/// <summary>
/// Basic optimization. Single-letter alternations can be replaced
/// by faster set specifications, and nested alternations with no
/// intervening operators can be flattened:
///
/// a|b|c|def|g|h -> [a-c]|def|[gh]
/// apple|(?:orange|pear)|grape -> apple|orange|pear|grape
/// </summary>
internal RegexNode ReduceAlternation()
{
// Combine adjacent sets/chars
bool wasLastSet;
bool lastNodeCannotMerge;
RegexOptions optionsLast;
RegexOptions optionsAt;
int i;
int j;
RegexNode at;
RegexNode prev;
if (_children == null)
{
return(new RegexNode(Nothing, _options));
}
wasLastSet = false;
lastNodeCannotMerge = false;
optionsLast = 0;
for (i = 0, j = 0; i < _children.Count; i++, j++)
{
at = _children[i];
if (j < i)
{
_children[j] = at;
}
for (; ;)
{
if (at._type == Alternate)
{
for (int k = 0; k < at._children.Count; k++)
{
at._children[k]._next = this;
}
_children.InsertRange(i + 1, at._children);
j--;
}
else if (at._type == Set || at._type == One)
{
// Cannot merge sets if L or I options differ, or if either are negated.
optionsAt = at._options & (RegexOptions.RightToLeft | RegexOptions.IgnoreCase);
if (at._type == Set)
{
if (!wasLastSet || optionsLast != optionsAt || lastNodeCannotMerge || !RegexCharClass.IsMergeable(at._str))
{
wasLastSet = true;
lastNodeCannotMerge = !RegexCharClass.IsMergeable(at._str);
optionsLast = optionsAt;
break;
}
}
else if (!wasLastSet || optionsLast != optionsAt || lastNodeCannotMerge)
{
wasLastSet = true;
lastNodeCannotMerge = false;
optionsLast = optionsAt;
break;
}
// The last node was a Set or a One, we're a Set or One and our options are the same.
// Merge the two nodes.
j--;
prev = _children[j];
RegexCharClass prevCharClass;
if (prev._type == One)
{
prevCharClass = new RegexCharClass();
prevCharClass.AddChar(prev._ch);
}
else
{
prevCharClass = RegexCharClass.Parse(prev._str);
}
if (at._type == One)
{
prevCharClass.AddChar(at._ch);
}
else
{
RegexCharClass atCharClass = RegexCharClass.Parse(at._str);
prevCharClass.AddCharClass(atCharClass);
}
prev._type = Set;
prev._str = prevCharClass.ToStringClass();
}
else if (at._type == Nothing)
{
j--;
}
else
{
wasLastSet = false;
lastNodeCannotMerge = false;
}
break;
}
}
if (j < i)
{
_children.RemoveRange(j, i - j);
}
return(StripEnation(Nothing));
}
/// <summary>
/// Basic optimization. Single-letter alternations can be replaced
/// by faster set specifications, and nested alternations with no
/// intervening operators can be flattened:
///
/// a|b|c|def|g|h -> [a-c]|def|[gh]
/// apple|(?:orange|pear)|grape -> apple|orange|pear|grape
/// </summary>
internal RegexNode ReduceAlternation()
{
// Combine adjacent sets/chars
bool wasLastSet;
bool lastNodeCannotMerge;
RegexOptions optionsLast;
RegexOptions optionsAt;
int i;
int j;
RegexNode at;
RegexNode prev;
if (_children == null)
return new RegexNode(Nothing, _options);
wasLastSet = false;
lastNodeCannotMerge = false;
optionsLast = 0;
for (i = 0, j = 0; i < _children.Count; i++, j++)
{
at = _children[i];
if (j < i)
_children[j] = at;
for (; ;)
{
if (at._type == Alternate)
{
for (int k = 0; k < at._children.Count; k++)
at._children[k]._next = this;
_children.InsertRange(i + 1, at._children);
j--;
}
else if (at._type == Set || at._type == One)
{
// Cannot merge sets if L or I options differ, or if either are negated.
optionsAt = at._options & (RegexOptions.RightToLeft | RegexOptions.IgnoreCase);
if (at._type == Set)
{
if (!wasLastSet || optionsLast != optionsAt || lastNodeCannotMerge || !RegexCharClass.IsMergeable(at._str))
{
wasLastSet = true;
lastNodeCannotMerge = !RegexCharClass.IsMergeable(at._str);
optionsLast = optionsAt;
break;
}
}
else if (!wasLastSet || optionsLast != optionsAt || lastNodeCannotMerge)
{
wasLastSet = true;
lastNodeCannotMerge = false;
optionsLast = optionsAt;
break;
}
// The last node was a Set or a One, we're a Set or One and our options are the same.
// Merge the two nodes.
j--;
prev = _children[j];
RegexCharClass prevCharClass;
if (prev._type == One)
{
prevCharClass = new RegexCharClass();
prevCharClass.AddChar(prev._ch);
}
else
{
prevCharClass = RegexCharClass.Parse(prev._str);
}
if (at._type == One)
{
prevCharClass.AddChar(at._ch);
}
else
{
RegexCharClass atCharClass = RegexCharClass.Parse(at._str);
prevCharClass.AddCharClass(atCharClass);
}
prev._type = Set;
prev._str = prevCharClass.ToStringClass();
}
else if (at._type == Nothing)
{
j--;
}
else
{
wasLastSet = false;
lastNodeCannotMerge = false;
}
break;
}
}
if (j < i)
_children.RemoveRange(j, i - j);
return StripEnation(Nothing);
}