api: CopyObjectPart was copying wrong offsets due to shadowing. (#3838)

startOffset was re-assigned to '0' so it would end up
copying wrong content ignoring the requested startOffset.

This also fixes the corruption issue we observed while
using docker registry.

Fixes https://github.com/docker/distribution/issues/2205

Also fixes #3842 - incorrect routing.

cmd/copy-part-range_test.go

@@ -0,0 +1,85 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import "testing"
+
+// Test parseCopyPartRange()
+func TestParseCopyPartRange(t *testing.T) {
+	// Test success cases.
+	successCases := []struct {
+		rangeString string
+		offsetBegin int64
+		offsetEnd   int64
+		length      int64
+	}{
+		{"bytes=2-5", 2, 5, 4},
+		{"bytes=2-9", 2, 9, 8},
+		{"bytes=2-2", 2, 2, 1},
+		{"bytes=0000-0006", 0, 6, 7},
+	}
+
+	for _, successCase := range successCases {
+		hrange, err := parseCopyPartRange(successCase.rangeString, 10)
+		if err != nil {
+			t.Fatalf("expected: <nil>, got: %s", err)
+		}
+
+		if hrange.offsetBegin != successCase.offsetBegin {
+			t.Fatalf("expected: %d, got: %d", successCase.offsetBegin, hrange.offsetBegin)
+		}
+
+		if hrange.offsetEnd != successCase.offsetEnd {
+			t.Fatalf("expected: %d, got: %d", successCase.offsetEnd, hrange.offsetEnd)
+		}
+		if hrange.getLength() != successCase.length {
+			t.Fatalf("expected: %d, got: %d", successCase.length, hrange.getLength())
+		}
+	}
+
+	// Test invalid range strings.
+	invalidRangeStrings := []string{
+		"bytes=8",
+		"bytes=5-2",
+		"bytes=+2-5",
+		"bytes=2-+5",
+		"bytes=2--5",
+		"bytes=-",
+		"",
+		"2-5",
+		"bytes = 2-5",
+		"bytes=2 - 5",
+		"bytes=0-0,-1",
+		"bytes=2-5 ",
+	}
+	for _, rangeString := range invalidRangeStrings {
+		if _, err := parseCopyPartRange(rangeString, 10); err == nil {
+			t.Fatalf("expected: an error, got: <nil> for range %s", rangeString)
+		}
+	}
+
+	// Test error range strings.
+	errorRangeString := []string{
+		"bytes=10-10",
+		"bytes=20-30",
+	}
+	for _, rangeString := range errorRangeString {
+		if _, err := parseCopyPartRange(rangeString, 10); err != errInvalidRangeSource {
+			t.Fatalf("expected: %s, got: %s", errInvalidRangeSource, err)
+		}
+	}
+}