py-xbc/xbc/__init__.py

# Copyright (c) 2024 Síle Ekaterin Liszka
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

"""
This module provides utilities for reading and writing files in the
Linux kernel's bootconfig format. This is not a strictly-conformant
implementation. In particular, this implementation does not restrict
key/block depths and makes no attempt whatsoever to ensure output is
under 32,767 bytes as mandated by the Linux kernel implementation.

XBC has three types of configuration:

- Keys are sequences of one or more characters in the range
	`[a-zA-Z0-9_-]`, namespaced with dots. They can be specified without a
	value, allowing their presence to be a boolean.
- Key/value pairs have a key component, an operator, and one or more
	values. Values have three flavours:
	- Bare values are sequences of one or more characters that are not in
		the range `{}#=+:;,\\n'" `.
	- Quoted strings are bounded by either single or double quotes, and
		cannot contain the quote being bounded. Escaped quotes (`\\'` and
		`\\"`) are not supported.
	- Arrays are bare values or strings delimited by commas.
- Blocks have a key component and a sequence of keys, key/value pairs,
	or blocks. Keys within blocks are not mapped separately; `a.a` is
	identical to `a { a }`, for example.

XBC supports single-line comments using the pound sign (`#`).
"""

import re

from collections.abc import Mapping, Sequence

from pyparsing import (
	alphas,
	CharsNotIn,
	DelimitedList,
	Forward,
	Group,
	nums,
	Literal,
	OneOrMore,
	Optional,
	Regex,
	restOfLine,
	QuotedString,
	Word,
	ZeroOrMore
)

from .utils import normalise

class Node:
	def __init__(self, *args, type=None):
		if isinstance(args[0], str):
			self.args = args[0]
		elif isinstance(args[0][0], str):
			self.args = args[0][0]
		else:
			self.args = args[0][0][0]
		self.type = type

	@property
	def key(self):
		return self.args[0]

class Key(Node):
	def __init__(self, *args):
		self.args = args[0]
		self.type = 'key'

class KeyValue(Node):
	def __init__(self, *args):
		super().__init__(args, type='kv')

	@property
	def op(self):
		return self.args[1]

	@property
	def value(self):
		return self.args[2]

class Block(Node):
	def __init__(self, *args):
		super().__init__(args, type='block')

	@property
	def contents(self):
		return self.args[1]

key_fragment = Word(alphas + nums + '_-')
key = DelimitedList(key_fragment, delim='.', combine=True)

bareval = CharsNotIn(' {}#=+:;,\n\'"')
strvals = QuotedString("'", multiline=True, unquote_results=False)
strvald = QuotedString('"', multiline=True, unquote_results=False)
value = bareval | strvald | strvals

assign = Literal('=')
update = Literal(':=')
append = Literal('+=')
op = assign | update | append
semi = Literal(';').suppress()
lbrace = Literal('{').suppress()
rbrace = Literal('}').suppress()

NL = Literal('\n').suppress()
WS = Word(' \t').suppress()
WS_NL = Word(' \t\n').suppress()
comment = Literal('#') + restOfLine

values = Group(value + ZeroOrMore(Literal(',').suppress() + Optional(WS_NL) + value), aslist=True)

keyvalue = Group(key + Optional(WS) + op + Optional(WS) + values, aslist=True)
keyvalue.set_parse_action(lambda x: KeyValue(x))

key_stmt = Optional(WS) + key + Optional(assign).suppress() + Optional(WS)
key_stmt.set_parse_action(lambda x: Key(x))
kv_stmt  = Optional(WS) + keyvalue + Optional(WS)

block = Forward()
statement = kv_stmt | key_stmt
term_stmt = kv_stmt | key_stmt + Optional(semi) + Optional(WS)

line_statements = Group(term_stmt + ZeroOrMore(NL + term_stmt))
term_stmt_list  = Group(statement + ZeroOrMore(semi + statement))

segment = OneOrMore(block | term_stmt_list | line_statements)

block << Group(key + Optional(WS) + lbrace + Group(segment, aslist=True) + rbrace + Optional(NL))
block.set_parse_action(lambda x: Block(x))

data = OneOrMore(block | (term_stmt + Optional(NL)))

XBCParser = data

XBCParser.ignore(comment)

class ParseError(Exception):
	pass

def lex(data):
	tree = XBCParser.parseString(data).asList()
	return tree

def parse_block(key, seq):
	if isinstance(seq, list) and len(seq) == 1 and isinstance(seq[0], list):
		seq = seq[0]

	ret = {}

	for item in seq:
		if key is not None:
			k = f'{key}.{item.key}'
		else:
			k = item.key

		if isinstance(item, Key):
			if k not in ret:
				ret[k] = True
			else:
				raise ParseError(f'key {k} already defined')
		elif isinstance(item, KeyValue):
			value = item.value
			op = item.op

			if op == '=':
				if k in ret:
					raise ParseError(f'key {k} already defined')
				assign = value
			else:
				if k not in ret:
					raise ParseError(f'key {k} not defined')

				if op == '+=':
					if isinstance(ret[k], str):
						assign = [ret[k]]
					else:
						assign = ret[k]
					if isinstance(value, str):
						assign.append(value)
					else:
						assign.extend(value)
				else:
					assign = value

			if isinstance(assign, list) and len(assign) == 1:
				assign = assign[0]

			ret[k] = assign
		elif isinstance(item, Block):
			value = item.contents

			if k not in ret:
				ret[k] = False

			ret.update(parse_block(k, value))

	return ret

def parse(data):
	tree = lex(data)

	d = parse_block(None, tree)

	return d

def loads_xbc(data):
	return parse(data)

def load_xbc(fp):
	with open(fp, mode='r') as f:
		return loads_xbc(f.read())

def longest_key(L):
	lens = [len(x) for x in L]
	shortest = min(lens)

	if shortest < 1:
		return None

	ret = []

	for i in range(shortest):
		count = {}

		for item in L:
			j = item[i]

			if j not in count:
				count[j] = 0

			count[j] += 1
		if len(count.keys()) == 1:
			ret.append(L[0][i])
		else:
			return '.'.join(ret)
	return None

def longest_keys(keys):
	keys = [k.split('.') for k in keys]
	ret = set()

	for i in range(len(keys)):
		for j in range(1, len(keys)):
			longest = longest_key([keys[i], keys[j]])
			if longest is not None:
				ret.add(longest)
	ret.discard('')
	return ret

def make_block(data):
	ret = []

	leafs = []
	blocks = set()
	block_keys = []

	for key in data.keys():
		if '.' not in key:
			leafs.append(key)
		else:
			k, rest = key.split('.', maxsplit=1)
			blocks.add(k)

	keys = [k for k in data.keys() if '.' in k]
	temp = longest_keys(keys)
	if len(temp):
		mindots = 99
		for i in temp:
			if 0 < i.count('.') < mindots:
				mindots = i.count('.')
		temp = [i for i in temp if i.count('.') == mindots]
		blocks = set(temp)

	for key in leafs:
		if data[key] is True:
			ret.append(f'{key}')
		elif data[key] is False:
			continue
		else:
			value = normalise(data[key])
			ret.append(f'{key} = {value}')

	for key in blocks:
		block = {}
		klen = len(key) + 1

		for k, v in data.items():
			if not k.startswith(f'{key}.'):
				continue
			block[k[klen:]] = v

		chunk = make_block(block)
		ret.append(key + ' {')
		for line in chunk:
			ret.append(f'\t{line}')
		ret.append('}')

	return ret

def saves_xbc(data):
	ret = make_block(data)
	return '\n'.join(ret)

def save_xbc(data, filename):
	with open(filename, mode='w') as f:
		f.write(saves_xbc(data))

__all__ = ['loads_xbc', 'load_xbc', 'saves_xbc', 'save_xbc', 'ParseError']