From d82243906a22a69126f371b8ecc4dfb6905b8cdf Mon Sep 17 00:00:00 2001
From: Jamie Wilkinson <jaq@spacepants.org>
Date: Sun, 22 Mar 2015 11:34:14 +1100
Subject: [PATCH] Test that a read of nonzero bytes from an InMemFile does not
 return EOF in the same read op.

---
 fs_test.go      | 21 +++++++++++++++++++++
 memfile.go      |  5 ++++-
 memfile_test.go | 27 ---------------------------
 3 files changed, 25 insertions(+), 28 deletions(-)
 delete mode 100644 memfile_test.go

diff --git a/fs_test.go b/fs_test.go
index 4fe6afe..225100e 100644
--- a/fs_test.go
+++ b/fs_test.go
@@ -69,6 +69,27 @@ func TestRead0(t *testing.T) {
 	}
 }
 
+func TestMemFileRead(t *testing.T) {
+	f := MemFileCreate("testfile")
+	f.WriteString("abcd")
+	f.Seek(0, 0)
+	b := make([]byte, 8)
+	n, err := f.Read(b)
+	if n != 4 {
+		t.Errorf("didn't read all bytes: %v %v %v", n, err, b)
+	}
+	if err != nil {
+		t.Errorf("err is not nil: %v %v %v", n, err, b)
+	}
+	n, err = f.Read(b)
+	if n != 0 {
+		t.Errorf("read more bytes: %v %v %v", n, err, b)
+	}
+	if err != io.EOF {
+		t.Errorf("error is not EOF: %v %v %v", n, err, b)
+	}
+}
+
 func TestRename(t *testing.T) {
 	for _, fs := range Fss {
 		from, to := testDir+"/renamefrom", testDir+"/renameto"
diff --git a/memfile.go b/memfile.go
index 4815c6b..6f4edb4 100644
--- a/memfile.go
+++ b/memfile.go
@@ -105,12 +105,15 @@ func (f *InMemoryFile) Read(b []byte) (n int, err error) {
 	if f.closed == true {
 		return 0, ErrFileClosed
 	}
+	if len(b) > 0 && int(f.at) == len(f.data) {
+		return 0, io.EOF
+	}
 	if len(f.data)-int(f.at) >= len(b) {
 		n = len(b)
 	} else {
 		n = len(f.data) - int(f.at)
-		err = io.EOF
 	}
+
 	copy(b, f.data[f.at:f.at+int64(n)])
 	atomic.AddInt64(&f.at, int64(n))
 	return
diff --git a/memfile_test.go b/memfile_test.go
deleted file mode 100644
index b77ae8e..0000000
--- a/memfile_test.go
+++ /dev/null
@@ -1,27 +0,0 @@
-package afero
-
-import (
-	"io"
-	"testing"
-)
-
-func TestMemFileRead(t *testing.T) {
-	f := MemFileCreate("testfile")
-	f.WriteString("abcd")
-	f.Seek(0, 0)
-	b := make([]byte, 8)
-	n, err := f.Read(b)
-	if n != 4 {
-		t.Errorf("didn't read all bytes: %v %v %v", n, err, b)
-	}
-	if err != nil {
-		t.Errorf("err is not nil: %v %v %v", n, err, b)
-	}
-	n, err = f.Read(b)
-	if n != 0 {
-		t.Errorf("read more bytes: %v %v %v", n, err, b)
-	}
-	if err != io.EOF {
-		t.Errorf("error is not EOF: %v %v %v", n, err, b)
-	}
-}