From f0cab0e28512de5eecc0412212425cc74d62af71 Mon Sep 17 00:00:00 2001
From: Kir Kolyshkin <kolyshkin@gmail.com>
Date: Wed, 6 Dec 2017 11:19:39 -0800
Subject: [PATCH] TestImportExtremelyLargeImageWorks: optimize DevZero

According to https://github.com/golang/go/issues/5373, go recognizes
(and optimizes for) the following syntax:

```go
for i := range b {
	b[i] = 0
}
```

so let's use it. Limited testing shows ~7.5x speed increase,
compared to the previously used syntax.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
---
 internal/testutil/helpers.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/internal/testutil/helpers.go b/internal/testutil/helpers.go
index 287b3cb48a..bb36322a80 100644
--- a/internal/testutil/helpers.go
+++ b/internal/testutil/helpers.go
@@ -20,8 +20,8 @@ var DevZero io.Reader = devZero{}
 type devZero struct{}
 
 func (d devZero) Read(p []byte) (n int, err error) {
-	for i := 0; i < len(p); i++ {
-		p[i] = '\x00'
+	for i := range p {
+		p[i] = 0
 	}
 	return len(p), nil
 }