Initial functionality of untar

+ Added skeleton "Tar" operation with no functionality
+ Added intial functionality of "Untar"
+ Added a function in `Utils` `HTMLFormat` to generalize HTML generation
of files and folders (could later be used in Unzip).

I had a brief search for a small library for tar and untar operations,
however they were mostly for node (if anyone finds one we can drop in
that would be appreciated) or unmaintained. Luckily the tar spec is
relatively easy to understand just from Wikipedia.

src/js/operations/Compress.js

@@ -345,5 +345,113 @@ var Compress = {
         plain = bzip2.simple(bzip2Reader);
         return plain;
     },
-    
+
+
+    /**
+     * @constant
+     * @default
+     */
+    TAR_FILENAME: "file.txt",
+
+
+    /**
+     * Tar unpack operation.
+     *
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {byteArray}
+     */
+    tar: function(input, args) {
+        // Not implemented yet
+        return input;
+    },
+
+
+    /**
+     * Untar unpack operation.
+     *
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {html}
+     */
+    untar: function(input, args) {
+        var Stream = function(input) {
+            this.bytes = input;
+            this.position = 0;
+        };
+
+        Stream.prototype.readString = function(numBytes) {
+            var result = "";
+            for(var i = this.position; i < this.position + numBytes; i++) {
+                var currentByte = this.bytes[i];
+                if(currentByte === 0) break;
+                result += String.fromCharCode(currentByte);
+            }
+            this.position += numBytes;
+            return result;
+        };
+
+        Stream.prototype.readInt = function(numBytes, base) {
+            var string = this.readString(numBytes);
+            return parseInt(string, base);
+        };
+
+        Stream.prototype.hasMore = function() {
+            return this.position < this.bytes.length;
+        };
+
+        var stream = new Stream(input),
+            files = [];
+
+        while(stream.hasMore()) {
+            var dataPosition = stream.position + 512;
+
+            var file = {
+                fileName: stream.readString(100),
+                fileMode: stream.readString(8),
+                ownerUID: stream.readString(8),
+                ownerGID: stream.readString(8),
+                size: parseInt(stream.readString(12), 8), // Octal
+                lastModTime: new Date(1000 * stream.readInt(12, 8)), // Octal
+                checksum: stream.readString(8),
+                type: stream.readString(1),
+                linkedFileName: stream.readString(100),
+                USTARFormat: stream.readString(6).indexOf("ustar") >= 0,
+            };
+
+            if(file.USTARFormat) {
+                file.version = stream.readString(2);
+                file.ownerUserName = stream.readString(32);
+                file.ownerGroupName = stream.readString(32);
+                file.deviceMajor = stream.readString(8);
+                file.deviceMinor = stream.readString(8);
+                file.filenamePrefix = stream.readString(155);
+            }
+
+            stream.position = dataPosition;
+
+            if(file.type === "0") {
+                // File
+                files.push(file);
+                var endPosition = stream.position + file.size;
+                if(file.size % 512 !== 0) {
+                    endPosition += 512 - (file.size % 512);
+                }
+
+                file.contents = "";
+
+                while(stream.position < endPosition) {
+                    file.contents += stream.readString(512);
+                }
+            } else if(file.type === "5") {
+                // Directory
+                files.push(file);
+            } else {
+                // Symlink or empty bytes
+            }
+        }
+
+        var output = Utils.HTMLFiles(files);
+        return output;
+    },
 };