59ba68ef84
In Python 2.x an unprefixed string literal produces a byte string. In Python 3.x an unprefixed string literal produces a textual string. To produce a byte string in both a b prefix is needed, e.g. b'foo'. Since I believe Hammer works predominantly with byte strings I have used b prefixes throughout.
60 lines
1.6 KiB
Python
60 lines
1.6 KiB
Python
#!/usr/bin/env python2
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# Example parser: Base64, syntax only.
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#
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# Demonstrates how to construct a Hammer parser that recognizes valid Base64
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# sequences.
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#
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# Note that no semantic evaluation of the sequence is performed, i.e. the
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# byte sequence being represented is not returned, or determined. See
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# base64_sem1.py and base64_sem2.py for examples how to attach appropriate
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# semantic actions to the grammar.
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from __future__ import absolute_import, division, print_function
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import sys
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import hammer as h
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def init_parser():
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# CORE
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digit = h.ch_range(0x30, 0x39)
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alpha = h.choice(h.ch_range(0x41, 0x5a), h.ch_range(0x61, 0x7a))
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# AUX.
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plus = h.ch(b'+')
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slash = h.ch(b'/')
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equals = h.ch(b'=')
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bsfdig = h.choice(alpha, digit, plus, slash)
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bsfdig_4bit = h.in_(b'AEIMQUYcgkosw048')
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bsfdig_2bit = h.in_(b'AQgw')
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base64_3 = h.repeat_n(bsfdig, 4)
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base64_2 = h.sequence(bsfdig, bsfdig, bsfdig_4bit, equals)
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base64_1 = h.sequence(bsfdig, bsfdig_2bit, equals, equals)
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base64 = h.sequence(h.many(base64_3),
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h.optional(h.choice(base64_2, base64_1)))
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return h.sequence(h.whitespace(base64), h.whitespace(h.end_p()))
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def main():
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document = init_parser()
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s = sys.stdin.read()
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inputsize = len(s)
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print('inputsize=%i' % inputsize, file=sys.stderr)
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print('input=%s' % s, file=sys.stderr, end='')
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result = document.parse(s)
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if result:
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#print('parsed=%i bytes', result.bit_length/8, file=sys.stderr)
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print(result)
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if __name__ == '__main__':
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import sys
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main()
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