Convert the byte array to java types

Question

I have a very specific requirement. I have a java application, where I have to convert byte array in to message having java types like int, String. The structure of the message is defined in c++ as below -

struct SMSMessage{ 
int    id;        
std::string name;       
std::string source;     

std::string destination;
std::string timestamp;  
int         type;       
int         status;     
std::string message;    
int         mesg_type;   
int         mesg_sub_type; };

What I receive in my java application is the byte array. I don't know wheather c++ application is using proto buffers or any other way to convert in to a byte array. But, if I parse the array using byte by byte, I could get the values. For example -

ByteBuffer.wrap(Arrays.copyOfRange(byteArray, 0, 4)).getInt();
//byteArray -- reference to the incoming byte array
// 0, 4-- range of bytes for integer type

This line will return correct id value (First property in structure is int).

My question are - If I write the proto for this structure, could I be able to parse this message in to java ?

Is there any other way to convert the byte array to java types ?(not using library like google protobuf )

I forget to mention that, the solution has to work with java 5 and java 8 — Gunwant
– Gunwant, Commented Sep 21, 2016 at 10:32
It sounds like this byte array is probably not a protocol buffer. If it were encoded as a protocol buffer then reading the first four bytes would not give you the first integer field directly unless by an unlikely coincidence. — Adam Cozzette
– Adam Cozzette, Commented Sep 23, 2016 at 18:06

RisuRyu · Accepted Answer · 2016-09-21 12:24:07Z

1

I'am not sure if you can convert it directly into a java structure but i guess it is not so easy possible. Also if it works you can't be sure that the size of the Datatypes are the same. If you run the C++ Application and the Java Application on a different Machine with a different architecture it can be different sizes.

So in my opinion the best option would be you write it first into a json or xml file and read it back from the other application.

If you want do it like you already wrote, then maybe you should sort the c++ struct by types. So you can better use a loop. Like, i have 5 times a integer of 4 bytes and 5 times a string with X Bytes.

mfg

answered Sep 21, 2016 at 12:24

RisuRyu

1347 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Gunwant Over a year ago

Well, I cannot use Json or any other format, because I don't have control over c++ application. Is it not possible using google-protobuf ?

Gunwant Over a year ago

Used Byte by Byte approach. Thanks

ARau · Accepted Answer · 2016-09-29 03:56:46Z

0

You may be able to use the open source javolution library specifically take a look at the Struct class which provides some support for directly mapping C structs to Java types.

You will encounter problems mapping the std::string type as the length of the string is not known beforehand. You will need to read this in as a byte stream until you find the null terminator which signifies the end of a string.

answered Sep 29, 2016 at 3:56

ARau

4892 silver badges9 bronze badges

Collectives™ on Stack Overflow

Convert the byte array to java types

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related