99 lines
2.7 KiB
Python
99 lines
2.7 KiB
Python
#!/usr/bin/env python
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#
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# Copyright (c) 2008-2012 WiredTiger, Inc.
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# All rights reserved.
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#
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# See the file LICENSE for redistribution information.
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#
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# WiredTiger fixed-size packing and unpacking functions, using the Python
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# struct library.
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import struct
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def __wt2struct(fmt):
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if not fmt:
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return None, fmt
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# Big endian with no alignment is the default
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if fmt[0] in '@=<>!':
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tfmt = fmt[0]
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fmt = fmt[1:]
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else:
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tfmt = '>'
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return tfmt, fmt.replace('r', 'Q')
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def unpack(fmt, s):
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tfmt, fmt = __wt2struct(fmt)
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if not fmt:
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return ()
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result = ()
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pfmt = tfmt
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sizebytes = 0
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for offset, f in enumerate(fmt):
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if f.isdigit():
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sizebytes += 1
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# With a fixed size, everything is encoded as a string
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if f in 'Su' and sizebytes > 0:
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f = 's'
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if f not in 'Su':
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pfmt += f
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sizebytes = 0
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continue
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# We've hit something that needs special handling, split any fixed-size
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# values we've already passed
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if len(pfmt) > 1:
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size = struct.calcsize(pfmt)
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result += struct.unpack_from(pfmt, s)
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s = s[size:]
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if f == 'S':
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l = s.find('\0')
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result += (s[:l],)
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s = s[l+1:]
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if f == 'u':
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if offset == len(fmt) - 1:
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result += (s,)
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else:
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l = struct.unpack_from(tfmt + 'l', s)[0]
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s = s[struct.calcsize(tfmt + 'l'):]
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result += (s[:l],)
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s = s[l:]
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pfmt = tfmt
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sizebytes = 0
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if len(pfmt) > 1:
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result += struct.unpack(pfmt, s)
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return result
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def pack(fmt, *values):
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pfmt, fmt = __wt2struct(fmt)
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if not fmt:
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return ''
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i = sizebytes = 0
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for offset, f in enumerate(fmt):
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if f == 'S':
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# Note: this code is being careful about embedded NUL characters
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if sizebytes == 0:
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l = values[i].find('\0') + 1
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if not l:
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l = len(values[i]) + 1
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pfmt += str(l)
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sizebytes = len(str(l))
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f = 's'
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elif f == 'u':
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if sizebytes == 0 and offset != len(fmt) - 1:
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l = len(values[i])
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pfmt += 'l' + str(l)
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values = values[:i] + (l,) + values[i:]
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sizebytes = len(str(l))
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f = 's'
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pfmt += f
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if f.isdigit():
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sizebytes += 1
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continue
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if f != 's' and sizebytes > 0:
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i += int(pfmt[-sizebytes:])
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else:
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i += 1
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sizebytes = 0
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return struct.pack(pfmt, *values)
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