@@ -1,70 +1,123 @@
-// Package ioutil contains various constructs for io operations
+// Package ioutil contains various constructs for io operations.
 package ioutil
 
 import (
 	"io"
 )
 
-// An function alias type that implements io.Writer
+// An function alias type that implements io.Writer.
 type WriterFunc func([]byte) (int, error)
 
-// Delegates the call to the WriterFunc while implementing io.Writer
+// Delegates the call to the WriterFunc while implementing io.Writer.
 func (w WriterFunc) Write(b []byte) (int, error) {
 	return w(b)
 }
 
-// An function alias type that implements io.Reader
+// An function alias type that implements io.Reader.
 type ReaderFunc func([]byte) (int, error)
 
-// Delegates the call to the WriterFunc while implementing io.Reader
+// Delegates the call to the WriterFunc while implementing io.Reader.
 func (r ReaderFunc) Read(b []byte) (int, error) {
 	return r(b)
 }
+
+// Returns a writer that delegates calls to Write(...) while ensuring
+// that it is never called with less bytes than the specified amount.
+//
+// Calls with fewer bytes are buffered while a call with a nil slice
+// causes the buffer to be flushed to the underlying writer.
+func SizedWriter(writer io.Writer, size int) io.Writer {
+	var buffer []byte = make([]byte, 0, size)
+	var write WriterFunc
+
+	write = func(input []byte) (int, error) {
+		var (
+			count int
+			err   error
+		)
+
+		// Flush the buffer when called with no bytes to write
+		if input == nil {
+			// Call the writer with whatever we have in store..
+			count, err = writer.Write(buffer)
+
+			// Advance the buffer
+			buffer = buffer[:copy(buffer, buffer[count:])]
+
+			return 0, err
+		}
+
+		// Delegate to the writer if the size is right
+		if len(buffer) == 0 && len(input) >= size {
+			return writer.Write(input)
+		}
+
+		// Append data to the buffer
+		count = copy(buffer[len(buffer):size], input)
+		buffer = buffer[:len(buffer)+count]
+
+		// Return if we don't have enough bytes to write
+		if len(buffer) < size {
+			return len(input), nil
+		}
+
+		// Flush the buffer as it is filled
+		_, err = write(nil)
+		if err != nil {
+			return count, err
+		}
+
+		// Handle the rest of the input
+		return write(input[count:])
+	}
+
+	return write
+}
 
 // Returns a reader that delegates calls to Read(...) while ensuring
 // that the output buffer is never smaller than the required size
-// and is downsized to a multiple of the required size if larger
+// and is downsized to a multiple of the required size if larger.
 func SizedReader(reader io.Reader, size int) io.Reader {
 	var buffer []byte = make([]byte, 0, size)
 
 	return ReaderFunc(func(output []byte) (int, error) {
 		var (
-			readCount int
-			err       error
+			count int
+			err   error
 		)
 	start:
 		// Reply with the buffered data if there is any
 		if len(buffer) > 0 {
-			readCount = copy(output, buffer)
+			count = copy(output, buffer)
 
 			// Advance the data in the buffer
-			buffer = buffer[:copy(buffer, buffer[readCount:])]
+			buffer = buffer[:copy(buffer, buffer[count:])]
 
 			// Return count and error if we have read the whole buffer
 			if len(buffer) == 0 {
-				return readCount, err
+				return count, err
 			}
 
 			// Do not propagate an error until the buffer is exhausted
-			return readCount, nil
+			return count, nil
 		}
 
 		// Delegate if the buffer is empty and the destination buffer is large enough
 		if len(output) >= size {
 			return reader.Read(output[:(len(output)/size)*size])
 		}
 
 		// Perform a read into the buffer
-		readCount, err = reader.Read(buffer[:size])
+		count, err = reader.Read(buffer[:size])
 
 		// Size the buffer down to the read data size
 		// and restart if we have successfully read some bytes
-		buffer = buffer[:readCount]
+		buffer = buffer[:count]
 		if len(buffer) > 0 {
 			goto start
 		}
 
 		// Returning on err/misbehaving noop reader
 		return 0, err
 	})
 }