Implement immutable byte string class for CEL

PiperOrigin-RevId: 576681833

common/src/main/java/dev/cel/common/values/BUILD.bazel

@@ -0,0 +1,19 @@
+package(
+    default_applicable_licenses = [
+        "//:license",
+    ],
+    default_visibility = [
+        "//common/values:__pkg__",
+    ],
+)
+
+java_library(
+    name = "cel_byte_string",
+    srcs = ["CelByteString.java"],
+    tags = [
+    ],
+    deps = [
+        "@maven//:com_google_errorprone_error_prone_annotations",
+        "@maven//:com_google_guava_guava",
+    ],
+)

common/src/main/java/dev/cel/common/values/CelByteString.java

@@ -0,0 +1,93 @@
+// Copyright 2023 Google LLC
+//
+// 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
+//
+//      https://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 dev.cel.common.values;
+
+import com.google.common.base.Preconditions;
+import com.google.errorprone.annotations.Immutable;
+import java.util.Arrays;
+
+/** CelByteString is an immutable sequence of a byte array. */
+@Immutable
+@SuppressWarnings("Immutable") // We make defensive copies on the byte array.
+public final class CelByteString {
+  private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
+  public static final CelByteString EMPTY = new CelByteString(EMPTY_BYTE_ARRAY);
+
+  private final byte[] data;
+
+  private volatile int hash = 0;
+
+  public static CelByteString of(byte[] buffer) {
+    Preconditions.checkNotNull(buffer);
+    if (buffer.length == 0) {
+      return EMPTY;
+    }
+    return new CelByteString(buffer);
+  }
+
+  public int size() {
+    return data.length;
+  }
+
+  public boolean isEmpty() {
+    return data.length == 0;
+  }
+
+  public byte[] toByteArray() {
+    int size = size();
+    if (size == 0) {
+      return EMPTY_BYTE_ARRAY;
+    }
+
+    return Arrays.copyOf(data, size);
+  }
+
+  private CelByteString(byte[] buffer) {
+    data = Arrays.copyOf(buffer, buffer.length);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == this) {
+      return true;
+    }
+
+    if (!(o instanceof CelByteString)) {
+      return false;
+    }
+
+    return Arrays.equals(data, ((CelByteString) o).data);
+  }
+
+  /**
+   * Note that we do not use Arrays.hashCode directly due to its implementation using 31 as an odd
+   * prime, which is outdated and is more prone to hash collisions. This code is very similar to
+   * what AutoValue generates.
+   */
+  @Override
+  public int hashCode() {
+    if (hash == 0) {
+      int h = 1;
+      h *= 1000003;
+      h ^= Arrays.hashCode(data);
+      if (h == 0) {
+        h = 1;
+      }
+      hash = h;
+    }
+
+    return hash;
+  }
+}

common/src/test/java/dev/cel/common/values/BUILD.bazel

@@ -0,0 +1,24 @@
+load("//:testing.bzl", "junit4_test_suites")
+
+package(default_applicable_licenses = ["//:license"])
+
+java_library(
+    name = "tests",
+    testonly = True,
+    srcs = glob(["*.java"]),
+    deps = [
+        "//:java_truth",
+        "//common/values:cel_byte_string",
+        "@maven//:com_google_guava_guava_testlib",
+        "@maven//:junit_junit",
+    ],
+)
+
+junit4_test_suites(
+    name = "test_suites",
+    sizes = [
+        "small",
+    ],
+    src_dir = "src/test/java",
+    deps = [":tests"],
+)

common/src/test/java/dev/cel/common/values/CelByteStringTest.java

@@ -0,0 +1,88 @@
+// Copyright 2023 Google LLC
+//
+// 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
+//
+//      https://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 dev.cel.common.values;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
+
+import com.google.common.testing.ClassSanityTester;
+import com.google.common.testing.EqualsTester;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class CelByteStringTest {
+
+  @Test
+  public void emptyBytes() {
+    CelByteString byteString = CelByteString.of(new byte[0]);
+
+    assertThat(byteString).isEqualTo(CelByteString.EMPTY);
+    assertThat(byteString.isEmpty()).isTrue();
+    assertThat(byteString.toByteArray()).isEqualTo(new byte[0]);
+  }
+
+  @Test
+  public void equalityTest() {
+    new EqualsTester()
+        .addEqualityGroup(CelByteString.of(new byte[0]), CelByteString.EMPTY)
+        .addEqualityGroup(CelByteString.of(new byte[] {0xa}), CelByteString.of(new byte[] {0xa}))
+        .addEqualityGroup(
+            CelByteString.of(new byte[] {0x1, 0x5, 0xc}),
+            CelByteString.of(new byte[] {0x1, 0x5, 0xc}))
+        .addEqualityGroup(CelByteString.of(new byte[] {0xf}))
+        .testEquals();
+  }
+
+  @Test
+  public void sanityTest() throws Exception {
+    new ClassSanityTester()
+        .setDefault(CelByteString.class, CelByteString.of(new byte[] {0x1, 0x5, 0xc}))
+        .setDistinctValues(
+            CelByteString.class,
+            CelByteString.of(new byte[] {0x1, 0x5, 0xc}),
+            CelByteString.of(new byte[] {0x2, 0x6, 0xc}))
+        .forAllPublicStaticMethods(CelByteString.class)
+        .thatReturn(CelByteString.class)
+        .testEquals()
+        .testNulls();
+  }
+
+  @Test
+  public void hashCode_smokeTest() {
+    assertThat(CelByteString.of(new byte[0]).hashCode()).isEqualTo(1000002);
+    assertThat(CelByteString.of(new byte[] {0x1}).hashCode()).isEqualTo(1000035);
+    assertThat(CelByteString.of(new byte[] {0x1, 0x5}).hashCode()).isEqualTo(999846);
+    assertThat(CelByteString.of(new byte[] {0x1, 0x5, 0xc}).hashCode()).isEqualTo(998020);
+  }
+
+  @Test
+  public void byteString_isImmutable() {
+    byte[] bytes = {0x1, 0xa, 0x3};
+    CelByteString byteString = CelByteString.of(bytes);
+
+    bytes[0] = 0x2;
+    byte[] newByteArray = byteString.toByteArray();
+    assertThat(newByteArray).isNotEqualTo(bytes);
+    bytes[0] = 0x1;
+    assertThat(newByteArray).isEqualTo(bytes);
+  }
+
+  @Test
+  public void nullBytes_throws() {
+    assertThrows(NullPointerException.class, () -> CelByteString.of(null));
+  }
+}

common/values/BUILD.bazel

@@ -0,0 +1,9 @@
+package(
+    default_applicable_licenses = ["//:license"],
+    default_visibility = ["//visibility:public"],  # TODO: Expose to public when ready
+)
+
+java_library(
+    name = "cel_byte_string",
+    exports = ["//common/src/main/java/dev/cel/common/values:cel_byte_string"],
+)