liyafan82 commented on a change in pull request #11067: URL: https://github.com/apache/arrow/pull/11067#discussion_r705017358
########## File path: java/ffi/src/main/java/org/apache/arrow/ffi/NativeUtil.java ########## @@ -0,0 +1,139 @@ +/* + * 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.ffi; + +import java.nio.ByteBuffer; +import java.nio.ByteOrder; +import java.nio.charset.StandardCharsets; + +import org.apache.arrow.memory.ArrowBuf; +import org.apache.arrow.memory.BufferAllocator; +import org.apache.arrow.memory.util.MemoryUtil; + +/** + * Utility functions for working with native memory. + */ +public final class NativeUtil { + public static final byte NULL = 0; + static final int MAX_STRING_LENGTH = Short.MAX_VALUE; + + private NativeUtil() { + } + + /** + * Convert a pointer to a null terminated string into a Java String. + * + * @param cstringPtr pointer to C string + * @return Converted string + */ + public static String toJavaString(long cstringPtr) { + if (cstringPtr == NULL) { + return null; + } + ByteBuffer reader = MemoryUtil.directBuffer(cstringPtr, MAX_STRING_LENGTH).order(ByteOrder.nativeOrder()); + + int length = 0; + while (reader.get() != NULL) { + length++; + } + byte[] bytes = new byte[length]; + ((ByteBuffer) reader.rewind()).get(bytes); + return new String(bytes, 0, length, StandardCharsets.UTF_8); + } + + /** + * Convert a native array pointer (void**) to Java array of pointers. + * + * @param arrayPtr Array pointer + * @param size Array size + * @return Array of pointer values as longs + */ + public static long[] toJavaArray(long arrayPtr, int size) { + if (size == 0 || arrayPtr == NULL) { Review comment: nit: please note that an empty array and a null are different things -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
