Tutorial :How to save a Java FloatBuffer (or any Buffer) to a file



Question:

I have a FloatBuffer of known size and just want to dump the data to a file (in binary) for inspection outside my app. What's the easiest way to do this?


Solution:1

UPDATE FOR BINARY OUTPUT:

// There are dependencies on how you create your floatbuffer for this to work  // I suggest starting with a byte buffer and using asFloatBuffer() when  // you need it as floats.  // ByteBuffer b = ByteBuffer.allocate(somesize);  // FloatBuffer fb = b.asFloatBuffer();  // There will also be endiance issues when you write binary since  // java is big-endian. You can adjust this with Buffer.order(...)  // b.order(ByteOrder.LITTLE_ENDIAN)  // If you're using a hex-editor you'll probably want little endian output  // since most consumer machines (unless you've got a sparc / old mac) are little      FileOutputStream fos = new FileOutputStream("some_binary_output_file_name");  FileChannel channel = fos.getChannel();    channel.write(byteBufferBackingYourFloatBuffer);    fos.close();  

TEXT OUTPUT: Since you want this to be viewable I assume you want a text file. You'll want to use a PrintStream.

// Try-catch omitted for simplicity    PrintStream ps = new PrintStream("some_output_file.txt");  for(int i = 0; i < yourFloatBuffer.capacity(); i++)  {     // put each float on one line     // use printf to get fancy (decimal places, etc)     ps.println(yourFloagBuffer.get(i));  }    ps.close();  

Didn't have time to post a full raw/binary (non-text) version of this. If you want to do that use a FileOutputStream, get the FileChannel, and directly write the FloatBuffer (since it's a ByteBuffer)


Solution:2

Asusming you want the data as binary:

Start with a ByteBuffer. Call asFloatBuffer to get your FloatBuffer. When you've finished doing your stuff, save the ByteBuffer out to a WritableByteChannel.

If you already have FloatBuffer it can be copied into the buffer from step 2 with a put.

A low performance but easier way would be to use Float.floatToIntBit.

(Watch for endianess, obviously.)


Solution:3

This iterates through the array backed by your buffer and outputs each float. Just replace the text file and floatBuffer with your own parameters.

PrintStream out = new PrintStream("target.txt");  for(float f : floatBuffer.array()){    out.println(f);  }  out.close();  

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