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Converting-between-strings-and-bytes

Definitions and Theorems

Function: bytes-to-charlist

(defun bytes-to-charlist (bytes)
  (declare (xargs :guard (byte-listp bytes)))
  (let ((__function__ 'bytes-to-charlist))
    (declare (ignorable __function__))
    (if (endp bytes)
        nil
      (cons (code-char (car bytes))
            (bytes-to-charlist (cdr bytes))))))

Theorem: character-listp-of-bytes-to-charlist

(defthm character-listp-of-bytes-to-charlist
  (implies (force (byte-listp bytes))
           (b* ((lst (bytes-to-charlist bytes)))
             (character-listp lst)))
  :rule-classes :type-prescription)

Function: charlist-to-bytes

(defun charlist-to-bytes (charlist)
  (declare (xargs :guard (character-listp charlist)))
  (let ((__function__ 'charlist-to-bytes))
    (declare (ignorable __function__))
    (if (endp charlist)
        nil
      (cons (char-code (car charlist))
            (charlist-to-bytes (cdr charlist))))))

Theorem: byte-listp-of-charlist-to-bytes

(defthm byte-listp-of-charlist-to-bytes
  (implies (force (character-listp bytes))
           (b* ((lst (charlist-to-bytes charlist)))
             (byte-listp lst)))
  :rule-classes :type-prescription)

Theorem: same-length-of-byte-and-character-lists

(defthm same-length-of-byte-and-character-lists
  (implies (character-listp charlist)
           (equal (len (charlist-to-bytes charlist))
                  (len charlist))))

Function: string-to-bytes

(defun string-to-bytes (str)
  (declare (xargs :guard (stringp str)))
  (let ((__function__ 'string-to-bytes))
    (declare (ignorable __function__))
    (charlist-to-bytes (coerce str 'list))))

Theorem: byte-listp-of-string-to-bytes

(defthm byte-listp-of-string-to-bytes
  (implies (force (stringp str))
           (b* ((lst (string-to-bytes str)))
             (byte-listp lst)))
  :rule-classes :type-prescription)

Function: bytes-to-string

(defun bytes-to-string (bytes)
  (declare (xargs :guard (byte-listp bytes)))
  (let ((__function__ 'bytes-to-string))
    (declare (ignorable __function__))
    (coerce (bytes-to-charlist bytes)
            'string)))

Theorem: stringp-of-bytes-to-string

(defthm stringp-of-bytes-to-string
  (implies (force (byte-listp bytes))
           (b* ((lst (bytes-to-string bytes)))
             (stringp lst)))
  :rule-classes :type-prescription)

Function: read-n-bytes-from-string

(defun read-n-bytes-from-string (n str)
  (declare (xargs :guard (and (natp n) (stringp str))))
  (let ((__function__ 'read-n-bytes-from-string))
    (declare (ignorable __function__))
    (let* ((bytes (string-to-bytes str))
           (n-bytes (take n bytes)))
      n-bytes)))

Theorem: take-byte-listp

(defthm take-byte-listp
  (implies (and (byte-listp xs)
                (natp n)
                (<= n (len xs)))
           (byte-listp (take n xs))))

Theorem: byte-listp-read-n-bytes-from-string

(defthm byte-listp-read-n-bytes-from-string
  (implies (and (natp n)
                (< n (len (string-to-bytes str)))
                (stringp str))
           (byte-listp (read-n-bytes-from-string n str)))
  :rule-classes :type-prescription)

Function: read-n-bytes-from-string-as-string

(defun read-n-bytes-from-string-as-string (n str)
  (declare (xargs :guard (and (natp n) (stringp str))))
  (let ((__function__ 'read-n-bytes-from-string-as-string))
    (declare (ignorable __function__))
    (b* ((n-bytes (read-n-bytes-from-string n str))
         ((when (not (byte-listp n-bytes))) nil)
         (new-charlist (bytes-to-charlist n-bytes))
         (new-str (coerce new-charlist 'string)))
      new-str)))

Theorem: stringp-read-n-bytes-from-string-as-string

(defthm stringp-read-n-bytes-from-string-as-string
  (implies (and (natp n)
                (< n (len (string-to-bytes str)))
                (stringp str))
           (stringp (read-n-bytes-from-string-as-string n str)))
  :rule-classes :type-prescription)