这里的一类是我为完成同样的事情而制定的。 所有现有的超声望图书馆都过于缓慢,而且速度太慢。 职能在法典评论中作了解释。 从我的基准来看,在亚马孙着陆页(包括以下)测试时,该代码比超声波包等值代码高出10X。
/// <summary>
/// The fast HTML text extractor class is designed to, as quickly and as ignorantly as possible,
/// extract text data from a given HTML character array. The class searches for and deletes
/// script and style tags in a first and second pass, with an optional third pass to do the same
/// to HTML comments, and then copies remaining non-whitespace character data to an ouput array.
/// All whitespace encountered is replaced with a single whitespace in to avoid multiple
/// whitespace in the output.
///
/// Note that the returned text content still may have named character and numbered character
/// references within that, when decoded, may produce multiple whitespace.
/// </summary>
public class FastHtmlTextExtractor
{
private readonly char[] SCRIPT_OPEN_TAG = new char[7] { < , s , c , r , i , p , t };
private readonly char[] SCRIPT_CLOSE_TAG = new char[9] { < , / , s , c , r , i , p , t , > };
private readonly char[] STYLE_OPEN_TAG = new char[6] { < , s , t , y , l , e };
private readonly char[] STYLE_CLOSE_TAG = new char[8] { < , / , s , t , y , l , e , > };
private readonly char[] COMMENT_OPEN_TAG = new char[3] { < , ! , - };
private readonly char[] COMMENT_CLOSE_TAG = new char[3] { - , - , > };
private int[] m_deletionDictionary;
public string Extract(char[] input, bool stripComments = false)
{
var len = input.Length;
int next = 0;
m_deletionDictionary = new int[len];
// Whipe out all text content between style and script tags.
FindAndWipe(SCRIPT_OPEN_TAG, SCRIPT_CLOSE_TAG, input);
FindAndWipe(STYLE_OPEN_TAG, STYLE_CLOSE_TAG, input);
if(stripComments)
{
// Whipe out everything between HTML comments.
FindAndWipe(COMMENT_OPEN_TAG, COMMENT_CLOSE_TAG, input);
}
// Whipe text between all other tags now.
while(next < len)
{
next = SkipUntil(next, < , input);
if(next < len)
{
var closeNext = SkipUntil(next, > , input);
if(closeNext < len)
{
m_deletionDictionary[next] = (closeNext + 1) - next;
WipeRange(next, closeNext + 1, input);
}
next = closeNext + 1;
}
}
// Collect all non-whitespace and non-null chars into a new
// char array. All whitespace characters are skipped and replaced
// with a single space char. Multiple whitespace is ignored.
var lastSpace = true;
var extractedPos = 0;
var extracted = new char[len];
for(next = 0; next < len; ++next)
{
if(m_deletionDictionary[next] > 0)
{
next += m_deletionDictionary[next];
continue;
}
if(char.IsWhiteSpace(input[next]) || input[next] == )
{
if(lastSpace)
{
continue;
}
extracted[extractedPos++] = ;
lastSpace = true;
}
else
{
lastSpace = false;
extracted[extractedPos++] = input[next];
}
}
return new string(extracted, 0, extractedPos);
}
/// <summary>
/// Does a search in the input array for the characters in the supplied open and closing tag
/// char arrays. Each match where both tag open and tag close are discovered causes the text
/// in between the matches to be overwritten by Array.Clear().
/// </summary>
/// <param name="openingTag">
/// The opening tag to search for.
/// </param>
/// <param name="closingTag">
/// The closing tag to search for.
/// </param>
/// <param name="input">
/// The input to search in.
/// </param>
private void FindAndWipe(char[] openingTag, char[] closingTag, char[] input)
{
int len = input.Length;
int pos = 0;
do
{
pos = FindNext(pos, openingTag, input);
if(pos < len)
{
var closenext = FindNext(pos, closingTag, input);
if(closenext < len)
{
m_deletionDictionary[pos - openingTag.Length] = closenext - (pos - openingTag.Length);
WipeRange(pos - openingTag.Length, closenext, input);
}
if(closenext > pos)
{
pos = closenext;
}
else
{
++pos;
}
}
}
while(pos < len);
}
/// <summary>
/// Skips as many characters as possible within the input array until the given char is
/// found. The position of the first instance of the char is returned, or if not found, a
/// position beyond the end of the input array is returned.
/// </summary>
/// <param name="pos">
/// The starting position to search from within the input array.
/// </param>
/// <param name="c">
/// The character to find.
/// </param>
/// <param name="input">
/// The input to search within.
/// </param>
/// <returns>
/// The position of the found character, or an index beyond the end of the input array.
/// </returns>
private int SkipUntil(int pos, char c, char[] input)
{
if(pos >= input.Length)
{
return pos;
}
do
{
if(input[pos] == c)
{
return pos;
}
++pos;
}
while(pos < input.Length);
return pos;
}
/// <summary>
/// Clears a given range in the input array.
/// </summary>
/// <param name="start">
/// The start position from which the array will begin to be cleared.
/// </param>
/// <param name="end">
/// The end position in the array, the position to clear up-until.
/// </param>
/// <param name="input">
/// The source array wherin the supplied range will be cleared.
/// </param>
/// <remarks>
/// Note that the second parameter is called end, not lenghth. This parameter is meant to be
/// a position in the array, not the amount of entries in the array to clear.
/// </remarks>
private void WipeRange(int start, int end, char[] input)
{
Array.Clear(input, start, end - start);
}
/// <summary>
/// Finds the next occurance of the supplied char array within the input array. This search
/// ignores whitespace.
/// </summary>
/// <param name="pos">
/// The position to start searching from.
/// </param>
/// <param name="what">
/// The sequence of characters to find.
/// </param>
/// <param name="input">
/// The input array to perform the search on.
/// </param>
/// <returns>
/// The position of the end of the first matching occurance. That is, the returned position
/// points to the very end of the search criteria within the input array, not the start. If
/// no match could be found, a position beyond the end of the input array will be returned.
/// </returns>
public int FindNext(int pos, char[] what, char[] input)
{
do
{
if(Next(ref pos, what, input))
{
return pos;
}
++pos;
}
while(pos < input.Length);
return pos;
}
/// <summary>
/// Probes the input array at the given position to determine if the next N characters
/// matches the supplied character sequence. This check ignores whitespace.
/// </summary>
/// <param name="pos">
/// The position at which to check within the input array for a match to the supplied
/// character sequence.
/// </param>
/// <param name="what">
/// The character sequence to attempt to match. Note that whitespace between characters
/// within the input array is accebtale.
/// </param>
/// <param name="input">
/// The input array to check within.
/// </param>
/// <returns>
/// True if the next N characters within the input array matches the supplied search
/// character sequence. Returns false otherwise.
/// </returns>
public bool Next(ref int pos, char[] what, char[] input)
{
int z = 0;
do
{
if(char.IsWhiteSpace(input[pos]) || input[pos] == )
{
++pos;
continue;
}
if(input[pos] == what[z])
{
++z;
++pos;
continue;
}
return false;
}
while(pos < input.Length && z < what.Length);
return z == what.Length;
}
}
HtmlAgility 包装:
// Where m_whitespaceRegex is a Regex with [s].
// Where sampleHtmlText is a raw HTML string.
var extractedSampleText = new StringBuilder();
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(sampleHtmlText);
if(doc != null && doc.DocumentNode != null)
{
foreach(var script in doc.DocumentNode.Descendants("script").ToArray())
{
script.Remove();
}
foreach(var style in doc.DocumentNode.Descendants("style").ToArray())
{
style.Remove();
}
var allTextNodes = doc.DocumentNode.SelectNodes("//text()");
if(allTextNodes != null && allTextNodes.Count > 0)
{
foreach(HtmlNode node in allTextNodes)
{
extractedSampleText.Append(node.InnerText);
}
}
var finalText = m_whitespaceRegex.Replace(extractedSampleText.ToString(), " ");
}