1+ function compress ( input ) {
2+ if ( input === null || input === undefined || input === "" ) // Handling empty input.
3+ return "" ;
4+ 5+ let dic = { } ;
6+ let character = w = wc = output = "" ;
7+ let enlargeIn = bitsCount = 2 ;
8+ let dictSize = 3 ;
9+ let val = pos = 0 ;
10+ 11+ function encode ( bitsCount , v , noShift ) {
12+ let m = noShift ? 0xFFFFFFFFFFFF : 1 ; // dictionary wont go over 48Bits???
13+ 14+ for ( let i = 0 ; i < bitsCount ; ++ i ) {
15+ val = ( val << 1 ) | ( v & m ) ;
16+ 17+ if ( pos === 15 ) {
18+ pos = 0 ;
19+ output += String . fromCharCode ( val ) ;
20+ val = 0 ;
21+ } else
22+ pos ++ ;
23+ 24+ if ( noShift )
25+ v = 0 ;
26+ else
27+ v >>= 1 ;
28+ }
29+ }
30+ 31+ for ( let i = 0 ; i < input . length ; ++ i ) {
32+ character = input . charAt ( i ) ;
33+ 34+ if ( dic [ character ] === undefined )
35+ dic [ character ] = {
36+ size : dictSize ++ ,
37+ create : true
38+ } ;
39+ wc = w + character ;
40+ 41+ if ( dic [ wc ] !== undefined )
42+ w = wc ;
43+ else {
44+ if ( dic [ w ] . create ) {
45+ if ( w . charCodeAt ( 0 ) < 256 ) {
46+ encode ( bitsCount , 0 ) ;
47+ encode ( 8 , w . charCodeAt ( 0 ) ) ;
48+ } else {
49+ encode ( bitsCount , 1 , true )
50+ encode ( 16 , w . charCodeAt ( 0 ) ) ;
51+ }
52+ enlargeIn -- ;
53+ 54+ if ( enlargeIn === 0 ) {
55+ enlargeIn = Math . pow ( 2 , bitsCount ) ;
56+ bitsCount ++ ;
57+ }
58+ dic [ w ] . create = false ;
59+ } else
60+ encode ( bitsCount , dic [ w ] . size ) ;
61+ enlargeIn -- ;
62+ 63+ if ( enlargeIn === 0 ) {
64+ enlargeIn = Math . pow ( 2 , bitsCount ) ;
65+ bitsCount ++ ;
66+ }
67+ 68+ if ( dic [ wc ] !== undefined )
69+ dic [ wc ] . size = dictSize ++ ;
70+ else
71+ dic [ wc ] = {
72+ size : dictSize ++ ,
73+ create : false
74+ } ;
75+ w = String ( character ) ;
76+ }
77+ }
78+ 79+ if ( w !== "" ) {
80+ if ( dic [ w ] . create ) {
81+ if ( w . charCodeAt ( 0 ) < 256 ) {
82+ encode ( bitsCount , 0 ) ;
83+ encode ( 8 , w . charCodeAt ( 0 ) ) ;
84+ } else {
85+ encode ( bitsCount , 1 , true )
86+ encode ( 16 , w . charCodeAt ( 0 ) ) ;
87+ }
88+ enlargeIn -- ;
89+ 90+ if ( enlargeIn === 0 ) {
91+ enlargeIn = Math . pow ( 2 , bitsCount ) ;
92+ bitsCount ++ ;
93+ }
94+ dic [ w ] . create = false ;
95+ } else
96+ encode ( bitsCount , dic [ w ] . size ) ;
97+ enlargeIn -- ;
98+ 99+ if ( enlargeIn === 0 ) {
100+ enlargeIn = Math . pow ( 2 , bitsCount ) ;
101+ bitsCount ++ ;
102+ }
103+ }
104+ encode ( bitsCount , 2 ) ;
105+ 106+ while ( true ) {
107+ val <<= 1 ;
108+ 109+ if ( pos == 15 ) {
110+ output += String . fromCharCode ( val ) ;
111+ break ;
112+ } else
113+ pos ++ ;
114+ }
115+ return output ;
116+ }
117+ 118+ function decompress ( input ) {
119+ if ( input === null || input === "" || input === undefined ) // Handling empty input.
120+ return "" ;
121+ 122+ let w ;
123+ let s = [ 256 , 65536 ] ;
124+ let dic = [ 0 , 1 , 2 ] ;
125+ let enlargeIn = dicSize = 4 ;
126+ let bitsCount = 3 ;
127+ let character = entry = result = "" ;
128+ let pos = 32768 ;
129+ let index = 1 ;
130+ let val = input . charCodeAt ( 0 ) ;
131+ 132+ function decode ( maxP ) {
133+ let p = 1 ,
134+ b = 0 ;
135+ 136+ while ( p != maxP ) {
137+ b |= ( ( val & pos ) > 0 ? 1 : 0 ) * p ;
138+ p <<= 1 ;
139+ pos >>= 1 ;
140+ 141+ if ( pos === 0 ) {
142+ pos = 32768 ;
143+ val = input . charCodeAt ( index ++ ) ;
144+ }
145+ }
146+ return b ;
147+ }
148+ 149+ let bits = decode ( 4 ) ;
150+ 151+ if ( bits === 2 )
152+ return "" ;
153+ else if ( bits < 2 )
154+ character = String . fromCharCode ( decode ( s [ bits ] ) ) ;
155+ dic [ 3 ] = w = result = character ;
156+ 157+ while ( true ) {
158+ if ( index > input . length )
159+ return "" ;
160+ character = bits = decode ( Math . pow ( 2 , bitsCount ) ) ;
161+ 162+ if ( bits === 2 )
163+ return result ;
164+ else if ( bits < 2 ) {
165+ bits = decode ( s [ bits ] ) ;
166+ dic [ dicSize ++ ] = String . fromCharCode ( bits ) ;
167+ character = dicSize - 1 ;
168+ enlargeIn -- ;
169+ }
170+ 171+ if ( enlargeIn === 0 ) {
172+ enlargeIn = Math . pow ( 2 , bitsCount ) ;
173+ bitsCount ++ ;
174+ }
175+ 176+ if ( dic [ character ] )
177+ entry = dic [ character ] ;
178+ else {
179+ if ( character === dicSize )
180+ entry = w + w . charAt ( 0 ) ;
181+ else
182+ return "" ;
183+ }
184+ 185+ result += entry ;
186+ dic [ dicSize ++ ] = w + entry . charAt ( 0 ) ;
187+ enlargeIn -- ;
188+ w = entry ;
189+ 190+ if ( enlargeIn === 0 ) {
191+ enlargeIn = Math . pow ( 2 , bitsCount ) ;
192+ bitsCount ++ ;
193+ }
194+ }
195+ }
196+ 197+ module . exports = {
198+ compress,
199+ decompress
200+ }
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