xds: implement simple safe and allocation-free xx_hash (#7912)

Implement a simple allocation-free xx_hash utility class without using sun.misc.Unsafe. The hash function mainly targets on xDS use case, which is mostly small strings (endpoint address, headers, etc) and primitive types.

In gRPC's use case, string characters need to be treated as ASCIIs to make the produced hash values match other implementations (Envoy, gRPC-Go, C-core, etc) would produce.

The hashing implementation and tests are borrowed from OpenHFT's XxHash implementation (https://github.com/OpenHFT/Zero-Allocation-Hashing/blob/master/src/main/java/net/openhft/hashing/XxHash.java, see commit 658079a50903c32c54f2ab5c86243244b3ac60ed), which is under Apache 2.0 license. For more details, see https://github.com/OpenHFT/Zero-Allocation-Hashing.

The code is made to be in third_party directory with LISENCE and NOTICE files.

xds/build.gradle

@@ -74,6 +74,9 @@ dependencies {
 
 sourceSets {
     main {
+        java {
+            srcDir "${projectDir}/third_party/zero-allocation-hashing/main/java"
+        }
         proto {
             srcDir 'third_party/envoy/src/main/proto'
             srcDir 'third_party/protoc-gen-validate/src/main/proto'
@@ -82,6 +85,11 @@ sourceSets {
             srcDir 'third_party/istio/src/main/proto'
         }
     }
+    test {
+        java {
+            srcDir "${projectDir}/third_party/zero-allocation-hashing/test/java"
+        }
+    }
 }
 
 configureProtoCompilation()

xds/third_party/zero-allocation-hashing/LICENSE

@@ -0,0 +1,202 @@
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xds/third_party/zero-allocation-hashing/NOTICE

@@ -0,0 +1,4 @@
+zero-allocation-hashing
+Copyright 2015 Higher Frequency Trading http://www.higherfrequencytrading.com
+
+Licensed under Apache License 2.0. See LICENSE for terms.

xds/third_party/zero-allocation-hashing/main/java/io/grpc/xds/XxHash64.java

@@ -0,0 +1,287 @@
+/*
+ * Copyright 2021 Higher Frequency Trading http://www.higherfrequencytrading.com
+ *
+ * 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.
+ */
+/*
+ * Forked from zero-allocation-hashing-0.14 (https://github.com/OpenHFT/Zero-Allocation-Hashing).
+ * Modified by the gRPC Authors
+ */
+
+package io.grpc.xds;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.nio.ByteOrder;
+
+/**
+ * The XxHash is a fast, non-cryptographic, 64-bit hash function that has excellent avalanche
+ * and 2-way bit independence properties.
+ *
+ * <p>This implementation is a simplified version adapted from
+ * <a href="https://github.com/OpenHFT/Zero-Allocation-Hashing/blob/master/src/main/java/net/openhft/hashing/XxHash.java">
+ * OpenHFT/Zero-Allocation-Hashing</a>.
+ */
+final class XxHash64 {
+  static final XxHash64 INSTANCE = new XxHash64(0);
+
+  // Primes if treated as unsigned
+  private static final long P1 = -7046029288634856825L;
+  private static final long P2 = -4417276706812531889L;
+  private static final long P3 = 1609587929392839161L;
+  private static final long P4 = -8796714831421723037L;
+  private static final long P5 = 2870177450012600261L;
+
+  private static final ByteOrder byteOrder = ByteOrder.nativeOrder();
+  private final long seed;
+  private final long voidHash;
+
+  XxHash64(long seed) {
+    this.seed = seed;
+    this.voidHash = finalize(seed + P5);
+  }
+
+  long hashLong(long input) {
+    input = byteOrder == ByteOrder.LITTLE_ENDIAN ? input : Long.reverseBytes(input);
+    long hash = seed + P5 + 8;
+    input *= P2;
+    input = Long.rotateLeft(input, 31);
+    input *= P1;
+    hash ^= input;
+    hash = Long.rotateLeft(hash, 27) * P1 + P4;
+    return finalize(hash);
+  }
+
+  long hashInt(int input) {
+    input = byteOrder == ByteOrder.LITTLE_ENDIAN ? input : Integer.reverseBytes(input);
+    long hash = seed + P5 + 4;
+    hash ^= (input & 0xFFFFFFFFL) * P1;
+    hash = Long.rotateLeft(hash, 23) * P2 + P3;
+    return finalize(hash);
+  }
+
+  long hashShort(short input) {
+    input = byteOrder == ByteOrder.LITTLE_ENDIAN ? input : Short.reverseBytes(input);
+    long hash = seed + P5 + 2;
+    hash ^= (input & 0xFFL) * P5;
+    hash = Long.rotateLeft(hash, 11) * P1;
+    hash ^= ((input >> 8) & 0xFFL) * P5;
+    hash = Long.rotateLeft(hash, 11) * P1;
+    return finalize(hash);
+  }
+
+  long hashChar(char input) {
+    return hashShort((short) input);
+  }
+
+  long hashByte(byte input) {
+    long hash = seed + P5 + 1;
+    hash ^= (input & 0xFF) * P5;
+    hash = Long.rotateLeft(hash, 11) * P1;
+    return finalize(hash);
+  }
+
+  long hashVoid() {
+    return voidHash;
+  }
+
+  long hashAsciiString(String input) {
+    ByteSupplier supplier = new AsciiStringByteSupplier(input);
+    return hashBytes(supplier);
+  }
+
+  long hashBytes(byte[] bytes) {
+    ByteSupplier supplier = new PlainByteSupplier(bytes);
+    return hashBytes(supplier);
+  }
+
+  long hashBytes(byte[] bytes, int offset, int len) {
+    ByteSupplier supplier = new PlainByteSupplier(bytes, offset, len);
+    return hashBytes(supplier);
+  }
+
+  private long hashBytes(ByteSupplier supplier) {
+    long hash;
+    if (supplier.remaining() >= 32) {
+      long v1 = seed + P1 + P2;
+      long v2 = seed + P2;
+      long v3 = seed;
+      long v4 = seed - P1;
+
+      do {
+        v1 += supplier.next64() * P2;
+        v1 = Long.rotateLeft(v1, 31);
+        v1 *= P1;
+
+        v2 += supplier.next64() * P2;
+        v2 = Long.rotateLeft(v2, 31);
+        v2 *= P1;
+
+        v3 += supplier.next64() * P2;
+        v3 = Long.rotateLeft(v3, 31);
+        v3 *= P1;
+
+        v4 += supplier.next64() * P2;
+        v4 = Long.rotateLeft(v4, 31);
+        v4 *= P1;
+      } while (supplier.remaining() >= 32);
+
+      hash = Long.rotateLeft(v1, 1)
+          + Long.rotateLeft(v2, 7)
+          + Long.rotateLeft(v3, 12)
+          + Long.rotateLeft(v4, 18);
+
+      v1 *= P2;
+      v1 = Long.rotateLeft(v1, 31);
+      v1 *= P1;
+      hash ^= v1;
+      hash = (hash * P1) + P4;
+
+      v2 *= P2;
+      v2 = Long.rotateLeft(v2, 31);
+      v2 *= P1;
+      hash ^= v2;
+      hash = (hash * P1) + P4;
+
+      v3 *= P2;
+      v3 = Long.rotateLeft(v3, 31);
+      v3 *= P1;
+      hash ^= v3;
+      hash = (hash * P1) + P4;
+
+      v4 *= P2;
+      v4 = Long.rotateLeft(v4, 31);
+      v4 *= P1;
+      hash ^= v4;
+      hash = (hash * P1) + P4;
+    } else {
+      hash = seed + P5;
+    }
+
+    hash += supplier.bytes();
+
+    while (supplier.remaining() >= 8) {
+      long k1 = supplier.next64();
+      k1 *= P2;
+      k1 = Long.rotateLeft(k1, 31);
+      k1 *= P1;
+      hash ^= k1;
+      hash = (Long.rotateLeft(hash, 27) * P1) + P4;
+    }
+
+    if (supplier.remaining() >= 4) { //treat as unsigned ints
+      hash ^= (supplier.next32() & 0xFFFFFFFFL) * P1;
+      hash = (Long.rotateLeft(hash, 23) * P2) + P3;
+    }
+
+    while (supplier.remaining() != 0) { //treat as unsigned bytes
+      hash ^= (supplier.next8() & 0xFF) * P5;
+      hash = Long.rotateLeft(hash, 11) * P1;
+    }
+
+    return finalize(hash);
+  }
+
+  private static long finalize(long hash) {
+    hash ^= hash >>> 33;
+    hash *= P2;
+    hash ^= hash >>> 29;
+    hash *= P3;
+    hash ^= hash >>> 32;
+    return hash;
+  }
+
+  private static class PlainByteSupplier extends ByteSupplier {
+    private final byte[] src;
+    private final int len;
+    private int pos;
+    private int remain;
+
+    private PlainByteSupplier(byte[] src) {
+      this(src, 0, src.length);
+    }
+
+    private PlainByteSupplier(byte[] src, int offset, int len) {
+      this.src = checkNotNull(src, "src");
+      checkArgument(offset <= src.length, "offset > src length");
+      checkArgument(offset + len <= src.length, "offset + len > src length");
+      this.len = len;
+      pos = offset;
+      remain = len;
+    }
+
+    @Override
+    public long bytes() {
+      return len;
+    }
+
+    @Override
+    public long remaining() {
+      return remain;
+    }
+
+    @Override
+    public byte next8() {
+      remain--;
+      return src[pos++];
+    }
+  }
+
+  private static class AsciiStringByteSupplier extends ByteSupplier {
+    private final String str;
+    private final int bytes;
+    private int pos;
+
+    private AsciiStringByteSupplier(String str) {
+      this.str = checkNotNull(str, "str");
+      this.bytes = str.length();
+    }
+
+    @Override
+    public long bytes() {
+      return bytes;
+    }
+
+    @Override
+    public long remaining() {
+      return (long) bytes - pos;
+    }
+
+    @Override
+    public byte next8() {
+      return (byte) str.charAt(pos++);
+    }
+  }
+
+  private abstract static class ByteSupplier {
+
+    public long next64() {
+      return ((next32() & 0xFFFFFFFFL) | ((next32() & 0xFFFFFFFFL) << 32));
+    }
+
+    public int next32() {
+      return ((next16() & 0xFFFF) | ((next16() & 0xFFFF) << 16));
+    }
+
+    char next16() {
+      return (char) ((next8() & 0xFF) | ((next8() & 0xFF) << 8));
+    }
+
+    abstract byte next8();
+
+    abstract long bytes();
+
+    abstract long remaining();
+  }
+}