com.goldencode.p2j.uast

Class FrameAstKey

java.lang.Object

com.goldencode.p2j.uast.FrameAstKey

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable

public class FrameAstKey
extends java.lang.Object
implements java.io.Externalizable

Objects of this class are used as keys for a hashtable that match frame definitions with compatible structure that can be used by shared frames partitions. If two frames are compatible then their FrameAstKey will be equals. If the keys are different, then the two frames belong to different partitions.

The matching algorithm takes into consideration:

• type and name of all fields and variables used in FORM/FRAME definition;
• type of all literals from frame definition;
• the order of the above;
• the frame's name.

The matching algorithm does NOT take into consideration:

• spacers (SKIP and SPACE);
• the value of the literals;
• any form item in the HEADER definition;
• any declaration from any frame format node.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
private Aast	fAst The Progress AST contained.
private java.lang.String	frameName The name of the FRAME.
private int	hash Cached value of hash.

Constructor Summary

Constructors

Constructor and Description
FrameAstKey() Default c'tor, used for (de)serialization.
FrameAstKey(Aast ast, java.lang.String frameName) The single constructor.

Method Summary

Modifier and Type	Method and Description
private int	computeHash() Compute the hashing value for the FRAME component.
boolean	equals(java.lang.Object obj) Check if another object obj and this are identical (represent FRAMES with compatible structure, which can be SHARED).
private static Aast	getNextSignificantNode(Aast frameDefNode) Utility method that searches next relevant item from a frame definition, starting from a current node, iterating its right siblings, until one is found or teh list ends.
int	hashCode() Obtain the hashing value for this container.
private void	initialize(Aast ast, java.lang.String frameName) Initialize this instance from the backing AST.
void	readExternal(java.io.ObjectInput in) Restore this instance by re-loading the AST with the given ID and initialize(com.goldencode.ast.Aast, java.lang.String) it.
void	writeExternal(java.io.ObjectOutput out) Write this instance to stream.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

fAst

private Aast fAst

The Progress AST contained. It must be a KW_FORM or DEFINE_FRAME node.

hash

private int hash

Cached value of hash. FrameAstKey is imutabil so once computed in constructor it remains unchanged during the lifetime of the container.

frameName

private java.lang.String frameName

The name of the FRAME. This attribute is not mandatory. More frames can share the same interface using different names, although this is rather strange. To have the code more readable and consistent we enforce this constraint.

Constructor Detail

FrameAstKey

public FrameAstKey()

Default c'tor, used for (de)serialization.

FrameAstKey

public FrameAstKey(Aast ast,
                   java.lang.String frameName)

The single constructor. Saves a copy of the input data and computes the hash for quick match as a hashing key.

Parameters:

ast - The content node. Must be a KW_FORM or DEFINE_FRAME

frameName - The name of the frame. It cannot be always extracted directly form ast.

Throws:

java.lang.NullPointerException - if any argument is null.

java.lang.RuntimeException - on parameter validation failure: the first argument is not a FRAME definition (KW_FORM or DEFINE_FRAME).

Method Detail

hashCode

public int hashCode()

Obtain the hashing value for this container. This method is fast as the value was already computed in constructor.

Overrides:

hashCode in class java.lang.Object

Returns:

the hash value for this object.

equals

public boolean equals(java.lang.Object obj)

Check if another object obj and this are identical (represent FRAMES with compatible structure, which can be SHARED). The algorithm iterates all relevant nodes from both containers and try to match them. Like the hashing algorithm, only FORM_ITEM that contains accessible information are taken into consideration (fields and variables). The constants also add to hashing value but their actual value is not important. Spacers are completely ignored.

Overrides:

equals in class java.lang.Object

Parameters:

obj - A second object to test for item structure.

Returns:

true if the obj and this contain compatible frame definitions.

writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

Write this instance to stream.

Specified by:

writeExternal in interface java.io.Externalizable

Parameters:

out - The object output stream.

Throws:

java.io.IOException

readExternal

public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException

Restore this instance by re-loading the AST with the given ID and initialize(com.goldencode.ast.Aast, java.lang.String) it.

Specified by:

readExternal in interface java.io.Externalizable

Parameters:

in - The object input stream.

Throws:

java.io.IOException

java.lang.ClassNotFoundException

getNextSignificantNode

private static Aast getNextSignificantNode(Aast frameDefNode)

Utility method that searches next relevant item from a frame definition, starting from a current node, iterating its right siblings, until one is found or teh list ends.

Parameters:

frameDefNode - the starting point for relevant node search.

Returns:

a significant sibling if anyone is found or null otherwise.

computeHash

private int computeHash()

Compute the hashing value for the FRAME component.

Iterate all nodes and create a hashing value for all relevant sub-nodes (the ones that are needed for frame matching). Only FORM_ITEM that contains accessible information are taken into consideration (fields and variables). The constants also add to hashing value but their actual value is not important. Spacers are totally ignored.

The order is also important but it is not enforced directly. However, because of the way the items are added and shifted sequentially, the result value should be sufficient for a hashing key.

Returns:

hashing value of this key.

Throws:

java.lang.RuntimeException - if some unexpected children are encountered.

initialize

private void initialize(Aast ast,
                        java.lang.String frameName)

Initialize this instance from the backing AST.

Parameters:

ast - The content node. Must be a KW_FORM or DEFINE_FRAME

frameName - The name of the frame. It cannot be always extracted directly form ast.

Throws:

java.lang.NullPointerException - if any argument is null.

java.lang.RuntimeException - on parameter validation failure: the first argument is not a FRAME definition (KW_FORM or DEFINE_FRAME).