feat(common): add ChecksumUtils for MD5/SHA*/CRC32/Adler32 with Base64 and multi-algorithm support (#4261)

app/common/src/test/java/stirling/software/common/util/ChecksumUtilsTest.java

@@ -0,0 +1,66 @@
+package stirling.software.common.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+public class ChecksumUtilsTest {
+
+    @Test
+    void computeChecksums_basic() throws Exception {
+        byte[] data = "hello".getBytes(StandardCharsets.UTF_8);
+
+        // MD5 (hex)
+        try (InputStream is = new ByteArrayInputStream(data)) {
+            assertEquals("5d41402abc4b2a76b9719d911017c592", ChecksumUtils.checksum(is, "MD5"));
+        }
+
+        // MD5 (Base64)
+        try (InputStream is = new ByteArrayInputStream(data)) {
+            assertEquals("XUFAKrxLKna5cZ2REBfFkg==", ChecksumUtils.checksumBase64(is, "MD5"));
+        }
+
+        // MD5 + CRC32 (hex map)
+        try (InputStream is = new ByteArrayInputStream(data)) {
+            Map<String, String> map = ChecksumUtils.checksums(is, "MD5", "CRC32");
+            assertEquals("5d41402abc4b2a76b9719d911017c592", map.get("MD5"));
+            assertEquals("3610a686", map.get("CRC32"));
+        }
+    }
+
+    @Test
+    void crc32_base64_bigEndianBytes_forHello() throws Exception {
+        // CRC32("hello") = 0x3610A686 → bytes: 36 10 A6 86 → Base64: "NhCmhg=="
+        byte[] data = "hello".getBytes(StandardCharsets.UTF_8);
+        try (InputStream is = new ByteArrayInputStream(data)) {
+            assertEquals("NhCmhg==", ChecksumUtils.checksumBase64(is, "CRC32"));
+        }
+    }
+
+    @Test
+    void crc32_unsignedFormatting_highBitSet() throws Exception {
+        // CRC32 of single zero byte (0x00) is 0xD202EF8D (>= 0x8000_0000)
+        byte[] data = new byte[] {0x00};
+
+        // Hex (unsigned, 8 chars, lowercase)
+        try (InputStream is = new ByteArrayInputStream(data)) {
+            assertEquals("d202ef8d", ChecksumUtils.checksum(is, "CRC32"));
+        }
+
+        // Base64 of the 4-byte big-endian representation
+        try (InputStream is = new ByteArrayInputStream(data)) {
+            assertEquals("0gLvjQ==", ChecksumUtils.checksumBase64(is, "CRC32"));
+        }
+
+        // matches(..) must be case-insensitive for hex
+        try (InputStream is = new ByteArrayInputStream("hello".getBytes(StandardCharsets.UTF_8))) {
+            assertTrue(ChecksumUtils.matches(is, "CRC32", "3610A686")); // uppercase expected
+        }
+    }
+}