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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2022/04/05 12:18:34 UTC
[GitHub] [arrow] lidavidm commented on a diff in pull request #12794: ARROW-15578: [Java][Doc] WIP - Document C Data and how to interface with other languages
lidavidm commented on code in PR #12794:
URL: https://github.com/apache/arrow/pull/12794#discussion_r842708704
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
Review Comment:
```suggestion
Arrow supports exchanging data without copying or serialization within the same process through the :ref:`c-data-interface`, even between different language runtimes.
```
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
Review Comment:
Link to the C++ build docs as well
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
+
+.. code-block:: shell
+
+ git clone https://github.com/apache/arrow.git
+ cd arrow/cpp
+ cmake --preset -N ninja-debug-minimal
+ mkdir build # from inside the `cpp` subdirectory
+ cd build
+ cmake .. --preset ninja-debug-minimal
+ cmake --build .
+ tree debug/
+ debug/
+ ├── libarrow.800.0.0.dylib
+ ├── libarrow.800.dylib -> libarrow.800.0.0.dylib
+ └── libarrow.dylib -> libarrow.800.dylib
+
+Define c++ code CDataInterfaceLibrary.h that export functions for third party like Java consumer:
+
+.. code-block:: cpp
+
+ #include <iostream>
+ #include <arrow/api.h>
+
+ #define ARROW_FLAG_DICTIONARY_ORDERED 1
+ #define ARROW_FLAG_NULLABLE 2
+ #define ARROW_FLAG_MAP_KEYS_SORTED 4
+
+ using arrow::Int64Builder;
+
+ struct ArrowSchema {
+ // Array type description
+ const char* format;
+ const char* name;
+ const char* metadata;
+ int64_t flags;
+ int64_t n_children;
+ struct ArrowSchema** children;
+ struct ArrowSchema* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowSchema*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ struct ArrowArray {
+ // Array data description
+ int64_t length;
+ int64_t null_count;
+ int64_t offset;
+ int64_t n_buffers;
+ int64_t n_children;
+ const void** buffers;
+ struct ArrowArray** children;
+ struct ArrowArray* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowArray*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ static void release_int32_type(struct ArrowSchema* schema) {
+ // Mark released
+ schema->release = NULL;
+ }
+
+ void export_int32_type(struct ArrowSchema* schema) {
+ *schema = (struct ArrowSchema) {
+ // Type description
+ .format = "l",
+ .name = "",
+ .metadata = NULL,
+ .flags = 0,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_type
+ };
+ std::cout << "C Data - Schema Pointer = " << schema << std::endl;
+ }
+
+ static void release_int32_array(struct ArrowArray* array) {
+ assert(array->n_buffers == 2);
+ // Free the buffers and the buffers array
+ free((void *) array->buffers[1]);
+ free(array->buffers);
+ // Mark released
+ array->release = NULL;
+ }
+
+ void export_int32_array(struct ArrowArray* array) {
+ arrow::Int64Builder builder;
+ builder.Append(1);
+ builder.Append(2);
+ builder.Append(3);
+ builder.AppendNull();
+ builder.Append(5);
+ builder.Append(6);
+ builder.Append(7);
+ builder.Append(8);
+
+ auto maybe_array = builder.Finish();
+ std::shared_ptr<arrow::Array> array_arrow = *maybe_array;
+ auto int64_array = std::static_pointer_cast<arrow::Int64Array>(array_arrow);
+ const int64_t* data = int64_array->raw_values();
+ std::cout << "Data To Exchange Pointer = " << data << std::endl;
+ for (int j = 0; j < int64_array->length(); j++){
+ std::cout << "Data To Exchange Value[" << j << "] = " << data[j] << std::endl;
+ }
+
+ *array = (struct ArrowArray) {
+ // Data description
+ .length = int64_array->length(),
+ .offset = 0,
+ .null_count = 0,
+ .n_buffers = 2,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_array
+ };
+
+ // Allocate list of buffers
+ array->buffers = (const void**) malloc(sizeof(void*) * array->n_buffers);
+ assert(array->buffers != NULL);
+ array->buffers[0] = NULL; // no nulls, null bitmap can be omitted
+ array->buffers[1] = data;
+
+ std::cout << "C Data - Array Pointer = " << array << std::endl;
+ std::cout << "C Data - Array Data Pointer Buffer array->buffers[1] = " << array->buffers[1] << std::endl;
+ }
+
+**Java Side**
+
+Define Java code CDataInterfaceLibraryConfig.java that consume by JNI C++ functions exported through
+C Data Interface:
Review Comment:
"For this example, we will use javacpp (link to project) to call our main C++ function from Java, without writing JNI bindings ourselves."
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
+
+.. code-block:: shell
+
+ git clone https://github.com/apache/arrow.git
+ cd arrow/cpp
+ cmake --preset -N ninja-debug-minimal
+ mkdir build # from inside the `cpp` subdirectory
+ cd build
+ cmake .. --preset ninja-debug-minimal
+ cmake --build .
+ tree debug/
+ debug/
+ ├── libarrow.800.0.0.dylib
+ ├── libarrow.800.dylib -> libarrow.800.0.0.dylib
+ └── libarrow.dylib -> libarrow.800.dylib
+
+Define c++ code CDataInterfaceLibrary.h that export functions for third party like Java consumer:
+
+.. code-block:: cpp
+
+ #include <iostream>
+ #include <arrow/api.h>
+
+ #define ARROW_FLAG_DICTIONARY_ORDERED 1
+ #define ARROW_FLAG_NULLABLE 2
+ #define ARROW_FLAG_MAP_KEYS_SORTED 4
+
+ using arrow::Int64Builder;
+
+ struct ArrowSchema {
+ // Array type description
+ const char* format;
+ const char* name;
+ const char* metadata;
+ int64_t flags;
+ int64_t n_children;
+ struct ArrowSchema** children;
+ struct ArrowSchema* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowSchema*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ struct ArrowArray {
+ // Array data description
+ int64_t length;
+ int64_t null_count;
+ int64_t offset;
+ int64_t n_buffers;
+ int64_t n_children;
+ const void** buffers;
+ struct ArrowArray** children;
+ struct ArrowArray* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowArray*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ static void release_int32_type(struct ArrowSchema* schema) {
+ // Mark released
+ schema->release = NULL;
+ }
+
+ void export_int32_type(struct ArrowSchema* schema) {
+ *schema = (struct ArrowSchema) {
+ // Type description
+ .format = "l",
+ .name = "",
+ .metadata = NULL,
+ .flags = 0,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_type
+ };
+ std::cout << "C Data - Schema Pointer = " << schema << std::endl;
+ }
+
+ static void release_int32_array(struct ArrowArray* array) {
+ assert(array->n_buffers == 2);
+ // Free the buffers and the buffers array
+ free((void *) array->buffers[1]);
+ free(array->buffers);
+ // Mark released
+ array->release = NULL;
+ }
+
+ void export_int32_array(struct ArrowArray* array) {
+ arrow::Int64Builder builder;
+ builder.Append(1);
+ builder.Append(2);
+ builder.Append(3);
+ builder.AppendNull();
+ builder.Append(5);
+ builder.Append(6);
+ builder.Append(7);
+ builder.Append(8);
+
+ auto maybe_array = builder.Finish();
+ std::shared_ptr<arrow::Array> array_arrow = *maybe_array;
+ auto int64_array = std::static_pointer_cast<arrow::Int64Array>(array_arrow);
+ const int64_t* data = int64_array->raw_values();
+ std::cout << "Data To Exchange Pointer = " << data << std::endl;
+ for (int j = 0; j < int64_array->length(); j++){
+ std::cout << "Data To Exchange Value[" << j << "] = " << data[j] << std::endl;
+ }
+
+ *array = (struct ArrowArray) {
+ // Data description
+ .length = int64_array->length(),
+ .offset = 0,
+ .null_count = 0,
+ .n_buffers = 2,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_array
+ };
+
+ // Allocate list of buffers
+ array->buffers = (const void**) malloc(sizeof(void*) * array->n_buffers);
+ assert(array->buffers != NULL);
+ array->buffers[0] = NULL; // no nulls, null bitmap can be omitted
+ array->buffers[1] = data;
+
+ std::cout << "C Data - Array Pointer = " << array << std::endl;
+ std::cout << "C Data - Array Data Pointer Buffer array->buffers[1] = " << array->buffers[1] << std::endl;
+ }
+
+**Java Side**
+
+Define Java code CDataInterfaceLibraryConfig.java that consume by JNI C++ functions exported through
+C Data Interface:
+
+.. code-block:: xml
+
+ <?xml version="1.0" encoding="UTF-8"?>
+ <project xmlns="http://maven.apache.org/POM/4.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+ <groupId>org.example</groupId>
+ <artifactId>cpp-java-cdata</artifactId>
+ <version>1.0-SNAPSHOT</version>
+ <properties>
+ <maven.compiler.source>8</maven.compiler.source>
+ <maven.compiler.target>8</maven.compiler.target>
+ </properties>
+ <dependencies>
+ <dependency>
+ <groupId>org.bytedeco</groupId>
+ <artifactId>javacpp</artifactId>
+ <version>1.5.7</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-c-data</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-memory-netty</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ </dependencies>
+ </project>
+
+.. code-block:: java
+
+ import org.bytedeco.javacpp.annotation.Platform;
+ import org.bytedeco.javacpp.annotation.Properties;
+ import org.bytedeco.javacpp.tools.InfoMap;
+ import org.bytedeco.javacpp.tools.InfoMapper;
+
+ @Properties(
+ target = "CDataInterfaceLibrary",
+ value = @Platform(
+ include = {"CDataInterfaceLibrary.h"},
+ compiler = {"cpp11"},
+ linkpath = {"/arrow/cpp/build/debug/"},
+ link = {"arrow"}
+ )
+ )
+ public class CDataInterfaceLibraryConfig implements InfoMapper {
+ @Override
+ public void map(InfoMap infoMap) {
+ }
+ }
+
+.. code-block:: shell
+
+ // Compile our Java code
+ javac -cp javacpp-1.5.7.jar CDataInterfaceLibraryConfig.java
+
+ // Generate CDataInterfaceLibrary
+ java -jar javacpp-1.5.7.jar CDataInterfaceLibraryConfig.java
+
+ // Generate libjniCDataInterfaceLibrary.dylib
+ java -jar javacpp-1.5.7.jar CDataInterfaceLibrary.java
+
+ // Validate libjniCDataInterfaceLibrary.dylib created
+ otool -L macosx-x86_64/libjniCDataInterfaceLibrary.dylib
+ macosx-x86_64/libjniCDataInterfaceLibrary.dylib:
+ libjniCDataInterfaceLibrary.dylib (compatibility version 0.0.0, current version 0.0.0)
+ @rpath/libarrow.800.dylib (compatibility version 800.0.0, current version 800.0.0)
+ /usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 1200.3.0)
+ /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.0.0)
+
+**Java Test**
+
+Let's create a Java class to Test C Data Interface from Java to C++:
+
+.. code-block:: java
+
+ import org.apache.arrow.c.ArrowArray;
+ import org.apache.arrow.c.ArrowSchema;
+ import org.apache.arrow.c.Data;
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.BigIntVector;
+
+ public class TestCDataInterfaceV5 {
+
+ public static void main(String[] args) {
+ CDataInterfaceLibrary.ArrowSchema arrowSchema = new CDataInterfaceLibrary.ArrowSchema();
+ CDataInterfaceLibrary.export_int32_type(arrowSchema);
+
+ ArrowSchema arrow_schema = ArrowSchema.wrap(arrowSchema.address());
+ System.out.println("Java C Data - Schema Pointer = = " + Long.toHexString(arrowSchema.address()));
+
+ CDataInterfaceLibrary.ArrowArray arrowArray = new CDataInterfaceLibrary.ArrowArray();
+ CDataInterfaceLibrary.export_int32_array(arrowArray);
+
+ ArrowArray arrow_array = ArrowArray.wrap(arrowArray.address());
+ System.out.println("Java C Data - Array Pointer = " + Long.toHexString(arrowArray.address()));
+ System.out.println("Java C Data - Array Data Pointer Buffer array->buffers[1] = " + Long.toHexString(arrowArray.buffers(1).address()));
+
+ BufferAllocator allocator = new RootAllocator();
+ BigIntVector bigIntVector = (BigIntVector) Data.importVector(allocator, arrow_array, arrow_schema, null);
+ System.out.println("Java C Data - BigIntVector: " + bigIntVector);
+
+ CDataInterfaceLibrary.release_int32_type(arrowSchema);
+ CDataInterfaceLibrary.release_int32_array(arrowArray);
Review Comment:
Why aren't we using the release callback of the C Data Interface objects?
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
+
+.. code-block:: shell
+
+ git clone https://github.com/apache/arrow.git
+ cd arrow/cpp
+ cmake --preset -N ninja-debug-minimal
+ mkdir build # from inside the `cpp` subdirectory
+ cd build
+ cmake .. --preset ninja-debug-minimal
+ cmake --build .
+ tree debug/
+ debug/
+ ├── libarrow.800.0.0.dylib
+ ├── libarrow.800.dylib -> libarrow.800.0.0.dylib
+ └── libarrow.dylib -> libarrow.800.dylib
+
+Define c++ code CDataInterfaceLibrary.h that export functions for third party like Java consumer:
+
+.. code-block:: cpp
+
+ #include <iostream>
+ #include <arrow/api.h>
+
+ #define ARROW_FLAG_DICTIONARY_ORDERED 1
+ #define ARROW_FLAG_NULLABLE 2
+ #define ARROW_FLAG_MAP_KEYS_SORTED 4
+
+ using arrow::Int64Builder;
+
+ struct ArrowSchema {
+ // Array type description
+ const char* format;
+ const char* name;
+ const char* metadata;
+ int64_t flags;
+ int64_t n_children;
+ struct ArrowSchema** children;
+ struct ArrowSchema* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowSchema*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ struct ArrowArray {
+ // Array data description
+ int64_t length;
+ int64_t null_count;
+ int64_t offset;
+ int64_t n_buffers;
+ int64_t n_children;
+ const void** buffers;
+ struct ArrowArray** children;
+ struct ArrowArray* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowArray*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ static void release_int32_type(struct ArrowSchema* schema) {
+ // Mark released
+ schema->release = NULL;
+ }
+
+ void export_int32_type(struct ArrowSchema* schema) {
+ *schema = (struct ArrowSchema) {
+ // Type description
+ .format = "l",
+ .name = "",
+ .metadata = NULL,
+ .flags = 0,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_type
+ };
+ std::cout << "C Data - Schema Pointer = " << schema << std::endl;
+ }
+
+ static void release_int32_array(struct ArrowArray* array) {
+ assert(array->n_buffers == 2);
+ // Free the buffers and the buffers array
+ free((void *) array->buffers[1]);
+ free(array->buffers);
+ // Mark released
+ array->release = NULL;
+ }
+
+ void export_int32_array(struct ArrowArray* array) {
+ arrow::Int64Builder builder;
+ builder.Append(1);
+ builder.Append(2);
+ builder.Append(3);
+ builder.AppendNull();
+ builder.Append(5);
+ builder.Append(6);
+ builder.Append(7);
+ builder.Append(8);
+
+ auto maybe_array = builder.Finish();
+ std::shared_ptr<arrow::Array> array_arrow = *maybe_array;
+ auto int64_array = std::static_pointer_cast<arrow::Int64Array>(array_arrow);
+ const int64_t* data = int64_array->raw_values();
+ std::cout << "Data To Exchange Pointer = " << data << std::endl;
+ for (int j = 0; j < int64_array->length(); j++){
+ std::cout << "Data To Exchange Value[" << j << "] = " << data[j] << std::endl;
+ }
+
+ *array = (struct ArrowArray) {
+ // Data description
+ .length = int64_array->length(),
+ .offset = 0,
+ .null_count = 0,
+ .n_buffers = 2,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_array
+ };
+
+ // Allocate list of buffers
+ array->buffers = (const void**) malloc(sizeof(void*) * array->n_buffers);
+ assert(array->buffers != NULL);
+ array->buffers[0] = NULL; // no nulls, null bitmap can be omitted
+ array->buffers[1] = data;
+
+ std::cout << "C Data - Array Pointer = " << array << std::endl;
+ std::cout << "C Data - Array Data Pointer Buffer array->buffers[1] = " << array->buffers[1] << std::endl;
+ }
+
+**Java Side**
+
+Define Java code CDataInterfaceLibraryConfig.java that consume by JNI C++ functions exported through
+C Data Interface:
+
+.. code-block:: xml
+
+ <?xml version="1.0" encoding="UTF-8"?>
+ <project xmlns="http://maven.apache.org/POM/4.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+ <groupId>org.example</groupId>
+ <artifactId>cpp-java-cdata</artifactId>
+ <version>1.0-SNAPSHOT</version>
+ <properties>
+ <maven.compiler.source>8</maven.compiler.source>
+ <maven.compiler.target>8</maven.compiler.target>
+ </properties>
+ <dependencies>
+ <dependency>
+ <groupId>org.bytedeco</groupId>
+ <artifactId>javacpp</artifactId>
+ <version>1.5.7</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-c-data</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-memory-netty</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ </dependencies>
+ </project>
+
+.. code-block:: java
+
+ import org.bytedeco.javacpp.annotation.Platform;
+ import org.bytedeco.javacpp.annotation.Properties;
+ import org.bytedeco.javacpp.tools.InfoMap;
+ import org.bytedeco.javacpp.tools.InfoMapper;
+
+ @Properties(
+ target = "CDataInterfaceLibrary",
+ value = @Platform(
+ include = {"CDataInterfaceLibrary.h"},
+ compiler = {"cpp11"},
+ linkpath = {"/arrow/cpp/build/debug/"},
+ link = {"arrow"}
+ )
+ )
+ public class CDataInterfaceLibraryConfig implements InfoMapper {
+ @Override
+ public void map(InfoMap infoMap) {
+ }
+ }
+
+.. code-block:: shell
+
+ // Compile our Java code
+ javac -cp javacpp-1.5.7.jar CDataInterfaceLibraryConfig.java
+
+ // Generate CDataInterfaceLibrary
+ java -jar javacpp-1.5.7.jar CDataInterfaceLibraryConfig.java
+
+ // Generate libjniCDataInterfaceLibrary.dylib
+ java -jar javacpp-1.5.7.jar CDataInterfaceLibrary.java
+
+ // Validate libjniCDataInterfaceLibrary.dylib created
+ otool -L macosx-x86_64/libjniCDataInterfaceLibrary.dylib
+ macosx-x86_64/libjniCDataInterfaceLibrary.dylib:
+ libjniCDataInterfaceLibrary.dylib (compatibility version 0.0.0, current version 0.0.0)
+ @rpath/libarrow.800.dylib (compatibility version 800.0.0, current version 800.0.0)
+ /usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 1200.3.0)
+ /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.0.0)
+
+**Java Test**
+
+Let's create a Java class to Test C Data Interface from Java to C++:
+
+.. code-block:: java
+
+ import org.apache.arrow.c.ArrowArray;
+ import org.apache.arrow.c.ArrowSchema;
+ import org.apache.arrow.c.Data;
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.BigIntVector;
+
+ public class TestCDataInterfaceV5 {
+
+ public static void main(String[] args) {
+ CDataInterfaceLibrary.ArrowSchema arrowSchema = new CDataInterfaceLibrary.ArrowSchema();
+ CDataInterfaceLibrary.export_int32_type(arrowSchema);
+
+ ArrowSchema arrow_schema = ArrowSchema.wrap(arrowSchema.address());
Review Comment:
I think in general, this example isn't structured correctly. The specification states that the consumer is expected to allocate the array. So what we should do is:
1. Use ArrowSchema.allocateNew to create the structure
2. Pass the address via javacpp to the JNI function, which populates the structure
We shouldn't be defining our own ArrowSchema class here, and we shouldn't be expecting the C++ code to allocate the ArrowSchema itself.
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
Review Comment:
```suggestion
Example: share an Int32 array from C++ to Java:
```
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
+
+.. code-block:: shell
+
+ git clone https://github.com/apache/arrow.git
+ cd arrow/cpp
+ cmake --preset -N ninja-debug-minimal
+ mkdir build # from inside the `cpp` subdirectory
+ cd build
+ cmake .. --preset ninja-debug-minimal
+ cmake --build .
+ tree debug/
+ debug/
+ ├── libarrow.800.0.0.dylib
+ ├── libarrow.800.dylib -> libarrow.800.0.0.dylib
+ └── libarrow.dylib -> libarrow.800.dylib
+
+Define c++ code CDataInterfaceLibrary.h that export functions for third party like Java consumer:
+
+.. code-block:: cpp
+
+ #include <iostream>
+ #include <arrow/api.h>
+
+ #define ARROW_FLAG_DICTIONARY_ORDERED 1
+ #define ARROW_FLAG_NULLABLE 2
+ #define ARROW_FLAG_MAP_KEYS_SORTED 4
+
+ using arrow::Int64Builder;
+
+ struct ArrowSchema {
+ // Array type description
+ const char* format;
+ const char* name;
+ const char* metadata;
+ int64_t flags;
+ int64_t n_children;
+ struct ArrowSchema** children;
+ struct ArrowSchema* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowSchema*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ struct ArrowArray {
+ // Array data description
+ int64_t length;
+ int64_t null_count;
+ int64_t offset;
+ int64_t n_buffers;
+ int64_t n_children;
+ const void** buffers;
+ struct ArrowArray** children;
+ struct ArrowArray* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowArray*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ static void release_int32_type(struct ArrowSchema* schema) {
+ // Mark released
+ schema->release = NULL;
+ }
+
+ void export_int32_type(struct ArrowSchema* schema) {
+ *schema = (struct ArrowSchema) {
+ // Type description
+ .format = "l",
+ .name = "",
+ .metadata = NULL,
+ .flags = 0,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_type
+ };
+ std::cout << "C Data - Schema Pointer = " << schema << std::endl;
+ }
+
+ static void release_int32_array(struct ArrowArray* array) {
+ assert(array->n_buffers == 2);
+ // Free the buffers and the buffers array
+ free((void *) array->buffers[1]);
+ free(array->buffers);
+ // Mark released
+ array->release = NULL;
+ }
+
+ void export_int32_array(struct ArrowArray* array) {
+ arrow::Int64Builder builder;
+ builder.Append(1);
+ builder.Append(2);
+ builder.Append(3);
+ builder.AppendNull();
+ builder.Append(5);
+ builder.Append(6);
+ builder.Append(7);
+ builder.Append(8);
+
+ auto maybe_array = builder.Finish();
+ std::shared_ptr<arrow::Array> array_arrow = *maybe_array;
+ auto int64_array = std::static_pointer_cast<arrow::Int64Array>(array_arrow);
+ const int64_t* data = int64_array->raw_values();
+ std::cout << "Data To Exchange Pointer = " << data << std::endl;
+ for (int j = 0; j < int64_array->length(); j++){
+ std::cout << "Data To Exchange Value[" << j << "] = " << data[j] << std::endl;
+ }
+
+ *array = (struct ArrowArray) {
+ // Data description
+ .length = int64_array->length(),
+ .offset = 0,
+ .null_count = 0,
+ .n_buffers = 2,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_array
+ };
+
+ // Allocate list of buffers
+ array->buffers = (const void**) malloc(sizeof(void*) * array->n_buffers);
+ assert(array->buffers != NULL);
+ array->buffers[0] = NULL; // no nulls, null bitmap can be omitted
+ array->buffers[1] = data;
+
+ std::cout << "C Data - Array Pointer = " << array << std::endl;
+ std::cout << "C Data - Array Data Pointer Buffer array->buffers[1] = " << array->buffers[1] << std::endl;
+ }
+
+**Java Side**
+
+Define Java code CDataInterfaceLibraryConfig.java that consume by JNI C++ functions exported through
+C Data Interface:
+
+.. code-block:: xml
+
+ <?xml version="1.0" encoding="UTF-8"?>
+ <project xmlns="http://maven.apache.org/POM/4.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+ <groupId>org.example</groupId>
+ <artifactId>cpp-java-cdata</artifactId>
+ <version>1.0-SNAPSHOT</version>
+ <properties>
+ <maven.compiler.source>8</maven.compiler.source>
+ <maven.compiler.target>8</maven.compiler.target>
+ </properties>
+ <dependencies>
+ <dependency>
+ <groupId>org.bytedeco</groupId>
+ <artifactId>javacpp</artifactId>
+ <version>1.5.7</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-c-data</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-memory-netty</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ </dependencies>
+ </project>
+
+.. code-block:: java
+
+ import org.bytedeco.javacpp.annotation.Platform;
+ import org.bytedeco.javacpp.annotation.Properties;
+ import org.bytedeco.javacpp.tools.InfoMap;
+ import org.bytedeco.javacpp.tools.InfoMapper;
+
+ @Properties(
+ target = "CDataInterfaceLibrary",
Review Comment:
I would rather name this something like "CDataInterfaceExample"
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
+
+.. code-block:: shell
+
+ git clone https://github.com/apache/arrow.git
+ cd arrow/cpp
+ cmake --preset -N ninja-debug-minimal
+ mkdir build # from inside the `cpp` subdirectory
+ cd build
+ cmake .. --preset ninja-debug-minimal
+ cmake --build .
+ tree debug/
+ debug/
+ ├── libarrow.800.0.0.dylib
+ ├── libarrow.800.dylib -> libarrow.800.0.0.dylib
+ └── libarrow.dylib -> libarrow.800.dylib
+
+Define c++ code CDataInterfaceLibrary.h that export functions for third party like Java consumer:
+
+.. code-block:: cpp
+
+ #include <iostream>
+ #include <arrow/api.h>
+
+ #define ARROW_FLAG_DICTIONARY_ORDERED 1
+ #define ARROW_FLAG_NULLABLE 2
+ #define ARROW_FLAG_MAP_KEYS_SORTED 4
+
+ using arrow::Int64Builder;
+
+ struct ArrowSchema {
+ // Array type description
+ const char* format;
+ const char* name;
+ const char* metadata;
+ int64_t flags;
+ int64_t n_children;
+ struct ArrowSchema** children;
+ struct ArrowSchema* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowSchema*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ struct ArrowArray {
+ // Array data description
+ int64_t length;
+ int64_t null_count;
+ int64_t offset;
+ int64_t n_buffers;
+ int64_t n_children;
+ const void** buffers;
+ struct ArrowArray** children;
+ struct ArrowArray* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowArray*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ static void release_int32_type(struct ArrowSchema* schema) {
+ // Mark released
+ schema->release = NULL;
+ }
+
+ void export_int32_type(struct ArrowSchema* schema) {
+ *schema = (struct ArrowSchema) {
+ // Type description
+ .format = "l",
+ .name = "",
+ .metadata = NULL,
+ .flags = 0,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_type
+ };
+ std::cout << "C Data - Schema Pointer = " << schema << std::endl;
+ }
+
+ static void release_int32_array(struct ArrowArray* array) {
+ assert(array->n_buffers == 2);
+ // Free the buffers and the buffers array
+ free((void *) array->buffers[1]);
+ free(array->buffers);
+ // Mark released
+ array->release = NULL;
+ }
+
+ void export_int32_array(struct ArrowArray* array) {
+ arrow::Int64Builder builder;
+ builder.Append(1);
+ builder.Append(2);
+ builder.Append(3);
+ builder.AppendNull();
+ builder.Append(5);
+ builder.Append(6);
+ builder.Append(7);
+ builder.Append(8);
+
+ auto maybe_array = builder.Finish();
+ std::shared_ptr<arrow::Array> array_arrow = *maybe_array;
+ auto int64_array = std::static_pointer_cast<arrow::Int64Array>(array_arrow);
+ const int64_t* data = int64_array->raw_values();
+ std::cout << "Data To Exchange Pointer = " << data << std::endl;
+ for (int j = 0; j < int64_array->length(); j++){
+ std::cout << "Data To Exchange Value[" << j << "] = " << data[j] << std::endl;
+ }
+
+ *array = (struct ArrowArray) {
+ // Data description
+ .length = int64_array->length(),
+ .offset = 0,
+ .null_count = 0,
+ .n_buffers = 2,
+ .n_children = 0,
+ .children = NULL,
+ .dictionary = NULL,
+ // Bookkeeping
+ .release = &release_int32_array
+ };
+
+ // Allocate list of buffers
+ array->buffers = (const void**) malloc(sizeof(void*) * array->n_buffers);
+ assert(array->buffers != NULL);
+ array->buffers[0] = NULL; // no nulls, null bitmap can be omitted
+ array->buffers[1] = data;
+
+ std::cout << "C Data - Array Pointer = " << array << std::endl;
+ std::cout << "C Data - Array Data Pointer Buffer array->buffers[1] = " << array->buffers[1] << std::endl;
+ }
+
+**Java Side**
+
+Define Java code CDataInterfaceLibraryConfig.java that consume by JNI C++ functions exported through
+C Data Interface:
+
+.. code-block:: xml
+
+ <?xml version="1.0" encoding="UTF-8"?>
+ <project xmlns="http://maven.apache.org/POM/4.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+ <groupId>org.example</groupId>
+ <artifactId>cpp-java-cdata</artifactId>
+ <version>1.0-SNAPSHOT</version>
+ <properties>
+ <maven.compiler.source>8</maven.compiler.source>
+ <maven.compiler.target>8</maven.compiler.target>
+ </properties>
+ <dependencies>
+ <dependency>
+ <groupId>org.bytedeco</groupId>
+ <artifactId>javacpp</artifactId>
+ <version>1.5.7</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-c-data</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ <dependency>
+ <groupId>org.apache.arrow</groupId>
+ <artifactId>arrow-memory-netty</artifactId>
+ <version>7.0.0</version>
+ </dependency>
+ </dependencies>
+ </project>
+
+.. code-block:: java
+
+ import org.bytedeco.javacpp.annotation.Platform;
+ import org.bytedeco.javacpp.annotation.Properties;
+ import org.bytedeco.javacpp.tools.InfoMap;
+ import org.bytedeco.javacpp.tools.InfoMapper;
+
+ @Properties(
+ target = "CDataInterfaceLibrary",
+ value = @Platform(
+ include = {"CDataInterfaceLibrary.h"},
+ compiler = {"cpp11"},
+ linkpath = {"/arrow/cpp/build/debug/"},
+ link = {"arrow"}
+ )
+ )
+ public class CDataInterfaceLibraryConfig implements InfoMapper {
+ @Override
+ public void map(InfoMap infoMap) {
+ }
+ }
+
+.. code-block:: shell
+
+ // Compile our Java code
+ javac -cp javacpp-1.5.7.jar CDataInterfaceLibraryConfig.java
+
+ // Generate CDataInterfaceLibrary
+ java -jar javacpp-1.5.7.jar CDataInterfaceLibraryConfig.java
+
+ // Generate libjniCDataInterfaceLibrary.dylib
+ java -jar javacpp-1.5.7.jar CDataInterfaceLibrary.java
+
+ // Validate libjniCDataInterfaceLibrary.dylib created
+ otool -L macosx-x86_64/libjniCDataInterfaceLibrary.dylib
+ macosx-x86_64/libjniCDataInterfaceLibrary.dylib:
+ libjniCDataInterfaceLibrary.dylib (compatibility version 0.0.0, current version 0.0.0)
+ @rpath/libarrow.800.dylib (compatibility version 800.0.0, current version 800.0.0)
+ /usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 1200.3.0)
+ /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.0.0)
+
+**Java Test**
+
+Let's create a Java class to Test C Data Interface from Java to C++:
+
+.. code-block:: java
+
+ import org.apache.arrow.c.ArrowArray;
+ import org.apache.arrow.c.ArrowSchema;
+ import org.apache.arrow.c.Data;
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.BigIntVector;
+
+ public class TestCDataInterfaceV5 {
+
+ public static void main(String[] args) {
+ CDataInterfaceLibrary.ArrowSchema arrowSchema = new CDataInterfaceLibrary.ArrowSchema();
Review Comment:
Can we pick different names for these variables? It gets very confusing to have lots of things with the same name.
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
Review Comment:
I don't think this paragraph is necessary (and it doesn't belong in this section in either case)
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
+
+.. code-block:: shell
+
+ git clone https://github.com/apache/arrow.git
+ cd arrow/cpp
+ cmake --preset -N ninja-debug-minimal
+ mkdir build # from inside the `cpp` subdirectory
+ cd build
+ cmake .. --preset ninja-debug-minimal
+ cmake --build .
+ tree debug/
+ debug/
+ ├── libarrow.800.0.0.dylib
+ ├── libarrow.800.dylib -> libarrow.800.0.0.dylib
+ └── libarrow.dylib -> libarrow.800.dylib
+
+Define c++ code CDataInterfaceLibrary.h that export functions for third party like Java consumer:
+
+.. code-block:: cpp
+
+ #include <iostream>
+ #include <arrow/api.h>
+
+ #define ARROW_FLAG_DICTIONARY_ORDERED 1
+ #define ARROW_FLAG_NULLABLE 2
+ #define ARROW_FLAG_MAP_KEYS_SORTED 4
+
+ using arrow::Int64Builder;
+
+ struct ArrowSchema {
+ // Array type description
+ const char* format;
+ const char* name;
+ const char* metadata;
+ int64_t flags;
+ int64_t n_children;
+ struct ArrowSchema** children;
+ struct ArrowSchema* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowSchema*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ struct ArrowArray {
+ // Array data description
+ int64_t length;
+ int64_t null_count;
+ int64_t offset;
+ int64_t n_buffers;
+ int64_t n_children;
+ const void** buffers;
+ struct ArrowArray** children;
+ struct ArrowArray* dictionary;
+
+ // Release callback
+ void (*release)(struct ArrowArray*);
+ // Opaque producer-specific data
+ void* private_data;
+ };
+
+ static void release_int32_type(struct ArrowSchema* schema) {
Review Comment:
Please follow Arrow coding conventions here.
##########
docs/source/java/cdata.rst:
##########
@@ -0,0 +1,313 @@
+.. 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.
+
+================
+C Data Interface
+================
+
+.. contents::
+
+Arrow supports exchanging data within the same process through the :ref:`c-data-interface`.
+
+Java to Python
+--------------
+
+Use this guide to implement :doc:`Java to Python <../python/integration/python_java.rst>`
+communication using the C Data Interface.
+
+Java to C++
+-----------
+
+The C Data Interface is a protocol implemented in Arrow to exchange data within different
+environments without the cost of marshaling and copying data.
+
+Example: How to expose an int32 array using C Data Interface?
+
+**C++ Side**
+
+Compile arrow minimal library:
+
+.. code-block:: shell
+
+ git clone https://github.com/apache/arrow.git
+ cd arrow/cpp
+ cmake --preset -N ninja-debug-minimal
+ mkdir build # from inside the `cpp` subdirectory
+ cd build
+ cmake .. --preset ninja-debug-minimal
+ cmake --build .
+ tree debug/
+ debug/
+ ├── libarrow.800.0.0.dylib
+ ├── libarrow.800.dylib -> libarrow.800.0.0.dylib
+ └── libarrow.dylib -> libarrow.800.dylib
+
+Define c++ code CDataInterfaceLibrary.h that export functions for third party like Java consumer:
Review Comment:
We should just use `bridge.h` we should not tell people to reimplement everything
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