I've found that Buffers admit to ask for the current limit or set a new one. So that wrapper channel (the one that limits the effective number of bytes read) could modify the buffer limit to avoid reading more...
Something like:
// LimitedChannel.java
// private int bytesLeft; // remaining amount of bytes to read
public int read(ByteBuffer buffer) {
if (bytesLeft <= 0) {
return -1;
}
int oldLimit = buffer.limit();
if (bytesLeft < buffer.remaining()) {
// ensure I'm not reading more than allowed
buffer.limit(buffer.position() + bytesLeft);
}
int bytesRead = delegateChannel.read(buffer);
bytesLeft -= bytesRead;
buffer.limit(oldLimit);
return bytesRead;
}
Anyway not sure if this already exists somewhere. It's difficult to find documentation about this use case...