1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
|
(in-package #:3bz)
(deftype octet () '(unsigned-byte 8))
(deftype octet-vector () '(simple-array octet (*)))
;; typed container for offsets and bounds of current input source, and
;; remaining bits of partially read octets
(defstruct (context-boxes (:conc-name cb-))
;; start of 'active' region of buffer
(start 0 :type size-t)
;; end of 'active' region of buffer
(end 0 :type size-t)
;; offset of next unread byte, (<= start offset end)
(offset 0 :type size-t))
(defmacro context-common ((boxes) &body body)
`(macrolet ((pos ()
`(cb-offset ,',boxes))
(end ()
`(cb-end ,',boxes))
(%octet (read-form
&optional (eob-form
'(error "read past end of buffer")))
`(progn
(when (>= (pos) (end))
,eob-form)
(prog1
,read-form
(incf (pos)))))
(octets-left ()
`(- (cb-end ,',boxes) (pos))))
,@body))
(defclass octet-vector-context ()
((octet-vector :reader octet-vector :initarg :octet-vector)
(boxes :reader boxes :initarg :boxes)))
(defun make-octet-vector-context (vector &key (start 0) (offset start)
(end (length vector)))
(make-instance 'octet-vector-context
:octet-vector vector
:boxes (make-context-boxes
:start start :offset offset :end end)))
(defclass octet-stream-context ()
((octet-stream :reader octet-stream :initarg :octet-stream)
(boxes :reader boxes :initarg :boxes)))
(defun make-octet-stream-context (file-stream &key (start 0) (offset 0)
(end (file-length file-stream)))
(make-instance 'octet-stream-context
:octet-stream file-stream
:boxes (make-context-boxes
:start start :offset offset :end end)))
;; hack to allow storing parts of a file to use as context later. call
;; before using context
(defmethod %resync-file-stream (context))
(defmethod %resync-file-stream ((context octet-stream-context))
(file-position (octet-stream context)
(cb-offset (boxes context))))
(defun valid-octet-stream (os)
(and (typep os 'stream)
(subtypep (stream-element-type os) 'octet)
(open-stream-p os)
(input-stream-p os)))
|
