lokinet/jni/lokinet_jni_common.hpp
Thomas Winget 7caa87862e standardize include format and pragma once
All #ifndef guards on headers have been removed, I think,
in favor of #pragma once

Headers are now included as `#include "filename"` if the included file
resides in the same directory as the file including it, or any
subdirectory therein.  Otherwise they are included as
`#include <project/top/dir/relative/path/filename>`

The above does not include system/os headers.
2021-03-09 19:01:41 -05:00

80 lines
2.3 KiB
C++

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