"""Source List Parser
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The syntax of a source list file is a very small subset of GNU Make. These
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features are supported
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operators: =, +=, :=
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line continuation
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non-nested variable expansion
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comment
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The goal is to allow Makefile's and SConscript's to share source listing.
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"""
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class SourceListParser(object):
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def __init__(self):
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self.symbol_table = {}
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self._reset()
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def _reset(self, filename=None):
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self.filename = filename
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self.line_no = 1
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self.line_cont = ''
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def _error(self, msg):
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raise RuntimeError('%s:%d: %s' % (self.filename, self.line_no, msg))
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def _next_dereference(self, val, cur):
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"""Locate the next $(...) in value."""
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deref_pos = val.find('$', cur)
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if deref_pos < 0:
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return (-1, -1)
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elif val[deref_pos + 1] != '(':
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self._error('non-variable dereference')
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deref_end = val.find(')', deref_pos + 2)
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if deref_end < 0:
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self._error('unterminated variable dereference')
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return (deref_pos, deref_end + 1)
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def _expand_value(self, val):
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"""Perform variable expansion."""
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expanded = ''
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cur = 0
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while True:
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deref_pos, deref_end = self._next_dereference(val, cur)
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if deref_pos < 0:
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expanded += val[cur:]
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break
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sym = val[(deref_pos + 2):(deref_end - 1)]
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expanded += val[cur:deref_pos] + self.symbol_table[sym]
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cur = deref_end
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return expanded
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def _parse_definition(self, line):
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"""Parse a variable definition line."""
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op_pos = line.find('=')
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op_end = op_pos + 1
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if op_pos < 0:
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self._error('not a variable definition')
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if op_pos > 0:
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if line[op_pos - 1] in [':', '+', '?']:
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op_pos -= 1
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else:
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self._error('only =, :=, and += are supported')
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# set op, sym, and val
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op = line[op_pos:op_end]
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sym = line[:op_pos].strip()
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val = self._expand_value(line[op_end:].lstrip())
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if op in ('=', ':='):
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self.symbol_table[sym] = val
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elif op == '+=':
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self.symbol_table[sym] += ' ' + val
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elif op == '?=':
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if sym not in self.symbol_table:
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self.symbol_table[sym] = val
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def _parse_line(self, line):
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"""Parse a source list line."""
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# more lines to come
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if line and line[-1] == '\\':
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# spaces around "\\\n" are replaced by a single space
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if self.line_cont:
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self.line_cont += line[:-1].strip() + ' '
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else:
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self.line_cont = line[:-1].rstrip() + ' '
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return 0
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# combine with previous lines
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if self.line_cont:
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line = self.line_cont + line.lstrip()
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self.line_cont = ''
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if line:
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begins_with_tab = (line[0] == '\t')
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line = line.lstrip()
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if line[0] != '#':
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if begins_with_tab:
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self._error('recipe line not supported')
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else:
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self._parse_definition(line)
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return 1
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def parse(self, filename):
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"""Parse a source list file."""
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if self.filename != filename:
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fp = open(filename)
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lines = fp.read().splitlines()
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fp.close()
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try:
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self._reset(filename)
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for line in lines:
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self.line_no += self._parse_line(line)
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except:
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self._reset()
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raise
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return self.symbol_table
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def add_symbol(self, name, value):
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self.symbol_table[name] = value
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