@@ -79,60 +79,67 @@
 		return write(input[count:])
 	}
 
 	return write
 }
+
+type sizedReader struct {
+	reader         io.Reader
+	buffer         []byte
+	from, to, size int
+}
 
 // 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.
 func SizedReader(reader io.Reader, size int) io.Reader {
-	var (
-		buffer   []byte = make([]byte, size)
-		from, to int    = 0, 0
-	)
-
-	return ReaderFunc(func(output []byte) (int, error) {
-		var (
-			count int
-			err   error
-		)
-
-	start:
-		// Reply with the buffered data if there is any
-		if to-from > 0 {
-			count = copy(output, buffer[from:to])
-
-			// Advance the data in the buffer
-			from += count
-
-			// Check whether we have reached the end of the buffer
-			if to-from == 0 {
-				// Reset the buffer
-				from, to = 0, 0
-
-				return count, err
-			}
-
-			// Do not propagate an error until the buffer is exhausted
-			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
-		count, err = reader.Read(buffer)
-
-		// Size the buffer down to the read data size
-		// and restart if we have successfully read some bytes
-		from, to = 0, count
-		if to-from > 0 {
-			goto start
-		}
-
-		// Returning on err/misbehaving noop reader
-		return 0, err
-	})
+	var sr sizedReader
+	sr.reader = reader
+	sr.buffer = make([]byte, size)
+	sr.size, sr.from, sr.to = size, 0, 0
+	return &sr
+}
+
+func (sr *sizedReader) Read(output []byte) (int, error) {
+	var (
+		count int
+		err   error
+	)
+
+start:
+	// Reply with the buffered data if there is any
+	if sr.to-sr.from > 0 {
+		count = copy(output, sr.buffer[sr.from:sr.to])
+
+		// Advance the data in the buffer
+		sr.from += count
+
+		// Check whether we have reached the end of the buffer
+		if sr.to-sr.from == 0 {
+			// Reset the buffer
+			sr.from, sr.to = 0, 0
+
+			return count, err
+		}
+
+		// Do not propagate an error until the buffer is exhausted
+		return count, nil
+	}
+
+	// Delegate if the buffer is empty and the destination buffer is large enough
+	if len(output) >= sr.size {
+		return sr.reader.Read(output[:(len(output)/sr.size)*sr.size])
+	}
+
+	// Perform a read into the buffer
+	count, err = sr.reader.Read(sr.buffer)
+
+	// Size the buffer down to the read data size
+	// and restart if we have successfully read some bytes
+	sr.from, sr.to = 0, count
+	if sr.to-sr.from > 0 {
+		goto start
+	}
+
+	// Returning on err/misbehaving noop reader
+	return 0, err
 }