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I have a method that takes an InputStream and reads data from it. I would like to use this method with a ByteBuffer also. Is there a way to wrap a ByteBuffer so it can be accessed as a stream?
923
wrap. Wraps a byte array into a buffer. The new buffer will be backed by the given byte array; that is, modifications to the buffer will cause the array to be modified and vice versa. The new buffer's capacity and limit will be array.
InputStream is; byte[] bytes = IOUtils. toByteArray(is); Internally this creates a ByteArrayOutputStream and copies the bytes to the output, then calls toByteArray() . It handles large files by copying the bytes in blocks of 4KiB.
Since Java 9, we can use the readAllBytes() method from InputStream class to read all bytes into a byte array. This method reads all bytes from an InputStream object at once and blocks until all remaining bytes have read and end of a stream is detected, or an exception is thrown.
A new ByteBuffer can be allocated using the method allocate() in the class java. nio. ByteBuffer. This method requires a single parameter i.e. the capacity of the buffer.
There seem to be some bugs with the implementation referred to by Thilo, and also copy and pasted on other sites verbatim:
ByteBufferBackedInputStream.read() returns a sign extended int representation of the byte it reads, which is wrong (value should be in range [-1..255])ByteBufferBackedInputStream.read(byte[], int, int) does not return -1 when there are no bytes remaining in the buffer, as per the API specByteBufferBackedOutputStream seems relatively sound.
I present a 'fixed' version below. If I find more bugs (or someone points them out) I'll update it here.
Updated: removed synchronized keywords from read/write methods
public class ByteBufferBackedInputStream extends InputStream { ByteBuffer buf; public ByteBufferBackedInputStream(ByteBuffer buf) { this.buf = buf; } public int read() throws IOException { if (!buf.hasRemaining()) { return -1; } return buf.get() & 0xFF; } public int read(byte[] bytes, int off, int len) throws IOException { if (!buf.hasRemaining()) { return -1; } len = Math.min(len, buf.remaining()); buf.get(bytes, off, len); return len; } } public class ByteBufferBackedOutputStream extends OutputStream { ByteBuffer buf; public ByteBufferBackedOutputStream(ByteBuffer buf) { this.buf = buf; } public void write(int b) throws IOException { buf.put((byte) b); } public void write(byte[] bytes, int off, int len) throws IOException { buf.put(bytes, off, len); } } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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