Read bin file java

You must call this method before closing the BufferedOutputStream instance to make sure that the remaining data in the internal buffer is flushed to the disk. If you are writing a binary file with an encoding other than the default character encoding of the operating system or if you want to write non-ASCII characters , you should the OutputStreamWriter class as shown below:.

For more file read and write examples, check out the Reading and Writing Files in Java tutorial. Follow me on Twitter and LinkedIn. You can also subscribe to RSS Feed. I started this blog as a place to share everything I have learned in the last decade.

I write about modern JavaScript, Node. This should do it. Vibhu Bhutani Vibhu Bhutani 21 1 1 bronze badge. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.

The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. If that's indeed the case, you're playing a very dangerous game.

At least in C, the standard doesn't enforce things like padding or aligning of members of a struct. So even if your code happens to run it's very non-portable and risky - you depend on the compiler's creator not changing its mind on future versions. Better to create an automaton to both validate the structure being read byte per byte from HD is valid, and filling an in-memory structure if it's indeed OK. You may loose some milliseconds not so much as it may seem for modern OSes do a lot of disk read caching though you gain platform and compiler independence.

Plus, your code will be easily ported to another language. Post Edit: In a way I sympathize with you. And used exactly the same technique. Everything was nice until I tried to compile it for Windows - oops!! Int was now 32 bits long, rather than 16! When I tried to compile on Linux, discovered gcc had very different rules for bit fields allocation than Microsoft C 6. I had to resort to macro tricks to make it portable Javolution provides classes that represent C types.

All you need to do is to write a class that describes the C structure. For example, from the C header file,. I guess FileInputStream lets you read in bytes. So, opening the file with FileInputStream and read in the sizeof header. I am assuming that the header has a fixed format and size. I don't see that mentioned in the initial post, but assuming that is the case as it would get much more complex if the header has optional args and different sizes.

Once you have the info, there can be a header class in which you assign the contents of the buffer that you've already read. And then parse the records in a similar fashion. As other people mention DataInputStream and Buffers are probably the low-level API's you are after for dealing with binary data in java. I don't know of any Java versions off hand, but taking that approach declaratively specifying the struct in code would probably be the right way to go.

With a suitable fluent interface in Java it would probably be quite similar to a DSL. Which might be the kind of thing you are looking for. I have no idea whether it works or is any good, but it looks like a sensible place to start. I would create an object that wraps around a ByteBuffer representation of the data and provide getters to read directly from the buffer.

In this way, you avoid copying data from the buffer to primitive types. Furthermore, you could use a MappedByteBuffer to get the byte buffer. If your binary data is complex, you can model it using classes and give each class a sliced version of your buffer. Also useful are the methods for reading unsigned values from byte buffers.

I've written up a technique to do this sort of thing in java - similar to the old C-like idiom of reading bit-fields. Note it is just a start but could be expanded upon. In the past I used DataInputStream to read data of arbitrary types in a specified order.