安全的截取指定长度的html或者ubb字符串代码,CSharp代码库,德仔网

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【CSharp】安全的截取指定长度的html或者ubb字符串

作者:京基 / 发布于2015/8/12/ 684


	static char END_SLASH = '/';

	/// <summary>
	/// 安全的截断字符串
	/// </summary>
	/// <param name="input">输入串</param>
	/// <param name="length">截断长度</param>
	/// <param name="trimHalfTag">true：截断半截标签；false：补全半截标签</param>
	/// <param name="tagStartChar">标签开始字符</param>
	/// <param name="tagEndChar">标签结束字符</param>
	/// <param name="mustCloseTags">需要关闭的标签数组</param>
	/// <returns>length长度的字符串</returns>
	public static string SafeTrim(string input, int length, bool trimHalfTag, char tagStartChar, char tagEndChar, string[] mustCloseTags)
	{
	if (length <= 0) throw new ArgumentException("length 必须是正数");
	if (mustCloseTags == null) throw new ArgumentNullException("mustCloseTags");

	int inputLen = input.Length;
	if (string.IsNullOrEmpty(input) || inputLen <= length) return input;

	string result = string.Empty;

	//声明堆栈用来放标签
	Stack<string> tags = new Stack<string>();

	for (int i = 0; i < length; i++)
	{
	char c = input[i];

	if (c == tagStartChar)
	{
	string tag = string.Empty;
	int tagIndex = i + 1;
	bool isTagEnd = false;
	bool isTagNameEnd = false;
	result += c;
	bool hasMarkTagInStack = false;
	while (tagIndex < inputLen)
	{
	char tagC = input[tagIndex];
	result += tagC;
	tagIndex++;
	if (tag == string.Empty && tagC == END_SLASH)
	{
	isTagEnd = true;
	continue;
	}
	if (!isTagNameEnd)
	{
	if (char.IsLetter(tagC) || char.IsNumber(tagC))
	{
	tag += tagC;
	}
	else
	{
	isTagNameEnd = true;
	}
	}

	if (!string.IsNullOrEmpty(tag))
	{
	if (isTagNameEnd && !hasMarkTagInStack)
	{
	if (isTagEnd)
	{
	tags.Pop();
	}
	else
	{
	tags.Push(tag);
	}
	hasMarkTagInStack = true;
	}
	}

	if (isTagNameEnd)
	{
	if (tagC == tagEndChar)
	{
	i = tagIndex - 1;
	break;
	}
	}

	}
	}
	else
	{
	result += c;
	}
	}

	while (tags.Count > 0)
	{
	string tag = tags.Pop();

	bool isMustCloseTag = false;
	foreach (string mustCloseTag in mustCloseTags)
	{
	if (string.Compare(mustCloseTag, tag, true) == 0)
	{
	isMustCloseTag = true;
	break;
	}
	}
	if (isMustCloseTag)
	{
	if (trimHalfTag)
	{
	int lastTagIndex = result.LastIndexOf(tagStartChar.ToString() + tag, StringComparison.CurrentCultureIgnoreCase);

	result = result.Substring(0, lastTagIndex);
	}
	else
	{
	result += (tagStartChar.ToString() + END_SLASH + tag + tagEndChar);
	}
	}
	}

	return result;
	}

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