7 DATEX Execution

7.1 Runtime Environments

A DATEX Runtime Environment has to take care of sequential execution of incoming instructions, handling of encrpytion, permissions, variables and pointers. Furthermore, it must have a DXB generator to automatically generate response and synchronization messages.

A full DATEX Compiler is not required for a Runtime.

A Runtime Environment can also provide an interface to the host system (e.g. to manipulate a UI, access a database, or communicate with peripherals)

7.2 Sandboxed Execution

Since arbitrary DATEX binary code can be executed from other directly or indirectly connected endpoints ("remote endpoints"), the Runtime has to provide a sandboxed environment in which the access to pointers and static scopes it restricted depending on the permissions of the remote endpoint.

Per default, a remote endpoint should not be allowed to execute instructions on a third party endpoint, because it could impersonate the intermediate endpoint that way.

7.3 Internal Slots

Each scope has a number of memory locations to store values that are relevant for the scope execution process. Some internal slots are directly accessible in the scope as internal variables (e.g. #result, #this). Internal variables can be readonly.

7.3.1 List of internal slots:

• [[ACTIVE_VALUE]]
• [[LAST_VALUE]]
• [[PROC_RESULT]]
• [[OPERATOR]]
• [[INSERT_LOCATION]]
• [[SCOPE_RESULT]]
• [[RESULT]]
• [[INDEX]]
• [[INSTRUCTION_CODE]]
• [[INSTRUCTION]]
• [[THIS]]
• [[ROOT]]

7.4 General procedure for instruction processing

1. READ THE INSTRUCTION

   • Store the Instruction Code in [[INSTRUCTION_CODE]]
   • Store the remaining instruction data in [[INSTRUCTION]] (length depends on the Instruction Code, can also be 0)

2. EXECUTE THE INSTRUCTION

   • Validate the parameter types depending on the [[INSTRUCTION_CODE]]
   • Run the custom instruction procedure depending on [[INSTRUCTION_CODE]]
   • Move [[ACTIVE_VALUE]] to [[LAST_VALUE]]
   • Move the return value of the instruction procedure ([[PROC_RESULT]]) to [[ACTIVE_VALUE]]

3. APPLY IN CONTEXT

   • If [[OPERATOR]] is set, apply the operator to [[LAST_VALUE]] and [[ACTIVE_VALUE]] and store the result value in [[ACTIVE_VALUE]]; clear [[OPERATOR]]
   • Else apply [[ACTIVE_VALUE]] directly to [[LAST_VALUE]] and store the result in [[ACTIVE_VALUE]]

4. INSERT THE VALUE

   • If [[INSERT_LOCATION]] is set, insert [[ACTIVE_VALUE]] at [[INSERT_LOCATION]]

7.5 Statements

The CLOSE_AND_STORE Instruction is used to separate groups of Instructions ("Statements").

The [[ACTIVE_VALUE]] is stored in [[SCOPE_RESULT]]. [[ACTIVE_VALUE]], [[LAST_VALUE]], [[OPERATOR]], and [[INSERT_LOCATION]] are cleared.

7.6 Global Runtime data

• global: Runtime.Global
• The scope keyword acts as context of the current scope (Runtime.Scope).

7.7 General Runtime procedures

7.7.1 runtimeExecution

function runtimeExecution(scope: Runtime.Scope, global: Runtime.Global):

   while scope.byteIndex < len(scope.executable):
      (instructionCode, scope.byteIndex) <- extractUint32(
         scope.executable,
         scope.byteIndex
      )
      instrDefinition <- global.instructionDefinitions[instructionCode]

      if len(scope.executable) - scope.byteIndex < 
         instrDefinition.minimumSize:
         scope.byteIndex <- scope.byteIndex - 2
         return

      data <- scope.executable[scope.byteIndex..len(scope.executable)]

      if instrDefinition.validation and
         not instrDefinition.validation(data)
            scope.byteIndex <- scope.byteIndex - 2
            return

      result <- instrDefinition.procedure(data as Instruction.*)
      
      scope.lastValue <- scope.activeValue
      scope.activeValue <- result

      if scope.operator:
         scope.activeValue <- applyOperator(scope.operator, scope.lastValue, scope.activeValue) // TODO
         scope.operator <- void
      else:
         scope.activeValue <- apply(scope.lastValue, scope.activeValue) // TODO

      if scope.insertLocation:
         insert(scope.insertLocation, scope.activeValue) // TODO
         scope.insertLocation <- void

7.7.2 newSubScope

function newSubScope(scope: Runtime.Scope)
   // TODO add new subscope to heap
   scope.subscopes += Runtime.Subscope {

   }

7.8 Instruction-specific procedures

7.8.1 COUNT

1. If [[ACTIVE_VALUE]] is primitive, set [[PROC_RESULT]] to 1

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