YggBitsImpl.mesa
Copyright Ó 1988 by Xerox Corporation. All rights reserved.
Bob Hagmann October 27, 1988 11:06:52 am PDT
This module implements the Bits datatype.
DIRECTORY
PBasics USING [ByteBlt, charsPerWord, RawBytes, UnsafeBlock],
Rope USING [ROPE],
YggRep USING [Bits, BitsRep];
YggBitsImpl: CEDAR PROGRAM
IMPORTS PBasics
EXPORTS YggRep
~ BEGIN
ROPE: TYPE ~ Rope.ROPE;
Exported procedures
BytesFromBits: PUBLIC PROC [bits: YggRep.Bits, startByte: CARD, block: PBasics.UnsafeBlock] ~ {
Fetch some bytes from an "uninterpreted bytes" object
WITH bits SELECT FROM
rBits: REF YggRep.BitsRep => TRUSTED {
nBytes: CARD;
IF rBits.length >= startByte + CARD[block.count] THEN ERROR;
nBytes ← PBasics.ByteBlt[
from: [blockPointer: LOOPHOLE[rBits, LONG 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 # CARD[block.count] THEN ERROR;
};
ENDCASE => ERROR;
};
BitsFromBits: PUBLIC PROC [bits: YggRep.Bits] RETURNS [copy: YggRep.Bits] ~ {
Fetch some bytes from an "uninterpreted bytes" object
WITH bits SELECT FROM
rBits: REF YggRep.BitsRep => TRUSTED {
bitsCopy: REF YggRep.BitsRep;
IF rBits.length < rBits.validBytes THEN ERROR;
copy ← bitsCopy ← NEW[YggRep.BitsRep[rBits.length]];
TRUSTED {
nBytes: CARD;
nBytes ← PBasics.ByteBlt[
from: [blockPointer: LOOPHOLE[rBits, LONG POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes],
to: [blockPointer: LOOPHOLE[bitsCopy, LONG POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes]
];
IF nBytes # rBits.validBytes THEN ERROR;
bitsCopy.validBytes ← rBits.validBytes;
};
};
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 If newRef is TRUE, then the old bits object is no longer valid.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 => {
wordLen: INT;
newBitsR: REF YggRep.BitsRep;
IF size <= rBits.length THEN {rBits.validBytes ← size; RETURN [FALSE, NIL]; };
wordLen ← ((rBits.length - 1 + PBasics.charsPerWord)/PBasics.charsPerWord); -- round up to words
wordLen ← IF wordLen < 20 THEN wordLen ← wordLen + 1 ELSE wordLen + wordLen/20;
newBitsR ← newBits ← NEW[YggRep.BitsRep[PBasics.charsPerWord * wordLen]];
TRUSTED {
nBytes: CARD;
nBytes ← PBasics.ByteBlt[
from: [blockPointer: LOOPHOLE[rBits, LONG POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes],
to: [blockPointer: LOOPHOLE[newBits, LONG POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes]
];
IF nBytes # rBits.validBytes THEN ERROR;
newBitsR.validBytes ← size;
};
RETURN[TRUE, newBits];
};
ENDCASE => ERROR;
};
BytesToBits: PUBLIC PROC [bits: YggRep.Bits, startByte: CARD, block: PBasics.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 + CARD[block.count] <= rBits.length THEN { -- it fits in the current object
nBytes: CARD;
TRUSTED {nBytes ← PBasics.ByteBlt[
from: [blockPointer: LOOPHOLE[block.base], startIndex: block.startIndex, stopIndexPlusOne: block.startIndex + block.count],
to: [blockPointer: LOOPHOLE[rBits, LONG POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: startByte, stopIndexPlusOne: startByte + block.count]
]; };
IF nBytes # rBits.validBytes THEN ERROR;
rBits.validBytes ← MAX[rBits.validBytes, startByte + CARD[block.count]];
RETURN[FALSE, NIL];
}
ELSE {
newBits: REF YggRep.BitsRep ← NIL;
wordLen: INT;
wordLen ← ((rBits.length - 1 + PBasics.charsPerWord)/PBasics.charsPerWord); -- round up to words
wordLen ← IF wordLen < 20 THEN wordLen ← wordLen + 1 ELSE wordLen + wordLen/20;
rBits ← NEW[YggRep.BitsRep[PBasics.charsPerWord * wordLen]];
TRUSTED {
nBytes: CARD;
nBytes ← PBasics.ByteBlt[
from: [blockPointer: LOOPHOLE[rBits, LONG POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes],
to: [blockPointer: LOOPHOLE[newBits, LONG POINTER] + SIZE[YggRep.BitsRep[0]], startIndex: 0, stopIndexPlusOne: rBits.validBytes]
];
IF nBytes # rBits.validBytes THEN ERROR;
nBytes ← PBasics.ByteBlt[
from: [blockPointer: block.base, startIndex: block.startIndex, stopIndexPlusOne: block.startIndex + block.count],
to: [blockPointer: LOOPHOLE[newBits, LONG 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.