Docs for size chunker

README.md

@@ -24,10 +24,10 @@ Simple transform stream which counts lines (`\n` is a separator) and emit data c
 ### Configuration
 
 ```javascript
-  new LineCounter({
+new LineCounter({
     numLines: 1,        // number of lines in a single output chunk. 1 is default
-    flushTail: false    // on stream, end flush or not remaining buffer. false is default
-  });
+    flushTail: false    // on stream end, flush or not remaining buffer. false is default
+});
 ```
 
 SeparatorChunker
@@ -40,8 +40,60 @@ By default separator sequence is set to `\n`, so it is equals to LineCounter wit
 ### Configuration
 
 ```javascript
-    new SeparatorChunker({
-        separator: '\n', // separator sequence
-        flushTail: false // on stream, end flush or not remaining buffer. false is default
-    });
+new SeparatorChunker({
+    separator: '\n', // separator sequence
+    flushTail: false // on stream end, flush or not remaining buffer. false is default
+});
+```
+
+SizeChunker
+-----------
+
+Split streams into chunks having at least specified size in bytes (but maybe more). It is **object mode** stream!
+Each data chunk is an object with the following fields:
+
+  - id: number of chunk (starts from 1)
+  - data: `Buffer` with data
+
+SizeChunker has 2 additional events:
+
+  - chunkStart: emitted on each chunk start.
+  - chunkEnd: emitted on each chunk finish.
+
+Both event handlers must accept two arguments:
+
+  - id: number of chunk
+  - done: callback function, **must** be called then processing is completed
+
+### Configuration
+
+```javascript
+new SizeChunker({
+    chunkSize: 1024 // must be a number greater than zero
+});
+```
+
+### Example
+```javascript
+var input = fs.createReadStream('./input'),
+    chunker = new SizeChunker({
+        chunkSize: 1024
+    }),
+    output;
+
+chunker.on('chunkStart', function(id, done) {
+    output = fs.createWriteStream('./output-' + id);
+    done();
+});
+
+chunker.on('chunkEnd', function(id, done) {
+    output.end();
+    done();
+});
+
+chunker.on('data', function(data) {
+    output.write(data.chunk);
+});
+
+input.pipe(chunker);
 ```

lib/size-chunker.js

@@ -14,7 +14,11 @@
       Transform.call(this, options);
       this._bytesPassed = 0;
       this._currentChunk = 0;
-      this._chunkSize = options && options.chunkSize || 10;
+      this._chunkSize = +(options && options.chunkSize);
+
+      if(isNaN(this._chunkSize) || this._chunkSize <= 0) {
+          throw new Error("Invalid chunk size. Must be a number greater than zero.");
+      }
 
       this._readableState.objectMode = true;