I am writing Byte Array value into a file using Java with Big Endian Byte Order format.. Now I need to read that file from C++ program...
That Byte Array which I am writing into a file is made up of three Byte Arrays as described below-
short employeeId = 32767;
long lastModifiedDate = "1379811105109L";
byte[] attributeValue = os.toByteArray();
I am writing employeeId , lastModifiedDate and attributeValue together into a single Byte Array and that resulting Byte Array I am writing into a file and then I will be having my C++ program which will retrieve that Byte Array data from file and then deserialize it to extract employeeId, lastModifiedDate and attributeValue from it.
Below is my working Java code, which writes Byte Array value into a file with Big Endian format:
public class ByteBufferTest {
public static void main(String[] args) {
String text = "Byte Array Test For Big Endian";
byte[] attributeValue = text.getBytes();
long lastModifiedDate = 1289811105109L;
short employeeId = 32767;
int size = 2 + 8 + 4 + attributeValue.length; // short is 2 bytes, long 8 and int 4
ByteBuffer bbuf = ByteBuffer.allocate(size);
bbuf.order(ByteOrder.BIG_ENDIAN);
bbuf.putShort(employeeId);
bbuf.putLong(lastModifiedDate);
bbuf.putInt(attributeValue.length);
bbuf.put(attributeValue);
bbuf.rewind();
// best approach is copy the internal buffer
byte[] bytesToStore = new byte[size];
bbuf.get(bytesToStore);
writeFile(bytesToStore);
}
/**
* Write the file in Java
* @param byteArray
*/
public static void writeFile(byte[] byteArray) {
try{
File file = new File("bytebuffertest");
FileOutputStream output = new FileOutputStream(file);
IOUtils.write(byteArray, output);
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
Now I need to retrieve Byte Array from that same file using the below C++ program and deserialize it to extract employeeId, lastModifiedDate and attributeValue from it. I am not sure what is the best way on the C++ side. Below is the code I have so far:
int main() {
string line;
std::ifstream myfile("bytebuffertest", std::ios::binary);
if (myfile.is_open()) {
uint16_t employeeId;
uint64_t lastModifiedDate;
uint32_t attributeLength;
char buffer[8]; // sized for the biggest read we want to do
// read two bytes (will be in the wrong order)
myfile.read(buffer, 2);
// swap the bytes
std::swap(buffer[0], buffer[1]);
// only now convert bytes to an integer
employeeId = *reinterpret_cast<uint16_t*>(buffer);
cout<< employeeId <<endl;
// read eight bytes (will be in the wrong order)
myfile.read(buffer, 8);
// swap the bytes
std::swap(buffer[0], buffer[7]);
std::swap(buffer[1], buffer[6]);
std::swap(buffer[2], buffer[5]);
std::swap(buffer[3], buffer[4]);
// only now convert bytes to an integer
lastModifiedDate = *reinterpret_cast<uint64_t*>(buffer);
cout<< lastModifiedDate <<endl;
// read 4 bytes (will be in the wrong order)
myfile.read(buffer, 4);
// swap the bytes
std::swap(buffer[0], buffer[3]);
std::swap(buffer[1], buffer[2]);
// only now convert bytes to an integer
attributeLength = *reinterpret_cast<uint32_t*>(buffer);
cout<< attributeLength <<endl;
myfile.read(buffer, attributeLength);
// now I am not sure how should I get the actual attribute value here?
//close the stream:
myfile.close();
}
else
cout << "Unable to open file";
return 0;
}
Can anybody take a look on C++ code and see what I can do to improve it, as I don't think it is looking much efficient? Any better way to deserialize the Byte Array and extract relevant information on the C++ side?
