1 ;;;; variable-length encoding and other i/o tricks for the debugger
3 ;;;; This software is part of the SBCL system. See the README file for
6 ;;;; This software is derived from the CMU CL system, which was
7 ;;;; written at Carnegie Mellon University and released into the
8 ;;;; public domain. The software is in the public domain and is
9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
10 ;;;; files for more information.
14 ;;;; reading variable length integers
16 ;;;; The debug info representation makes extensive use of integers
17 ;;;; encoded in a byte vector using a variable number of bytes:
18 ;;;; 0..253 => the integer
19 ;;;; 254 => read next two bytes for integer
20 ;;;; 255 => read next four bytes for integer
22 ;;; Given a byte vector VEC and an index variable INDEX, read a
23 ;;; variable length integer and advance index.
25 ;;; FIXME: This is called O(20) times. It should be reimplemented
26 ;;; with much of its logic in a single service function which can
27 ;;; be called by the macro expansion:
28 ;;; `(SETF ,INDEX (%READ-VAR-INTEGER ,VEC ,INDEX)).
29 (defmacro read-var-integer
(vec index
)
30 (once-only ((val `(aref ,vec
,index
)))
36 (logior (aref ,vec
(+ ,index
1))
37 (ash (aref ,vec
(+ ,index
2)) 8))
41 (logior (aref ,vec
(+ ,index
1))
42 (ash (aref ,vec
(+ ,index
2)) 8)
43 (ash (aref ,vec
(+ ,index
3)) 16)
44 (ash (aref ,vec
(+ ,index
4)) 24))
47 ;;; Take an adjustable vector VEC with a fill pointer and push the
48 ;;; variable length representation of INT on the end.
49 (defun write-var-integer (int vec
)
50 (declare (type (unsigned-byte 32) int
))
52 (vector-push-extend int vec
))
54 (let ((32-p (> int
#xFFFF
)))
55 (vector-push-extend (if 32-p
255 254) vec
)
56 (vector-push-extend (ldb (byte 8 0) int
) vec
)
57 (vector-push-extend (ldb (byte 8 8) int
) vec
)
59 (vector-push-extend (ldb (byte 8 16) int
) vec
)
60 (vector-push-extend (ldb (byte 8 24) int
) vec
)))))
65 ;;;; A packed string is a variable length integer length followed by
66 ;;;; the character codes.
68 ;;; Read a packed string from VEC starting at INDEX, advancing INDEX.
69 (defmacro read-var-string
(vec index
)
70 (once-only ((len `(read-var-integer ,vec
,index
)))
71 (once-only ((res `(make-string ,len
)))
73 (%byte-blt
,vec
,index
,res
0 ,len
)
77 ;;; Write STRING into VEC (adjustable, with fill-pointer) represented
78 ;;; as the length (in a var-length integer) followed by the codes of
80 (defun write-var-string (string vec
)
81 (declare (simple-string string
))
82 (let ((len (length string
)))
83 (write-var-integer len vec
)
85 (vector-push-extend (char-code (schar string i
)) vec
)))
88 ;;;; packed bit vectors
90 ;;; Read the specified number of BYTES out of VEC at INDEX and convert
91 ;;; them to a BIT-VECTOR. INDEX is incremented.
92 (defmacro read-packed-bit-vector
(bytes vec index
)
93 (once-only ((n-bytes bytes
))
94 (once-only ((n-res `(make-array (* ,n-bytes
8) :element-type
'bit
)))
96 (%byte-blt
,vec
,index
,n-res
0 ,n-bytes
)
97 (incf ,index
,n-bytes
)