• Top
  • Documentation
  • Books
  • Recursion-and-induction
  • Boolean-reasoning
  • Projects
  • Debugging
  • Std
    • Std/lists
    • Std/alists
    • Obags
    • Std/util
    • Std/strings
    • Std/io
      • Open-channel-lemmas
      • Std/io/read-char$
      • Std/io/read-object
      • Std/io/open-output-channel
      • Unsound-read
      • Read-string
      • Read-bytes$
      • File-measure
      • Read-bytes$-n
      • Std/io/read-byte$
      • Std/io/open-input-channel
      • Print-compressed
      • Read-file-lines-no-newlines
      • Nthcdr-bytes
      • Read-file-lines
      • Std/io/close-output-channel
      • Read-file-characters
      • Read-file-bytes
      • Print-legibly
      • Std/io/close-input-channel
      • Read-file-objects
      • Logical-story-of-io
      • Take-bytes
      • Std/io/peek-char$
      • Read-file-characters-rev
      • Read-file-as-string
      • Std/io/write-byte$
      • Std/io/set-serialize-character
      • Std/io/print-object$
      • Std/io/princ$
      • Std/io/read-file-into-string
      • *file-types*
    • Std/osets
    • Std/system
    • Std/basic
    • Std/typed-lists
    • Std/bitsets
    • Std/testing
    • Std/typed-alists
    • Std/stobjs
    • Std-extensions
  • Proof-automation
  • Macro-libraries
  • ACL2
  • Interfacing-tools
  • Hardware-verification
  • Software-verification
  • Testing-utilities
  • Math

• Std/io

Take-bytes

Read the first n bytes from an open file.

(take-bytes n channel state) is like take for an :byte input channel. That is, it just reads n bytes and returns them as a list, and also returns the updated state.

Definitions and Theorems

Function: take-bytes

(defun
   take-bytes (n channel state)
   (declare (xargs :guard (and (natp n)
                               (state-p state)
                               (symbolp channel)
                               (open-input-channel-p channel
                                                     :byte state))))
   (b* (((when (zp n)) (mv nil state))
        ((mv a state)
         (read-byte$ channel state))
        ((mv x state)
         (take-bytes (1- n) channel state)))
       (mv (cons a x) state)))

Theorem: state-p1-of-take-bytes

(defthm
     state-p1-of-take-bytes
     (implies (and (force (state-p1 state))
                   (force (symbolp channel))
                   (force (open-input-channel-p1 channel
                                                 :byte state)))
              (state-p1 (mv-nth 1 (take-bytes n channel state)))))

Theorem: open-input-channel-p1-of-take-bytes

(defthm
     open-input-channel-p1-of-take-bytes
     (implies (and (force (state-p1 state))
                   (force (symbolp channel))
                   (force (open-input-channel-p1 channel
                                                 :byte state)))
              (open-input-channel-p1
                   channel
                   :byte (mv-nth 1 (take-bytes n channel state)))))

Theorem: mv-nth0-of-take-bytes

(defthm
 mv-nth0-of-take-bytes
 (implies (and (force (state-p1 state))
               (force (symbolp channel))
               (force (open-input-channel-p1 channel
                                             :byte state)))
          (equal (mv-nth 0 (take-bytes n channel state))
                 (take n
                       (mv-nth 0 (read-byte$-all channel state))))))

Theorem: mv-nth1-of-take-bytes$

(defthm mv-nth1-of-take-bytes$
        (implies (and (force (state-p1 state))
                      (force (symbolp channel))
                      (force (open-input-channel-p1 channel
                                                    :byte state)))
                 (equal (mv-nth 1 (take-bytes n channel state))
                        (nthcdr-bytes n channel state))))