Added an object that lets you hold a copyable reference to a java array. Also

renamed the objects and generally improved documentation.

dlib/java/cmake_swig_jni

@@ -119,8 +119,26 @@ FILE(WRITE ${CMAKE_CURRENT_BINARY_DIR}/swig.i
     %module global 
 
     %{
-    #include \"swig_api.h\"
     #include <exception>
+    #include <stdexcept>
+    static JavaVM *cached_jvm = 0;
+
+    JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *jvm, void *reserved) {
+        cached_jvm = jvm;
+        return JNI_VERSION_1_6;
+    }
+
+    static JNIEnv * JNI_GetEnv() {
+        JNIEnv *env;
+        jint rc = cached_jvm->GetEnv((void **)&env, JNI_VERSION_1_6);
+        if (rc == JNI_EDETACHED)
+            throw std::runtime_error(\"current thread not attached\");
+        if (rc == JNI_EVERSION)
+            throw std::runtime_error(\"jni version not supported\");
+        return env;
+    }
+
+    #include \"swig_api.h\"
     %}
 
     // Convert all C++ exceptions into java.lang.Exception

dlib/java/jvector.h

-// Copyright (C) 2017  Davis E. King (davis@dlib.net)
-// License: Boost Software License   See LICENSE.txt for the full license.
-#ifndef DLIB_SWIG_JVECTOR_H_
-#define DLIB_SWIG_JVECTOR_H_
-
-
-/*
-
-    This file defines two special classes, jvector and jvector_crit.  Both of them have the
-    interface defined by jvector_base, that is, the interface of a simple array object like
-    std::vector (except without any ability to be resized).  These classes are simple
-    interfaces to java native arrays.  So for example, suppose you had an array of int in
-    java and you wanted to pass it to C++.  You could create a C++ function like this:
-
-        void my_function(const jvector<int>& array);
-
-    and then within java you could call it with code like this:
-
-       int[] array = new int[100];
-       my_function(array);
-
-    and it will work just like you would expect.  The jvector<int> will usually result in
-    the JVM doing a copy in the background.  However, you can also declare your function
-    like this:
-
-        void my_function(const jvector_crit<int>& array);
-
-    and still call it the same way in java, however, using jvector_crit<int> will usually
-    not result in any copying, and is therefore very fast.  jvector_crit uses the JNI
-    routine GetPrimitiveArrayCritical() to get a lock on the java memory underlying the
-    array.  So it will probably prevent the garbage collector from running while your
-    function is executing.  The JNI documentation is somewhat vague on the limitations of
-    GetPrimitiveArrayCritical(), saying only that you shouldn't hold the lock on the array
-    for "an extended period" or call back into the JVM.  Deciding whether or not this
-    matters in your application is left as an exercise for the reader.
-
-
-    There are two ways you can declare your methods.  Taking a const reference or a
-    non-const reference.  E.g.:
-        void my_function(const jvector<int>& array);
-        void my_function(jvector<int>& array);
-    The non-const version allows you to modify the contents of the array and the
-    modifications will be visible to java, as you would expect.
-
-    You can also of course use functions taking many arguments, as is normally the case
-    with SWIG.  Finally, jvector works with the following primitive types:
-        - int16_t
-        - int32_t
-        - int64_t
-        - char     (corresponding to java byte)
-        - float
-        - double
-*/
-
-
-// ----------------------------------------------------------------------------------------
-
-template <typename T>
-class jvector_base
-{
-public:
-    jvector_base() = default;
-
-    size_t size() const { return sz; }
-    T* data() { return pdata; }
-    const T* data() const { return pdata; }
-
-    T* begin() { return pdata; }
-    T* end() { return pdata+sz; }
-    const T* begin() const { return pdata; }
-    const T* end() const { return pdata+sz; }
-
-    T& operator[](size_t i) { return pdata[i]; }
-    const T& operator[](size_t i) const { return pdata[i]; }
-
-protected:
-    T* pdata = nullptr;
-    size_t sz = 0;
-
-private:
-    // this object is non-copyable
-    jvector_base(const jvector_base&);
-    jvector_base& operator=(const jvector_base&);
-
-};
-
-
-// ----------------------------------------------------------------------------------------
-// ----------------------------------------------------------------------------------------
-// ----------------------------------------------------------------------------------------
-
-template <typename T> class jvector;
-
-#define JVECTOR_CLASS_SPEC(ctype, type, Type)                                               \
-template <> class jvector<ctype> : public jvector_base<ctype>                               \
-{                                                                                           \
-public:                                                                                     \
-    ~jvector() { clear(); }                                                                 \
-    void reset(JNIEnv* jenv_, j##type##Array arr, bool mightBeModified_) {                  \
-        clear();                                                                            \
-        jenv = jenv_;                                                                       \
-        oldArr = arr;                                                                       \
-        pdata = (ctype*)jenv->Get##Type##ArrayElements(arr, 0);                             \
-        sz = jenv->GetArrayLength(arr);                                                     \
-        mightBeModified = mightBeModified_;                                                 \
-    }                                                                                       \
-private:                                                                                    \
-    void clear() {                                                                          \
-        if (pdata) {                                                                        \
-            jenv->Release##Type##ArrayElements(oldArr, (j##type*)pdata, mightBeModified?0:JNI_ABORT); \
-            pdata = nullptr;                                                                \
-        }                                                                                   \
-    }                                                                                       \
-    JNIEnv* jenv = nullptr;                                                                 \
-    j##type##Array oldArr;                                                                  \
-    bool mightBeModified;                                                                   \
-};
-
-JVECTOR_CLASS_SPEC(int16_t,short, Short)
-JVECTOR_CLASS_SPEC(int32_t,int, Int)
-JVECTOR_CLASS_SPEC(int64_t,long, Long)
-JVECTOR_CLASS_SPEC(char,byte, Byte)
-JVECTOR_CLASS_SPEC(float,float, Float)
-JVECTOR_CLASS_SPEC(double,double, Double)
-
- 
-// ----------------------------------------------------------------------------------------
-// ----------------------------------------------------------------------------------------
-// ----------------------------------------------------------------------------------------
-
-template <typename T, typename JARR> 
-class jvector_crit_base 
-{
-public:
-    jvector_crit_base() = default;
-
-    size_t size() const { return sz; }
-    T* data() { return pdata; }
-    const T* data() const { return pdata; }
-
-    T* begin() { return pdata; }
-    T* end() { return pdata+sz; }
-    const T* begin() const { return pdata; }
-    const T* end() const { return pdata+sz; }
-    T& operator[](size_t i) { return pdata[i]; }
-    const T& operator[](size_t i) const { return pdata[i]; }
-
-    ~jvector_crit_base() { clear(); }
-
-    void reset(JNIEnv* jenv_, JARR arr, bool mightBeModified_)
-    {
-        clear();
-        jenv = jenv_;
-        oldArr = arr;
-        pdata = (T*)jenv->GetPrimitiveArrayCritical(arr, 0);
-        sz = jenv->GetArrayLength(arr);
-        mightBeModified = mightBeModified_;
-    }
-
-private:
-
-    void clear()
-    {
-        if (pdata) {
-            jenv->ReleasePrimitiveArrayCritical(oldArr, pdata, mightBeModified?0:JNI_ABORT);
-            pdata = nullptr;
-        }
-    }
-
-    // this object is non-copyable
-    jvector_crit_base(const jvector_crit_base&);
-    jvector_crit_base& operator=(const jvector_crit_base&);
-
-    T* pdata = nullptr;
-    size_t sz = 0;
-    JNIEnv* jenv = nullptr;
-    JARR oldArr;
-    bool mightBeModified;
-};
-
-template <typename T> class jvector_crit;
-
-template <> class jvector_crit<int16_t> : public jvector_crit_base<int16_t,jshortArray> {};
-template <> class jvector_crit<int32_t> : public jvector_crit_base<int32_t,jintArray> {};
-template <> class jvector_crit<int64_t> : public jvector_crit_base<int64_t,jlongArray> {};
-template <> class jvector_crit<char>    : public jvector_crit_base<char,jbyteArray> {};
-template <> class jvector_crit<float>   : public jvector_crit_base<float,jfloatArray> {};
-template <> class jvector_crit<double>  : public jvector_crit_base<double,jdoubleArray> {};
- 
-// ----------------------------------------------------------------------------------------
-
-// Define SWIG typemaps so SWIG will know what to do with the jvector and jvector_crit
-// objects.
-#ifdef SWIG
-%define tostring(token) 
-    #token
-%enddef
-
-%define define_jvector_converion(type, java_type)
-    // Define array conversions for non-const arrays
-    %typemap(jtype)       (jvector<type>&)  "java_type[]"
-    %typemap(jstype)      (jvector<type>&)  "java_type[]"
-    %typemap(jni)         (jvector<type>&)  tostring(j##java_type##Array)
-    %typemap(javain)      (jvector<type>&)  "$javainput"
-    %typemap(arginit)     (jvector<type>&)  { $1 = &temp$argnum; }
-    %typemap(in)          (jvector<type>&) (jvector<type> temp)  { $1->reset(jenv, $input, true); }
-
-    %typemap(jtype)       (const jvector<type>&)  "java_type[]"
-    %typemap(jstype)      (const jvector<type>&)  "java_type[]"
-    %typemap(jni)         (const jvector<type>&)  tostring(j##java_type##Array)
-    %typemap(javain)      (const jvector<type>&)  "$javainput"
-    %typemap(arginit)     (const jvector<type>&)  { $1 = &temp$argnum; }
-    %typemap(in)          (const jvector<type>&) (jvector<type> temp)  { $1->reset(jenv, $input, false); }
-%enddef
-define_jvector_converion(int16_t,short)
-define_jvector_converion(int32_t,int)
-define_jvector_converion(int64_t,long)
-define_jvector_converion(char,byte)
-define_jvector_converion(float,float)
-define_jvector_converion(double,double)
-
-
-
-%define define_jvector_crit_converion(type, java_type)
-    // Define array conversions for non-const arrays
-    %typemap(jtype)       (jvector_crit<type>&)  "java_type[]"
-    %typemap(jstype)      (jvector_crit<type>&)  "java_type[]"
-    %typemap(jni)         (jvector_crit<type>&)  tostring(j##java_type##Array)
-    %typemap(javain)      (jvector_crit<type>&)  "$javainput"
-    %typemap(arginit)     (jvector_crit<type>&)  { $1 = &temp$argnum; }
-    %typemap(in)          (jvector_crit<type>&) (jvector_crit<type> temp)  { $1->reset(jenv, $input, true); }
-
-    %typemap(jtype)       (const jvector_crit<type>&)  "java_type[]"
-    %typemap(jstype)      (const jvector_crit<type>&)  "java_type[]"
-    %typemap(jni)         (const jvector_crit<type>&)  tostring(j##java_type##Array)
-    %typemap(javain)      (const jvector_crit<type>&)  "$javainput"
-    %typemap(arginit)     (const jvector_crit<type>&)  { $1 = &temp$argnum; }
-    %typemap(in)          (const jvector_crit<type>&) (jvector_crit<type> temp)  { $1->reset(jenv, $input, false); }
-%enddef
-define_jvector_crit_converion(int16_t,short)
-define_jvector_crit_converion(int32_t,int)
-define_jvector_crit_converion(int64_t,long)
-define_jvector_crit_converion(char,byte)
-define_jvector_crit_converion(float,float)
-define_jvector_crit_converion(double,double)
-
-#endif // SWIG
-
-#endif // DLIB_SWIG_JVECTOR_H_
-

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
+// This file is essentially a small unit test for the swig cmake scripts and the java array
 // 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"
+// Let's use java_array.h, 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 java::array, java::array_view, and
+// java::array_view_crit classes.  
+#include "java_array.h"
 #ifdef SWIG
-%include "jvector.h"
+%include "java_array.h"
 #endif
 
 
-// ----------------------------------------------------------------------------------------
+using namespace java;
+
 
 // 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 tsum(const array_view_crit<T>& arr)
 {
     T s = 0;
     for (auto& v : arr)
@@ -32,7 +34,7 @@ T tsum(const jvector_crit<T>& arr)
     return s;
 }
 template <typename T>
-T tsum(const jvector<T>& arr)
+T tsum(const array_view<T>& arr)
 {
     T s = 0;
     for (auto& v : arr)
@@ -56,41 +58,64 @@ void tassign(T& arr)
 // "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 array_view_crit<int16_t>& arr) { return tsum(arr); }
+inline int sum(const array_view<int16_t>& arr) { return tsum(arr); }
+inline void assign_crit(array_view_crit<int16_t>& arr) { tassign(arr); }
+inline void assign(array_view<int16_t>& arr) { tassign(arr); }
+
+
+inline int sum_crit(const array_view_crit<int32_t>& arr) { return tsum(arr); }
+inline int sum(const array_view<int32_t>& arr) { return tsum(arr); }
+inline void assign_crit(array_view_crit<int32_t>& arr) { tassign(arr); }
+inline void assign(array_view<int32_t>& arr) { tassign(arr); }
+
 
+inline int sum_crit(const array_view_crit<int64_t>& arr) { return tsum(arr); }
+inline int sum(const array_view<int64_t>& arr) { return tsum(arr); }
+inline void assign_crit(array_view_crit<int64_t>& arr) { tassign(arr); }
+inline void assign(array_view<int64_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 array_view_crit<char>& arr) { return tsum(arr); }
+inline int sum(const array_view<char>& arr) { return tsum(arr); }
+inline void assign_crit(array_view_crit<char>& arr) { tassign(arr); }
+inline void assign(array_view<char>& 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 array_view_crit<double>& arr) { return tsum(arr); }
+inline double sum(const array_view<double>& arr) { return tsum(arr); }
+inline void assign_crit(array_view_crit<double>& arr) { tassign(arr); }
+inline void assign(array_view<double>& arr) { tassign(arr); }
 
 
+inline float sum_crit(array<float> arr) 
+{ 
+    array_view_crit<float> a(arr);
+    return tsum(a); 
+}
+inline float sum(const array<float>& arr) 
+{ 
+    array_view<float> a(arr);
+    return tsum(a); 
+}
+inline void assign_crit(array_view_crit<float>& arr) { tassign(arr); }
+inline void assign(array<float>& arr) 
+{ 
+    array_view<float> a(arr);
+    tassign(a); 
+}
 
-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); }
+array<int32_t> make_an_array(size_t s)
+{
+    array<int32_t> arr(s);
+    array_view_crit<int32_t> a(arr);
 
+    for (size_t i = 0; i < a.size(); ++i)
+        a[i] = i;
 
-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); }
+    return arr;
+}
 
 
 // ----------------------------------------------------------------------------------------

dlib/java/swig_test.java

@@ -69,6 +69,14 @@ public class swig_test
         }
     }
 
+    public static void assertIsEqual(int val1, int val2)
+    {
+        if (val1 != val2)
+        {
+            throw new RuntimeException("Test failed " + val1 + " should be equal to " + val2);
+        }
+    }
+
     public static double sum(double[] arr)
     {
         double s = 0;
@@ -233,6 +241,13 @@ public class swig_test
                 assertIs28(global.sum_crit(arr));
             }
         }
+        {
+            int[] a = global.make_an_array(4);
+            for (int i = 0; i < a.length; ++i)
+            {
+                assertIsEqual(a[i], i);
+            }
+        }
 
         System.out.println("\n\n   ALL TESTS COMPLETED SUCCESSFULLY\n");
     }