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80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
#pragma once
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#include <jni.h>
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#include <string_view>
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#include <functional>
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/// visit string as native bytes
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/// jvm uses some unholy encoding internally so we convert it to utf-8
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template <typename T, typename V>
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static T
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VisitStringAsStringView(JNIEnv* env, jobject str, V visit)
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{
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const jclass stringClass = env->GetObjectClass(str);
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const jmethodID getBytes = env->GetMethodID(stringClass, "getBytes", "(Ljava/lang/String;)[B");
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const jstring charsetName = env->NewStringUTF("UTF-8");
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const jbyteArray stringJbytes = (jbyteArray)env->CallObjectMethod(str, getBytes, charsetName);
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env->DeleteLocalRef(charsetName);
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const size_t length = env->GetArrayLength(stringJbytes);
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jbyte* pBytes = env->GetByteArrayElements(stringJbytes, NULL);
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T result = visit(std::string_view((const char*)pBytes, length));
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env->ReleaseByteArrayElements(stringJbytes, pBytes, JNI_ABORT);
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env->DeleteLocalRef(stringJbytes);
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return result;
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}
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/// cast jni buffer to T *
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template <typename T>
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static T*
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FromBuffer(JNIEnv* env, jobject o)
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{
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if (o == nullptr)
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return nullptr;
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return static_cast<T*>(env->GetDirectBufferAddress(o));
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}
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/// get T * from object member called membername
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template <typename T>
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static T*
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FromObjectMember(JNIEnv* env, jobject self, const char* membername)
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{
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jclass cl = env->GetObjectClass(self);
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jfieldID name = env->GetFieldID(cl, membername, "Ljava/nio/ByteBuffer;");
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jobject buffer = env->GetObjectField(self, name);
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return FromBuffer<T>(env, buffer);
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}
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/// visit object string member called membername as bytes
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template <typename T, typename V>
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static T
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VisitObjectMemberStringAsStringView(JNIEnv* env, jobject self, const char* membername, V v)
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{
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jclass cl = env->GetObjectClass(self);
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jfieldID name = env->GetFieldID(cl, membername, "Ljava/lang/String;");
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jobject str = env->GetObjectField(self, name);
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return VisitStringAsStringView<T, V>(env, str, v);
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}
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/// get object member int called membername
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template <typename Int_t>
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Int_t
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GetObjectMemberAsInt(JNIEnv* env, jobject self, const char* membername)
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{
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jclass cl = env->GetObjectClass(self);
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jfieldID name = env->GetFieldID(cl, membername, "I");
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return env->GetIntField(self, name);
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}
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/// get implementation on jni type
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template <typename T>
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T*
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GetImpl(JNIEnv* env, jobject self)
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{
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return FromObjectMember<T>(env, self, "impl");
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}
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