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• Read-bytes$

Read-8s

(read-8s channel state) reads a signed byte from the input channel.

Definitions and Theorems

Function: read-8s

(defun read-8s (channel state)
  (declare (xargs :guard (and (state-p state)
                              (symbolp channel)
                              (open-input-channel-p channel
                                                    :byte state))))
  (b* (((mv byte state)
        (read-byte$ channel state))
       ((unless byte) (mv nil state)))
    (mv (fast-logext 8 byte) state)))

Theorem: read-8s-signed-byte

(defthm read-8s-signed-byte
  (implies (and (mv-nth 0 (read-8s channel state))
                (force (state-p1 state))
                (force (open-input-channel-p1 channel
                                              :byte state))
                (force (symbolp channel)))
           (signed-byte-p 8 (mv-nth 0 (read-8s channel state)))))

Theorem: read-8s-integer

(defthm read-8s-integer
  (implies (mv-nth 0 (read-8s channel state))
           (integerp (mv-nth 0 (read-8s channel state)))))

Theorem: read-8s-range

(defthm read-8s-range
  (implies (and (mv-nth 0 (read-8s channel state))
                (force (state-p1 state))
                (force (open-input-channel-p1 channel
                                              :byte state))
                (force (symbolp channel)))
           (and (<= -128 (mv-nth 0 (read-8s channel state)))
                (<= (- (expt 2 7))
                    (mv-nth 0 (read-8s channel state)))
                (< (mv-nth 0 (read-8s channel state))
                   128)
                (< (mv-nth 0 (read-8s channel state))
                   (expt 2 7))))
  :rule-classes :linear)

Theorem: read-8s-state

(defthm read-8s-state
  (implies (and (force (state-p1 state))
                (force (open-input-channel-p1 channel
                                              :byte state))
                (force (symbolp channel)))
           (state-p1 (mv-nth 1 (read-8s channel state)))))

Theorem: read-8s-open-input-channel-p1

(defthm read-8s-open-input-channel-p1
 (implies
  (and (force (state-p1 state))
       (force (open-input-channel-p1 channel
                                     :byte state))
       (force (symbolp channel)))
  (open-input-channel-p1 channel
                         :byte (mv-nth 1 (read-8s channel state)))))