deflaterhuffman.cs

SharpZipLib之前叫做NZipLib

					} else if (count <= 10) {
						blTree.WriteSymbol(REP_3_10);
						dh.pending.WriteBits(count - 3, 3);
					} else {
						blTree.WriteSymbol(REP_11_138);
						dh.pending.WriteBits(count - 11, 7);
					}
				}
			}

			void BuildLength(int[] childs)
			{
				this.length = new byte [freqs.Length];
				int numNodes = childs.Length / 2;
				int numLeafs = (numNodes + 1) / 2;
				int overflow = 0;
				
				for (int i = 0; i < maxLength; i++) {
					bl_counts[i] = 0;
				}
				
				// First calculate optimal bit lengths
				int[] lengths = new int[numNodes];
				lengths[numNodes-1] = 0;
				
				for (int i = numNodes - 1; i >= 0; i--) {
					if (childs[2 * i + 1] != -1) {
						int bitLength = lengths[i] + 1;
						if (bitLength > maxLength) {
							bitLength = maxLength;
							overflow++;
						}
						lengths[childs[2 * i]] = lengths[childs[2 * i + 1]] = bitLength;
					} else {
						// A leaf node
						int bitLength = lengths[i];
						bl_counts[bitLength - 1]++;
						this.length[childs[2*i]] = (byte) lengths[i];
					}
				}
				
				//				if (DeflaterConstants.DEBUGGING) {
				//					//Console.WriteLine("Tree "+freqs.Length+" lengths:");
				//					for (int i=0; i < numLeafs; i++) {
				//						//Console.WriteLine("Node "+childs[2*i]+" freq: "+freqs[childs[2*i]]
				//						                  + " len: "+length[childs[2*i]]);
				//					}
				//				}
				
				if (overflow == 0) {
					return;
				}
				
				int incrBitLen = maxLength - 1;
				do {
					// Find the first bit length which could increase:
					while (bl_counts[--incrBitLen] == 0)
						;
					
					// Move this node one down and remove a corresponding
					// number of overflow nodes.
					do {
						bl_counts[incrBitLen]--;
						bl_counts[++incrBitLen]++;
						overflow -= 1 << (maxLength - 1 - incrBitLen);
					} while (overflow > 0 && incrBitLen < maxLength - 1);
				} while (overflow > 0);
				
				/* We may have overshot above.  Move some nodes from maxLength to
				* maxLength-1 in that case.
				*/
				bl_counts[maxLength-1] += overflow;
				bl_counts[maxLength-2] -= overflow;
				
				/* Now recompute all bit lengths, scanning in increasing
				* frequency.  It is simpler to reconstruct all lengths instead of
				* fixing only the wrong ones. This idea is taken from 'ar'
				* written by Haruhiko Okumura.
				*
				* The nodes were inserted with decreasing frequency into the childs
				* array.
				*/
				int nodePtr = 2 * numLeafs;
				for (int bits = maxLength; bits != 0; bits--) {
					int n = bl_counts[bits-1];
					while (n > 0) {
						int childPtr = 2*childs[nodePtr++];
						if (childs[childPtr + 1] == -1) {
							// We found another leaf
							length[childs[childPtr]] = (byte) bits;
							n--;
						}
					}
				}
				//				if (DeflaterConstants.DEBUGGING) {
				//					//Console.WriteLine("*** After overflow elimination. ***");
				//					for (int i=0; i < numLeafs; i++) {
				//						//Console.WriteLine("Node "+childs[2*i]+" freq: "+freqs[childs[2*i]]
				//						                  + " len: "+length[childs[2*i]]);
				//					}
				//				}
			}
			
		}

		#region Instance Fields
		/// <summary>
		/// Pending buffer to use
		/// </summary>
		public DeflaterPending pending;
		
		Tree literalTree;
		Tree distTree;
		Tree blTree;
		
		// Buffer for distances
		short[] d_buf;
		byte[]  l_buf;
		int last_lit;
		int extra_bits;
		#endregion

		static DeflaterHuffman() 
		{
			// See RFC 1951 3.2.6
			// Literal codes
			staticLCodes = new short[LITERAL_NUM];
			staticLLength = new byte[LITERAL_NUM];

			int i = 0;
			while (i < 144) {
				staticLCodes[i] = BitReverse((0x030 + i) << 8);
				staticLLength[i++] = 8;
			}

			while (i < 256) {
				staticLCodes[i] = BitReverse((0x190 - 144 + i) << 7);
				staticLLength[i++] = 9;
			}

			while (i < 280) {
				staticLCodes[i] = BitReverse((0x000 - 256 + i) << 9);
				staticLLength[i++] = 7;
			}

			while (i < LITERAL_NUM) {
				staticLCodes[i] = BitReverse((0x0c0 - 280 + i)  << 8);
				staticLLength[i++] = 8;
			}
			
			// Distance codes
			staticDCodes = new short[DIST_NUM];
			staticDLength = new byte[DIST_NUM];
			for (i = 0; i < DIST_NUM; i++) {
				staticDCodes[i] = BitReverse(i << 11);
				staticDLength[i] = 5;
			}
		}
		
		/// <summary>
		/// Construct instance with pending buffer
		/// </summary>
		/// <param name="pending">Pending buffer to use</param>
		public DeflaterHuffman(DeflaterPending pending)
		{
			this.pending = pending;
			
			literalTree = new Tree(this, LITERAL_NUM, 257, 15);
			distTree    = new Tree(this, DIST_NUM, 1, 15);
			blTree      = new Tree(this, BITLEN_NUM, 4, 7);
			
			d_buf = new short[BUFSIZE];
			l_buf = new byte [BUFSIZE];
		}

		/// <summary>
		/// Reset internal state
		/// </summary>		
		public void Reset() 
		{
			last_lit = 0;
			extra_bits = 0;
			literalTree.Reset();
			distTree.Reset();
			blTree.Reset();
		}
		
		/// <summary>
		/// Write all trees to pending buffer
		/// </summary>		
		public void SendAllTrees(int blTreeCodes)
		{
			blTree.BuildCodes();
			literalTree.BuildCodes();
			distTree.BuildCodes();
			pending.WriteBits(literalTree.numCodes - 257, 5);
			pending.WriteBits(distTree.numCodes - 1, 5);
			pending.WriteBits(blTreeCodes - 4, 4);
			for (int rank = 0; rank < blTreeCodes; rank++) {
				pending.WriteBits(blTree.length[BL_ORDER[rank]], 3);
			}
			literalTree.WriteTree(blTree);
			distTree.WriteTree(blTree);

#if DebugDeflation
			if (DeflaterConstants.DEBUGGING) {
				blTree.CheckEmpty();
			}
#endif
		}

		/// <summary>
		/// Compress current buffer writing data to pending buffer
		/// </summary>
		public void CompressBlock()
		{
			for (int i = 0; i < last_lit; i++) {
				int litlen = l_buf[i] & 0xff;
				int dist = d_buf[i];
				if (dist-- != 0) {
					//					if (DeflaterConstants.DEBUGGING) {
					//						Console.Write("["+(dist+1)+","+(litlen+3)+"]: ");
					//					}
					
					int lc = Lcode(litlen);
					literalTree.WriteSymbol(lc);
					
					int bits = (lc - 261) / 4;
					if (bits > 0 && bits <= 5) {
						pending.WriteBits(litlen & ((1 << bits) - 1), bits);
					}
					
					int dc = Dcode(dist);
					distTree.WriteSymbol(dc);
					
					bits = dc / 2 - 1;
					if (bits > 0) {
						pending.WriteBits(dist & ((1 << bits) - 1), bits);
					}
				} else {
					//					if (DeflaterConstants.DEBUGGING) {
					//						if (litlen > 32 && litlen < 127) {
					//							Console.Write("("+(char)litlen+"): ");
					//						} else {
					//							Console.Write("{"+litlen+"}: ");
					//						}
					//					}
					literalTree.WriteSymbol(litlen);
				}
			}

#if DebugDeflation
			if (DeflaterConstants.DEBUGGING) {
				Console.Write("EOF: ");
			}
#endif
			literalTree.WriteSymbol(EOF_SYMBOL);

#if DebugDeflation
			if (DeflaterConstants.DEBUGGING) {
				literalTree.CheckEmpty();
				distTree.CheckEmpty();
			}
#endif
		}
		
		/// <summary>
		/// Flush block to output with no compression
		/// </summary>
		/// <param name="stored">Data to write</param>
		/// <param name="storedOffset">Index of first byte to write</param>
		/// <param name="storedLength">Count of bytes to write</param>
		/// <param name="lastBlock">True if this is the last block</param>
		public void FlushStoredBlock(byte[] stored, int storedOffset, int storedLength, bool lastBlock)
		{
#if DebugDeflation
			//			if (DeflaterConstants.DEBUGGING) {
			//				//Console.WriteLine("Flushing stored block "+ storedLength);
			//			}
#endif
			pending.WriteBits((DeflaterConstants.STORED_BLOCK << 1) + (lastBlock ? 1 : 0), 3);
			pending.AlignToByte();
			pending.WriteShort(storedLength);
			pending.WriteShort(~storedLength);
			pending.WriteBlock(stored, storedOffset, storedLength);
			Reset();
		}

		/// <summary>
		/// Flush block to output with compression
		/// </summary>		
		/// <param name="stored">Data to flush</param>
		/// <param name="storedOffset">Index of first byte to flush</param>
		/// <param name="storedLength">Count of bytes to flush</param>
		/// <param name="lastBlock">True if this is the last block</param>
		public void FlushBlock(byte[] stored, int storedOffset, int storedLength, bool lastBlock)
		{
			literalTree.freqs[EOF_SYMBOL]++;
			
			// Build trees
			literalTree.BuildTree();
			distTree.BuildTree();
			
			// Calculate bitlen frequency
			literalTree.CalcBLFreq(blTree);
			distTree.CalcBLFreq(blTree);
			
			// Build bitlen tree
			blTree.BuildTree();
			
			int blTreeCodes = 4;
			for (int i = 18; i > blTreeCodes; i--) {
				if (blTree.length[BL_ORDER[i]] > 0) {
					blTreeCodes = i+1;
				}
			}
			int opt_len = 14 + blTreeCodes * 3 + blTree.GetEncodedLength() + 
				literalTree.GetEncodedLength() + distTree.GetEncodedLength() + 
				extra_bits;
			
			int static_len = extra_bits;
			for (int i = 0; i < LITERAL_NUM; i++) {
				static_len += literalTree.freqs[i] * staticLLength[i];
			}
			for (int i = 0; i < DIST_NUM; i++) {
				static_len += distTree.freqs[i] * staticDLength[i];
			}
			if (opt_len >= static_len) {
				// Force static trees
				opt_len = static_len;
			}
			
			if (storedOffset >= 0 && storedLength + 4 < opt_len >> 3) {
				// Store Block

				//				if (DeflaterConstants.DEBUGGING) {
				//					//Console.WriteLine("Storing, since " + storedLength + " < " + opt_len
				//					                  + " <= " + static_len);
				//				}
				FlushStoredBlock(stored, storedOffset, storedLength, lastBlock);
			} else if (opt_len == static_len) {
				// Encode with static tree
				pending.WriteBits((DeflaterConstants.STATIC_TREES << 1) + (lastBlock ? 1 : 0), 3);
				literalTree.SetStaticCodes(staticLCodes, staticLLength);
				distTree.SetStaticCodes(staticDCodes, staticDLength);
				CompressBlock();
				Reset();
			} else {
				// Encode with dynamic tree
				pending.WriteBits((DeflaterConstants.DYN_TREES << 1) + (lastBlock ? 1 : 0), 3);
				SendAllTrees(blTreeCodes);
				CompressBlock();
				Reset();
			}
		}
		
		/// <summary>
		/// Get value indicating if internal buffer is full
		/// </summary>
		/// <returns>true if buffer is full</returns>
		public bool IsFull()
		{
			return last_lit >= BUFSIZE;
		}
		
		/// <summary>
		/// Add literal to buffer
		/// </summary>
		/// <param name="literal">Literal value to add to buffer.</param>
		/// <returns>Value indicating internal buffer is full</returns>
		public bool TallyLit(int literal)
		{
			//			if (DeflaterConstants.DEBUGGING) {
			//				if (lit > 32 && lit < 127) {
			//					//Console.WriteLine("("+(char)lit+")");
			//				} else {
			//					//Console.WriteLine("{"+lit+"}");
			//				}
			//			}
			d_buf[last_lit] = 0;
			l_buf[last_lit++] = (byte)literal;
			literalTree.freqs[literal]++;
			return IsFull();
		}
		
		/// <summary>
		/// Add distance code and length to literal and distance trees
		/// </summary>
		/// <param name="distance">Distance code</param>
		/// <param name="length">Length</param>
		/// <returns>Value indicating if internal buffer is full</returns>
		public bool TallyDist(int distance, int length)
		{
			//			if (DeflaterConstants.DEBUGGING) {
			//				//Console.WriteLine("[" + distance + "," + length + "]");
			//			}
			
			d_buf[last_lit]   = (short)distance;
			l_buf[last_lit++] = (byte)(length - 3);
			
			int lc = Lcode(length - 3);
			literalTree.freqs[lc]++;
			if (lc >= 265 && lc < 285) {
				extra_bits += (lc - 261) / 4;
			}
			
			int dc = Dcode(distance - 1);
			distTree.freqs[dc]++;
			if (dc >= 4) {
				extra_bits += dc / 2 - 1;
			}
			return IsFull();
		}

		
		/// <summary>
		/// Reverse the bits of a 16 bit value.
		/// </summary>
		/// <param name="toReverse">Value to reverse bits</param>
		/// <returns>Value with bits reversed</returns>
		public static short BitReverse(int toReverse) 
		{
			return (short) (bit4Reverse[toReverse & 0xF] << 12 | 
			                bit4Reverse[(toReverse >> 4) & 0xF] << 8 | 
			                bit4Reverse[(toReverse >> 8) & 0xF] << 4 |
			                bit4Reverse[toReverse >> 12]);
		}
		
		static int Lcode(int length) 
		{
			if (length == 255) {
				return 285;
			}
			
			int code = 257;
			while (length >= 8) {
				code += 4;
				length >>= 1;
			}
			return code + length;
		}
		
		static int Dcode(int distance) 
		{
			int code = 0;
			while (distance >= 4) {
				code += 2;
				distance >>= 1;
			}
			return code + distance;
		}
	}
}