/// <summary>
/// Parse meta-info from torrent file.
/// </summary>
/// <param name="fileName">The filename of torrent</param>
/// <returns>Return the metainfo</returns>
public static MetaInfo Parse(string fileName)
{
MetaInfo result = null;
DictNode rootNode;
byte[] source;
if (File.Exists(fileName))
{
source = File.ReadAllBytes(fileName);
rootNode = BEncodingFactory.Decode(source) as DictNode;
Debug.Assert(rootNode != null);
}
else
{
return(null);
}
DictNode infoNode = rootNode["info"] as DictNode;
Debug.Assert(infoNode != null);
if (infoNode.ContainsKey("length"))
{
result = GetSingleFileMetaInfo(rootNode, infoNode);
}
else
{
result = GetMultiFileMetaInfo(rootNode, infoNode);
}
result.InfoHash = Globals.GetSha1Hash(BEncodingFactory.ByteArrayEncode(rootNode["info"]));//Globals.Sha1.ComputeHash(BEncodingFactory.ByteArrayEncode(rootNode["info"]));
return(result);
}
/// <summary>
/// Node字典类的解码函数
/// </summary>
/// <param name="source">待解码的字节数组</param>
/// <param name="index">字节数组的解码位置</param>
/// <returns>解码的字节数组长度</returns>
public override int Decode(byte[] source, ref int index)
{
//保存初始位置
int start = index;
//跳过字符'd'
index++;
try
{
//当遇到'e'(ASCII码为101),解析结束
while (source[index] != 101)
{
//解析字符串
BytesNode keyNode = new BytesNode();
keyNode.Decode(source, ref index);
if (keyNode.ByteArray.LongLength == 0)
{
throw new BitTorrentException("待添加的字符串长度为0");
}
//解析Handler
BEncodedNode valueNode = BEncodingFactory.Decode(source, ref index);
//'e'(ASCII码为101),解析结束
if (valueNode == null)
{
throw new BitTorrentException("待添加的Handler节点为空");
}
//字典添加key和value
_dict.Add(keyNode.StringText, valueNode);
}
}
//当捕捉IndexOutOfRangeException,抛出BitTorrentException
catch (IndexOutOfRangeException)
{
throw new BitTorrentException("BEncode字典类的字符串长度异常");
}
//当捕捉ArgumentException,抛出BitTorrentException
catch (ArgumentException)
{
throw new BitTorrentException("BEncode字典类中包含相同的字符串关键字");
}
//跳过字符'e'
index++;
//返回所解析的数组长度
return(index - start);
}
/// <summary>
/// Handler列表类的解码函数
/// </summary>
/// <param name="source">待解码的字节数组</param>
/// <param name="index">字节数组的解码位置</param>
/// <returns>解码的字节数组长度</returns>
public override int Decode(byte[] source, ref int index)
{
//保存初始位置
int start = index;
//跳过字符'l'
index++;
try
{
//当遇到'e'(ASCII码为101),解析结束
while (source[index] != 101)
{
BEncodedNode node = BEncodingFactory.Decode(source, ref index);
//当遇到'e'(ASCII码为101),解析结束
if (node == null)
{
break;
}
//列表添加handler
_items.Add(node);
}
}
//当捕捉IndexOutOfRangeException,抛出BitTorrentException
catch (IndexOutOfRangeException)
{
throw new BitTorrentException("BEnocde列表类的字节数组长度异常");
}
//跳过字符'e'
index++;
//返回所解析的数组长度
return(index - start);
}