116 lines
2.5 KiB
Python
116 lines
2.5 KiB
Python
from six.moves import range
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import struct
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def body_and_tail(data):
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l = len(data)
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nblocks = l // 16
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tail = l % 16
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if nblocks:
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# we use '<', specifying little-endian byte order for data bigger than
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# a byte so behavior is the same on little- and big-endian platforms
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return struct.unpack_from('<' + ('qq' * nblocks), data), struct.unpack_from('b' * tail, data, -tail), l
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else:
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return tuple(), struct.unpack_from('b' * tail, data, -tail), l
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def rotl64(x, r):
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# note: not a general-purpose function because it leaves the high-order bits intact
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# suitable for this use case without wasting cycles
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mask = 2 ** r - 1
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rotated = (x << r) | ((x >> 64 - r) & mask)
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return rotated
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def fmix(k):
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# masking off the 31s bits that would be leftover after >> 33 a 64-bit number
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k ^= (k >> 33) & 0x7fffffff
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k *= 0xff51afd7ed558ccd
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k ^= (k >> 33) & 0x7fffffff
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k *= 0xc4ceb9fe1a85ec53
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k ^= (k >> 33) & 0x7fffffff
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return k
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INT64_MAX = int(2 ** 63 - 1)
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INT64_MIN = -INT64_MAX - 1
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INT64_OVF_OFFSET = INT64_MAX + 1
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INT64_OVF_DIV = 2 * INT64_OVF_OFFSET
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def truncate_int64(x):
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if not INT64_MIN <= x <= INT64_MAX:
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x = (x + INT64_OVF_OFFSET) % INT64_OVF_DIV - INT64_OVF_OFFSET
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return x
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def _murmur3(data):
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h1 = h2 = 0
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c1 = -8663945395140668459 # 0x87c37b91114253d5
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c2 = 0x4cf5ad432745937f
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body, tail, total_len = body_and_tail(data)
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# body
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for i in range(0, len(body), 2):
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k1 = body[i]
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k2 = body[i + 1]
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k1 *= c1
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k1 = rotl64(k1, 31)
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k1 *= c2
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h1 ^= k1
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h1 = rotl64(h1, 27)
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h1 += h2
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h1 = h1 * 5 + 0x52dce729
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k2 *= c2
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k2 = rotl64(k2, 33)
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k2 *= c1
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h2 ^= k2
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h2 = rotl64(h2, 31)
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h2 += h1
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h2 = h2 * 5 + 0x38495ab5
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# tail
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k1 = k2 = 0
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len_tail = len(tail)
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if len_tail > 8:
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for i in range(len_tail - 1, 7, -1):
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k2 ^= tail[i] << (i - 8) * 8
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k2 *= c2
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k2 = rotl64(k2, 33)
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k2 *= c1
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h2 ^= k2
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if len_tail:
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for i in range(min(7, len_tail - 1), -1, -1):
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k1 ^= tail[i] << i * 8
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k1 *= c1
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k1 = rotl64(k1, 31)
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k1 *= c2
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h1 ^= k1
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# finalization
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h1 ^= total_len
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h2 ^= total_len
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h1 += h2
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h2 += h1
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h1 = fmix(h1)
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h2 = fmix(h2)
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h1 += h2
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return truncate_int64(h1)
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try:
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from cassandra.cmurmur3 import murmur3
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except ImportError:
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murmur3 = _murmur3
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