Implemented RegexBlockStream

src/streamHandler/RegexBlockStream.js

@@ -0,0 +1,65 @@
+const { Transform } = require('stream')
+
+/**
+ * Matches whole blocks as regex and passes them on
+ */
+class RegexBlockStream extends Transform{
+    matcher;
+    withholdLastBlock;
+    matchAllOnFlush;
+
+    /**
+     * @param {RegExp} matcher Block-match - WARNING: It should match a clean-block (including e.g. newline)! Otherwise buffer will get dirty and use more and more ressources.
+     * @param {boolean} withholdLastBlock When true, the last matches block will not be submitted to prevent submitting incomplete blocks.
+     * @param {boolean} matchAllOnFlush (Only in combination with withholdLastBlock) When enabled, the buffer will be matched on last time on _flush (stream deconstruction) and write any, also incomplete, blocks
+     */
+    constructor(matcher, withholdLastBlock = true, matchAllOnFlush = false){
+        super({
+            readableObjectMode: true,
+            writableObjectMode: true
+        });
+        
+        this.matcher = matcher;
+        this.withholdLastBlock = withholdLastBlock;
+        this.matchAllOnFlush = matchAllOnFlush;
+
+        this._buffer = "";
+    }
+
+    _transform(chunk, encoding, next){
+        chunk = this._buffer + chunk;     // Add previous buffer to current chunk
+
+        let matches = chunk.match(this.matcher);    // Match
+        if(matches){
+            if(this.withholdLastBlock) matches.pop();       // Remove last if we want to withhold it
+            chunk = this._writeMatches(chunk, matches);
+        }
+        
+        this._buffer = chunk;   // Store remaining data in buffer
+        next();     // Get next chunk
+    }
+
+    _writeMatches(matches, chunk = null){
+        if(matches){
+            matches.forEach((match) => {
+                this.push(match);   // Write match to stream
+                if(chunk) chunk = chunk.replace(match, '');   // Remove match from chunks
+            });
+        }
+        if(chunk) return chunk;
+    }
+
+    _flush(next){
+        if(matchAllOnFlush){    // When requested, we'll match one last time over the remaining buffer
+            let matches = this._buffer.match(this.matcher);    // Match remaining buffer
+            _writeMatches(this._buffer);    // Write matches including last element
+        }
+        
+        next();     // Tell system we are done
+    }
+}
+
+// Specify exports
+module.exports = {
+    RegexBlockStream
+};