private static int TagCost(HTMLBalancerCostFilter costFilter, ArrayList openTags, Tag tag)
{
try
{
checked
{
int baseTagCost = costFilter.ElementCost(tag);
if (tag is BeginTag)
{
return(baseTagCost + ((TagRequiresClose(tag.Name)) ? costFilter.ElementCost(MakeEndTag(tag.Name)) : 0));
}
else if (tag is EndTag)
{
if (LastIndexOf(openTags, tag) != -1)
{
return(baseTagCost - costFilter.ElementCost(MakeEndTag(tag.Name)));
}
else
{
return(baseTagCost);
}
}
else
{
Trace.Fail("Unknown tag type");
return(baseTagCost);
}
}
}
catch (OverflowException)
{
return(int.MaxValue);
}
}
private static long LengthToClose(HTMLBalancerCostFilter costFilter, ArrayList openTags)
{
long total = 0;
try
{
checked
{
for (int i = openTags.Count - 1; i >= 0; i--)
{
total += costFilter.ElementCost(MakeEndTag((string)openTags[i]));
}
}
}
catch (OverflowException)
{
return(int.MaxValue);
}
return(total);
}
/// <summary>
/// Balances the HTML and safely truncates it, using a custom algorithm
/// to determine how much each character/string counts against maxCost.
/// </summary>
public static string Balance(string html, int maxCost, HTMLBalancerCostFilter costFilter, bool ellipsis)
{
bool appendEllipsis = false;
SimpleHtmlParser parser = new SimpleHtmlParser(html);
ArrayList openTags = new ArrayList();
StringBuilder output = new StringBuilder();
long balance = 0; // long to make sure that int32.MaxValue does not cause overflow
if (costFilter == null)
costFilter = new DefaultCostFilter();
Element el;
while (null != (el = parser.Next()))
{
if (el is StyleElement ||
el is ScriptElement ||
el is Comment ||
el is MarkupDirective)
{
continue;
}
long lenLeft = Math.Max(0, maxCost - balance - LengthToClose(costFilter, openTags));
if (el is Tag)
{
if (el is BeginTag && ((BeginTag)el).Unterminated)
continue; // skip corrupted tags
if (TagCost(costFilter, openTags, (Tag)el) > lenLeft)
break; // don't use this tag; we're done
else
{
RegisterTag(openTags, (Tag)el);
output.Append(el.ToString());
balance += costFilter.ElementCost(el);
}
}
else if (el is Text)
{
if (costFilter.ElementCost(el) > lenLeft)
{
// shrink down the text to fit
output.Append(costFilter.TruncateText((Text)el, (int)lenLeft));
appendEllipsis = true;
break;
}
else
{
// plenty of room
output.Append(el.ToString());
balance += costFilter.ElementCost(el);
}
//update the text end index
}
else
{
if (costFilter.ElementCost(el) > lenLeft)
break;
else
{
output.Append(el.ToString());
balance += costFilter.ElementCost(el);
}
}
}
// Append an ellipsis if we truncated text
// We use "..." here rather than TextHelper.Ellipsis, because some mail clients don't understand "\u2026".
if (ellipsis && appendEllipsis)
output.Append("...");
for (int i = openTags.Count - 1; i >= 0; i--)
{
output.Append(MakeEndTag((string)openTags[i]));
}
return output.ToString();
}
private static int TagCost(HTMLBalancerCostFilter costFilter, ArrayList openTags, Tag tag)
{
try
{
checked
{
int baseTagCost = costFilter.ElementCost(tag);
if (tag is BeginTag)
{
return baseTagCost + ((TagRequiresClose(tag.Name)) ? costFilter.ElementCost(MakeEndTag(tag.Name)) : 0);
}
else if (tag is EndTag)
{
if (LastIndexOf(openTags, tag) != -1)
return baseTagCost - costFilter.ElementCost(MakeEndTag(tag.Name));
else
return baseTagCost;
}
else
{
Trace.Fail("Unknown tag type");
return baseTagCost;
}
}
}
catch (OverflowException)
{
return int.MaxValue;
}
}
private static long LengthToClose(HTMLBalancerCostFilter costFilter, ArrayList openTags)
{
long total = 0;
try
{
checked
{
for (int i = openTags.Count - 1; i >= 0; i--)
{
total += costFilter.ElementCost(MakeEndTag((string)openTags[i]));
}
}
}
catch (OverflowException)
{
return int.MaxValue;
}
return total;
}
/// <summary>
/// Balances the HTML and safely truncates it, using a custom algorithm
/// to determine how much each character/string counts against maxCost.
/// </summary>
public static string Balance(string html, int maxCost, HTMLBalancerCostFilter costFilter, bool ellipsis)
{
bool appendEllipsis = false;
SimpleHtmlParser parser = new SimpleHtmlParser(html);
ArrayList openTags = new ArrayList();
StringBuilder output = new StringBuilder();
long balance = 0; // long to make sure that int32.MaxValue does not cause overflow
if (costFilter == null)
{
costFilter = new DefaultCostFilter();
}
Element el;
while (null != (el = parser.Next()))
{
if (el is StyleElement ||
el is ScriptElement ||
el is Comment ||
el is MarkupDirective)
{
continue;
}
long lenLeft = Math.Max(0, maxCost - balance - LengthToClose(costFilter, openTags));
if (el is Tag)
{
if (el is BeginTag && ((BeginTag)el).Unterminated)
{
continue; // skip corrupted tags
}
if (TagCost(costFilter, openTags, (Tag)el) > lenLeft)
{
break; // don't use this tag; we're done
}
else
{
RegisterTag(openTags, (Tag)el);
output.Append(el.ToString());
balance += costFilter.ElementCost(el);
}
}
else if (el is Text)
{
if (costFilter.ElementCost(el) > lenLeft)
{
// shrink down the text to fit
output.Append(costFilter.TruncateText((Text)el, (int)lenLeft));
appendEllipsis = true;
break;
}
else
{
// plenty of room
output.Append(el.ToString());
balance += costFilter.ElementCost(el);
}
//update the text end index
}
else
{
if (costFilter.ElementCost(el) > lenLeft)
{
break;
}
else
{
output.Append(el.ToString());
balance += costFilter.ElementCost(el);
}
}
}
// Append an ellipsis if we truncated text
// We use "..." here rather than TextHelper.Ellipsis, because some mail clients don't understand "\u2026".
if (ellipsis && appendEllipsis)
{
output.Append("...");
}
for (int i = openTags.Count - 1; i >= 0; i--)
{
output.Append(MakeEndTag((string)openTags[i]));
}
return(output.ToString());
}
