YggBitsImpl.mesa
Copyright Ó 1988 by Xerox Corporation. All rights reserved.
Bob Hagmann April 13, 1988 4:03:18 pm PDT
This module implements the Bits datatype.
DIRECTORY
Basics USING [ByteBlt, charsPerWord, RawBytes, UnsafeBlock],
Rope USING [ROPE],
YggRep USING [Bits, BitsRep];
YggBitsImpl: CEDAR PROGRAM
IMPORTS Basics
EXPORTS YggRep
~ BEGIN
ROPE: TYPE ~ Rope.ROPE;
Exported procedures
BytesFromBits: PUBLIC PROC [bits: YggRep.Bits, startByte: CARD, block: Basics.UnsafeBlock] ~ {
Fetch some bytes from an "uninterpreted bytes" object
WITH bits SELECT FROM
rBits: REF YggRep.BitsRep => TRUSTED {
nBytes: CARD;
IF rBits.length >= startByte + block.count THEN ERROR;
nBytes ← Basics.ByteBlt[
from: [blockPointer: LOOPHOLE[rBits, POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: startByte, stopIndexPlusOne: startByte+block.count],
to: [blockPointer: LOOPHOLE[block.base], startIndex: block.startIndex, stopIndexPlusOne: block.startIndex + block.count]
];
IF nBytes # block.count THEN ERROR;
};
ENDCASE => ERROR;
};
SizeOfBits: PUBLIC PROC [bits: YggRep.Bits] RETURNS [size: CARD] ~ {
Size in bytes of an "uninterpreted bytes" object.
WITH bits SELECT FROM
rBits: REF YggRep.BitsRep => {
RETURN[rBits.length];
};
ENDCASE => ERROR;
};
SetSizeOfBits: PUBLIC PROC [bits: YggRep.Bits, size: CARD] RETURNS [newRef: BOOL ← FALSE, newBits: YggRep.Bits ← NIL] ~ {
Set the size in bytes of an "uninterpreted bytes" object. If this grows the object, the new bytes are uninitalized. This may grow the object and change its representation. All callers must look at the newRef and newBits return values. If newRef is TRUE, then the old bits object is no longer valid. The caller is responsible for updating the data structure from which it obtained the bits.
WITH bits SELECT FROM
rBits: REF YggRep.BitsRep => {
newBits: REF YggRep.BitsRep ← NIL;
wordLen: INT;
IF size <= rBits.length THEN {rBits.validBytes ← size; RETURN [FALSE, NIL]; };
wordLen ← ((rBits.length - 1 + Basics.charsPerWord)/Basics.charsPerWord); -- round up to words
wordLen ← IF wordLen < 20 THEN wordLen ← wordLen + 1 ELSE wordLen + wordLen/20;
rBits ← NEW[YggRep.BitsRep[Basics.charsPerWord * wordLen]];
TRUSTED {
nBytes: CARD;
nBytes ← Basics.ByteBlt[
from: [blockPointer: LOOPHOLE[rBits, POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes],
to: [blockPointer: LOOPHOLE[newBits, POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes]
];
IF nBytes # rBits.validBytes THEN ERROR;
newBits.validBytes ← size;
};
RETURN[TRUE, newBits];
};
ENDCASE => ERROR;
};
BytesToBits: PUBLIC PROC [bits: YggRep.Bits, startByte: CARD, block: Basics.UnsafeBlock] RETURNS [newRef: BOOL ← FALSE, newBits: YggRep.Bits ← NIL] ~ {
Store some bytes into an uninterpreted bytes" object. This may grow the object and change its representation. All callers must look at the newRef and newBits return values. If newRef is TRUE, then the old bits object is no longer valid. The caller is responsible for updating the data structure from which it obtained the bits.
WITH bits SELECT FROM
rBits: REF YggRep.BitsRep => {
IF startByte + block.count <= rBits.length THEN { -- it fits in the current object
nBytes: CARD;
TRUSTED {nBytes ← Basics.ByteBlt[
from: [blockPointer: LOOPHOLE[block.base], startIndex: block.startIndex, stopIndexPlusOne: block.startIndex + block.count],
to: [blockPointer: LOOPHOLE[rBits, POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: startByte, stopIndexPlusOne: startByte + block.count]
]; };
IF nBytes # rBits.validBytes THEN ERROR;
rBits.validBytes ← MAX[rBits.validBytes, startByte + block.count];
RETURN[FALSE, NIL];
}
ELSE {
newBits: REF YggRep.BitsRep ← NIL;
wordLen: INT;
wordLen ← ((rBits.length - 1 + Basics.charsPerWord)/Basics.charsPerWord); -- round up to words
wordLen ← IF wordLen < 20 THEN wordLen ← wordLen + 1 ELSE wordLen + wordLen/20;
rBits ← NEW[YggRep.BitsRep[Basics.charsPerWord * wordLen]];
TRUSTED {
nBytes: CARD;
nBytes ← Basics.ByteBlt[
from: [blockPointer: LOOPHOLE[rBits, POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes],
to: [blockPointer: LOOPHOLE[newBits, POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes]
];
IF nBytes # rBits.validBytes THEN ERROR;
nBytes ← Basics.ByteBlt[
from: [blockPointer: block.base, startIndex: block.startIndex, stopIndexPlusOne: block.startIndex + block.count],
to: [blockPointer: LOOPHOLE[newBits, POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: startByte, stopIndexPlusOne: startByte + block.count]
];
IF nBytes # rBits.validBytes THEN ERROR;
newBits.validBytes ← startByte + block.count;
};
RETURN[TRUE, newBits];
};
};
ENDCASE => ERROR;
};
END.