/// <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; }
// 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 + (bits - (long)tree[m*2 + 1])*tree[m*2]); tree[m*2 + 1] = (short)bits; } n--; } } }
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); }
// 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)(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); }