Java InputStream to ByteBuffer

Question

I am reading dds textures, but since once built the jar I can't access those textures through url and file and have to use InputStream instead.

So I would need to know how I can obtain a java.nio.ByteBuffer from an java.io.InputStream.

Ps: no matter through 3rd part libraries, I just need it working

Jordi Castilla · Accepted Answer · 2018-08-08T10:01:51.093

53

For me the best in this case is Apache commons-io to handle this and similar tasks.

The IOUtils type has a static method to read an InputStream and return a byte[].

InputStream is;
byte[] bytes = IOUtils.toByteArray(is);

Internally this creates a ByteArrayOutputStream and copies the bytes to the output, then calls toByteArray().

UPDATE: as long as you have the byte array, as @Peter pointed, you have to convert to ByteBuffer

ByteBuffer.wrap(bytes)

JAVA 9 UPDATE: as stated by @saka1029 if you're using java 9+ you can use the default InputStream API which now includes InputStream::readAllBytes function, so no external libraries needed

InputStream is;
byte[] bytes = is.readAllBytes()

edited Aug 08 '18 at 10:01

answered May 04 '15 at 08:52

Jordi Castilla

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4

and then to ByteBuffer? – elect May 04 '15 at 08:53
8

@elect yes, `ByteBuffer.wrap(bytes)` – Peter Lawrey May 04 '15 at 08:54
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it may OutOfMemory – chen May 28 '20 at 05:52
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@chen it may OOM. This method is for small files only. That's why people invented InputStream API :-) >> to read something as a stream (some piece after piece). – digital_infinity Aug 10 '20 at 18:03

score 3 · Answer 2 · answered Jan 11 '21 at 16:21

3

What is about:

ReadableByteChannel channel = Channels.newChannel(inputStream);
ByteBuffer buffer = ByteBuffer.allocate(bufferSize);

while (channel.read(buffer) != -1) {
  //write buffer

};

answered Jan 11 '21 at 16:21

swepss

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Are you sure that `read()` returns -1 when input stream ends? Sometimes it returns 0. – happy_marmoset Apr 18 '21 at 11:57
Yes, I am %)) this is from javadoc from ReadableByteChannel ```Returns: The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream``` – swepss May 12 '21 at 11:38
If the buffer isn't big enough to read the entire input stream this can get stuck in a busy loop trying to read 0 bytes over and over. Depending on how the body of the loop deals with the buffer. e.g. if you just want to read everything into a buffer and return the buffer, so the buffer won't be emptied or flipped in the loop. – swpalmer Aug 19 '21 at 21:11

score 2 · Answer 3 · answered Jan 27 '21 at 20:02

2

A neat solution with no 3rd party library needed is

ByteBuffer byteBuffer = ByteBuffer.allocate(inputStream.available());
Channels.newChannel(inputStream).read(byteBuffer);

See ReadableByteChannel#read(ByteBuffer)

answered Jan 27 '21 at 20:02

James Mudd

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Are you sure that one `read()` is enough to read all input stream? – happy_marmoset Apr 18 '21 at 11:52
No, it depends on the `InputStream` you are using. If it has all the bytes available then it will work. – James Mudd Apr 19 '21 at 15:20

Java InputStream to ByteBuffer

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