1 files changed, 136 insertions, 0 deletions
diff --git a/src/internal/saferio/io_test.go b/src/internal/saferio/io_test.go
new file mode 100644
index 0000000..356c9eb
--- /dev/null
+++ b/src/internal/saferio/io_test.go
@@ -0,0 +1,136 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package saferio
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+func TestReadData(t *testing.T) {
+	const count = 100
+	input := bytes.Repeat([]byte{'a'}, count)
+
+	t.Run("small", func(t *testing.T) {
+		got, err := ReadData(bytes.NewReader(input), count)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(got, input) {
+			t.Errorf("got %v, want %v", got, input)
+		}
+	})
+
+	t.Run("large", func(t *testing.T) {
+		_, err := ReadData(bytes.NewReader(input), 10<<30)
+		if err == nil {
+			t.Error("large read succeeded unexpectedly")
+		}
+	})
+
+	t.Run("maxint", func(t *testing.T) {
+		_, err := ReadData(bytes.NewReader(input), 1<<62)
+		if err == nil {
+			t.Error("large read succeeded unexpectedly")
+		}
+	})
+
+	t.Run("small-EOF", func(t *testing.T) {
+		_, err := ReadData(bytes.NewReader(nil), chunk-1)
+		if err != io.EOF {
+			t.Errorf("ReadData = %v, want io.EOF", err)
+		}
+	})
+
+	t.Run("large-EOF", func(t *testing.T) {
+		_, err := ReadData(bytes.NewReader(nil), chunk+1)
+		if err != io.EOF {
+			t.Errorf("ReadData = %v, want io.EOF", err)
+		}
+	})
+
+	t.Run("large-UnexpectedEOF", func(t *testing.T) {
+		_, err := ReadData(bytes.NewReader(make([]byte, chunk)), chunk+1)
+		if err != io.ErrUnexpectedEOF {
+			t.Errorf("ReadData = %v, want io.ErrUnexpectedEOF", err)
+		}
+	})
+}
+
+func TestReadDataAt(t *testing.T) {
+	const count = 100
+	input := bytes.Repeat([]byte{'a'}, count)
+
+	t.Run("small", func(t *testing.T) {
+		got, err := ReadDataAt(bytes.NewReader(input), count, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(got, input) {
+			t.Errorf("got %v, want %v", got, input)
+		}
+	})
+
+	t.Run("large", func(t *testing.T) {
+		_, err := ReadDataAt(bytes.NewReader(input), 10<<30, 0)
+		if err == nil {
+			t.Error("large read succeeded unexpectedly")
+		}
+	})
+
+	t.Run("maxint", func(t *testing.T) {
+		_, err := ReadDataAt(bytes.NewReader(input), 1<<62, 0)
+		if err == nil {
+			t.Error("large read succeeded unexpectedly")
+		}
+	})
+
+	t.Run("SectionReader", func(t *testing.T) {
+		// Reading 0 bytes from an io.SectionReader at the end
+		// of the section will return EOF, but ReadDataAt
+		// should succeed and return 0 bytes.
+		sr := io.NewSectionReader(bytes.NewReader(input), 0, 0)
+		got, err := ReadDataAt(sr, 0, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(got) > 0 {
+			t.Errorf("got %d bytes, expected 0", len(got))
+		}
+	})
+}
+
+func TestSliceCap(t *testing.T) {
+	t.Run("small", func(t *testing.T) {
+		c := SliceCap((*int)(nil), 10)
+		if c != 10 {
+			t.Errorf("got capacity %d, want %d", c, 10)
+		}
+	})
+
+	t.Run("large", func(t *testing.T) {
+		c := SliceCap((*byte)(nil), 1<<30)
+		if c < 0 {
+			t.Error("SliceCap failed unexpectedly")
+		} else if c == 1<<30 {
+			t.Errorf("got capacity %d which is too high", c)
+		}
+	})
+
+	t.Run("maxint", func(t *testing.T) {
+		c := SliceCap((*byte)(nil), 1<<63)
+		if c >= 0 {
+			t.Errorf("SliceCap returned %d, expected failure", c)
+		}
+	})
+
+	t.Run("overflow", func(t *testing.T) {
+		c := SliceCap((*int64)(nil), 1<<62)
+		if c >= 0 {
+			t.Errorf("SliceCap returned %d, expected failure", c)
+		}
+	})
+}