blob: 052dcf9a8960b255af8950a89d9434650328d8a4 [file] [log] [blame]
* Copyright 2015 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include "webrtc/api/java/jni/jni_helpers.h"
#include "webrtc/api/java/jni/classreferenceholder.h"
#include <asm/unistd.h>
#include <sys/prctl.h>
#include <sys/syscall.h>
#include <unistd.h>
namespace webrtc_jni {
static JavaVM* g_jvm = nullptr;
static pthread_once_t g_jni_ptr_once = PTHREAD_ONCE_INIT;
// Key for per-thread JNIEnv* data. Non-NULL in threads attached to |g_jvm| by
// AttachCurrentThreadIfNeeded(), NULL in unattached threads and threads that
// were attached by the JVM because of a Java->native call.
static pthread_key_t g_jni_ptr;
JavaVM *GetJVM() {
RTC_CHECK(g_jvm) << "JNI_OnLoad failed to run?";
return g_jvm;
// Return a |JNIEnv*| usable on this thread or NULL if this thread is detached.
JNIEnv* GetEnv() {
void* env = nullptr;
jint status = g_jvm->GetEnv(&env, JNI_VERSION_1_6);
RTC_CHECK(((env != nullptr) && (status == JNI_OK)) ||
((env == nullptr) && (status == JNI_EDETACHED)))
<< "Unexpected GetEnv return: " << status << ":" << env;
return reinterpret_cast<JNIEnv*>(env);
static void ThreadDestructor(void* prev_jni_ptr) {
// This function only runs on threads where |g_jni_ptr| is non-NULL, meaning
// we were responsible for originally attaching the thread, so are responsible
// for detaching it now. However, because some JVM implementations (notably
// Oracle's also use the pthread_key_create mechanism,
// the JVMs accounting info for this thread may already be wiped out by the
// time this is called. Thus it may appear we are already detached even though
// it was our responsibility to detach! Oh well.
if (!GetEnv())
RTC_CHECK(GetEnv() == prev_jni_ptr)
<< "Detaching from another thread: " << prev_jni_ptr << ":" << GetEnv();
jint status = g_jvm->DetachCurrentThread();
RTC_CHECK(status == JNI_OK) << "Failed to detach thread: " << status;
RTC_CHECK(!GetEnv()) << "Detaching was a successful no-op???";
static void CreateJNIPtrKey() {
RTC_CHECK(!pthread_key_create(&g_jni_ptr, &ThreadDestructor))
<< "pthread_key_create";
jint InitGlobalJniVariables(JavaVM *jvm) {
RTC_CHECK(!g_jvm) << "InitGlobalJniVariables!";
g_jvm = jvm;
RTC_CHECK(g_jvm) << "InitGlobalJniVariables handed NULL?";
RTC_CHECK(!pthread_once(&g_jni_ptr_once, &CreateJNIPtrKey)) << "pthread_once";
JNIEnv* jni = nullptr;
if (jvm->GetEnv(reinterpret_cast<void**>(&jni), JNI_VERSION_1_6) != JNI_OK)
return -1;
return JNI_VERSION_1_6;
// Return thread ID as a string.
static std::string GetThreadId() {
char buf[21]; // Big enough to hold a kuint64max plus terminating NULL.
RTC_CHECK_LT(snprintf(buf, sizeof(buf), "%ld",
<< "Thread id is bigger than uint64??";
return std::string(buf);
// Return the current thread's name.
static std::string GetThreadName() {
char name[17] = {0};
if (prctl(PR_GET_NAME, name) != 0)
return std::string("<noname>");
return std::string(name);
// Return a |JNIEnv*| usable on this thread. Attaches to |g_jvm| if necessary.
JNIEnv* AttachCurrentThreadIfNeeded() {
JNIEnv* jni = GetEnv();
if (jni)
return jni;
<< "TLS has a JNIEnv* but not attached?";
std::string name(GetThreadName() + " - " + GetThreadId());
JavaVMAttachArgs args;
args.version = JNI_VERSION_1_6; = &name[0]; = nullptr;
// Deal with difference in signatures between Oracle's jni.h and Android's.
#ifdef _JAVASOFT_JNI_H_ // Oracle's jni.h violates the JNI spec!
void* env = nullptr;
JNIEnv* env = nullptr;
RTC_CHECK(!g_jvm->AttachCurrentThread(&env, &args))
<< "Failed to attach thread";
RTC_CHECK(env) << "AttachCurrentThread handed back NULL!";
jni = reinterpret_cast<JNIEnv*>(env);
RTC_CHECK(!pthread_setspecific(g_jni_ptr, jni)) << "pthread_setspecific";
return jni;
// Return a |jlong| that will correctly convert back to |ptr|. This is needed
// because the alternative (of silently passing a 32-bit pointer to a vararg
// function expecting a 64-bit param) picks up garbage in the high 32 bits.
jlong jlongFromPointer(void* ptr) {
static_assert(sizeof(intptr_t) <= sizeof(jlong),
"Time to rethink the use of jlongs");
// Going through intptr_t to be obvious about the definedness of the
// conversion from pointer to integral type. intptr_t to jlong is a standard
// widening by the static_assert above.
jlong ret = reinterpret_cast<intptr_t>(ptr);
RTC_DCHECK(reinterpret_cast<void*>(ret) == ptr);
return ret;
// JNIEnv-helper methods that RTC_CHECK success: no Java exception thrown and
// found object/class/method/field is non-null.
jmethodID GetMethodID(
JNIEnv* jni, jclass c, const std::string& name, const char* signature) {
jmethodID m = jni->GetMethodID(c, name.c_str(), signature);
CHECK_EXCEPTION(jni) << "error during GetMethodID: " << name << ", "
<< signature;
RTC_CHECK(m) << name << ", " << signature;
return m;
jmethodID GetStaticMethodID(
JNIEnv* jni, jclass c, const char* name, const char* signature) {
jmethodID m = jni->GetStaticMethodID(c, name, signature);
CHECK_EXCEPTION(jni) << "error during GetStaticMethodID: " << name << ", "
<< signature;
RTC_CHECK(m) << name << ", " << signature;
return m;
jfieldID GetFieldID(
JNIEnv* jni, jclass c, const char* name, const char* signature) {
jfieldID f = jni->GetFieldID(c, name, signature);
CHECK_EXCEPTION(jni) << "error during GetFieldID";
RTC_CHECK(f) << name << ", " << signature;
return f;
jclass GetObjectClass(JNIEnv* jni, jobject object) {
jclass c = jni->GetObjectClass(object);
CHECK_EXCEPTION(jni) << "error during GetObjectClass";
RTC_CHECK(c) << "GetObjectClass returned NULL";
return c;
jobject GetObjectField(JNIEnv* jni, jobject object, jfieldID id) {
jobject o = jni->GetObjectField(object, id);
CHECK_EXCEPTION(jni) << "error during GetObjectField";
RTC_CHECK(!IsNull(jni, o)) << "GetObjectField returned NULL";
return o;
jobject GetNullableObjectField(JNIEnv* jni, jobject object, jfieldID id) {
jobject o = jni->GetObjectField(object, id);
CHECK_EXCEPTION(jni) << "error during GetObjectField";
return o;
jstring GetStringField(JNIEnv* jni, jobject object, jfieldID id) {
return static_cast<jstring>(GetObjectField(jni, object, id));
jlong GetLongField(JNIEnv* jni, jobject object, jfieldID id) {
jlong l = jni->GetLongField(object, id);
CHECK_EXCEPTION(jni) << "error during GetLongField";
return l;
jint GetIntField(JNIEnv* jni, jobject object, jfieldID id) {
jint i = jni->GetIntField(object, id);
CHECK_EXCEPTION(jni) << "error during GetIntField";
return i;
bool GetBooleanField(JNIEnv* jni, jobject object, jfieldID id) {
jboolean b = jni->GetBooleanField(object, id);
CHECK_EXCEPTION(jni) << "error during GetBooleanField";
return b;
bool IsNull(JNIEnv* jni, jobject obj) {
return jni->IsSameObject(obj, nullptr);
// Given a UTF-8 encoded |native| string return a new (UTF-16) jstring.
jstring JavaStringFromStdString(JNIEnv* jni, const std::string& native) {
jstring jstr = jni->NewStringUTF(native.c_str());
CHECK_EXCEPTION(jni) << "error during NewStringUTF";
return jstr;
// Given a (UTF-16) jstring return a new UTF-8 native string.
std::string JavaToStdString(JNIEnv* jni, const jstring& j_string) {
const char* chars = jni->GetStringUTFChars(j_string, nullptr);
CHECK_EXCEPTION(jni) << "Error during GetStringUTFChars";
std::string str(chars, jni->GetStringUTFLength(j_string));
CHECK_EXCEPTION(jni) << "Error during GetStringUTFLength";
jni->ReleaseStringUTFChars(j_string, chars);
CHECK_EXCEPTION(jni) << "Error during ReleaseStringUTFChars";
return str;
// Return the (singleton) Java Enum object corresponding to |index|;
jobject JavaEnumFromIndex(JNIEnv* jni, jclass state_class,
const std::string& state_class_name, int index) {
jmethodID state_values_id = GetStaticMethodID(
jni, state_class, "values", ("()[L" + state_class_name + ";").c_str());
jobjectArray state_values = static_cast<jobjectArray>(
jni->CallStaticObjectMethod(state_class, state_values_id));
CHECK_EXCEPTION(jni) << "error during CallStaticObjectMethod";
jobject ret = jni->GetObjectArrayElement(state_values, index);
CHECK_EXCEPTION(jni) << "error during GetObjectArrayElement";
return ret;
std::string GetJavaEnumName(JNIEnv* jni,
const std::string& className,
jobject j_enum) {
jclass enumClass = FindClass(jni, className.c_str());
jmethodID nameMethod =
GetMethodID(jni, enumClass, "name", "()Ljava/lang/String;");
jstring name =
reinterpret_cast<jstring>(jni->CallObjectMethod(j_enum, nameMethod));
CHECK_EXCEPTION(jni) << "error during CallObjectMethod for " << className
<< ".name";
return JavaToStdString(jni, name);
jobject NewGlobalRef(JNIEnv* jni, jobject o) {
jobject ret = jni->NewGlobalRef(o);
CHECK_EXCEPTION(jni) << "error during NewGlobalRef";
return ret;
void DeleteGlobalRef(JNIEnv* jni, jobject o) {
CHECK_EXCEPTION(jni) << "error during DeleteGlobalRef";
// Scope Java local references to the lifetime of this object. Use in all C++
// callbacks (i.e. entry points that don't originate in a Java callstack
// through a "native" method call).
ScopedLocalRefFrame::ScopedLocalRefFrame(JNIEnv* jni) : jni_(jni) {
RTC_CHECK(!jni_->PushLocalFrame(0)) << "Failed to PushLocalFrame";
ScopedLocalRefFrame::~ScopedLocalRefFrame() {
// Creates an iterator representing the end of any collection.
Iterable::Iterator::Iterator() : iterator_(nullptr) {}
// Creates an iterator pointing to the beginning of the specified collection.
Iterable::Iterator::Iterator(JNIEnv* jni, jobject iterable) : jni_(jni) {
jclass j_class = GetObjectClass(jni, iterable);
jmethodID iterator_id =
GetMethodID(jni, j_class, "iterator", "()Ljava/util/Iterator;");
iterator_ = jni->CallObjectMethod(iterable, iterator_id);
CHECK_EXCEPTION(jni) << "error during CallObjectMethod";
RTC_CHECK(iterator_ != nullptr);
jclass iterator_class = GetObjectClass(jni, iterator_);
has_next_id_ = GetMethodID(jni, iterator_class, "hasNext", "()Z");
next_id_ = GetMethodID(jni, iterator_class, "next", "()Ljava/lang/Object;");
// Start at the first element in the collection.
// Move constructor - necessary to be able to return iterator types from
// functions.
Iterable::Iterator::Iterator(Iterator&& other)
: jni_(std::move(other.jni_)),
// Advances the iterator one step.
Iterable::Iterator& Iterable::Iterator::operator++() {
if (AtEnd()) {
// Can't move past the end.
return *this;
bool has_next = jni_->CallBooleanMethod(iterator_, has_next_id_);
CHECK_EXCEPTION(jni_) << "error during CallBooleanMethod";
if (!has_next) {
iterator_ = nullptr;
value_ = nullptr;
return *this;
value_ = jni_->CallObjectMethod(iterator_, next_id_);
CHECK_EXCEPTION(jni_) << "error during CallObjectMethod";
return *this;
// Provides a way to compare the iterator with itself and with the end iterator.
// Note: all other comparison results are undefined, just like for C++ input
// iterators.
bool Iterable::Iterator::operator==(const Iterable::Iterator& other) {
// Two different active iterators should never be compared.
RTC_DCHECK(this == &other || AtEnd() || other.AtEnd());
return AtEnd() == other.AtEnd();
jobject Iterable::Iterator::operator*() {
return value_;
bool Iterable::Iterator::AtEnd() const {
return jni_ == nullptr || IsNull(jni_, iterator_);
} // namespace webrtc_jni