blob: f52b4f962b47b28a7f341baa44c52e6d4000642e (
plain)
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
70
71
72
73
74
75
76
77
|
(in-package #:lempel)
(declaim (optimize (debug 3) (safety 3)))
(declaim (ftype (function ((array (unsigned-byte 8)) (unsigned-byte 8)) (array (unsigned-byte 8)))
prefix-decode))
(defun prefix-decode (data prefix)
(let ((bits (make-array (* 8 (length data)) :element-type '(unsigned-byte 1)))
(result (queue:new))
(point-count 0))
(dotimes (i (length data))
(byte->bits (elt data i) bits (* 8 i)))
(do ((i 0)) ((>= i (length bits)) nil)
(cond ((and (<= i (- (length bits) 8))
(= (bits->byte bits i) prefix))
(incf point-count)
(let ((point (byte-pair->point (bits->byte bits (+ i 8))
(bits->byte bits (+ i 16)))))
(if (= (point-size point) 0)
(progn
(let ((prefix-bits (make-array 8 :element-type '(unsigned-byte 1))))
(byte->bits prefix prefix-bits 0)
(dotimes (j 8)
(queue:push (elt prefix-bits j) result))
(incf i 16)))
(progn
(queue:push point result)
(incf i 24)))))
(t (queue:push (elt bits i) result)
(incf i))))
(format t "point count: ~a~&" point-count)
(let* ((uncompressed-data (decompress (queue:to-list result)))
(output (make-array (/ (length uncompressed-data) 8) :element-type '(unsigned-byte 8))))
(dotimes (i (length output))
(setf (elt output i) (bits->byte uncompressed-data (* i 8))))
output)))
(declaim (ftype (function (list) (array (unsigned-byte 1))) decompress))
(defun decompress (data)
(let ((result (make-array (get-uncompressed-size data) :element-type '(unsigned-byte 1)))
(fill-count 0))
(format t "uncompressed size: ~a bits ~a bytes~&" (length result) (/ (length result) 8))
(dolist (point data)
(cond ((point-p point)
(let ((start (- fill-count (point-offset point))))
(dotimes (j (point-size point))
(setf (elt result (+ fill-count j)) (if (> (+ start j) 0)
(elt result (+ start j))
0)))
(incf fill-count (point-size point))))
((typep point '(unsigned-byte 1))
(setf (elt result fill-count) point)
(incf fill-count))
(t (error (format nil "cannot handle type ~a" (type-of point))))))
(assert (= fill-count (length result)))
result))
(declaim (ftype (function ((unsigned-byte 8) (unsigned-byte 8)) point) byte-pair->point))
(defun byte-pair->point (b1 b2)
(let ((offset (if reversed-byte-order b2 b1))
(size (if reversed-byte-order b1 b2))
(max-word-length (1- (ash 1 (- 16 window-bits)))))
(make-point :offset (* 8 (logior offset
(ash (logand size (logxor #xff max-word-length))
(- window-bits 8))))
:size (* 8 (logand size max-word-length)))))
(declaim (ftype (function (list) fixnum) get-uncompressed-size))
(defun get-uncompressed-size (data)
(let ((size 0))
(dolist (point data)
(cond ((point-p point)
(if (= (point-size point) 0)
(incf size 8)
(incf size (point-size point))))
(t (incf size))))
size))
|
