From d1ed507a5a624811ce873c6361471e1019243f26 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Mon, 19 Dec 2016 13:01:45 +1100
Subject: [PATCH] OutMessage.GrowNoZero

---
 internal/buffer/out_message.go | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/internal/buffer/out_message.go b/internal/buffer/out_message.go
index 02e1bf6..49a43ca 100644
--- a/internal/buffer/out_message.go
+++ b/internal/buffer/out_message.go
@@ -81,7 +81,18 @@ func (m *OutMessage) Grow(n int) (p unsafe.Pointer)
 
 // GrowNoZero is equivalent to Grow, except the new segment is not zeroed. Use
 // with caution!
-func (m *OutMessage) GrowNoZero(n int) (p unsafe.Pointer)
+func (m *OutMessage) GrowNoZero(n int) (p unsafe.Pointer) {
+	// Will we overflow the buffer?
+	o := m.payloadOffset
+	if len(m.payload)-o < n {
+		return
+	}
+
+	p = unsafe.Pointer(uintptr(unsafe.Pointer(&m.payload)) + uintptr(o))
+	m.payloadOffset = o + n
+
+	return
+}
 
 // ShrinkTo shrinks m to the given size. It panics if the size is greater than
 // Len() or less than OutMessageHeaderSize.