
<<FrameImpl.mesa>>
<<last modified by Levin on July 1, 1983 4:58 pm>>

DIRECTORY
MesaRuntimeInit USING [],
PrincOps USING [
ControlLink, EPRange, GFT, GFTItem, GlobalFrameHandle, NullProgram, SD, sGFTLength, UnboundLink],
PrincOpsUtils USING [],
RuntimeError USING [UnboundProcedure];

FrameImpl: PROGRAM
IMPORTS RuntimeError
EXPORTS MesaRuntimeInit, PrincOpsUtils =

BEGIN

OPEN PrincOps;
<<>>
<<Exported to PrincOpsUtils (Global Frame stuff)>>

GlobalFrame: PUBLIC SAFE PROC [link: --ControlLink--UNSPECIFIED]
RETURNS [PROGRAM] = TRUSTED {
DO
OPEN l: LOOPHOLE[link, ControlLink];
SELECT TRUE FROM
l = UnboundLink => link _ SIGNAL RuntimeError.UnboundProcedure[link];
l.proc =>
IF l.gfi IN [1..SD[sGFTLength]) THEN {
gftItem: GFTItem _ GFT[l.gfi];
gftItem.epbias _ 0;
RETURN[LOOPHOLE[gftItem.framePtr]]
}
ELSE RETURN[NullProgram];
l.indirect => link _ l.link^;
link = 0 => RETURN[NullProgram];
ENDCASE => RETURN[LOOPHOLE[l.frame.accesslink]]
ENDLOOP;
};

GlobalFrameAndEntryPoint: PUBLIC SAFE PROC [link: --ControlLink--UNSPECIFIED]
RETURNS [gf: GlobalFrameHandle, ep: CARDINAL] = TRUSTED {
DO
OPEN l: LOOPHOLE[link, ControlLink];
SELECT TRUE FROM
l = UnboundLink => link _ SIGNAL RuntimeError.UnboundProcedure[link];
l.proc =>
IF l.gfi IN [1..SD[sGFTLength]) THEN {
gftItem: GFTItem _ GFT[l.gfi];
RETURN[gf: gftItem.framePtr, ep: gftItem.epbias*EPRange+l.ep]
}
ELSE ERROR;
l.indirect => link _ l.link^;
ENDCASE => ERROR;  -- not meaningful for type-0 control links
ENDLOOP;
};

END.