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PeerConnection Java: explicitly cast DataChannel* to jlong for Java.

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Otherwise on 32-bit ARM Android the nativeDataChannel param the Java ctor sees
is a 64-bit value whose low 32 bits are the pointer, and whose high 32-bits are
garbage.

BUG=2302
R=wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2114004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4665 4adac7df-926f-26a2-2b94-8c16560cd09d
This commit is contained in:
fischman@webrtc.org 2013-09-03 18:58:12 +00:00
parent c8c32638be
commit 8788167b9b
1 changed files with 30 additions and 1 deletions
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31
talk/app/webrtc/java/jni/peerconnection_jni.cc
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@ -131,6 +131,12 @@ using webrtc::VideoRendererInterface;
CHECK(!count, "Unexpected refcount"); \
} while (0)
// Lifted from chromium's base/basictypes.h.
template <bool>
struct CompileAssert {};
#define COMPILE_ASSERT(expr, msg) \
typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1]
namespace {
static JavaVM* g_jvm = NULL; // Set in JNI_OnLoad().
@ -189,6 +195,24 @@ static JNIEnv* AttachCurrentThreadIfNeeded() {
return jni;
}
// Return a |jlong| that will automatically convert back to |ptr| when assigned
// to a |uint64|
static jlong jlongFromPointer(void* ptr) {
COMPILE_ASSERT(sizeof(intptr_t) <= sizeof(uint64),
Time_to_rethink_the_use_of_jlongs);
// Guaranteed to fit by the COMPILE_ASSERT above.
uint64 u64 = reinterpret_cast<intptr_t>(ptr);
// If the unsigned value fits in the signed type, return it directly.
if (u64 <= std::numeric_limits<int64>::max())
return u64;
// Otherwise, we need to get move u64 into the range of [int64min, -1] subject
// to the constraints of remaining equal to |u64| modulo |2^64|.
u64 = std::numeric_limits<uint64>::max() - u64; // In [0,int64max].
int64 i64 = -u64; // In [-int64max, 0].
i64 -= 1; // In [int64min, -1], and i64+2^64==u64.
return i64;
}
// Android's FindClass() is trickier than usual because the app-specific
// ClassLoader is not consulted when there is no app-specific frame on the
// stack. Consequently, we only look up classes once in JNI_OnLoad.
@ -1346,11 +1370,16 @@ JOW(jobject, PeerConnection_createDataChannel)(
talk_base::scoped_refptr<DataChannelInterface> channel(
ExtractNativePC(jni, j_pc)->CreateDataChannel(
JavaToStdString(jni, j_label), &init));
// Mustn't pass channel.get() directly through NewObject to avoid reading its
// vararg parameter as 64-bit and reading memory that doesn't belong to the
// 32-bit parameter.
jlong nativeChannelPtr = jlongFromPointer(channel.get());
CHECK(nativeChannelPtr, "Failed to create DataChannel");
jclass j_data_channel_class = FindClass(jni, "org/webrtc/DataChannel");
jmethodID j_data_channel_ctor = GetMethodID(
jni, j_data_channel_class, "<init>", "(J)V");
jobject j_channel = jni->NewObject(
j_data_channel_class, j_data_channel_ctor, channel.get());
j_data_channel_class, j_data_channel_ctor, nativeChannelPtr);
CHECK_EXCEPTION(jni, "error during NewObject");
// Channel is now owned by Java object, and will be freed from there.
int bumped_count = channel->AddRef();