Exemplo n.º 1
0
 // Construct one Huffman tree and assigns the code bit strings and lengths.
 // Update the total bit length for the current block.
 // IN assertion: the field freq is set for all tree elements.
 // OUT assertions: the fields len and code are set to the optimal bit length
 //     and corresponding code. The length opt_len is updated; static_len is
 //     also updated if stree is not null. The field max_code is set.
 internal void  build_tree(DeflateManager s)
 {
     short[] tree  = dyn_tree;
     short[] stree = staticTree.treeCodes;
     int elems     = staticTree.elems;
     int n, m;            // iterate over heap elements
     int max_code  = -1;  // largest code with non zero frequency
     int node;            // new node being created
                 
     // Construct the initial heap, with least frequent element in
     // heap[1]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
     // heap[0] is not used.
     s.heap_len = 0;
     s.heap_max = HEAP_SIZE;
                 
     for (n = 0; n < elems; n++)
     {
         if (tree[n * 2] != 0)
         {
             s.heap[++s.heap_len] = max_code = n;
             s.depth[n] = 0;
         }
         else
         {
             tree[n * 2 + 1] = 0;
         }
     }
                 
     // The pkzip format requires that at least one distance code exists,
     // and that at least one bit should be sent even if there is only one
     // possible code. So to avoid special checks later on we force at least
     // two codes of non zero frequency.
     while (s.heap_len < 2)
     {
         node = s.heap[++s.heap_len] = (max_code < 2?++max_code:0);
         tree[node * 2] = 1;
         s.depth[node] = 0;
         s.opt_len--;
         if (stree != null)
             s.static_len -= stree[node * 2 + 1];
         // node is 0 or 1 so it does not have extra bits
     }
     this.max_code = max_code;
                 
     // The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
     // establish sub-heaps of increasing lengths:
                 
     for (n = s.heap_len / 2; n >= 1; n--)
         s.pqdownheap(tree, n);
                 
     // Construct the Huffman tree by repeatedly combining the least two
     // frequent nodes.
                 
     node = elems; // next internal node of the tree
     do 
     {
         // n = node of least frequency
         n = s.heap[1];
         s.heap[1] = s.heap[s.heap_len--];
         s.pqdownheap(tree, 1);
         m = s.heap[1]; // m = node of next least frequency
                         
         s.heap[--s.heap_max] = n; // keep the nodes sorted by frequency
         s.heap[--s.heap_max] = m;
                         
         // Create a new node father of n and m
         tree[node * 2] = unchecked((short) (tree[n * 2] + tree[m * 2]));
         s.depth[node] = (sbyte) (System.Math.Max((byte) s.depth[n], (byte) s.depth[m]) + 1);
         tree[n * 2 + 1] = tree[m * 2 + 1] = (short) node;
                         
         // and insert the new node in the heap
         s.heap[1] = node++;
         s.pqdownheap(tree, 1);
     }
     while (s.heap_len >= 2);
                 
     s.heap[--s.heap_max] = s.heap[1];
                 
     // At this point, the fields freq and dad are set. We can now
     // generate the bit lengths.
                 
     gen_bitlen(s);
                 
     // The field len is now set, we can generate the bit codes
     gen_codes(tree, max_code, s.bl_count);
 }
Exemplo n.º 2
0
 /// <summary>
 /// End a deflation session.
 /// </summary>
 /// <remarks>
 /// Call this after making a series of one or more calls to Deflate(). All buffers are flushed.
 /// </remarks>
 /// <returns>Z_OK if all goes well.</returns>
 public int EndDeflate()
 {
     if (dstate == null)
         throw new ZlibException("No Deflate State!");
     // TODO: dinoch Tue, 03 Nov 2009  15:39 (test this)
     //int ret = dstate.End();
     dstate = null;
     return ZlibConstants.Z_OK; //ret;
 }
Exemplo n.º 3
0
 internal StaticTree staticTree; // the corresponding static tree
         
 // Compute the optimal bit lengths for a tree and update the total bit length
 // for the current block.
 // IN assertion: the fields freq and dad are set, heap[heap_max] and
 //    above are the tree nodes sorted by increasing frequency.
 // OUT assertions: the field len is set to the optimal bit length, the
 //     array bl_count contains the frequencies for each bit length.
 //     The length opt_len is updated; static_len is also updated if stree is
 //     not null.
 internal void  gen_bitlen(DeflateManager s)
 {
     short[] tree = dyn_tree;
     short[] stree = staticTree.treeCodes;
     int[] extra = staticTree.extraBits;
     int base_Renamed = staticTree.extraBase;
     int max_length = staticTree.maxLength;
     int h; // heap index
     int n, m; // iterate over the tree elements
     int bits; // bit length
     int xbits; // extra bits
     short f; // frequency
     int overflow = 0; // number of elements with bit length too large
                 
     for (bits = 0; bits <= InternalConstants.MAX_BITS; bits++)
         s.bl_count[bits] = 0;
                 
     // In a first pass, compute the optimal bit lengths (which may
     // overflow in the case of the bit length tree).
     tree[s.heap[s.heap_max] * 2 + 1] = 0; // root of the heap
                 
     for (h = s.heap_max + 1; h < HEAP_SIZE; h++)
     {
         n = s.heap[h];
         bits = tree[tree[n * 2 + 1] * 2 + 1] + 1;
         if (bits > max_length)
         {
             bits = max_length; overflow++;
         }
         tree[n * 2 + 1] = (short) bits;
         // We overwrite tree[n*2+1] which is no longer needed
                         
         if (n > max_code)
             continue; // not a leaf node
                         
         s.bl_count[bits]++;
         xbits = 0;
         if (n >= base_Renamed)
             xbits = extra[n - base_Renamed];
         f = tree[n * 2];
         s.opt_len += f * (bits + xbits);
         if (stree != null)
             s.static_len += f * (stree[n * 2 + 1] + xbits);
     }
     if (overflow == 0)
         return ;
                 
     // This happens for example on obj2 and pic of the Calgary corpus
     // Find the first bit length which could increase:
     do 
     {
         bits = max_length - 1;
         while (s.bl_count[bits] == 0)
             bits--;
         s.bl_count[bits]--; // move one leaf down the tree
         s.bl_count[bits + 1] = (short) (s.bl_count[bits + 1] + 2); // move one overflow item as its brother
         s.bl_count[max_length]--;
         // The brother of the overflow item also moves one step up,
         // but this does not affect bl_count[max_length]
         overflow -= 2;
     }
     while (overflow > 0);
                 
     for (bits = max_length; bits != 0; bits--)
     {
         n = s.bl_count[bits];
         while (n != 0)
         {
             m = s.heap[--h];
             if (m > max_code)
                 continue;
             if (tree[m * 2 + 1] != bits)
             {
                 s.opt_len = (int) (s.opt_len + ((long) bits - (long) tree[m * 2 + 1]) * (long) tree[m * 2]);
                 tree[m * 2 + 1] = (short) bits;
             }
             n--;
         }
     }
 }
Exemplo n.º 4
0
        private int _InternalInitializeDeflate(bool wantRfc1950Header)
        {
            if (istate != null) throw new ZlibException("You may not call InitializeDeflate() after calling InitializeInflate().");
            dstate = new DeflateManager();
            dstate.WantRfc1950HeaderBytes = wantRfc1950Header;

            return dstate.Initialize(this, this.CompressLevel, this.WindowBits, this.Strategy);
        }