// 2nd bit
+        {
+        if( rdec.decode_bit( bm_rep0[state()] ) == 0 )		// 3rd bit
+          {
+          if( rdec.decode_bit( bm_len[state()][pos_state] ) == 0 ) // 4th bit
+            { state.set_short_rep(); put_byte( get_byte( rep0 ) ); continue; }
+          }
+        else
+          {
+          unsigned distance;
+          if( rdec.decode_bit( bm_rep1[state()] ) == 0 )	// 4th bit
+            distance = rep1;
+          else
+            {
+            if( rdec.decode_bit( bm_rep2[state()] ) == 0 )	// 5th bit
+              distance = rep2;
+            else
+              { distance = rep3; rep3 = rep2; }
+            rep2 = rep1;
+            }
+          rep1 = rep0;
+          rep0 = distance;
+          }
+        len = rdec.decode_len( rep_len_model, pos_state );
+        state.set_rep();
+        }
+      else
+        {
+        rep3 = rep2; rep2 = rep1; rep1 = rep0;
+        len = rdec.decode_len( match_len_model, pos_state );
+        const int dis_state = std::min( len - min_match_len, max_dis_states - 1 );
+        const int dis_slot =
+          rdec.decode_tree( bm_dis_slot[dis_state], dis_slot_bits );
+        if( dis_slot < start_dis_model ) rep0 = dis_slot;
+        else
+          {
+          const int direct_bits = ( dis_slot >> 1 ) - 1;
+          rep0 = ( 2 | ( dis_slot & 1 ) ) << direct_bits;
+          if( dis_slot < end_dis_model )
+            rep0 += rdec.decode_tree_reversed( bm_dis + rep0 - dis_slot - 1,
+                                               direct_bits );
+          else
+            {
+            rep0 += rdec.decode( direct_bits - dis_align_bits ) << dis_align_bits;
+            rep0 += rdec.decode_tree_reversed( bm_align, dis_align_bits );
+            if( rep0 == 0xFFFFFFFFU )		// Marker found
+              {
+              flush_data();
+              return ( len == min_match_len );	// End Of Stream marker
+              }
+            }
+          }
+        state.set_match();
+        if( rep0 >= dictionary_size || ( rep0 >= pos && !partial_data_pos ) )
+          return false;
+        }
+      for( int i = 0; i < len; ++i )
+        put_byte( get_byte( rep0 ) );
+      }
+    }
+  return false;
+  }