March 2014 update

Task/LZW-compression/D/lzw-compression-1.d

@@ -1,31 +1,31 @@
 import std.stdio, std.array;
 
-auto compress(string original) {
+auto compress(in string original) pure nothrow {
     int[string] dict;
-    foreach (b; 0 .. 256)
-        dict[[cast(immutable char)b]] = b;
+    foreach (immutable char c; char.min .. char.max + 1)
+        dict[[c]] = c;
 
     string w;
     int[] result;
-    foreach (ch; original)
+    foreach (immutable ch; original)
         if (w ~ ch in dict)
             w = w ~ ch;
         else {
             result ~= dict[w];
-            dict[w ~ ch] = dict.length - 1;
+            dict[w ~ ch] = dict.length;
             w = [ch];
         }
     return w.empty ? result : (result ~ dict[w]);
 }
 
-auto decompress(int[] compressed) {
-    auto dict = new string[256];
-    foreach (b; 0 .. 256)
-        dict[b] = [cast(char)b];
+auto decompress(in int[] compressed) pure nothrow {
+    auto dict = new string[char.max - char.min + 1];
+    foreach (immutable char c; char.min .. char.max + 1)
+        dict[c] = [c];
 
     auto w = dict[compressed[0]];
     auto result = w;
-    foreach (k; compressed[1 .. $]) {
+    foreach (immutable k; compressed[1 .. $]) {
         auto entry = (k < dict.length) ? dict[k] : w ~ w[0];
         result ~= entry;
         dict ~= w ~ entry[0];
@@ -35,6 +35,6 @@ auto decompress(int[] compressed) {
 }
 
 void main() {
-    auto comp = compress("TOBEORNOTTOBEORTOBEORNOT");
-    writeln(comp, "\n", decompress(comp));
+    auto comp = "TOBEORNOTTOBEORTOBEORNOT".compress;
+    writeln(comp, "\n", comp.decompress);
 }

Task/LZW-compression/D/lzw-compression-2.d

@@ -10,8 +10,8 @@ struct LZW {
     enum int initDictSize = 256;
     static immutable ubyte[initDictSize] bytes;
     static this() {
-        foreach (immutable i; 0 .. initDictSize)
-            bytes[i] = cast(T)i; //*
+        foreach (immutable T i; 0 .. initDictSize)
+            bytes[i] = i;
     }
 
     static Tcomp[] compress(immutable scope T[] original) pure nothrow

Task/LZW-compression/Groovy/lzw-compression-1.groovy

@@ -0,0 +1,33 @@
+def compress = { text ->
+    def dictionary = (1..255).inject([:]) { map, ch -> map."${(char)ch}" = ch; map }
+    def w = '', compressed = []
+    text.each { ch ->
+        def wc = "$w$ch"
+        if (dictionary[wc]) {
+            w = wc
+        } else {
+            compressed << dictionary[w]
+            dictionary[wc] = dictionary.size() + 1
+            w = "$ch"
+        }
+    }
+    if (w) { compressed << dictionary[w] }
+    compressed
+}
+
+def decompress = { compressed ->
+    def dictionary = (1..255).inject([:])  { map, ch -> map[ch] = "${(char)ch}"; map }
+    String w = "${(char)compressed.remove(0)}"
+    StringBuffer result = new StringBuffer(w)
+    compressed.each { k ->
+        String entry = dictionary[k]
+        if (!entry) {
+            if (k != dictionary.size()) throw new IllegalArgumentException("Bad compressed k $k")
+            entry = "$w${w[0]}"
+        }
+        result << entry
+        dictionary[dictionary.size() + 1] = "$w${entry[0]}"
+        w = entry
+    }
+    result.toString()
+}

Task/LZW-compression/Groovy/lzw-compression-2.groovy

@@ -0,0 +1,8 @@
+def plaintext = 'TOBEORNOTTOBEORTOBEORNOT'
+def compressed = compress(plaintext)
+def result = decompress(compressed)
+
+println """\
+    Plaintext:    '$plaintext'
+    Compressed:   $compressed
+    Uncompressed: '$result'""".stripIndent()

Task/LZW-compression/Objective-C/lzw-compression-1.m

@@ -9,8 +9,8 @@
     NSUInteger codemark;
 }
 
--(LZWCompressor *) init;
--(LZWCompressor *) initWithArray: (NSMutableArray *) stream;
+-(instancetype) init;
+-(instancetype) initWithArray: (NSMutableArray *) stream;
 -(BOOL) compressData: (NSData *) string;
 -(void) setArray: (NSMutableArray *) stream;
 -(NSArray *) getArray;
@@ -18,7 +18,7 @@
 
 @implementation LZWCompressor : NSObject
 
--(LZWCompressor *) init
+-(instancetype) init
 {
    self = [super init];
    if ( self )
@@ -30,7 +30,7 @@
    return self;
 }
 
--(LZWCompressor *) initWithArray: (NSMutableArray *) stream
+-(instancetype) initWithArray: (NSMutableArray *) stream
 {
    self = [self init];
    if ( self )
@@ -40,51 +40,40 @@
    return self;
 }
 
--(void) dealloc
-{
-   [dict release];
-   [iostream release];
-   [super dealloc];
-}
-
 -(void) setArray: (NSMutableArray *) stream
 {
-   iostream = [stream retain];
+   iostream = stream;
 }
 
 -(BOOL) compressData: (NSData *) string;
 {
-    NSUInteger i;
-    unsigned char j;
-
     // prepare dict
-    for(i=0; i < 256; i++)
+    for(NSUInteger i=0; i < 256; i++)
     {
-       j = i;
+       unsigned char j = i;
        NSData *s = [NSData dataWithBytes: &j length: 1];
-       [dict setObject: [NSNumber numberWithUnsignedInt: i] forKey: s];
+       dict[s] = @(i);
     }
 
-    NSMutableData *w = [NSMutableData data];
-    NSMutableData *wc = [NSMutableData data];
+    NSData *w = [NSData data];
 
-    for(i=0; i < [string length]; i++)
+    for(NSUInteger i=0; i < [string length]; i++)
     {
-       [wc setData: w];
+       NSMutableData *wc = [NSMutableData dataWithData: w];
        [wc appendData: [string subdataWithRange: NSMakeRange(i, 1)]];
-       if ( [dict objectForKey: wc] != nil )
+       if ( dict[wc] != nil )
        {
-          [w setData: wc];
+          w = wc;
        } else {
-          [iostream addObject: [dict objectForKey: w]];
-          [dict setObject: [NSNumber numberWithUnsignedInt: codemark] forKey: wc];
+          [iostream addObject: dict[w]];
+          dict[wc] = @(codemark);
           codemark++;
-          [w setData: [string subdataWithRange: NSMakeRange(i, 1)]];
+          w = [string subdataWithRange: NSMakeRange(i, 1)];
        }
     }
     if ( [w length] != 0 )
     {
-       [iostream addObject: [dict objectForKey: w]];
+       [iostream addObject: dict[w]];
     }
     return YES;
 }

Task/LZW-compression/Objective-C/lzw-compression-2.m

@@ -1,26 +1,21 @@
-const char *text = "TOBEORNOTTOBEORTOBEORNOT";
+NSString *text = @"TOBEORNOTTOBEORTOBEORNOT";
 
 int main()
 {
-  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
+  @autoreleasepool {
+
+    NSMutableArray *array = [[NSMutableArray alloc] init];
+    LZWCompressor *lzw = [[LZWCompressor alloc]
+                          initWithArray: array ];
+    if ( lzw )
+    {
+       [lzw compressData: [text dataUsingEncoding: NSUTF8StringEncoding]];
+       for ( id obj in array )
+       {
+          printf("%u\n", [obj unsignedIntValue]);
+       }
+    }
 
-  NSMutableArray *array = [[NSMutableArray alloc] init];
-  LZWCompressor *lzw = [[LZWCompressor alloc]
-                        initWithArray: array ];
-  if ( lzw )
-  {
-     [lzw compressData: [NSData dataWithBytes: text
-                         length: strlen(text)]];
-     NSEnumerator *en = [array objectEnumerator];
-     id obj;
-     while( (obj = [en nextObject]) )
-     {
-        printf("%u\n", [obj unsignedIntValue]);
-     }
-     [lzw release];
   }
-  [array release];
-
-  [pool release];
   return EXIT_SUCCESS;
 }

Task/LZW-compression/PHP/lzw-compression.php

@@ -0,0 +1,64 @@
+class LZW
+{
+    function compress($unc) {
+        $i;$c;$wc;
+        $w = "";
+        $dictionary = array();
+        $result = array();
+        $dictSize = 256;
+        for ($i = 0; $i < 256; $i += 1) {
+            $dictionary[chr($i)] = $i;
+        }
+        for ($i = 0; $i < strlen($unc); $i++) {
+            $c = $unc[$i];
+            if (property_exists($dictionary, $w.$c)) {
+                $w = $w.$c;
+            } else {
+                array_push($result,$dictionary[$w]);
+                $dictionary[$wc] = $dictSize++;
+                $w = (string)$c;
+            }
+        }
+        if ($w !== "") {
+            array_push($result,$dictionary[$w]);
+        }
+        array_shift($result);
+        return implode(",",$result);
+    }
+
+    function decompress($com) {
+        $com = explode(",",$com);
+        $i;$w;$k;$result;
+        $dictionary = array();
+        $entry = "";
+        $dictSize = 256;
+        for ($i = 0; $i < 256; $i++) {
+            $dictionary[$i] = chr($i);
+        }
+        $w = chr($com[0]);
+        $result = $w;
+        for ($i = 1; $i < count($com);$i++) {
+            $k = $com[$i];
+            if ($dictionary[$k]) {
+                $entry = $dictionary[$k];
+            } else {
+                if ($k === $dictSize) {
+                    $entry = $w.$w[0];
+                } else {
+                    return null;
+                }
+            }
+            $result .= $entry;
+            $dictionary[$dictSize++] = $w + $entry[0];
+            $w = $entry;
+        }
+        return $result;
+    }
+}
+
+//How to use
+$str = 'TOBEORNOTTOBEORTOBEORNOT';
+$lzw = new LZW();
+$com = $lzw->compress($str);
+$dec = $lzw->decompress($com);
+echo $com . "<br>" . $dec;