The Attribute Service Class

The service class Attribute contains those methods used by both the Xml Script Language processor and the runtime engine to process the values of the entries in attribute classes. The information associated with an attribute class is stored in a linear information vector. There are two types of vectors: word aligned and byte aligned. Each attribute has a binary type, a starting offset, and various processing control flags associated with it.

The method Attribute_Define

Prototype

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int Attribute_Define(char* command,int stateRoot,int* info);

The Attribute_Define method processes the Attribute statement which defines an information vector. This statement specifies the information needed to store and retrieve attribute values from Xml-attribute value strings, binary information vectors, and the runtime data queue. Semantically they are distinguished from Properties in that an attribute can be stored and accessed directly based on its location in a binary information vector, its type and its support info. Its initial input conversion does not require any individual runtime support. A property on the other hand is simply a shorthand notation for possibly two different methods -- get and set.

The attributes of the Attribute command are as follows:

The members of the tLibComp structure are used as follows by the statement:

Its parameters are as follows:

A zero value is returned by this method if all went well; else a non-zero error code is returned. The errors detected directly by this method are:

There may be additional lower level errors detected by the XML processing methods used.

The method Attribute_LoadVector

Prototype

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int Attribute_LoadVector(CONST char* statement,char* command,void* vector);

The Attribute_LoadVector method processes script statements that first load an information vector and then use that information to perform some action. Using information about the statement as described in the metalanguage, this method calls the appropriate parsing method to isolate the attribute information and then to load the values. Its parameters are as follows:

If all goes well, this method returns a zero else a one is returned with the error code set.

The method Attribute_PopValue

Prototype

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void Attribute_PopValue(int attrRoot,int* vector);

The Attribute_PopValue method pops an information vector value from the runtime data queue and stores it in an information vector. This method is used by the engine when it encounters a set operation on an attribute. Its parameters are as follows:

This method itself returns no value.

The method Attribute_PushValue

Prototype

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void Attribute_PushValue(int attrRoot,int* vector);

The Attribute_PushValue method pushes an information vector value into the runtime data queue. This method is used by the engine when it encounters a get operation on an attribute. Its parameters are as follows:

This method has no return value.

The method Attribute_Select

Prototype

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void Attribute_Select(char* command);

The Attribute_Select method executes the Select script command which specifies Select attribute values. It simply uses the Attribute_LoadVector method and then checks for a change to the codeSize attribute, which requires that the code storage area be reallocated. Its parameter is:

This method has no return value.

The method Attribute_XeqStatements

Prototype

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int Attribute_XeqStatements(char* command,int nCommand,int langRoot);

The Attribute_XeqStatements method executes the gmPL Statements statement, which initiates the definition of the statements within an Xml-style language to be processed. Its parameters are:

This method returns a zero value if all went well; else it returns one with the global error code set to a nonzero value.