Add LRU cache for generated parsers to FnInvisibleXml

[GuntherRademacher]

This PR adds an LRU cache for Markup-Blitz-generated parsers to FnInvisibleXml (generated parsers are stateless and safe to share concurrently). The cache is limited to a fixed size of 15.

The XQuery code below can be used to demonstrate the performance difference that is gained by adding the cache. It repeatedly parses a number of small documents with a JSON grammar (returning the count of result nodes). It runs about 20 times faster with the cache.

JSON parser cache benchmark

declare variable $n external := 100;

declare variable $grammar := ``[        -json: ws, -value, ws.
        value: map;
               array;
               number;
               string;
               boolean;
               null.
      boolean: 'false';
               'true'.
         null: -'null'.
          map: -'{', ws, (member, ws)**(-',', ws), -'}'.
       member: key, ws, -':', ws, value.
          key: -string.
        array: -'[', ws, (-value, ws)**(-',', ws), -']'.
       number: '-'?, int, frac?, exp?.
    -digit1-9: ['1'-'9'].
           -e: ['eE'].
         -exp: e, ['-+']?, DIGIT+.
        -frac: '.', DIGIT+.
         -int: '0';
               digit1-9, DIGIT*.
       string: -'"', char*, -'"'.
        -char: ~['"\'; #9; #a; #d];
               -'\', escaped.
     -escaped: '"';
               '\';
               '/';
               -'b', +#8;
               -'f', +#c;
               -'n', +#a;
               -'r', +#d;
               -'t', +#9;
               unicode.
      unicode: -'u', code.
        @code: HEXDIG, HEXDIG, HEXDIG, HEXDIG.
       -DIGIT: ['0'-'9'].
      -HEXDIG: DIGIT;
               ['a'-'f'; 'A'-'F'].
          -ws: -[' '; #9; #a; #d]*.
]``;

declare variable $documents := (
  '{"id":1,"ok":true,"tag":"a"}',
  '{"id":2,"ok":false,"tag":"bb"}',
  '{"n":3,"name":"alfa","v":0}',
  '{"n":4,"name":"bravo","v":12}',
  '{"city":"Bonn","temp":21.5}',
  '{"city":"Kiel","rain":false}',
  '{"a":[1,2,3],"b":"short"}',
  '{"a":[true,false],"b":null}',
  '{"user":"ana","roles":["r"]}',
  '{"user":"bert","roles":["r","w"]}',
  '{"x":-17,"y":42,"unit":"m"}',
  '{"x":0.125,"y":-4,"unit":"m"}',
  '{"code":"A-17","active":true}',
  '{"code":"B-29","active":false}',
  '{"k":"plain","items":[1,1,2]}',
  '{"k":"quote","text":"hello"}',
  '{"path":"/a/b","depth":2}',
  '{"path":"/alpha/beta","depth":2}',
  '{"hex":"00ff","bytes":[0,255]}',
  '{"hex":"cafe","bytes":[202,254]}',
  '{"date":"2026-08-29","z":0}',
  '{"date":"2025-01-01","z":1}',
  '{"flag":true,"score":99.75}',
  '{"flag":false,"score":12.5}',
  '{"meta":{"a":1},"list":[2,3]}',
  '{"meta":{"b":2},"list":[4,5]}',
  '{"s":"escape\\nline","ok":true}',
  '{"s":"slash\\/path","ok":true}',
  '{"u":"\\u0041","name":"unicode"}',
  '{"u":"\\u20ac","name":"euro"}',
  '{"mix":[null,true,3,"x"]}',
  '{"mix":[false,null,4,"yy"]}',
  '{"title":"Small JSON sample","count":7}',
  '{"title":"Another compact sample","count":8}',
  '{"bounds":{"min":1,"max":9},"closed":true}',
  '{"bounds":{"min":-2,"max":11},"closed":false}',
  '{"points":[{"x":1,"y":2},{"x":3,"y":4}]}',
  '{"points":[{"x":-1,"y":0},{"x":5,"y":8}]}',
  '{"catalog":"a","ids":[101,102,103],"valid":true}',
  '{"catalog":"b","ids":[201,202,203],"valid":false}',
  '{"message":"this is still a tiny json document"}',
  '{"message":"small payloads make parser setup visible"}',
  '{"array":[10,20,30,40,50],"label":"five"}',
  '{"array":[5,4,3,2,1],"label":"reverse"}',
  '{"nested":{"left":{"v":1},"right":{"v":2}}}',
  '{"nested":{"left":{"v":3},"right":{"v":4}}}',
  '{"name":"delta","tags":["red","green"],"rank":4}',
  '{"name":"echo","tags":["blue","gray"],"rank":5}',
  '{"config":{"retry":3,"delay":1.25},"enabled":true}',
  '{"config":{"retry":5,"delay":0.75},"enabled":false}',
  '{"records":[{"id":1},{"id":2},{"id":3}],"page":1}',
  '{"records":[{"id":4},{"id":5},{"id":6}],"page":2}',
  '{"text":"abcdefghijklmnopqrstuvwxyz","len":26}',
  '{"text":"ABCDEFGHIJKLMNOPQRSTUVWXYZ","len":26}',
  '{"route":["start","middle","end"],"cost":14}',
  '{"route":["north","east","south"],"cost":21}',
  '{"sensor":"alpha-01","values":[0.1,0.2,0.3]}',
  '{"sensor":"beta-02","values":[9.8,9.7,9.6]}',
  '{"long":"012345678901234567890123456789","ok":true}',
  '{"long":"abcdefghijklmnopqrstuvwxyzzzzzzzz","ok":false}',
  '{"obj":{"a":[1,2],"b":{"c":"d"}},"tail":null}',
  '{"obj":{"a":[3,4],"b":{"c":"e"}},"tail":true}',
  '{"final":64,"payload":{"name":"last","items":[1,2,3]}}',
  '{"final":65,"payload":{"name":"extra","items":[4,5,6]}}'
);

declare function local:parse($input as xs:string) {
  invisible-xml($grammar, { 'fail-on-error': true() })($input)//*
};

prof:time(
    (1 to $n)
    ! $documents
    =!> local:parse()
    => count()
    => sum()
)