Add BloomFilter.serializedSize().

RELNOTES=`hash`: Added `BloomFilter.serializedSize()`.
PiperOrigin-RevId: 881649496

Author: kluever

android/guava-tests/test/com/google/common/hash/BloomFilterTest.java

@@ -378,11 +378,13 @@ public void testBitSizeMatchesSerializationSize() throws Exception {
         // Header: 1 byte (strategy) + 1 byte (hash functions) + 4 bytes (array length) = 6 bytes
         // Data: bitSize / 8 bytes
         long predictedSize = bf.bitSize() / 8 + 6;
+        assertThat(bf.serializedSize()).isEqualTo(predictedSize);
 
         // Serialize and measure actual size
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         bf.writeTo(out);
         int actualSize = out.size();
+        assertThat(bf.serializedSize()).isEqualTo(actualSize);
 
         assertWithMessage(
                 "Serialization size mismatch for expectedInsertions=%s, fpp=%s",

android/guava/src/com/google/common/hash/BloomFilter.java

@@ -226,6 +226,25 @@ long bitSize() {
     return bits.bitSize();
   }
 
+  /**
+   * Returns the number of bytes required to serialize this bloom filter using the {@link
+   * #writeTo(OutputStream)} method. This method can be useful if you need to know the serialization
+   * size before writing to pre-allocated space (e.g., for memory-mapped files or fixed-size
+   * records).
+   *
+   * @since NEXT
+   */
+  public long serializedSize() {
+    // We return a long (and not an int) because the max serialized size is approximately
+    // 17 billion bytes (2^31 * 8 bytes).
+
+    // The serialization header is 6 bytes:
+    //   1 byte for the strategy
+    //   1 byte for the number of hash functions
+    //   4 bytes for the array length
+    return (bits.bitSize() / 8) + 6;
+  }
+
   /**
    * Determines whether a given Bloom filter is compatible with this Bloom filter. For two Bloom
    * filters to be compatible, they must:

guava-tests/test/com/google/common/hash/BloomFilterTest.java

@@ -380,11 +380,13 @@ public void testBitSizeMatchesSerializationSize() throws Exception {
         // Header: 1 byte (strategy) + 1 byte (hash functions) + 4 bytes (array length) = 6 bytes
         // Data: bitSize / 8 bytes
         long predictedSize = bf.bitSize() / 8 + 6;
+        assertThat(bf.serializedSize()).isEqualTo(predictedSize);
 
         // Serialize and measure actual size
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         bf.writeTo(out);
         int actualSize = out.size();
+        assertThat(bf.serializedSize()).isEqualTo(actualSize);
 
         assertWithMessage(
                 "Serialization size mismatch for expectedInsertions=%s, fpp=%s",

guava/src/com/google/common/hash/BloomFilter.java

@@ -238,6 +238,25 @@ long bitSize() {
     return bits.bitSize();
   }
 
+  /**
+   * Returns the number of bytes required to serialize this bloom filter using the {@link
+   * #writeTo(OutputStream)} method. This method can be useful if you need to know the serialization
+   * size before writing to pre-allocated space (e.g., for memory-mapped files or fixed-size
+   * records).
+   *
+   * @since NEXT
+   */
+  public long serializedSize() {
+    // We return a long (and not an int) because the max serialized size is approximately
+    // 17 billion bytes (2^31 * 8 bytes).
+
+    // The serialization header is 6 bytes:
+    //   1 byte for the strategy
+    //   1 byte for the number of hash functions
+    //   4 bytes for the array length
+    return (bits.bitSize() / 8) + 6;
+  }
+
   /**
    * Determines whether a given Bloom filter is compatible with this Bloom filter. For two Bloom
    * filters to be compatible, they must: