Thread: how to read c++ unsigned long in java

im not getting the proper values unsigned long

Please post the input value and its results.

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[code=java]
YOUR CODE GOES HERE
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Thanks for quick reply

DataInputStream input = new DataInputStream(new FileInputStream("-----\\sample.mdx"));

First we are reading the header later readUnsignedLong(DataInputStream in),i mentioned in the above post
------------------------------------------------
Long ObjectId = readUnsignedLong(input);
-------------------------------------------------
Output--UnsignedLong----------------3114199

expected output value ---3435927511

Sorry, I don't understand how you get 3435927511 from 40? Please explain.
Also what are the ---- shown in the post for?

Please edit your post and wrap your code with code tags:
[code=java]
YOUR CODE GOES HERE
[/code]
to get highlighting and preserve formatting.

Thanks for update,

how you get 3435927511 from 40?

40 is the first reading short value from the DataInputStream.

3435927511 is the second reading unsignedlong from the DataInputStream.

I have input mdx file which i am reading through this below ,what functionality is trying convert c++ unsignedlong to signedlong in java

DataInputStream input = new DataInputStream(new FileInputStream("sample.mdx"));

Short st=input.readShort();
------------------------------------------------
long ObjectId = readUnsignedLong(input);
-------------------------------------------------

This is the method i am using to read unsignedLong
=================================
long readUnsignedLong(DataInputStream in) throws IOException {
int bytemask = 0x000000ff;
byte b1 = in.readByte();
byte b2 = in.readByte();
byte b3 = in.readByte();
byte b4 = in.readByte();
int a1 = bytemask & b1;
int a2 = bytemask & b2;
int a3 = bytemask & b3;
int a4 = bytemask & b4;
return ((a4) << 24) + (a3 << 16) + (a2 << 8) + a1;

}

==========================================
while running
Output:
40--these reading from short of DataInputStream
3114199---------method readunsignedlong(DataInputStream in) ,so i am getting Output for UnsignedLong value for DataInputStream.

But exact output value i have to get this 3435927511 value, while i crosschecked Database for above Sample.mdx
------------------

Is this an assignment for college? It is quite a strange program to design.

All data types are signed by default - meaning they can be negative. C++ used
the unsigned keyword to ensure a value could never be negative.

byte b1 = in.readByte();
byte b2 = in.readByte();
byte b3 = in.readByte();
byte b4 = in.readByte();
int a1 = bytemask & b1;
int a2 = bytemask & b2;
int a3 = bytemask & b3;
int a4 = bytemask & b4;
return ((a4) << 24) + (a3 << 16) + (a2 << 8) + a1;

If I am understanding that correctly each of the integer variables labelled 'a'
are assigned the reference of byte through the bytemask not sure if this is
a type of template system or not.

In C++, '<<' was the insertion operator that would read data along the output stream.
I am not very versed in byte code - but from what I can gather is the reason that your
output is not correct is perhaps the references that are assigned to each 'a' variable are
containing incorrect values? Just an insight and I could be totally wrong - but I guess it
might be worth a check. Java does use a byte-code verifier and a class loader - again,
the bytecode statement looks like a mask for something.

Wishes Ada xx

convert c++ unsignedlong to signedlong in java

Can you show what the data input looks like in hex bytes?
For example if the value is 40
is it this: 0x2800000000000000
or this: 0x0000000000000028
or something else