Added cmake scripts and some related tooling that makes it easy to call C++

code from java.

dlib/java/CMakeLists.txt

+
+cmake_minimum_required (VERSION 2.8.12)
+project (myproject)
+set(java_package_name net.dlib)
+set(source_files
+   )
+
+include(../cmake_utils/use_cpp_11.cmake)
+include(../cmake_utils/release_build_by_default)
+
+include_directories(
+   .
+   )
+
+# Additional dependencies
+#include(../../dlib/cmake)
+#set(additional_link_libraries dlib)
+
+# tell swig to put the output files into the local folder.
+set(install_target_output_folder .)
+
+
+include(cmake_swig_jni)
+
+

dlib/java/cmake_swig_jni

+# This file is used to create SWIG based JNI interfaces to C++ code.  You use
+# it by defining some CMake variables and then include(cmake_swig_jni).  You
+# would make a CMakeLists.txt file that looks like the following:
+#
+#   cmake_minimum_required (VERSION 2.8.4)
+#   project (example)
+#   set(java_package_name "org.mycompany")
+#   set(source_files
+#       your_cpp_source.cpp
+#       more_cpp_source.cpp
+#   )
+#
+#   ### We might need to link our code to some other C++ library like dlib.  You
+#   ### can do that by setting additional_link_libraries.  Here is an example of
+#   ### linking to dlib:
+#   include(../../dlib/dlib/cmake)
+#   set(additional_link_libraries dlib)
+#
+#   ### tell swig to put the output files into the parent folder of your CMakeLists.txt 
+#   ### file when you run make install.
+#   set(install_target_output_folder ..)
+#   include(cmake_swig_jni)
+
+
+
+
+
+
+
+################################################################################
+################################################################################
+#                             IMPLEMENTATION DETAILS
+################################################################################
+################################################################################
+
+cmake_minimum_required (VERSION 2.8.4)
+
+# This block of code tries to figure out what the JAVA_HOME environment
+# variable should be by looking at the folder that contains the java
+# executable.
+if (NOT DEFINED ENV{JAVA_HOME})
+   message(STATUS "JAVA_HOME environment variable not set, trying to guess it...")
+   find_program(JAVA_EXECUTABLE java)
+   # Resolve symbolic links, hopefully this will give us a path in the proper
+   # java home directory.
+   get_filename_component(JAVA_EXECUTABLE ${JAVA_EXECUTABLE} REALPATH)
+   # Pick out the parent directories
+   get_filename_component(JAVA_PATH1 ${JAVA_EXECUTABLE} PATH)
+   get_filename_component(JAVA_PATH2 ${JAVA_PATH1} PATH)
+   get_filename_component(JAVA_PATH3 ${JAVA_PATH2} PATH)
+   # and search them for include/jni.h.  If we find that then we probably have
+   # a good java home candidate.
+   find_path(AUTO_JAVA_HOME include/jni.h
+      PATHS
+      ${JAVA_PATH1}
+      ${JAVA_PATH2}
+      ${JAVA_PATH3}
+      "C:/Program Files/Java/jdk*"
+      "C:/Program Files (x86)/Java/jdk*"
+      )
+
+   if (AUTO_JAVA_HOME)
+      set(ENV{JAVA_HOME} ${AUTO_JAVA_HOME})
+      message(STATUS "Using JAVA_HOME OF " ${AUTO_JAVA_HOME})
+   else()
+      message(FATAL_ERROR "Couldn't find a folder for JAVA_HOME.  You must set the JAVA_HOME environment variable before running CMake.")
+   endif()
+endif()
+
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/lib")
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY_RELEASE "${CMAKE_CURRENT_BINARY_DIR}/lib")
+
+find_package(SWIG REQUIRED)
+find_package(Java REQUIRED)
+find_package(JNI REQUIRED)
+include(UseSWIG)
+
+macro (add_global_switch def_name )
+   if (NOT CMAKE_CXX_FLAGS MATCHES "${def_name}")
+      set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${def_name}" 
+         CACHE STRING "Flags used by the compiler during all C++ builds." 
+         FORCE)
+   endif ()
+   if (NOT CMAKE_C_FLAGS MATCHES "${def_name}")
+      set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${def_name}" 
+         CACHE STRING "Flags used by the compiler during all C builds." 
+         FORCE)
+   endif ()
+endmacro()
+
+# SWIG doesn't work if optimizations are enabled and strict aliasing is not
+# turned off.  This is a little wonky but it's how SWIG is.
+if (CMAKE_COMPILER_IS_GNUCXX)
+    add_definitions(-fno-strict-aliasing)
+endif()
+if (UNIX)
+    # we need to make sure all the code is compiled with -fPIC. In particular,
+    # it's important that all the code for the whole project is, not just the
+    # stuff immediately compiled by us in this cmake file.  So we add -fPIC to
+    # the top level cmake flags variables.
+    add_global_switch(-fPIC)
+endif()
+
+
+string(REGEX REPLACE "\\." "/" package_path ${java_package_name})
+string(REGEX REPLACE "\\..*" "" package_root_name ${java_package_name})
+
+set(CMAKE_SWIG_FLAGS -package ${java_package_name})
+set(CMAKE_SWIG_OUTDIR ${CMAKE_CURRENT_BINARY_DIR}/lib/java_src/${package_path})
+
+set(output_library_name ${PROJECT_NAME})
+
+# Create the swig.i interface file that swig will run on.  We do it here in
+# the cmake script because this lets us automatically include the correct
+# output library name into the call to System.loadLibrary().
+FILE(WRITE ${CMAKE_CURRENT_BINARY_DIR}/swig.i 
+        "
+    // Put the global functions in our api into a java class called global.
+    %module global 
+
+    %{
+    #include \"swig_api.h\"
+    #include <exception>
+    %}
+
+    // Convert all C++ exceptions into java.lang.Exception
+    %exception {
+        try {
+            $action
+        } catch(std::exception& e) {
+            jclass clazz = jenv->FindClass(\"java/lang/Exception\");
+            jenv->ThrowNew(clazz, e.what());
+            return $null;
+        }
+    }
+
+    %pragma(java) jniclasscode=%{
+    static {
+        try {
+            System.loadLibrary(\"${output_library_name}\");
+        } catch (UnsatisfiedLinkError e) {
+        System.err.println(\"Native code library failed to load. \\n\" + e);
+        System.exit(1);
+        }
+    }
+    %}
+
+    %include \"swig_api.h\"
+    "
+)
+
+# There is a bug in CMake's Swig scripts that causes the build to fail if the
+# binary folder doesn't contain a folder with the same name as the binary dir.
+# So we make a subfolder of the same name to avoid that bug.
+get_filename_component(binary_dir_name "${CMAKE_CURRENT_BINARY_DIR}" NAME)
+FILE(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${binary_dir_name}")
+
+set_source_files_properties(${CMAKE_CURRENT_BINARY_DIR}/swig.i PROPERTIES CPLUSPLUS ON)
+swig_add_module(${output_library_name} java ${CMAKE_CURRENT_BINARY_DIR}/swig.i ${source_files})
+
+include_directories(${JNI_INCLUDE_DIRS})
+swig_link_libraries(${output_library_name}  ${additional_link_libraries})
+
+# Things to delete when "make clean" is run.
+set(clean_files
+    ${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled
+    ${CMAKE_CURRENT_BINARY_DIR}/lib/java_src 
+    )
+set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES "${clean_files}")
+
+# Compile the java files into a jar file and stick it in the lib folder.
+add_custom_command(TARGET ${output_library_name} 
+   POST_BUILD
+   COMMAND cmake -E echo "compiling Java files..."
+   COMMAND cmake -E make_directory "${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled"
+   COMMAND ${Java_JAVAC_EXECUTABLE} ${CMAKE_SWIG_OUTDIR}/*.java -d "${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled"
+   COMMAND cmake -E echo "Making jar file..."
+   COMMAND ${Java_JAR_EXECUTABLE} cvf "${CMAKE_CURRENT_BINARY_DIR}/lib/${PROJECT_NAME}.jar" -C "${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled" ${package_root_name}
+   )
+
+
+#if the including cmake script set the install_target_output_folder variable
+#then make it so we install the compiled library and jar into that folder
+if (install_target_output_folder)
+    # Determine the path to our CMakeLists.txt file.
+    # There is either a bug (or break in compatability maybe) between versions
+    # of cmake that cause the or expression in this regular expression to be
+    # necessary.
+    string(REGEX REPLACE "(cmake_swig_jni|CMakeLists.txt)$" "" base_path ${CMAKE_PARENT_LIST_FILE})
+    # The directory we will write the output files to.
+    set(install_dir "${base_path}${install_target_output_folder}")
+    set(CMAKE_INSTALL_PREFIX "${install_dir}")
+    set(CMAKE_INSTALL_SYSTEM_RUNTIME_DESTINATION "${install_dir}")
+    install(TARGETS ${output_library_name} 
+        DESTINATION "${install_dir}"
+        )
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/lib/${PROJECT_NAME}.jar 
+        DESTINATION "${install_dir}"
+        )
+endif()
+
+# Copy any system libraries to the output folder.  This really only matters on
+# windows where it's good to have the visual studio runtime show up in the lib
+# folder so that you don't forget to include it in your binary distribution.
+INCLUDE(InstallRequiredSystemLibraries)
+foreach (file_i ${CMAKE_INSTALL_SYSTEM_RUNTIME_LIBS})
+   add_custom_command(TARGET ${output_library_name}
+      POST_BUILD
+      COMMAND cmake -E copy ${file_i} "${CMAKE_CURRENT_BINARY_DIR}/lib/"
+      )
+endforeach()
+

dlib/java/run_test.sh

+
+# build the jar and shared library of C++ code needed by the JVM
+mkdir build
+cd build
+cmake ..
+cmake --build . --config Release --target install
+cd ..
+
+
+# setup paths so the JVM can find our jar and shared library.
+export LD_LIBRARY_PATH=.
+export DYLD_LIBRARY_PATH=.
+export CLASSPATH=myproject.jar:. 
+
+# Now compile and run our java test that calls our C++ code.
+javac swig_test.java
+java swig_test

dlib/java/swig_api.h

+#ifndef EXAMPLE_SWIG_ApI_H_ 
+#define EXAMPLE_SWIG_ApI_H_
+
+// This file is essentially a small unit test for the swig cmake scripts and the jvector
+// classes.  All it does it define a few simple functions for writing to and summing
+// arrays.  The swig_test.java file then calls these C++ functions and checks if they work
+// correctly.  
+
+
+
+// Let's use the jvector, a tool for efficiently binding java native arrays to C++ function
+// arguments.  You do this by putting this pair of include statements in your swig_api.h
+// file.  Then after that you can use the jvector and jvector_crit classes.  
+#include "jvector.h"
+#ifdef SWIG
+%include "jvector.h"
+#endif
+
+
+// ----------------------------------------------------------------------------------------
+
+// SWIG can't expose templated functions to java.  We declare these here as helper
+// functions to make the non-templated routines swig will expose easier to write.  You can
+// see these java exposed methods below (i.e. sum(), sum_crit(), assign(), and
+// assign_crit()).
+template <typename T>
+T tsum(const jvector_crit<T>& arr)
+{
+    T s = 0;
+    for (auto& v : arr)
+        s += v;
+    return s;
+}
+template <typename T>
+T tsum(const jvector<T>& arr)
+{
+    T s = 0;
+    for (auto& v : arr)
+        s += v;
+    return s;
+}
+template <typename T>
+void tassign(T& arr)
+{
+    for (size_t i = 0; i < arr.size(); ++i)
+        arr[i] = i;
+}
+
+// ----------------------------------------------------------------------------------------
+
+// Now write some functions SWIG will expose to java.  SWIG will automatically expose
+// pretty much any non-template C++ code to java.  So just by defining these functions here
+// we expose them to java.
+// 
+// All global C++ functions will appear in java as static member functions of class called
+// "global", which is where these sum and assign routines will appear.  You can see
+// examples of java code that calls them in swig_test.java.
+
+inline int sum_crit(const jvector_crit<int16_t>& arr) { return tsum(arr); }
+inline int sum(const jvector<int16_t>& arr) { return tsum(arr); }
+inline void assign_crit(jvector_crit<int16_t>& arr) { tassign(arr); }
+inline void assign(jvector<int16_t>& arr) { tassign(arr); }
+
+
+inline int sum_crit(const jvector_crit<int32_t>& arr) { return tsum(arr); }
+inline int sum(const jvector<int32_t>& arr) { return tsum(arr); }
+inline void assign_crit(jvector_crit<int32_t>& arr) { tassign(arr); }
+inline void assign(jvector<int32_t>& arr) { tassign(arr); }
+
+
+inline int sum_crit(const jvector_crit<int64_t>& arr) { return tsum(arr); }
+inline int sum(const jvector<int64_t>& arr) { return tsum(arr); }
+inline void assign_crit(jvector_crit<int64_t>& arr) { tassign(arr); }
+inline void assign(jvector<int64_t>& arr) { tassign(arr); }
+
+
+inline int sum_crit(const jvector_crit<char>& arr) { return tsum(arr); }
+inline int sum(const jvector<char>& arr) { return tsum(arr); }
+inline void assign_crit(jvector_crit<char>& arr) { tassign(arr); }
+inline void assign(jvector<char>& arr) { tassign(arr); }
+
+
+
+inline double sum_crit(const jvector_crit<double>& arr) { return tsum(arr); }
+inline double sum(const jvector<double>& arr) { return tsum(arr); }
+inline void assign_crit(jvector_crit<double>& arr) { tassign(arr); }
+inline void assign(jvector<double>& arr) { tassign(arr); }
+
+
+inline float sum_crit(const jvector_crit<float>& arr) { return tsum(arr); }
+inline float sum(const jvector<float>& arr) { return tsum(arr); }
+inline void assign_crit(jvector_crit<float>& arr) { tassign(arr); }
+inline void assign(jvector<float>& arr) { tassign(arr); }
+
+
+// ----------------------------------------------------------------------------------------
+
+
+#endif // EXAMPLE_SWIG_ApI_H_
+
+

dlib/java/swig_test.java

+
+/*
+
+    This file tests all the ways of using jvector and jvector_crit. 
+
+*/
+
+
+import net.dlib.*;
+
+public class swig_test
+{
+    public static int sum(long[] arr)
+    {
+        int s = 0;
+        for (int i = 0; i < arr.length; ++i)
+            s += arr[i];
+        return s;
+    }
+    public static void zero(long[] arr)
+    {
+        for (int i = 0; i < arr.length; ++i)
+            arr[i] = 0;
+    }
+
+    public static int sum(byte[] arr)
+    {
+        int s = 0;
+        for (int i = 0; i < arr.length; ++i)
+            s += arr[i];
+        return s;
+    }
+    public static void zero(byte[] arr)
+    {
+        for (int i = 0; i < arr.length; ++i)
+            arr[i] = 0;
+    }
+    public static int sum(short[] arr)
+    {
+        int s = 0;
+        for (int i = 0; i < arr.length; ++i)
+            s += arr[i];
+        return s;
+    }
+    public static void zero(short[] arr)
+    {
+        for (int i = 0; i < arr.length; ++i)
+            arr[i] = 0;
+    }
+
+    public static int sum(int[] arr)
+    {
+        int s = 0;
+        for (int i = 0; i < arr.length; ++i)
+            s += arr[i];
+        return s;
+    }
+    public static void zero(int[] arr)
+    {
+        for (int i = 0; i < arr.length; ++i)
+            arr[i] = 0;
+    }
+
+    public static void assertIs28(int val)
+    {
+        if (val != 28)
+        {
+            throw new RuntimeException("Test failed " + val);
+        }
+    }
+
+    public static double sum(double[] arr)
+    {
+        double s = 0;
+        for (int i = 0; i < arr.length; ++i)
+            s += arr[i];
+        return s;
+    }
+    public static void zero(double[] arr)
+    {
+        for (int i = 0; i < arr.length; ++i)
+            arr[i] = 0;
+    }
+
+    public static void assertIs28(double val)
+    {
+        if (val != 28)
+        {
+            throw new RuntimeException("Test failed " + val);
+        }
+    }
+
+    public static float sum(float[] arr)
+    {
+        float s = 0;
+        for (int i = 0; i < arr.length; ++i)
+            s += arr[i];
+        return s;
+    }
+    public static void zero(float[] arr)
+    {
+        for (int i = 0; i < arr.length; ++i)
+            arr[i] = 0;
+    }
+
+    public static void assertIs28(float val)
+    {
+        if (val != 28)
+        {
+            throw new RuntimeException("Test failed " + val);
+        }
+    }
+
+    public static void main(String[] args)
+    {
+        {
+            float[] arr = new float[8];
+
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+            }
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum_crit(arr));
+            }
+        }
+        {
+            double[] arr = new double[8];
+
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+            }
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum_crit(arr));
+            }
+        }
+        {
+            byte[] arr = new byte[8];
+
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+            }
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum_crit(arr));
+            }
+        }
+        {
+            long[] arr = new long[8];
+
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+            }
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum_crit(arr));
+            }
+        }
+        {
+            short[] arr = new short[8];
+
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+            }
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum_crit(arr));
+            }
+        }
+        {
+            int[] arr = new int[8];
+
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+            }
+            for (int round = 0; round < 100; ++round)
+            {
+                zero(arr); global.assign(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum(arr));
+                zero(arr); global.assign_crit(arr);
+                assertIs28(sum(arr));
+                assertIs28(global.sum_crit(arr));
+            }
+        }
+
+        System.out.println("\n\n   ALL TESTS COMPLETED SUCCESSFULLY\n");
+    }
+}