context: /*
   * $Id: Inflate.cs,v 1.2 2008-05-10 09:35:40 bouncy Exp $
   *
  Copyright (c) 2000,2001,2002,2003 ymnk, JCraft,Inc. All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:
  
    1. Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
  
    2. Redistributions in binary form must reproduce the above copyright 
       notice, this list of conditions and the following disclaimer in 
       the documentation and/or other materials provided with the distribution.
  
    3. The names of the authors may not be used to endorse or promote products
       derived from this software without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
  INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
  OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
  EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  /*
   * This program is based on zlib-1.1.3, so all credit should go authors
   * Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
   * and contributors of zlib.
   */
  
  namespace Org.BouncyCastle.Utilities.Zlib {
  
      internal sealed class Inflate{
    
          private const int MAX_WBITS=15; // 32K LZ77 window
  
          // preset dictionary flag in zlib header
          private const int PRESET_DICT=0x20;
  
          internal const int Z_NO_FLUSH=0;
          internal const int Z_PARTIAL_FLUSH=1;
          internal const int Z_SYNC_FLUSH=2;
          internal const int Z_FULL_FLUSH=3;
          internal const int Z_FINISH=4;
  
          private const int Z_DEFLATED=8;
  
          private const int Z_OK=0;
          private const int Z_STREAM_END=1;
          private const int Z_NEED_DICT=2;
          private const int Z_ERRNO=-1;
          private const int Z_STREAM_ERROR=-2;
          private const int Z_DATA_ERROR=-3;
          private const int Z_MEM_ERROR=-4;
          private const int Z_BUF_ERROR=-5;
          private const int Z_VERSION_ERROR=-6;
  
          private const int METHOD=0;   // waiting for method byte
          private const int FLAG=1;     // waiting for flag byte
          private const int DICT4=2;    // four dictionary check bytes to go
          private const int DICT3=3;    // three dictionary check bytes to go
          private const int DICT2=4;    // two dictionary check bytes to go
          private const int DICT1=5;    // one dictionary check byte to go
          private const int DICT0=6;    // waiting for inflateSetDictionary
          private const int BLOCKS=7;   // decompressing blocks
          private const int CHECK4=8;   // four check bytes to go
          private const int CHECK3=9;   // three check bytes to go
          private const int CHECK2=10;  // two check bytes to go
          private const int CHECK1=11;  // one check byte to go
          private const int DONE=12;    // finished check, done
          private const int BAD=13;     // got an error--stay here
  
          internal int mode;                            // current inflate mode
  
          // mode dependent information
          internal int method;        // if FLAGS, method byte
  
          // if CHECK, check values to compare
          internal long[] was=new long[1] ; // computed check value
          internal long need;               // stream check value
  
          // if BAD, inflateSync's marker bytes count
          internal int marker;
  
          // mode independent information
          internal int  nowrap;          // flag for no wrapper
          internal int wbits;            // log2(window size)  (8..15, defaults to 15)
  
          internal InfBlocks blocks;     // current inflate_blocks state
  
          internal int inflateReset(ZStream z){
              if(z == null || z.istate == null) return Z_STREAM_ERROR;
      
              z.total_in = z.total_out = 0;
              z.msg = null;
              z.istate.mode = z.istate.nowrap!=0 ? BLOCKS : METHOD;
              z.istate.blocks.reset(z, null);
              return Z_OK;
          }
  
          internal int inflateEnd(ZStream z){
              if(blocks != null)
                  blocks.free(z);
              blocks=null;
              //    ZFREE(z, z->state);
              return Z_OK;
          }
  
          internal int inflateInit(ZStream z, int w){
              z.msg = null;
              blocks = null;
  
              // handle undocumented nowrap option (no zlib header or check)
              nowrap = 0;
              if(w < 0){
                  w = - w;
                  nowrap = 1;
              }
  
              // set window size
              if(w<8 ||w>15){
                  inflateEnd(z);
                  return Z_STREAM_ERROR;
              }
              wbits=w;
  
              z.istate.blocks=new InfBlocks(z, 
                  z.istate.nowrap!=0 ? null : this,
                  1<<w);
  
              // reset state
              inflateReset(z);
              return Z_OK;
          }
  
          internal int inflate(ZStream z, int f){
              int r;
              int b;
  
              if(z == null || z.istate == null || z.next_in == null)
                  return Z_STREAM_ERROR;
              f = f == Z_FINISH ? Z_BUF_ERROR : Z_OK;
              r = Z_BUF_ERROR;
              while (true){
                  //System.out.println("mode: "+z.istate.mode);
                  switch (z.istate.mode){
                      case METHOD:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          if(((z.istate.method = z.next_in[z.next_in_index++])&0xf)!=Z_DEFLATED){
                              z.istate.mode = BAD;
                              z.msg="unknown compression method";
                              z.istate.marker = 5;       // can't try inflateSync
                              break;
                          }
                          if((z.istate.method>>4)+8>z.istate.wbits){
                              z.istate.mode = BAD;
                              z.msg="invalid window size";
                              z.istate.marker = 5;       // can't try inflateSync
                              break;
                          }
                          z.istate.mode=FLAG;
                          goto case FLAG;
                      case FLAG:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          b = (z.next_in[z.next_in_index++])&0xff;
  
                          if((((z.istate.method << 8)+b) % 31)!=0){
                              z.istate.mode = BAD;
                              z.msg = "incorrect header check";
                              z.istate.marker = 5;       // can't try inflateSync
                              break;
                          }
  
                          if((b&PRESET_DICT)==0){
                              z.istate.mode = BLOCKS;
                              break;
                          }
                          z.istate.mode = DICT4;
                          goto case DICT4;
                      case DICT4:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need=((z.next_in[z.next_in_index++]&0xff)<<24)&0xff000000L;
                          z.istate.mode=DICT3;
                          goto case DICT3;
                      case DICT3:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need+=((z.next_in[z.next_in_index++]&0xff)<<16)&0xff0000L;
                          z.istate.mode=DICT2;
                          goto case DICT2;
                      case DICT2:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need+=((z.next_in[z.next_in_index++]&0xff)<<8)&0xff00L;
                          z.istate.mode=DICT1;
                          goto case DICT1;
                      case DICT1:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need += (z.next_in[z.next_in_index++]&0xffL);
                          z.adler = z.istate.need;
                          z.istate.mode = DICT0;
                          return Z_NEED_DICT;
                      case DICT0:
                          z.istate.mode = BAD;
                          z.msg = "need dictionary";
                          z.istate.marker = 0;       // can try inflateSync
                          return Z_STREAM_ERROR;
                      case BLOCKS:
  
                          r = z.istate.blocks.proc(z, r);
                          if(r == Z_DATA_ERROR){
                              z.istate.mode = BAD;
                              z.istate.marker = 0;     // can try inflateSync
                              break;
                          }
                          if(r == Z_OK){
                              r = f;
                          }
                          if(r != Z_STREAM_END){
                              return r;
                          }
                          r = f;
                          z.istate.blocks.reset(z, z.istate.was);
                          if(z.istate.nowrap!=0){
                              z.istate.mode=DONE;
                              break;
                          }
                          z.istate.mode=CHECK4;
                          goto case CHECK4;
                      case CHECK4:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need=((z.next_in[z.next_in_index++]&0xff)<<24)&0xff000000L;
                          z.istate.mode=CHECK3;
                          goto case CHECK3;
                      case CHECK3:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need+=((z.next_in[z.next_in_index++]&0xff)<<16)&0xff0000L;
                          z.istate.mode = CHECK2;
                          goto case CHECK2;
                      case CHECK2:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need+=((z.next_in[z.next_in_index++]&0xff)<<8)&0xff00L;
                          z.istate.mode = CHECK1;
                          goto case CHECK1;
                      case CHECK1:
  
                          if(z.avail_in==0)return r;r=f;
  
                          z.avail_in--; z.total_in++;
                          z.istate.need+=(z.next_in[z.next_in_index++]&0xffL);
  
                          if(((int)(z.istate.was[0])) != ((int)(z.istate.need))){
                              z.istate.mode = BAD;
                              z.msg = "incorrect data check";
                              z.istate.marker = 5;       // can't try inflateSync
                              break;
                          }
  
                          z.istate.mode = DONE;
                          goto case DONE;
                      case DONE:
                          return Z_STREAM_END;
                      case BAD:
                          return Z_DATA_ERROR;
                      default:
                          return Z_STREAM_ERROR;
                  }
              }
          }
  
  
          internal int inflateSetDictionary(ZStream z, byte[] dictionary, int dictLength){
              int index=0;
              int length = dictLength;
              if(z==null || z.istate == null|| z.istate.mode != DICT0)
                  return Z_STREAM_ERROR;
  
              if(z._adler.adler32(1L, dictionary, 0, dictLength)!=z.adler){
                  return Z_DATA_ERROR;
              }
  
              z.adler = z._adler.adler32(0, null, 0, 0);
  
              if(length >= (1<<z.istate.wbits)){
                  length = (1<<z.istate.wbits)-1;
                  index=dictLength - length;
              }
              z.istate.blocks.set_dictionary(dictionary, index, length);
              z.istate.mode = BLOCKS;
              return Z_OK;
          }
  
          private static readonly byte[] mark = {(byte)0, (byte)0, (byte)0xff, (byte)0xff};
  
          internal int inflateSync(ZStream z){
              int n;       // number of bytes to look at
              int p;       // pointer to bytes
              int m;       // number of marker bytes found in a row
              long r, w;   // temporaries to save total_in and total_out
  
              // set up
              if(z == null || z.istate == null)
                  return Z_STREAM_ERROR;
              if(z.istate.mode != BAD){
                  z.istate.mode = BAD;
                  z.istate.marker = 0;
              }
              if((n=z.avail_in)==0)
                  return Z_BUF_ERROR;
              p=z.next_in_index;
              m=z.istate.marker;
  
              // search
              while (n!=0 && m < 4){
                  if(z.next_in[p] == mark[m]){
                      m++;
                  }
                  else if(z.next_in[p]!=0){
                      m = 0;
                  }
                  else{
                      m = 4 - m;
                  }
                  p++; n--;
              }
  
              // restore
              z.total_in += p-z.next_in_index;
              z.next_in_index = p;
              z.avail_in = n;
              z.istate.marker = m;
  
              // return no joy or set up to restart on a new block
              if(m != 4){
                  return Z_DATA_ERROR;
              }
              r=z.total_in;  w=z.total_out;
              inflateReset(z);
  
gt:             z.total_in=r;  z.total_out = w;