CODEWITHSUNDEEP
javac++java-native-interface
Mirza Dobric
Mirza Dobric

Reputation: 1537

How to detect endianness from JNI code?

I need to call the native function int getSize(uint_64& out) through JNI. There are obviously a few problems here that I intend to solve by passing byte[] to the JNI code, populating it with the value of uint64_t &out, and then creating a BigInteger out of the result. So, from Java I call getSize(byte[] size), in JNI C code I pass a new uint64_t to getSize(uint64_t& out) and then copy the value from it back to the byte array, and finally I create a BigInteger out of this byte array. My question is how do I copy the uint64_t value into the byte array? I know that on the Java side the value has to be in big-endian order but how do I figure out what the byte order is of the uint64_t?

Upvotes: 0

Views: 1010

Answers (1)

user207421
user207421

Reputation: 310869

The byte order of the uint64_t is the native byte order, of course, but you don't need to deal with endianness-ness at all here. Just return a jlong from your native method. It will arrive in big-endian order in the Java code, where the Java code can deal with it any way you like.

Upvotes: 3

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