| ⊦ abs-failed(buf) ↔ # buf ≥ NODE_HEADER_SIZE ∧ is-aligned(# buf, NODE_HEADER_SIZE) ∧ (∃ buf0, buf1. buf = buf0 + buf1 ∧ # buf0 = NODE_HEADER_SIZE ∧ (is-garbage-header(buf0) ∨ (∃ ndhd. is-encoded(ndhd, buf0) ∧ # buf1 ≤ align↑(ndhd.size, 2 * NODE_HEADER_SIZE)))) |