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zcash-test-vectors
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zc_utils.py: optionally enforce the MAX_SIZE limit (enforced by default). 

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
This commit is contained in:
Daira Hopwood 2021-09-17 20:39:53 +01:00
parent efee9dcb03
commit bc6bc8a375
1 changed files with 42 additions and 27 deletions
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69
zc_utils.py
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@ -3,7 +3,10 @@ import sys; assert sys.version_info[0] >= 3, "Python 3 required."
import struct import struct
def write_compact_size(n): MAX_SIZE = 0x2000000
def write_compact_size(n, allow_u64=False):
assert allow_u64 or n <= MAX_SIZE
if n < 253: if n < 253:
return struct.pack('B', n) return struct.pack('B', n)
elif n <= 0xFFFF: elif n <= 0xFFFF:
@ -13,7 +16,12 @@ def write_compact_size(n):
else: else:
return struct.pack('B', 255) + struct.pack('<Q', n) return struct.pack('B', 255) + struct.pack('<Q', n)
def parse_compact_size(rest): def parse_compact_size(rest, allow_u64=False):
(n, rest) = parse_compact_u64(rest)
assert allow_u64 or n <= MAX_SIZE
return (n, rest)
def parse_compact_u64(rest):
assert len(rest) >= 1 assert len(rest) >= 1
b = rest[0] b = rest[0]
if b < 253: if b < 253:
@ -35,36 +43,43 @@ def parse_compact_size(rest):
return (n, rest[9:]) return (n, rest[9:])
def assert_parse_fails(encoding): def assert_parse_fails(encoding, allow_u64):
try: try:
parse_compact_size(encoding) parse_compact_size(encoding, allow_u64)
except AssertionError: except AssertionError:
pass pass
else: else:
raise AssertionError("parse_compact_size(%r) failed to raise AssertionError" % (encoding,)) raise AssertionError("parse_compact_size(%r) failed to raise AssertionError" % (encoding,))
def test_round_trip(n, encoding): def test_round_trip(n, encoding, allow_u64):
assert write_compact_size(n) == encoding assert write_compact_size(n, allow_u64) == encoding
assert parse_compact_size(encoding) == (n, b'') assert parse_compact_size(encoding, allow_u64) == (n, b'')
assert parse_compact_size(encoding + b'*') == (n, b'*') assert parse_compact_size(encoding + b'*', allow_u64) == (n, b'*')
assert_parse_fails(encoding[:-1]) assert_parse_fails(encoding[:-1], allow_u64)
test_round_trip(0, b'\x00') for allow_u64 in (False, True):
test_round_trip(1, b'\x01') test_round_trip(0, b'\x00', allow_u64)
test_round_trip(252, b'\xFC') test_round_trip(1, b'\x01', allow_u64)
test_round_trip(253, b'\xFD\xFD\x00') test_round_trip(252, b'\xFC', allow_u64)
test_round_trip(254, b'\xFD\xFE\x00') test_round_trip(253, b'\xFD\xFD\x00', allow_u64)
test_round_trip(255, b'\xFD\xFF\x00') test_round_trip(254, b'\xFD\xFE\x00', allow_u64)
test_round_trip(256, b'\xFD\x00\x01') test_round_trip(255, b'\xFD\xFF\x00', allow_u64)
test_round_trip(0xFFFE, b'\xFD\xFE\xFF') test_round_trip(256, b'\xFD\x00\x01', allow_u64)
test_round_trip(0xFFFF, b'\xFD\xFF\xFF') test_round_trip(0xFFFE, b'\xFD\xFE\xFF', allow_u64)
test_round_trip(0x010000, b'\xFE\x00\x00\x01\x00') test_round_trip(0xFFFF, b'\xFD\xFF\xFF', allow_u64)
test_round_trip(0x010001, b'\xFE\x01\x00\x01\x00') test_round_trip(0x010000, b'\xFE\x00\x00\x01\x00', allow_u64)
test_round_trip(0xFFFFFFFE, b'\xFE\xFE\xFF\xFF\xFF') test_round_trip(0x010001, b'\xFE\x01\x00\x01\x00', allow_u64)
test_round_trip(0xFFFFFFFF, b'\xFE\xFF\xFF\xFF\xFF') test_round_trip(0x02000000, b'\xFE\x00\x00\x00\x02', allow_u64)
test_round_trip(0x0100000000, b'\xFF\x00\x00\x00\x00\x01\x00\x00\x00')
test_round_trip(0xFFFFFFFFFFFFFFFF, b'\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF')
assert_parse_fails(b'\xFD\xFC\x00') assert_parse_fails(b'\xFD\xFC\x00', allow_u64)
assert_parse_fails(b'\xFE\xFF\xFF\x00\x00') assert_parse_fails(b'\xFE\xFF\xFF\x00\x00', allow_u64)
assert_parse_fails(b'\xFF\xFF\xFF\xFF\xFF\x00\x00\x00\x00') assert_parse_fails(b'\xFF\xFF\xFF\xFF\xFF\x00\x00\x00\x00', allow_u64)
assert_parse_fails(b'\xFE\x01\x00\x00\x02', False)
assert_parse_fails(b'\xFF\x00\x00\x00\x00\x01\x00\x00\x00', False)
assert_parse_fails(b'\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF', False)
test_round_trip(0xFFFFFFFE, b'\xFE\xFE\xFF\xFF\xFF', True)
test_round_trip(0xFFFFFFFF, b'\xFE\xFF\xFF\xFF\xFF', True)
test_round_trip(0x0100000000, b'\xFF\x00\x00\x00\x00\x01\x00\x00\x00', True)
test_round_trip(0xFFFFFFFFFFFFFFFF, b'\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF', True)