Class ExtensionFunctionDefinition
- java.lang.Object
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- net.sf.saxon.lib.ExtensionFunctionDefinition
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- Direct Known Subclasses:
IsIdRef
public abstract class ExtensionFunctionDefinition extends java.lang.Object
This abstract class is provided to allow user-written extension functions to be implemented with the full capabilities of functions that are an intrinsic part of the Saxon product. In particular, the class has the opportunity to save data from the static context and to optimize itself at compile time.There should be one class implementing this interface for each function name; if there are several functions with the same name but different arity, the same class should implement them all.
Note that an IntegratedFunction is trusted; calls are allowed even if the configuration option
FeatureKeys.ALLOW_EXTERNAL_FUNCTIONS
is false. In cases where an IntegratedFunction is used to load and execute untrusted code, it should check this configuration option before doing so.- Since:
- 9.2
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Constructor Summary
Constructors Constructor Description ExtensionFunctionDefinition()
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description Function
asFunction()
Get a Function item representing this ExtensionFunctionDefinitionboolean
dependsOnFocus()
Ask whether the result of the function depends on the focus, or on other variable parts of the context.abstract SequenceType[]
getArgumentTypes()
Get the required types for the arguments of this function.abstract StructuredQName
getFunctionQName()
Get the name of the function, as a QName.int
getMaximumNumberOfArguments()
Get the maximum number of arguments allowed by the function.int
getMinimumNumberOfArguments()
Get the minimum number of arguments required by the functionabstract SequenceType
getResultType(SequenceType[] suppliedArgumentTypes)
Get the type of the result of the functionboolean
hasSideEffects()
Ask whether the function has side-effects.abstract ExtensionFunctionCall
makeCallExpression()
Create a call on this function.boolean
trustResultType()
Ask whether the result actually returned by the function can be trusted, or whether it should be checked against the declared type.
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Method Detail
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getFunctionQName
public abstract StructuredQName getFunctionQName()
Get the name of the function, as a QName.This method must be implemented in all subclasses
- Returns:
- the function name
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getMinimumNumberOfArguments
public int getMinimumNumberOfArguments()
Get the minimum number of arguments required by the functionThe default implementation returns the number of items in the result of calling
getArgumentTypes()
- Returns:
- the minimum number of arguments that must be supplied in a call to this function
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getMaximumNumberOfArguments
public int getMaximumNumberOfArguments()
Get the maximum number of arguments allowed by the function.The default implementation returns the value of
getMinimumNumberOfArguments()
- Returns:
- the maximum number of arguments that may be supplied in a call to this function
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getArgumentTypes
public abstract SequenceType[] getArgumentTypes()
Get the required types for the arguments of this function.This method must be implemented in all subtypes.
- Returns:
- the required types of the arguments, as defined by the function signature. Normally
this should be an array of size
getMaximumNumberOfArguments()
; however for functions that allow a variable number of arguments, the array can be smaller than this, with the last entry in the array providing the required type for all the remaining arguments.
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getResultType
public abstract SequenceType getResultType(SequenceType[] suppliedArgumentTypes)
Get the type of the result of the functionThis method must be implemented in all subtypes.
- Parameters:
suppliedArgumentTypes
- the static types of the supplied arguments to the function. This is provided so that a more precise result type can be returned in the common case where the type of the result depends on the types of the arguments.- Returns:
- the return type of the function, as defined by its function signature
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trustResultType
public boolean trustResultType()
Ask whether the result actually returned by the function can be trusted, or whether it should be checked against the declared type.- Returns:
- true if the function implementation warrants that the value it returns will be an instance of the declared result type. The default value is false, in which case the result will be checked at run-time to ensure that it conforms to the declared type. If the value true is returned, but the function returns a value of the wrong type, the consequences are unpredictable.
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dependsOnFocus
public boolean dependsOnFocus()
Ask whether the result of the function depends on the focus, or on other variable parts of the context.- Returns:
- true if the result of the function depends on the context item, position, or size.
Despite the method name, the method should also return true if the function depends on other
parts of the context that vary from one part of the query/stylesheet to another, for example
the XPath default namespace.
The default implementation returns false.
The method must return true if the function makes use of any of these values from the dynamic context. Returning true inhibits certain optimizations, such as moving the function call out of the body of an xsl:for-each loop, or extracting it into a global variable.
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hasSideEffects
public boolean hasSideEffects()
Ask whether the function has side-effects. If the function does have side-effects, the optimizer will be less aggressive in moving or removing calls to the function. However, calls on functions with side-effects can never be guaranteed.- Returns:
- true if the function has side-effects (including creation of new nodes, if the identity of those nodes is significant). The default implementation returns false.
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makeCallExpression
public abstract ExtensionFunctionCall makeCallExpression()
Create a call on this function. This method is called by the compiler when it identifies a function call that calls this function.- Returns:
- an expression representing a call of this extension function
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asFunction
public final Function asFunction()
Get a Function item representing this ExtensionFunctionDefinition- Returns:
- a function item corresponding to this extension function
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