Read NUL-terminated String from ByteBuffer

Question

How can I read NUL-terminated UTF-8 string from Java ByteBuffer starting at ByteBuffer#position()?

ByteBuffer b = /* 61 62 63 64 00 31 32 34 00 (hex) */;
String s0 = /* read first string */;
String s1 = /* read second string */;

// `s0` will now contain “ABCD” and `s1` will contain “124”.

I have already tried using Charsets.UTF_8.decode(b) but it seems this function is ignoring current ByteBuffer postision and reads until the end of the buffer.

Is there more idiomatic way to read such string from byte buffer than seeking for byte containing 0 and the limiting the buffer to it (or copying the part with string into separate buffer)?

Answer 1

Idiomatic meaning "one liner" not that I know of (unsurprising since NUL-terminated strings are not part of the Java spec).

The first thing I came up with is using b.slice().limit(x) to create a lightweight view onto the desired bytes only (better than copying them anywhere as you might be able to work directly with the buffer)

ByteBuffer b = ByteBuffer.wrap(new byte[] {0x61, 0x62, 0x63, 0x64, 0x00, 0x31, 0x32, 0x34, 0x00 });
int i;
while (b.hasRemaining()) {
  ByteBuffer nextString = b.slice(); // View on b with same start position
  for (i = 0; b.hasRemaining() && b.get() != 0x00; i++) {
    // Count to next NUL
  }
  nextString.limit(i); // view now stops before NUL
  CharBuffer s = StandardCharsets.UTF_8.decode(nextString);
  System.out.println(s);
}