Index: src/0dev.org/ioutil/ioutil.go
==================================================================
--- src/0dev.org/ioutil/ioutil.go
+++ src/0dev.org/ioutil/ioutil.go
@@ -84,27 +84,34 @@
 
 // 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, 0, size)
+	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 len(buffer) > 0 {
-			count = copy(output, buffer)
+		if to-from > 0 {
+			count = copy(output, buffer[from:to])
 
 			// Advance the data in the buffer
-			buffer = buffer[:copy(buffer, buffer[count:])]
+			from += count
 
-			// Return count and error if we have read the whole buffer
-			if len(buffer) == 0 {
+			// 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
@@ -114,18 +121,18 @@
 		if len(output) >= size {
 			return reader.Read(output[:(len(output)/size)*size])
 		}
 
 		// Perform a read into the buffer
-		count, err = reader.Read(buffer[:size])
+		count, err = reader.Read(buffer)
 
 		// Size the buffer down to the read data size
 		// and restart if we have successfully read some bytes
-		buffer = buffer[:count]
-		if len(buffer) > 0 {
+		from, to = 0, count
+		if to-from > 0 {
 			goto start
 		}
 
 		// Returning on err/misbehaving noop reader
 		return 0, err
 	})
 }