creates "combined child content expression" and gathers "elements of concern"
and its "attribute-pruned" content model.
Intuitively, "combined child content expression" is a set of
content models of "elements of concern",
which is appropriately combined to express dependency between elements.
"Elements of concern" are ElementExps that are possibly applicable to
the next element. These gathered element declarations are then tested against
next XML element.
"Attribute-pruned" content model is a content model after consuming
AttributeTokens and removing unused AttributeExp nodes.
For example, when the current expression is
<!-- javadoc escape -->
..(A)..
..(B)..
...
..(C)..
....
then the combined child expression is
..(A')..
..(B')..
..(C')..
and elements of concern and its attribute-pruned content models are
..(A).. -> ..(A')..
..(B).. -> ..(B')..
..(C).. -> ..(C')..
(A'),(B'), and (C') are attribute-pruned content models of (A),(B), and (C)
respectively.
Note that combined child pattern contains only <choice> and <concur> as
its grue (of course, except ..(A').. , ..(B').. , and ..(C').. ).
This function object also calculates "continuation", which is the residual
expression after eating elements of concern.
For example, say the expression is "(A|(B,C))?,D".
When EoC is B, then the continuation will be C,D.
When EoC is A, then the continuation will be D.
When EoC is D, then the continuation will be epsilon.
When there are multiple EoC, (say A and B), then
the continuation will be meaningless (because it depends on which EoC will
be accepted), and thus won't be used.
However, the implementator must be aware that it is possible for a
binary operator to have EoC on both branch and EoC is still unique.
The following expression is an example.
(A|B)*,C?,(A|B)*
when A is EoC, SequenceExp of (A|B)* and C?,(A|B)* has EoC on both branch.
get
public CombinedChildContentExpCreator.ExpressionPair get(Expression combinedPattern,
StartTagInfo info,
boolean checkTagName)
computes a combined child content pattern and its continuation, with error recovery.
After calling this method, caller can call getElementsOfConcern to obtain
each EoC.
If both feedAttributes and checkTagName are false, then StartTagInfo is
also unnecessary.
checkTagName
- if this flag is false, tag name check is skipped.
getMatchedElements
public final ElementExp[] getMatchedElements()
obtains matched elements.
This method should be called after calling the get method. The result is
in effect until the next invocation of get method.
The extra care should be taken not to hold reference to the result
longer than necessary.
The contents of the result is valid only until the next invocation.
Because OwnerAndContent objects are reused.
Apparently this is a bad design, but this design gives us better performance.
isComplex
public final boolean isComplex()
checks if the result of 'get' method is not the union of all
elements of concern.
Within this class, combined child content expression is
always the union of all elements of concern. However, some derived
class does not guarantee this property.
- true if the combined child content expression is not
the union of all elements of concern.
false if otherwise.
numMatchedElements
public final int numMatchedElements()
gets the number of matched elements.
This method should be called after calling get method. The result is
in effect until next invocation of get method.
Apparently this is a bad design, but this design gives us better performance.