1 files changed, 54 insertions, 0 deletions
diff --git a/src/compress/flate/copy_test.go b/src/compress/flate/copy_test.go
new file mode 100644
index 000000000..2011b1547
--- /dev/null
+++ b/src/compress/flate/copy_test.go
@@ -0,0 +1,54 @@
+// Copyright 2012 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 flate
+
+import (
+	"testing"
+)
+
+func TestForwardCopy(t *testing.T) {
+	testCases := []struct {
+		dst0, dst1 int
+		src0, src1 int
+		want       string
+	}{
+		{0, 9, 0, 9, "012345678"},
+		{0, 5, 4, 9, "45678"},
+		{4, 9, 0, 5, "01230"},
+		{1, 6, 3, 8, "34567"},
+		{3, 8, 1, 6, "12121"},
+		{0, 9, 3, 6, "345"},
+		{3, 6, 0, 9, "012"},
+		{1, 6, 0, 9, "00000"},
+		{0, 4, 7, 8, "7"},
+		{0, 1, 6, 8, "6"},
+		{4, 4, 6, 9, ""},
+		{2, 8, 6, 6, ""},
+		{0, 0, 0, 0, ""},
+	}
+	for _, tc := range testCases {
+		b := []byte("0123456789")
+		n := tc.dst1 - tc.dst0
+		if tc.src1-tc.src0 < n {
+			n = tc.src1 - tc.src0
+		}
+		forwardCopy(b, tc.dst0, tc.src0, n)
+		got := string(b[tc.dst0 : tc.dst0+n])
+		if got != tc.want {
+			t.Errorf("dst=b[%d:%d], src=b[%d:%d]: got %q, want %q",
+				tc.dst0, tc.dst1, tc.src0, tc.src1, got, tc.want)
+		}
+		// Check that the bytes outside of dst[:n] were not modified.
+		for i, x := range b {
+			if i >= tc.dst0 && i < tc.dst0+n {
+				continue
+			}
+			if int(x) != '0'+i {
+				t.Errorf("dst=b[%d:%d], src=b[%d:%d]: copy overrun at b[%d]: got '%c', want '%c'",
+					tc.dst0, tc.dst1, tc.src0, tc.src1, i, x, '0'+i)
+			}
+		}
+	}
+}