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• Read-bytes$

Read-16sbe

(read-16sbe channel state) reads a 16-bit, signed, big-endian value from the input channel.

Definitions and Theorems

Function: read-16sbe

(defun
   read-16sbe (channel state)
   (declare (xargs :guard (and (state-p state)
                               (symbolp channel)
                               (open-input-channel-p channel
                                                     :byte state))))
   (b* (((mv x1 state)
         (read-byte$ channel state))
        ((mv x2 state)
         (read-byte$ channel state))
        ((unless x1) (mv nil state))
        ((unless x2) (mv 'fail state)))
       (mv (combine16s x1 x2) state)))

Theorem: read-16sbe-signed-byte

(defthm
    read-16sbe-signed-byte
    (implies (and (force (state-p1 state))
                  (force (open-input-channel-p1 channel
                                                :byte state))
                  (force (symbolp channel))
                  (mv-nth 0 (read-16sbe channel state))
                  (not (equal (mv-nth 0 (read-16sbe channel state))
                              'fail)))
             (signed-byte-p 16
                            (mv-nth 0 (read-16sbe channel state)))))

Theorem: read-16sbe-integer

(defthm
     read-16sbe-integer
     (implies (and (mv-nth 0 (read-16sbe channel state))
                   (not (equal (mv-nth 0 (read-16sbe channel state))
                               'fail)))
              (integerp (mv-nth 0 (read-16sbe channel state)))))

Theorem: read-16sbe-range

(defthm
     read-16sbe-range
     (implies (and (force (state-p1 state))
                   (force (open-input-channel-p1 channel
                                                 :byte state))
                   (force (symbolp channel))
                   (mv-nth 0 (read-16sbe channel state))
                   (not (equal (mv-nth 0 (read-16sbe channel state))
                               'fail)))
              (and (<= -32768
                       (mv-nth 0 (read-16sbe channel state)))
                   (<= (- (expt 2 15))
                       (mv-nth 0 (read-16sbe channel state)))
                   (< (mv-nth 0 (read-16sbe channel state))
                      32768)
                   (< (mv-nth 0 (read-16sbe channel state))
                      (expt 2 15))))
     :rule-classes :linear)

Theorem: read-16sbe-state

(defthm read-16sbe-state
        (implies (and (force (state-p1 state))
                      (force (open-input-channel-p1 channel
                                                    :byte state))
                      (force (symbolp channel)))
                 (state-p1 (mv-nth 1 (read-16sbe channel state)))))

Theorem: read-16sbe-open-input-channel-p1

(defthm read-16sbe-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-16sbe channel state)))))