XML压缩单元测试代码
测试输出
原始文件长度:740
Deflate压缩后长度: 438
XML压缩后长度:295
还原后长度:727
先XML压缩，再Deflate压缩后的长度：357
可以看到，XML压缩后的数据约是原来数据的3分之一，可能没有其它专有的压缩算法的压缩率高，但效果还算是满意吧，而且我的算法是比较通用的，只要通信双方知道了XML的Schema，甚至双方只需要有一段完整的示例代码，就可以进行压缩通信，只做了功能测试，没做性能测试，大家可以先借鉴下思路。
完整代码
大致原理，就是通信双方各持有一个XML文档节点名称，属性名称的一个字典，然后发送方传输的时候用ushort代替原有的XML标签和属性名，接收方通过字典把ushort再转换成原始的元素名和属性名，这样大量不必要的重复的标签等就省去了。
代码只做本文的示例，写的比较随意，没有什么防御性和健壮性。
internal enum ItemType { Element, Attritube 
} 
internal class XmlNodeItem { 
public string Xpath { get; set; } public string Text { get; set; } public ItemType ItemType { get; set; } 
public override string ToString() { return Xpath; } } internal class MyXpath { LinkedList<string> _node = new LinkedList<string>(); public void AddElement(string name) { _node.AddLast(string.Format("/{0}", name)); } public void AddAttribute(string name) { _node.AddLast(string.Format("/@{0}", name)); } public void RemoveLastElement() { _node.RemoveLast(); } public override string ToString() { StringBuilder sb = new StringBuilder(); LinkedListNode<string> node = _node.First; sb.Append(node.Value); while ((nodenode = node.Next) != null) { sb.Append(node.Value); } return sb.ToString(); } } class XmlZip { Dictionary<ushort, XmlNodeItem> _map = new Dictionary<ushort, XmlNodeItem>(); Dictionary<string, ushort> _map2 = new Dictionary<string, ushort>(); MyXpath _path = new MyXpath(); public void Init(string xmlInput) { StringReader sr = new StringReader(xmlInput); XmlReader reader = XmlReader.Create(sr); MemoryStream ms = new MemoryStream(); ushort i = 1; while (reader.Read()) { switch (reader.NodeType) { case XmlNodeType.Element: _path.AddElement(reader.Name); _map[i++] = new XmlNodeItem() { Xpath = _path.ToString(), Text = reader.Name, ItemTypeItemType = ItemType.Element }; if (reader.HasAttributes) { reader.MoveToFirstAttribute(); _path.AddAttribute(reader.Name); _map[i++] = new XmlNodeItem() { Xpath = _path.ToString(), Text = reader.Name, ItemTypeItemType = ItemType.Attritube }; _path.RemoveLastElement(); while (reader.MoveToNextAttribute()) { _path.AddAttribute(reader.Name); _map[i++] = new XmlNodeItem() { Xpath = _path.ToString(), Text = reader.Name, ItemTypeItemType = ItemType.Attritube }; _path.RemoveLastElement(); } reader.MoveToElement(); } if (reader.IsEmptyElement) _path.RemoveLastElement(); break; case XmlNodeType.EndElement: _path.RemoveLastElement(); break; default: break; } } foreach (KeyValuePair<ushort, XmlNodeItem> pair in _map) { _map2[pair.Value.Xpath] = pair.Key; } } public byte[] XmlToBytes(string xmlInput) { StringReader sr = new StringReader(xmlInput); XmlReader reader = XmlReader.Create(sr); MemoryStream ms = new MemoryStream(); BinaryWriter bw = new BinaryWriter(ms); while (reader.Read()) { ushort index; byte[] bs; switch (reader.NodeType) { case XmlNodeType.Element: _path.AddElement(reader.Name); if (_map2.TryGetValue(_path.ToString(), out index)) { bw.Write(index); } if (reader.HasAttributes) { reader.MoveToFirstAttribute(); _path.AddAttribute(reader.Name); if (_map2.TryGetValue(_path.ToString(), out index)) { _path.RemoveLastElement(); bw.Write(index); bs = Encoding.UTF8.GetBytes(reader.Value); bw.Write((ushort)bs.Length); bw.Write(bs); } while (reader.MoveToNextAttribute()) { _path.AddAttribute(reader.Name); if (_map2.TryGetValue(_path.ToString(), out index)) { _path.RemoveLastElement(); bw.Write(index); bs = Encoding.UTF8.GetBytes(reader.Value); bw.Write((ushort)bs.Length); bw.Write(bs); } } reader.MoveToElement(); } if (reader.IsEmptyElement) { _path.RemoveLastElement(); bw.Write(ushort.MaxValue); } break; case XmlNodeType.EndElement: _path.RemoveLastElement(); bw.Write(ushort.MaxValue); break; case XmlNodeType.Text: bw.Write((ushort)0); bs = Encoding.UTF8.GetBytes(reader.Value); bw.Write((ushort)bs.Length); bw.Write(bs); break; default: break; } } bw.Close(); ms.Close(); reader.Close(); return ms.ToArray(); } public string BytesToXml(byte[] bytes) { MemoryStream ms = new MemoryStream(bytes); BinaryReader br = new BinaryReader(ms); StringBuilder sb = new StringBuilder(); StringWriter sw = new StringWriter(sb); XmlWriterSettings settings = new XmlWriterSettings(); settings.Indent = true; XmlWriter writer = XmlWriter.Create(sw, settings); XmlNodeItem item; while (br.PeekChar() != -1) { ushort readFlag = br.ReadUInt16(); int len; byte[] bs; string str; if (_map.TryGetValue(readFlag, out item)) { if (item.ItemType == ItemType.Element) writer.WriteStartElement(item.Text); else if (item.ItemType == ItemType.Attritube) { len = br.ReadUInt16(); bs = br.ReadBytes(len); str = Encoding.UTF8.GetString(bs); writer.WriteAttributeString(item.Text, str); } } else if (readFlag == 0) { len = br.ReadUInt16(); bs = br.ReadBytes(len); str = Encoding.UTF8.GetString(bs); writer.WriteString(str); } else if (readFlag == ushort.MaxValue) { writer.WriteEndElement(); } 
} writer.Flush(); writer.Close(); sw.Close(); br.Close(); return sb.ToString(); 
internal class XmlNodeItem 
public override string ToString()