
    <<DocCacheImpl.mesa>>
        <<Copyright Ó 1990, 1992 by Xerox Corporation.  All rights reserved.>>
        <<Mike Spreitzer July 27, 1990 9:22 am PDT>>
        <<Willie-s, April 3, 1992 5:44 pm PST>>

    DIRECTORY Basics, DocCache, PFS, PFSNames, SymTab, RedBlackTree, Rope, TiogaIO, TiogaOps, ViewerClasses, ViewerOps;

    DocCacheImpl: CEDAR MONITOR
        IMPORTS PFS, PFSNames, SymTab, RedBlackTree, Rope, TiogaIO, TiogaOps, ViewerOps
        EXPORTS DocCache
        =

    BEGIN OPEN DocCache;

    byRef: RedBlackTree.Table = RedBlackTree.Create[GetRef, CompareRef];
    byName: SymTab.Ref = SymTab.Create[case: FALSE];
    lastRef: INT ¬ FIRST[INT];
    lastFile: ROPE ¬ NIL;
    lastDoc: TiogaNode ¬ NIL;
    cacheLimit: NAT ¬ 10;

    GetRef: PROC [data: REF ANY] RETURNS [key: REF INT] --RedBlackTree.GetKey-- = {
        e: Entry = NARROW[data];
        key ¬ e.ref;
        };

    CompareRef: PROC [k, data: REF ANY] RETURNS [c: Basics.Comparison] --RedBlackTree.Compare-- = {
        k1: REF INT = NARROW[k];
        k2: REF INT = GetRef[data];
        c ¬ SELECT k1­ FROM
            < k2­ => less,
            = k2­ => equal,
            > k2­ => greater,
            ENDCASE => ERROR;
        };

    Entry: TYPE = REF EntryPrivate;
    EntryPrivate: TYPE = RECORD [
        fullFileName: ROPE,
        doc: TiogaNode,
        ref: REF INT
        ];

    GetDoc: PUBLIC PROC [fileName: ROPE] RETURNS [doc: TiogaNode] = {
        fullFileName: ROPE; --for debugging, until Cirio can read PFS.PATHs
        fullPath: PFS.PATH;
        short: PFSNames.Component;
        Search: PROC [v: ViewerClasses.Viewer] RETURNS [continue: BOOL ¬ TRUE]--ViewerOps.EnumProc-- = {
            IF v.file.Equal[fullFileName, FALSE] AND v.class.flavor = $Text THEN {
                tor: TiogaOps.Ref = TiogaOps.ViewerDoc[v];
                IF tor # NIL THEN {
                    TRUSTED {doc ¬ LOOPHOLE[tor]};
                    continue ¬ FALSE;
                    };
                };
            };
        GetFromCache: ENTRY PROC = {
            ENABLE UNWIND => {
                byRef.DestroyTable[];
                byName.Erase[];
                lastRef ¬ FIRST[INT]};
            e: Entry;
            IF fullFileName.Equal[lastFile, FALSE] THEN {doc ¬ lastDoc; RETURN};
            e ¬ NARROW[byName.Fetch[fullFileName].val];
            IF e = NIL THEN {
                doc ¬ TiogaIO.FromFile[PFS.PathFromRope[fullFileName] ! TiogaIO.Error, PFS.Error => CONTINUE].root;
                IF doc=NIL THEN RETURN;
                e ¬ NEW [EntryPrivate ¬ [
                    fullFileName,
                    doc,
                    NEW [INT ¬ lastRef ¬ lastRef + 1]
                    ]];
                WHILE byRef.Size[] >= cacheLimit DO
                    lru: Entry = NARROW[byRef.LookupSmallest[]];
                    [] ¬ byRef.Delete[lru.ref];
                    [] ¬ byName.Delete[lru.fullFileName];
                    ENDLOOP;
                IF NOT byName.Insert[fullFileName, e] THEN ERROR;
                byRef.Insert[e, e.ref];
                }
            ELSE {
                doc ¬ e.doc;
                [] ¬ byRef.Delete[e.ref];
                e.ref­ ¬ lastRef ¬ lastRef + 1;
                byRef.Insert[e, e.ref];
                };
            lastFile ¬ fullFileName;
            lastDoc ¬ doc;
            };
        doc ¬ NIL;
        {ENABLE PFS.Error => {doc ¬ NIL; CONTINUE};
        fullPath ¬ PFS.AbsoluteName[PFS.PathFromRope[fileName]];
        short ¬ fullPath.ShortName[];
        IF short.version = [none] THEN fullPath ¬ PFS.FileInfo[fullPath].fullFName;
        fullFileName ¬ PFS.RopeFromPath[fullPath];
        ViewerOps.EnumerateViewers[Search];
        IF doc # NIL THEN RETURN;
        GetFromCache[];
        }};

    END.