int svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 max_bytes, u8 * copy_here);
int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes);
int svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 max_bytes, u8 * copy_here);
int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes);