The VarValues Service Class

The service class VarValues contains those methods used by the engine to allocate, store, and retrieve variable values.

The members of the tVariable structure used by this class are as follows:

The method VarValues_Construct

Prototype

The VarValues_Constuct method initializes the values of the local variables associated with a subprogram. Each call to a subprogram constructs a variable values vector. In the case of recursion there is one varvalues vector for each active call to the subprogram. Its parameter is:

Each parameter and local variable defined for the subprogram is assigned a sequence number starting at one by the method VarValues_SetLocalVariables. The corresponding entry in the values vector controls the values for that component during the current call to the subprogram. The zero member of the values vector contains the control information for the values vector itself.

The method returns an opaque handle to the variable values vector. It is this handle that is referred to as This in methods using this vector.

The method VarValues_Destroy

Prototype

The VarValues_Destroy method destroys a variable values vector for a subprogram call when that call exits the subprogram. All scratch information storage associated with the parameters and local variables associated with the subprgram call is released to the scratch information manager. This includes the variable values vector itself. Its parameter is:

The method VarValues_GetHandle

Prototype

The VarValues_GetHandle method is called when a member of a variable with a structure type is being accessed. Its parameters are as follows:

The method returns a pointer to the start of the value vector for this instance of the structure.

The method VarValues_GetType

Prototype

The VarValues_GetType method simply gets the type of a variable instance from the variable values vector. Its parameters are as follows:

The engines using this class support variant types that are not imposed on a variable until runtime. The consequence of this is that variables do not necessarily have the same type in different executions of their subprogram. The type is recorded in the variable value vector and not in the information vector of the variable itself.

The method VarValues_GetValue

Prototype

The VarValues_GetValue method simply gets the value entry of a variable instance from the variable values vector. Its parameters are as follows:

The method VarValues_PopHandle

Prototype

The VarValues_PopHandle method pops a handle to a value that is to be passed to a method expecting a pointer to a structure, array, or ByRef parameter. Its parameter is:

The method pops a value or vector from the runtime data queue and returns a pointer obtained from the information popped to an actual value or value vector that is being passed to a method.

The method VarValues_PopObject

Prototype

The VarValues_PopObject method pops an object handle of a value instance. Its parameter is:

First, the sequence number of a variable is popped fron the stack. If that variable has an object type with values associated with it then the handle to those values is returned. If no values are associated with the object type, they are initialized in scratch information storage and the handle is returned. If not an object type, then a simple pointer to the values is returned.

The method VarValues_PushObject

Prototype

The VarValues_PushObject method creates an object and pushes its attribute vector onto the runtime data queue. Its parameters are as follows:

The method VarValues_PushValue

Prototype

The method pushes the possibly subscripted value of a variable onto the runtime data queue. Its parameters are as follows:

The method VarValues_SetExternalCall

Prototype

The VarValues_SetExternalCall method sets the parameter values of a subprogram when that subprogram is being called via from an external source. Its parameters are as follows:

The method VarValues_SetInternalCall

Prototype

The VarValues_SetInternalCall method sets the parameter values of a subprogram when that subprogram is being called via from an internal source. Its parameters ar as follows:

The actual initial parameter values for the subprogram are popped from the runtime data queue.

The method VarValues_SetLocalVariables

Prototype

The VarValues_SetLocalVariables method is called by the gmSL compiler after the code for a subprogram has been compiled. It scans the symbols associated with the subprogram for local variables and their control structures as required by the runtime engine. The control structure for the subprogram is modified as well to specify the number of local variables. Its parameter is as follows:

The method VarValues_SetValue

Prototype

The VarValues_SetValue method sets the simple value of a variable instance. Its parameters are as follows:

The method VarValues_StoreValue

Prototype

The method pops a value from the runtime data queue and stores it in the possibly subscripted value of a variable. Its parameters are as follows: