deflater.cs

SharpZipLib之前叫做NZipLib

		/// </summary>
		/// <param name="input">
		/// the buffer containing the input data.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// if the buffer was finished() or ended().
		/// </exception>
		public void SetInput(byte[] input)
		{
			SetInput(input, 0, input.Length);
		}
		
		/// <summary>
		/// Sets the data which should be compressed next.  This should be
		/// only called when needsInput indicates that more input is needed.
		/// The given byte array should not be changed, before needsInput() returns
		/// true again.
		/// </summary>
		/// <param name="input">
		/// the buffer containing the input data.
		/// </param>
		/// <param name="offset">
		/// the start of the data.
		/// </param>
		/// <param name="count">
		/// the number of data bytes of input.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// if the buffer was Finish()ed or if previous input is still pending.
		/// </exception>
		public void SetInput(byte[] input, int offset, int count)
		{
			if ((state & IS_FINISHING) != 0) {
				throw new InvalidOperationException("Finish() already called");
			}
			engine.SetInput(input, offset, count);
		}
		
		/// <summary>
		/// Sets the compression level.  There is no guarantee of the exact
		/// position of the change, but if you call this when needsInput is
		/// true the change of compression level will occur somewhere near
		/// before the end of the so far given input.
		/// </summary>
		/// <param name="level">
		/// the new compression level.
		/// </param>
		public void SetLevel(int level)
		{
			if (level == DEFAULT_COMPRESSION) {
				level = 6;
			} else if (level < NO_COMPRESSION || level > BEST_COMPRESSION) {
				throw new ArgumentOutOfRangeException("level");
			}
			
			if (this.level != level) {
				this.level = level;
				engine.SetLevel(level);
			}
		}
		
		/// <summary>
		/// Get current compression level
		/// </summary>
		/// <returns>Returns the current compression level</returns>
		public int GetLevel() {
			return level;
		}
		
		/// <summary>
		/// Sets the compression strategy. Strategy is one of
		/// DEFAULT_STRATEGY, HUFFMAN_ONLY and FILTERED.  For the exact
		/// position where the strategy is changed, the same as for
		/// SetLevel() applies.
		/// </summary>
		/// <param name="strategy">
		/// The new compression strategy.
		/// </param>
		public void SetStrategy(DeflateStrategy strategy)
		{
			engine.Strategy = strategy;
		}
		
		/// <summary>
		/// Deflates the current input block with to the given array.
		/// </summary>
		/// <param name="output">
		/// The buffer where compressed data is stored
		/// </param>
		/// <returns>
		/// The number of compressed bytes added to the output, or 0 if either
		/// IsNeedingInput() or IsFinished returns true or length is zero.
		/// </returns>
		public int Deflate(byte[] output)
		{
			return Deflate(output, 0, output.Length);
		}
		
		/// <summary>
		/// Deflates the current input block to the given array.
		/// </summary>
		/// <param name="output">
		/// Buffer to store the compressed data.
		/// </param>
		/// <param name="offset">
		/// Offset into the output array.
		/// </param>
		/// <param name="length">
		/// The maximum number of bytes that may be stored.
		/// </param>
		/// <returns>
		/// The number of compressed bytes added to the output, or 0 if either
		/// needsInput() or finished() returns true or length is zero.
		/// </returns>
		/// <exception cref="System.InvalidOperationException">
		/// If Finish() was previously called.
		/// </exception>
		/// <exception cref="System.ArgumentOutOfRangeException">
		/// If offset or length don't match the array length.
		/// </exception>
		public int Deflate(byte[] output, int offset, int length)
		{
			int origLength = length;
			
			if (state == CLOSED_STATE) {
				throw new InvalidOperationException("Deflater closed");
			}
			
			if (state < BUSY_STATE) {
				// output header
				int header = (DEFLATED +
					((DeflaterConstants.MAX_WBITS - 8) << 4)) << 8;
				int level_flags = (level - 1) >> 1;
				if (level_flags < 0 || level_flags > 3) {
					level_flags = 3;
				}
				header |= level_flags << 6;
				if ((state & IS_SETDICT) != 0) {
					// Dictionary was set
					header |= DeflaterConstants.PRESET_DICT;
				}
				header += 31 - (header % 31);
				
				pending.WriteShortMSB(header);
				if ((state & IS_SETDICT) != 0) {
					int chksum = engine.Adler;
					engine.ResetAdler();
					pending.WriteShortMSB(chksum >> 16);
					pending.WriteShortMSB(chksum & 0xffff);
				}
				
				state = BUSY_STATE | (state & (IS_FLUSHING | IS_FINISHING));
			}
			
			for (;;) {
				int count = pending.Flush(output, offset, length);
				offset   += count;
				totalOut += count;
				length   -= count;
				
				if (length == 0 || state == FINISHED_STATE) {
					break;
				}
				
				if (!engine.Deflate((state & IS_FLUSHING) != 0, (state & IS_FINISHING) != 0)) {
					if (state == BUSY_STATE) {
						// We need more input now
						return origLength - length;
					} else if (state == FLUSHING_STATE) {
						if (level != NO_COMPRESSION) {
							/* We have to supply some lookahead.  8 bit lookahead
							 * is needed by the zlib inflater, and we must fill
							 * the next byte, so that all bits are flushed.
							 */
							int neededbits = 8 + ((-pending.BitCount) & 7);
							while (neededbits > 0) {
								/* write a static tree block consisting solely of
								 * an EOF:
								 */
								pending.WriteBits(2, 10);
								neededbits -= 10;
							}
						}
						state = BUSY_STATE;
					} else if (state == FINISHING_STATE) {
						pending.AlignToByte();

						// Compressed data is complete.  Write footer information if required.
						if (!noZlibHeaderOrFooter) {
							int adler = engine.Adler;
							pending.WriteShortMSB(adler >> 16);
							pending.WriteShortMSB(adler & 0xffff);
						}
						state = FINISHED_STATE;
					}
				}
			}
			return origLength - length;
		}
		
		/// <summary>
		/// Sets the dictionary which should be used in the deflate process.
		/// This call is equivalent to <code>setDictionary(dict, 0, dict.Length)</code>.
		/// </summary>
		/// <param name="dictionary">
		/// the dictionary.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// if SetInput () or Deflate () were already called or another dictionary was already set.
		/// </exception>
		public void SetDictionary(byte[] dictionary)
		{
			SetDictionary(dictionary, 0, dictionary.Length);
		}
		
		/// <summary>
		/// Sets the dictionary which should be used in the deflate process.
		/// The dictionary is a byte array containing strings that are
		/// likely to occur in the data which should be compressed.  The
		/// dictionary is not stored in the compressed output, only a
		/// checksum.  To decompress the output you need to supply the same
		/// dictionary again.
		/// </summary>
		/// <param name="dictionary">
		/// The dictionary data
		/// </param>
		/// <param name="index">
		/// The index where dictionary information commences.
		/// </param>
		/// <param name="count">
		/// The number of bytes in the dictionary.
		/// </param>
		/// <exception cref="System.InvalidOperationException">
		/// If SetInput () or Deflate() were already called or another dictionary was already set.
		/// </exception>
		public void SetDictionary(byte[] dictionary, int index, int count)
		{
			if (state != INIT_STATE) {
				throw new InvalidOperationException();
			}
			
			state = SETDICT_STATE;
			engine.SetDictionary(dictionary, index, count);
		}
		#region Instance Fields
		/// <summary>
		/// Compression level.
		/// </summary>
		int level;
		
		/// <summary>
		/// If true no Zlib/RFC1950 headers or footers are generated
		/// </summary>
		bool noZlibHeaderOrFooter;
		
		/// <summary>
		/// The current state.
		/// </summary>
		int state;
		
		/// <summary>
		/// The total bytes of output written.
		/// </summary>
		long totalOut;
		
		/// <summary>
		/// The pending output.
		/// </summary>
		DeflaterPending pending;
		
		/// <summary>
		/// The deflater engine.
		/// </summary>
		DeflaterEngine engine;
		#endregion
	}
}