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; bindat (strz): Move all pack logic to pack function (bug#56048)

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Motivation/rationale:
  * Improve code readability.  Now `bindat--pack-strz` is used for all
    `strz` packing, not just variable-length `strz` packing.
  * Make it easier to change the behavior of fixed-length `strz`
    packing without also affecting the behavior of `str` packing.  (A
    future commit will modify `strz` to write a null terminator if
    there is room.)
This commit is contained in:
Richard Hansen 2022-05-29 21:23:57 -04:00 • committed by Eli Zaretskii
parent 5f1bd87247
commit eff42dc0af
1 changed files with 23 additions and 26 deletions
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49
lisp/emacs-lisp/bindat.el
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@ -440,20 +440,27 @@ e.g. corresponding to STRUCT.FIELD1[INDEX2].FIELD3..."
(aset bindat-raw (+ bindat-idx i) (aref v i)))
(setq bindat-idx (+ bindat-idx len))))
(defun bindat--pack-strz (v)
(defun bindat--pack-strz (len v)
(let* ((v (string-to-unibyte v))
(len (length v)))
(dotimes (i len)
(when (= (aref v i) 0)
;; Alternatively we could pretend that this was the end of
;; the string and stop packing, but then bindat-length would
;; need to scan the input string looking for a null byte.
(error "Null byte encountered in input strz string"))
(aset bindat-raw (+ bindat-idx i) (aref v i)))
;; Explicitly write a null terminator in case the user provided a
;; pre-allocated string to bindat-pack that wasn't zeroed first.
(aset bindat-raw (+ bindat-idx len) 0)
(setq bindat-idx (+ bindat-idx len 1))))
(vlen (length v)))
(if len
;; When len is specified, behave the same as the str type
;; since we don't actually add the terminating zero anyway
;; (because we rely on the fact that `bindat-raw' was
;; presumably initialized with all-zeroes before we started).
(bindat--pack-str len v)
(dotimes (i vlen)
(when (= (aref v i) 0)
;; Alternatively we could pretend that this was the end of
;; the string and stop packing, but then bindat-length would
;; need to scan the input string looking for a null byte.
(error "Null byte encountered in input strz string"))
(aset bindat-raw (+ bindat-idx i) (aref v i)))
;; Explicitly write a null terminator in case the user provided
;; a pre-allocated string to `bindat-pack' that wasn't already
;; zeroed.
(aset bindat-raw (+ bindat-idx vlen) 0)
(setq bindat-idx (+ bindat-idx vlen 1)))))
(defun bindat--pack-bits (len v)
(let ((bnum (1- (* 8 len))) j m)
@ -482,7 +489,8 @@ e.g. corresponding to STRUCT.FIELD1[INDEX2].FIELD3..."
('u24r (bindat--pack-u24r v))
('u32r (bindat--pack-u32r v))
('bits (bindat--pack-bits len v))
((or 'str 'strz) (bindat--pack-str len v))
('str (bindat--pack-str len v))
('strz (bindat--pack-strz len v))
('vec
(let ((l (length v)) (vlen 1))
(if (consp vectype)
@ -699,18 +707,7 @@ is the name of a variable that will hold the value we need to pack.")
((numberp len) len)
;; General expression support.
(t `(or ,len (1+ (length ,val)))))))
(`(pack . ,args)
;; When len is specified, behave the same as the str type since we don't
;; actually add the terminating zero anyway (because we rely on the fact
;; that `bindat-raw' was presumably initialized with all-zeroes before we
;; started).
(cond ; Same optimizations as 'length above.
((null len) `(bindat--pack-strz . ,args))
((numberp len) `(bindat--pack-str ,len . ,args))
(t (macroexp-let2 nil len len
`(if ,len
(bindat--pack-str ,len . ,args)
(bindat--pack-strz . ,args))))))))
(`(pack . ,args) `(bindat--pack-strz ,len . ,args))))
(cl-defmethod bindat--type (op (_ (eql 'bits)) len)
(bindat--pcase op