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
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
|
# build-aux/kicad_sexpr.py - A KiCad-compatible S-expression unmarshaler/marshaler
#
# Copyright (C) 2025 Luke T. Shumaker <lukeshu@lukeshu.com>
# SPDX-License-Identifier: AGPL-3.0-or-later
# At first I wanted to use
# https://gitlab.com/kicad/libraries/kicad-library-utils/-/blob/master/common/sexpr.py
# but
# 1. It doesn't differentiate between symbols and strings.
# 2. Its license is unclear; Rosetta Code is GFDL-1.3-only, while
# kicad-library-utils is GPL-3.0-or-later.
# 3. It's just over-complicated for what it is.
#
# Instead, this parser is based on:
# - https://gitlab.com/kicad/code/kicad/-/blob/master/libs/sexpr/sexpr_parser.cpp (the main syntax)
# - https://gitlab.com/kicad/code/kicad/-/blob/master/common/dsnlexer.cpp (string escapes)
#
# See-also:
# - https://dev-docs.kicad.org/en/components/sexpr/index.html
import re
import typing
# pylint: disable=unused-variable
__all__ = [
"Symbol",
"Atom",
"List",
"Expr",
"marshal",
"unmarshal",
]
class Symbol:
name: str
__match_args__ = ("name",)
def __init__(self, name: str) -> None:
self.name = name
def __repr__(self) -> str:
return f"Symbol({self.name!r})"
def __eq__(self, other: typing.Any) -> bool:
return isinstance(other, Symbol) and other.name == self.name
type Atom = Symbol | str | int | float
type List = list["Expr"]
type Expr = Atom | List
class _StrIterator:
val: str
filename: str
row: int
col: int
off: int
row_off: int
def __init__(self, s: str, filename: str = "<string>") -> None:
self.val = s
self.filename = filename
self.row = 1
self.col = 0
self.off = 0
self.row_off = 0
def advance(self, n: int = 1) -> None:
for _ in range(n):
if self.val[self.off] == "\n":
self.row += 1
self.col = 0
self.row_off = self.off + 1
else:
self.col += 1
self.off += 1
def char(self) -> str | None:
if self.off == len(self.val):
return None
return self.val[self.off]
def syntax_error(self, msg: str, length: int = -1) -> SyntaxError:
e = SyntaxError(msg)
e.text = self.val[self.row_off :]
if length > 0:
e.text = e.text[:length]
else:
e.text = e.text.split("\n", 1)[0]
e.filename = self.filename
e.lineno = self.row
e.end_lineno = e.lineno + e.text.count("\n")
e.offset = self.col
if length <= 0:
e.end_offset = -1
else:
e.end_offset = e.offset + len(e.text)
return e
_whitespace_characters = " \t\n\r\b\f\v"
_re_atom_end = re.compile("[" + _whitespace_characters + "()]|$")
_re_int = re.compile(r"^-?[0-9]+$")
_re_float = re.compile(r"^-?[0-9]*\.[0-9]*$")
def _unmarshal(iterator: _StrIterator) -> Expr | None:
while True:
char: str | None
match char := iterator.char():
case None: # EOF
return None
case "(":
iterator.advance()
l: List = []
while True:
item = _unmarshal(iterator)
if item is None:
break
l.append(item)
if iterator.char() != ")":
raise iterator.syntax_error("Expected close-paren")
iterator.advance()
return l
case ")":
return None
case '"':
iterator.advance()
s: str = ""
while True:
match char := iterator.char():
case None:
raise iterator.syntax_error("Expected close-quote")
case "\\":
iterator.advance()
match char := iterator.char():
case '"' | "\\":
s += char
iterator.advance()
case "a":
s += "\x07"
iterator.advance()
case "b":
s += "\x08"
iterator.advance()
case "f":
s += "\x0c"
iterator.advance()
case "n":
s += "\n"
iterator.advance()
case "r":
s += "\r"
iterator.advance()
case "t":
s += "\x09"
iterator.advance()
case "t":
s += "\x0b"
iterator.advance()
case "x":
tbuf = ""
iterator.advance()
for _ in range(2):
if (
char := iterator.char()
) and char in "0123456789abcdefABCDEF":
tbuf += char
iterator.advance()
if tbuf:
s += chr(int(tbuf, 16))
else:
s += "x"
case _:
tbuf = ""
for _ in range(3):
if (
char := iterator.char()
) and char in "01234567":
tbuf += char
iterator.advance()
if tbuf:
s += chr(int(tbuf, 8))
else:
s += "\\"
case '"':
iterator.advance()
return s
case _:
iterator.advance()
s += char
case _:
if char in _whitespace_characters:
iterator.advance()
else:
end = _re_atom_end.search(iterator.val, iterator.off)
assert end
tok = iterator.val[iterator.off : end.start()]
iterator.advance(len(tok))
if _re_int.fullmatch(tok):
return int(tok, 10)
if _re_float.fullmatch(tok):
return float(tok)
return Symbol(tok)
def unmarshal(s: str, filename: str = "<string>") -> Expr:
iterator = _StrIterator(s, filename)
o = _unmarshal(iterator)
if o is None:
raise iterator.syntax_error("Empty S-Expression")
char: str | None
while (char := iterator.char()) and char in _whitespace_characters:
iterator.advance()
if iterator.char():
raise iterator.syntax_error(
"Extra text after S-Expression", len(iterator.val) - iterator.off
)
return o
def _marshal(o: Expr, indent: str) -> str:
match o:
case list():
ret = "("
seen_list = False
for child in o:
sep = " "
if isinstance(child, list):
seen_list = True
if seen_list:
sep = "\n" + indent + "\t"
if len(o) > 0 and o[0] == Symbol("pts") and (ret.count("(") - 1) % 6:
sep = " "
if ret == "(":
sep = ""
ret += sep + _marshal(child, indent + "\t")
if o and isinstance(o[-1], list):
ret += "\n" + indent
ret += ")"
return ret
case Symbol():
return o.name
case str():
ret = '"'
for char in o:
match char:
case "\r":
ret += "\\r"
case "\n":
ret += "\\n"
case "\\":
ret += "\\\\"
case '"':
ret += '\\"'
case _:
ret += char
ret += '"'
return ret
case int():
return str(o)
case float():
return str(o)
case _:
assert False
def marshal(o: Expr) -> str:
return _marshal(o, "")
|
