Convert FloatBuffer[] to byte[]

Question

I've been searching for a way to convert a FloatBuffer array to a byte array. I have found a way to convert a FloatBuffer object to byte[]: convert from floatbuffer to byte[]

But after searching the Internet for several hours I haven't been able to find something equivalent to convert from FloatBuffer[].

And to do the inverse, to convert from byte[] to FloatBuffer[], I've only found this:

ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(floatBufferObject); byte [] descriptorsBytes = bos.toByteArray();

But it seems a little strange there is not a simpler way to do this. Maybe I'm missing something very obvious, maybe I should convert the FloatBuffer array to other type that is simpler to convert to a byte array?

score 3 · Answer 1 · answered Feb 28 '13 at 04:05

3

Do you want one FloatBuffer, or multiple?

To convert from a FloatBuffer to a byte[], you could do something like

 FloatBuffer input;
 byte[] output = new byte[input.capacity() * 4];
 ByteBuffer.wrap(output).asFloatBuffer().put(input);

The other direction would just be

 ByteBuffer.wrap(byteArray).asFloatBuffer()

answered Feb 28 '13 at 04:05

Louis Wasserman

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The problem is I don't have a simple FloatBuffer, I have an array of FloatBuffer objects. This "FloatBuffer[]" object doesn't have methods like "get", "put", "wrap". Only each row of the FloatBuffer Array, that can be accessed as floatBufferArray[i] has those methods avaible. – Maria Garcia Feb 28 '13 at 04:09
Then you'll have to do it one at a time, but these implementations should give you an idea as to how to convert each row between `FloatBuffer` and bytes. – Louis Wasserman Feb 28 '13 at 04:12
But, because I need the byte array to store this info in a database, I have to store this as just one byte array, not one for each FloatBuffer row of the FloatBuffer array. So if I do it one FloatBuffer at a time, I'll have multiple byte arrays... – Maria Garcia Feb 28 '13 at 04:15
Create one big `ByteBuffer`, call its `asFloatBuffer()` method, and then put each of the small `FloatBuffer`s into that big `FloatBuffer`. – Louis Wasserman Feb 28 '13 at 04:38
Thanks, it works. The conversion in the other direction works too, with ByteBuffer.wrap(byteArray).asFloatBuffer(); but I obtain the result as just a FloatBuffer, not a FloatBuffer array. Is there a way to obtain each of the original FloatBuffer rows separated? – Maria Garcia Feb 28 '13 at 05:56

score 1 · Accepted Answer · answered Feb 28 '13 at 04:25

1

You already had the answer on how to convert one FloatBuffer into a byte array, so simply extend that to convert an array of them:

final FloatBuffer[] floatBuffers = new FloatBuffer[] {...};
final ByteBuffer byteBuffer = ByteBuffer.allocate(sumOfFloatBufferCapacities) * 4);
final FloatBuffer floatBufView = byteBuffer.asFloatBuffer();
for (final FloatBuffer fBuf : floatBuffers) {
    floatBufView.put(fBuf);
}
byte[] data = byteBuffer.array();

The above is pseudocode, you can adapt it to your needs.

answered Feb 28 '13 at 04:25

Perception

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Thanks, it works. Now I'm trying to convert the byte array back to FloatBuffer[] doing something like this: FloatBuffer fb = ByteBuffer.wrap(byteArray).asFloatBuffer(); But this retrieves the array as just one row. Is there a way to get it as FloatBuffer[] or I have to do another for to divide it in diferent rows...? – Maria Garcia Feb 28 '13 at 05:34
@MarciaGarcia - Once you merge the arrays there is no way of determining which floats should go where, unless you keep track externally (say in a list of integers), of the number of floats that should go into each FloatBuffer. – Perception Feb 28 '13 at 06:32

score 0 · Answer 3 · answered Feb 28 '13 at 05:14

Convert FloatBuffer[] to byte[]:

    FloatBuffer[] buffers = ...
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    for (FloatBuffer fb : buffers) {
        ByteBuffer byteBuffer = ByteBuffer.allocate(fb.capacity() * 4);
        byteBuffer.asFloatBuffer().put(fb);
        bos.write(byteBuffer.array());
    }
    byte[] ba = bos.toByteArray();

Convert FloatBuffer[] to byte[]

3 Answers3