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* lisp/emacs-lisp/bindat.el: Allow non-fixed size of strz

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(bindat--unpack-strz): Allow `len` to be nil.
(bindat--pack-strz): New function.
(bindat--type) <strz>: Make `len` arg optional.
(bindat-type): Adjust debug spec and docstring accordingly.

* doc/lispref/processes.texi (Bindat Types): Adjust accordingly.
This commit is contained in:
Stefan Monnier 2021-04-15 11:27:52 -04:00
parent 7893945cc8
commit 0c3ce42c8f
2 changed files with 27 additions and 11 deletions
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5
doc/lispref/processes.texi
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@ -3410,8 +3410,9 @@ Unsigned integer in little endian order, with @var{bitlen} bits.
@item str @var{len}
String of bytes of length @var{len}.
@item strz @var{len}
Zero-terminated string of bytes, in a fixed-size field with length @var{len}.
@item strz &optional @var{len}
Zero-terminated string of bytes, can be of arbitrary length or in a fixed-size
field with length @var{len}.
@item vec @var{len} [@var{type}]
Vector of @var{len} elements. The type of the elements is given by

33
lisp/emacs-lisp/bindat.el
View File

@ -167,7 +167,7 @@
(defun bindat--unpack-strz (len)
(let ((i 0) s)
(while (and (< i len) (/= (aref bindat-raw (+ bindat-idx i)) 0))
(while (and (if len (< i len) t) (/= (aref bindat-raw (+ bindat-idx i)) 0))
(setq i (1+ i)))
(setq s (substring bindat-raw bindat-idx (+ bindat-idx i)))
(setq bindat-idx (+ bindat-idx len))
@ -439,6 +439,12 @@ 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)
(let ((len (length v)))
(dotimes (i len)
(aset bindat-raw (+ bindat-idx i) (aref v i)))
(setq bindat-idx (+ bindat-idx len 1))))
(defun bindat--pack-bits (len v)
(let ((bnum (1- (* 8 len))) j m)
(while (>= bnum 0)
@ -677,14 +683,23 @@ is the name of a variable that will hold the value we need to pack.")
(`(length . ,_) `(cl-incf bindat-idx ,len))
(`(pack . ,args) `(bindat--pack-str ,len . ,args))))
(cl-defmethod bindat--type (op (_ (eql strz)) len)
(cl-defmethod bindat--type (op (_ (eql strz)) &optional len)
(bindat--pcase op
('unpack `(bindat--unpack-strz ,len))
(`(length . ,_) `(cl-incf bindat-idx ,len))
;; Here we don't add the terminating zero because we rely
;; on the fact that `bindat-raw' was presumably initialized with
;; all-zeroes before we started.
(`(pack . ,args) `(bindat--pack-str ,len . ,args))))
(`(length ,val)
`(cl-incf bindat-idx ,(cond
((null len) `(length ,val))
((numberp len) len)
(t `(or ,len (length ,val))))))
(`(pack . ,args)
(macroexp-let2 nil len len
`(if ,len
;; Same as non-zero terminated strings 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 . ,args)
(bindat--pack-strz . ,args))))))
(cl-defmethod bindat--type (op (_ (eql bits)) len)
(bindat--pcase op
@ -812,7 +827,7 @@ is the name of a variable that will hold the value we need to pack.")
'(&or ["uint" def-form]
["uintr" def-form]
["str" def-form]
["strz" def-form]
["strz" &optional def-form]
["bits" def-form]
["fill" def-form]
["align" def-form]
@ -832,7 +847,7 @@ TYPE is a Bindat type expression. It can take the following forms:
uint BITLEN - Big-endian unsigned integer
uintr BITLEN - Little-endian unsigned integer
str LEN - Byte string
strz LEN - Zero-terminated byte-string
strz [LEN] - Zero-terminated byte-string
bits LEN - Bit vector (LEN is counted in bytes)
fill LEN - Just a filler
align LEN - Fill up to the next multiple of LEN bytes