DIRECTORYBasics USING [bytesPerWord],Checksum USING [ComputeChecksum],Rope,RopePrivate,RopeHash USING [PureText],RefText USING [ObtainScratch, ReleaseScratch];RopeHashImpl: CEDAR PROGRAMIMPORTS Checksum, Rope, RopePrivate, RefTextEXPORTS RopeHashSHARES Rope= BEGIN OPEN RopeHash;ROPE: TYPE = Rope.ROPE;Text: TYPE = Rope.Text;defaultSeed: CARDINAL = 31415;bytesPerWord: NAT = Basics.bytesPerWord;bufSize: NAT = 128*bytesPerWord;TextSize: NAT = SIZE[TEXT[0]];WordAsChars: TYPE = PACKED ARRAY [0..bytesPerWord) OF CHAR;FromRefText: PUBLIC PROC [text: PureText, seed: CARDINAL] RETURNS [hash: CARDINAL] = TRUSTED {len: NAT _ text.length;nLeft: NAT = len MOD bytesPerWord;nWhole: NAT = len - nLeft;p: LONG POINTER = LOOPHOLE[text, LONG POINTER] + TextSize;hash _ seed;IF nWhole >= bytesPerWord THEN {hash _ Checksum.ComputeChecksum[hash, nWhole/bytesPerWord, p];};IF nLeft # 0 THEN TRUSTED {leftovers: WordAsChars _ ALL[0C];FOR j: NAT IN [0..nLeft) DOleftovers[j] _ Rope.QFetch[LOOPHOLE[text], nWhole+j];ENDLOOP;hash _ Checksum.ComputeChecksum[hash, SIZE[WordAsChars], @leftovers];};};FromRope: PUBLIC PROC [rope: ROPE, case: BOOL, start: INT, len: INT, seed: CARDINAL] RETURNS [hash: CARDINAL] = TRUSTED {rem: INT _ RopePrivate.NonNeg[Rope.InlineLength[rope] - RopePrivate.NonNeg[start]];IF rem < len THEN len _ rem;IF case AND start = 0 AND rem = len THEN WITH rope SELECT FROMtext: Text => RETURN[FromRefText[LOOPHOLE[text], seed]];ENDCASE;{buf: REF TEXT _ RefText.ObtainScratch[bufSize];p: LONG POINTER = LOOPHOLE[buf, LONG POINTER] + SIZE[TEXT[0]];bytes: NAT _ 0;hash _ seed;WHILE rem > 0 DObuf.length _ 0;bytes _ Rope.AppendChars[buf, rope, start, rem];IF NOT case THENFOR i: NAT IN [0..bytes) DOc: CHAR = Rope.QFetch[LOOPHOLE[buf], i];IF c <= 'Z AND c >= 'A THEN RopePrivate.QStore[c + ('a-'A), LOOPHOLE[buf], i];ENDLOOP;hash _ FromRefText[buf, hash];start _ start + bytes;rem _ rem - bytes;ENDLOOP;RefText.ReleaseScratch[buf];RETURN [hash];};};END.   ~  RopeHashImpl.mesaCopyright (C) 1984, 1985 Xerox Corporation.  All rights reserved.Michael Plass, January 18, 1985 12:48:44 pm PSTRuss Atkinson (RRA) May 15, 1985 2:38:58 pm PDTLimit len to be at worst the remainder of the stringIf case does not matter, and we have a flat rope, and the whole rope is to be hashed, then we have the fast case.In the hard case we have to move the bytes from the rope into a buffer, adjust the buffer for lower case, then perform the checksum on the buffer.  We keep doing this until there are no more chars to be moved.Make the buffer lower case.  We avoid bounds checking to speed things up. Э╩ж  Ш codeЩKЩAKЩ/KЩ/ЧKШ Ъ╧k	Ш	KЪЬЭЬШKЪЬ	ЭЬШ!KЪЬШKЪЬШKЪЬ	ЭЬШKЪЬЭЬ!Ш.KШ ЧЪЬЭШKЪЭЬ%Ш,KЪЭЬ	ШKЪЭЬШЪЬЭЬЭЬ
ШKШ ЧKЪЭЬЭЬЭЬШKЪЬЭЬШKЪЬЭЬ	ШKЪЬЭЬШ(KЪЬ	ЭЬШ KШ KЪЬ
ЭЬЭЬЭЬШЪЬЭЬЭЬЭЬЭЬЭЬШ;KШ ЧЪ╧nЬЭЬЭЬЭЬЭЬЭЬЭЬШ^KЪЬЭЬШKЪЬЭЬЭЬШ"KЪЬЭЬШKЪЬЭЬЭЬЭЬЭЬЭЬШ:KЪЬШЪЭЬЭЬШ KЪЬ>Ш>KШЧЪЭЬЭЬЭЬШKЪЬЭЬШ!ЪЭЬЭЬЭЬЭШKЪЬЭЬШ5KЪЭЬШЧKЪЬ&ЭЬШEKШЧKЪЬШKШ ЧЪЮЬЭЬЭЬЭЬЭЬ	ЭЬЭЬЭЬЭЬЭЬЭЬШyKЪЬЭЬKШSЪЭЬЭЬШKЪЬ4Щ4ЧЪЭЬЭЬЭЬЭЬЭЬЭЬЭШ>ЪЬШKЪЬqЩqKЪЭЬЭЬШ*ЧKЪЭЬШЧЪЬШKЪЬ╤Щ╤KЪЬЭЬЭЬ"Ш/KЪЬЭЬЭЬЭЬЭЬЭЬЭЬЭЬШ>KЪЬЭЬШKЪЬШЪЭЬ	ЭШKЪЬШKЪЬ0Ш0ЪЭЬЭЬЭШKЪЬIЩIЪЭЬЭЬЭЬЭШKЪЬЭЬЭЬ
Ш(KЪЭЬ	ЭЬ	ЭЬ!ЭЬ
ШNKЪЭЬШЧЧKЪЬШKЪЬШKЪЬШKЪЭЬШЧKЪЬШKЪЭЬШKЪЬШЧKЪЬШKШ ЧKЪЭЬШKШ ЧЧ ЕЧ    ъ    