/** Returns a temporary buffer of at least the given size */
public static ByteBuffer getTemporaryDirectBuffer(int size) {
// If a buffer of this size is too large for the cache, there
// should not be a buffer in the cache that is at least as
// large. So we'll just create a new one. Also, we don't have
// to remove the buffer from the cache (as this method does
// below) given that we won't put the new buffer in the cache.
if (isBufferTooLarge(size)) {
return ByteBuffer.allocateDirect(size);
}
BufferCache cache = bufferCache.get();
ByteBuffer buf = cache.get(size);
if (buf != null) {
return buf;
} else {
// No suitable buffer in the cache so we need to allocate a new
// one. To avoid the cache growing then we remove the first
// buffer from the cache and free it.
if (!cache.isEmpty()) {
buf = cache.removeFirst();
free(buf);
}
return ByteBuffer.allocateDirect(size);
}
}
/**
* Releases a temporary buffer by returning to the cache or freeing it. If returning to the cache
* then insert it at the end. This makes it suitable for scatter/gather operations where the
* buffers are returned to cache in same order that they were obtained.
*/
static void offerLastTemporaryDirectBuffer(ByteBuffer buf) {
// If the buffer is too large for the cache we don't have to
// check the cache. We'll just free it.
if (isBufferTooLarge(buf)) {
free(buf);
return;
}
assert buf != null;
BufferCache cache = bufferCache.get();
if (!cache.offerLast(buf)) {
// cache is full
free(buf);
}
}