有关LZF算法的相关解析文档比较少，但是Apple对LZF的开源，可以让我们对该算法进行一个简单的解析。LZFSE 基于 Lempel-Ziv ，并使用了有限状态熵编码。LZF采用类似lz77和lzss的混合编码。使用3种“起始标记”来代表每段输出的数据串。

接下来看一下开源的LZF算法的实现源码。

1.定义的全局字段：

        private readonly long[] _hashTable = new long[Hsize];private const uint Hlog = 14;private const uint Hsize = (1 << 14);private const uint MaxLit = (1 << 5);private const uint MaxOff = (1 << 13);private const uint MaxRef = ((1 << 8) + (1 << 3));

2.使用LibLZF算法压缩数据：

        /// <summary>/// 使用LibLZF算法压缩数据/// </summary>/// <param name="input">需要压缩的数据</param>/// <param name="inputLength">要压缩的数据的长度</param>/// <param name="output">引用将包含压缩数据的缓冲区</param>/// <param name="outputLength">压缩缓冲区的长度（应大于输入缓冲区）</param>/// <returns>输出缓冲区中压缩归档的大小</returns>public int Compress(byte[] input, int inputLength, byte[] output, int outputLength){Array.Clear(_hashTable, 0, (int)Hsize);uint iidx = 0;uint oidx = 0;var hval = (uint)(((input[iidx]) << 8) | input[iidx + 1]);var lit = 0;for (; ; ){if (iidx < inputLength - 2){hval = (hval << 8) | input[iidx + 2];long hslot = ((hval ^ (hval << 5)) >> (int)(((3 * 8 - Hlog)) - hval * 5) & (Hsize - 1));var reference = _hashTable[hslot];_hashTable[hslot] = iidx;long off;if ((off = iidx - reference - 1) < MaxOff&& iidx + 4 < inputLength&& reference > 0&& input[reference + 0] == input[iidx + 0]&& input[reference + 1] == input[iidx + 1]&& input[reference + 2] == input[iidx + 2]){uint len = 2;var maxlen = (uint)inputLength - iidx - len;maxlen = maxlen > MaxRef ? MaxRef : maxlen;if (oidx + lit + 1 + 3 >= outputLength)return 0;dolen++;while (len < maxlen && input[reference + len] == input[iidx + len]);if (lit != 0){output[oidx++] = (byte)(lit - 1);lit = -lit;dooutput[oidx++] = input[iidx + lit];while ((++lit) != 0);}len -= 2;iidx++;if (len < 7){output[oidx++] = (byte)((off >> 8) + (len << 5));}else{output[oidx++] = (byte)((off >> 8) + (7 << 5));output[oidx++] = (byte)(len - 7);}output[oidx++] = (byte)off;iidx += len - 1;hval = (uint)(((input[iidx]) << 8) | input[iidx + 1]);hval = (hval << 8) | input[iidx + 2];_hashTable[((hval ^ (hval << 5)) >> (int)(((3 * 8 - Hlog)) - hval * 5) & (Hsize - 1))] = iidx;iidx++;hval = (hval << 8) | input[iidx + 2];_hashTable[((hval ^ (hval << 5)) >> (int)(((3 * 8 - Hlog)) - hval * 5) & (Hsize - 1))] = iidx;iidx++;continue;}}else if (iidx == inputLength)break;lit++;iidx++;if (lit != MaxLit) continue;if (oidx + 1 + MaxLit >= outputLength)return 0;output[oidx++] = (byte)(MaxLit - 1);lit = -lit;dooutput[oidx++] = input[iidx + lit];while ((++lit) != 0);}if (lit == 0) return (int)oidx;if (oidx + lit + 1 >= outputLength)return 0;output[oidx++] = (byte)(lit - 1);lit = -lit;dooutput[oidx++] = input[iidx + lit];while ((++lit) != 0);return (int)oidx;}

3.使用LibLZF算法重载压缩数据：

        /// <summary>/// 使用LibLZF算法解压缩数据/// </summary>/// <param name="input">参考数据进行解压缩</param>/// <param name="inputLength">要解压缩的数据的长度</param>/// <param name="output">引用包含解压缩数据的缓冲区</param>/// <param name="outputLength">输出缓冲区中压缩归档的大小</param>/// <returns>返回解压缩大小</returns>public int Decompress(byte[] input, int inputLength, byte[] output, int outputLength){uint iidx = 0;uint oidx = 0;do{uint ctrl = input[iidx++];if (ctrl < (1 << 5)){ctrl++;if (oidx + ctrl > outputLength){return 0;}dooutput[oidx++] = input[iidx++];while ((--ctrl) != 0);}else{var len = ctrl >> 5;var reference = (int)(oidx - ((ctrl & 0x1f) << 8) - 1);if (len == 7)len += input[iidx++];reference -= input[iidx++];if (oidx + len + 2 > outputLength){return 0;}if (reference < 0){return 0;}output[oidx++] = output[reference++];output[oidx++] = output[reference++];dooutput[oidx++] = output[reference++];while ((--len) != 0);}}while (iidx < inputLength);return (int)oidx;}

以上是LZF算法的代码。