ARROW-5970: [Java] Provide pointer to Arrow buffer

java/memory/src/main/java/org/apache/arrow/memory/util/ArrowBufPointer.java

@@ -0,0 +1,106 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.arrow.memory.util;
+
+import io.netty.buffer.ArrowBuf;
+
+/**
+ * Pointer to a memory region within an {@link io.netty.buffer.ArrowBuf}.
+ * It will be used as the basis for calculating hash code within a vector, and equality determination.
+ */
+public final class ArrowBufPointer {
+
+  private ArrowBuf buf;
+
+  private int offset;
+
+  private int length;
+
+  /**
+   * The default constructor.
+   */
+  public ArrowBufPointer() {
+
+  }
+
+  /**
+   * Constructs an Arrow buffer pointer.
+   * @param buf the underlying {@link ArrowBuf}, which can be null.
+   * @param offset the start off set of the memory region pointed to.
+   * @param length the length off set of the memory region pointed to.
+   */
+  public ArrowBufPointer(ArrowBuf buf, int offset, int length) {
+    set(buf, offset, length);
+  }
+
+  /**
+   * Sets this pointer.
+   * @param buf the underlying {@link ArrowBuf}, which can be null.
+   * @param offset the start off set of the memory region pointed to.
+   * @param length the length off set of the memory region pointed to.
+   */
+  public void set(ArrowBuf buf, int offset, int length) {
+    this.buf = buf;
+    this.offset = offset;
+    this.length = length;
+  }
+
+  /**
+   * Gets the underlying buffer, or null if the underlying data is invalid or null.
+   * @return the underlying buffer, if any, or null if the underlying data is invalid or null.
+   */
+  public ArrowBuf getBuf() {
+    return buf;
+  }
+
+  public int getOffset() {
+    return offset;
+  }
+
+  public int getLength() {
+    return length;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+
+    ArrowBufPointer other = (ArrowBufPointer) o;
+    if (buf == null || other.buf == null) {
+      if (buf == null && other.buf == null) {
+        return true;
+      } else {
+        return false;
+      }
+    }
+
+    return ByteFunctionHelpers.equal(buf, offset, offset + length,
+            other.buf, other.offset, other.offset + other.length) != 0;
+  }
+
+  @Override
+  public int hashCode() {
+    // implement after ARROW-5898
+    throw new UnsupportedOperationException();
+  }
+}

java/memory/src/main/java/org/apache/arrow/memory/util/ByteFunctionHelpers.java

@@ -0,0 +1,290 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.arrow.memory.util;
+
+import org.apache.arrow.memory.BoundsChecking;
+
+import io.netty.buffer.ArrowBuf;
+import io.netty.util.internal.PlatformDependent;
+
+/**
+ * Utility methods for memory comparison at a byte level.
+ */
+public class ByteFunctionHelpers {
+  static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ByteFunctionHelpers.class);
+
+  private ByteFunctionHelpers() {}
+
+  /**
+   * Helper function to check for equality of bytes in two ArrowBufs.
+   *
+   * @param left   Left ArrowBuf for comparison
+   * @param lStart start offset in the buffer
+   * @param lEnd   end offset in the buffer
+   * @param right  Right ArrowBuf for comparison
+   * @param rStart start offset in the buffer
+   * @param rEnd   end offset in the buffer
+   * @return 1 if equals, 0 otherwise
+   */
+  public static final int equal(final ArrowBuf left, int lStart, int lEnd, final ArrowBuf right, int rStart, int rEnd) {
+    if (BoundsChecking.BOUNDS_CHECKING_ENABLED) {
+      left.checkBytes(lStart, lEnd);
+      right.checkBytes(rStart, rEnd);
+    }
+    return memEqual(left.memoryAddress(), lStart, lEnd, right.memoryAddress(), rStart, rEnd);
+  }
+
+  private static int memEqual(final long laddr, int lStart, int lEnd, final long raddr, int rStart,
+                                    final int rEnd) {
+
+    int n = lEnd - lStart;
+    if (n == rEnd - rStart) {
+      long lPos = laddr + lStart;
+      long rPos = raddr + rStart;
+
+      while (n > 7) {
+        long leftLong = PlatformDependent.getLong(lPos);
+        long rightLong = PlatformDependent.getLong(rPos);
+        if (leftLong != rightLong) {
+          return 0;
+        }
+        lPos += 8;
+        rPos += 8;
+        n -= 8;
+      }
+
+      while (n > 3) {
+        int leftInt = PlatformDependent.getInt(lPos);
+        int rightInt = PlatformDependent.getInt(rPos);
+        if (leftInt != rightInt) {
+          return 0;
+        }
+        lPos += 4;
+        rPos += 4;
+        n -= 4;
+      }
+
+      while (n-- != 0) {
+        byte leftByte = PlatformDependent.getByte(lPos);
+        byte rightByte = PlatformDependent.getByte(rPos);
+        if (leftByte != rightByte) {
+          return 0;
+        }
+        lPos++;
+        rPos++;
+      }
+      return 1;
+    } else {
+      return 0;
+    }
+  }
+
+  /**
+   * Helper function to compare a set of bytes in two ArrowBufs.
+   *
+   * <p>Function will check data before completing in the case that
+   *
+   * @param left   Left ArrowBuf to compare
+   * @param lStart start offset in the buffer
+   * @param lEnd   end offset in the buffer
+   * @param right  Right ArrowBuf to compare
+   * @param rStart start offset in the buffer
+   * @param rEnd   end offset in the buffer
+   * @return 1 if left input is greater, -1 if left input is smaller, 0 otherwise
+   */
+  public static final int compare(
+      final ArrowBuf left,
+      int lStart,
+      int lEnd,
+      final ArrowBuf right,
+      int rStart,
+      int rEnd) {
+    if (BoundsChecking.BOUNDS_CHECKING_ENABLED) {
+      left.checkBytes(lStart, lEnd);
+      right.checkBytes(rStart, rEnd);
+    }
+    return memcmp(left.memoryAddress(), lStart, lEnd, right.memoryAddress(), rStart, rEnd);
+  }
+
+  private static int memcmp(
+      final long laddr,
+      int lStart,
+      int lEnd,
+      final long raddr,
+      int rStart,
+      final int rEnd) {
+    int lLen = lEnd - lStart;
+    int rLen = rEnd - rStart;
+    int n = Math.min(rLen, lLen);
+    long lPos = laddr + lStart;
+    long rPos = raddr + rStart;
+
+    while (n > 7) {
+      long leftLong = PlatformDependent.getLong(lPos);
+      long rightLong = PlatformDependent.getLong(rPos);
+      if (leftLong != rightLong) {
+        return unsignedLongCompare(leftLong, rightLong);
+      }
+      lPos += 8;
+      rPos += 8;
+      n -= 8;
+    }
+
+    while (n > 3) {
+      int leftInt = PlatformDependent.getInt(lPos);
+      int rightInt = PlatformDependent.getInt(rPos);
+      if (leftInt != rightInt) {
+        return unsignedIntCompare(leftInt, rightInt);
+      }
+      lPos += 4;
+      rPos += 4;
+      n -= 4;
+    }
+
+    while (n-- != 0) {
+      byte leftByte = PlatformDependent.getByte(lPos);
+      byte rightByte = PlatformDependent.getByte(rPos);
+      if (leftByte != rightByte) {
+        return ((leftByte & 0xFF) - (rightByte & 0xFF)) > 0 ? 1 : -1;
+      }
+      lPos++;
+      rPos++;
+    }
+
+    if (lLen == rLen) {
+      return 0;
+    }
+
+    return lLen > rLen ? 1 : -1;
+
+  }
+
+  /**
+   * Helper function to compare a set of bytes in ArrowBuf to a ByteArray.
+   *
+   * @param left   Left ArrowBuf for comparison purposes
+   * @param lStart start offset in the buffer
+   * @param lEnd   end offset in the buffer
+   * @param right  second input to be compared
+   * @param rStart start offset in the byte array
+   * @param rEnd   end offset in the byte array
+   * @return 1 if left input is greater, -1 if left input is smaller, 0 otherwise
+   */
+  public static final int compare(
+      final ArrowBuf left,
+      int lStart,
+      int lEnd,
+      final byte[] right,
+      int rStart,
+      final int rEnd) {
+    if (BoundsChecking.BOUNDS_CHECKING_ENABLED) {
+      left.checkBytes(lStart, lEnd);
+    }
+    return memcmp(left.memoryAddress(), lStart, lEnd, right, rStart, rEnd);
+  }
+
+
+  /**
+   * Compares the two specified {@code long} values, treating them as unsigned values between
+   * {@code 0} and {@code 2^64 - 1} inclusive.
+   *
+   * @param a the first unsigned {@code long} to compare
+   * @param b the second unsigned {@code long} to compare
+   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
+   *     greater than {@code b}; or zero if they are equal
+   */
+  public static int unsignedLongCompare(long a, long b) {
+    return Long.compare(a ^ Long.MIN_VALUE, b ^ Long.MIN_VALUE);
+  }
+
+  public static int unsignedIntCompare(int a, int b) {
+    return Integer.compare(a ^ Integer.MIN_VALUE, b ^ Integer.MIN_VALUE);
+  }
+
+  private static int memcmp(
+      final long laddr,
+      int lStart,
+      int lEnd,
+      final byte[] right,
+      int rStart,
+      final int rEnd) {
+    int lLen = lEnd - lStart;
+    int rLen = rEnd - rStart;
+    int n = Math.min(rLen, lLen);
+    long lPos = laddr + lStart;
+    int rPos = rStart;
+
+    while (n-- != 0) {
+      byte leftByte = PlatformDependent.getByte(lPos);
+      byte rightByte = right[rPos];
+      if (leftByte != rightByte) {
+        return ((leftByte & 0xFF) - (rightByte & 0xFF)) > 0 ? 1 : -1;
+      }
+      lPos++;
+      rPos++;
+    }
+
+    if (lLen == rLen) {
+      return 0;
+    }
+
+    return lLen > rLen ? 1 : -1;
+  }
+
+  /**
+   * Compute hashCode with the given {@link ArrowBuf} and start/end index.
+   */
+  public static final int hash(final ArrowBuf buf, int start, int end) {
+    long addr = buf.memoryAddress();
+    int len = end - start;
+    long pos = addr + start;
+
+    int hash = 0;
+
+    while (len > 7) {
+      long value = PlatformDependent.getLong(pos);
+      hash = comebineHash(hash, Long.hashCode(value));
+
+      pos += 8;
+      len -= 8;
+    }
+
+    while (len > 3) {
+      int value = PlatformDependent.getInt(pos);
+      hash = comebineHash(hash, value);
+
+      pos += 4;
+      len -= 4;
+    }
+
+    while (len-- != 0) {
+      byte value = PlatformDependent.getByte(pos);
+      hash = comebineHash(hash, value);
+      pos ++;
+    }
+
+    return hash;
+  }
+
+  /**
+   * Generate a new hashCode with the given current hashCode and new hashCode.
+   */
+  public static int comebineHash(int currentHash, int newHash) {
+    return currentHash * 31 + newHash;
+  }
+}