3582893d8b
1) Applied special case from C code for POS_2BYTE_MAX + 1. 2) Handle B/b format chars directly. Up to now these would have been encoded using default int encoding (so values above 63 get errors when encoding.
207 lines
6.7 KiB
Python
207 lines
6.7 KiB
Python
#!/usr/bin/env python
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#
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# Public Domain 2014-2015 MongoDB, Inc.
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# Public Domain 2008-2014 WiredTiger, Inc.
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#
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# This is free and unencumbered software released into the public domain.
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#
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# Anyone is free to copy, modify, publish, use, compile, sell, or
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# distribute this software, either in source code form or as a compiled
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# binary, for any purpose, commercial or non-commercial, and by any
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# means.
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#
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# In jurisdictions that recognize copyright laws, the author or authors
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# of this software dedicate any and all copyright interest in the
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# software to the public domain. We make this dedication for the benefit
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# of the public at large and to the detriment of our heirs and
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# successors. We intend this dedication to be an overt act of
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# relinquishment in perpetuity of all present and future rights to this
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# software under copyright law.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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# IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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# OTHER DEALINGS IN THE SOFTWARE.
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#
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# WiredTiger variable-length packing and unpacking functions
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"""Packing and unpacking functions
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The format string uses the following conversions:
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Format Python Notes
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x N/A pad byte, no associated value
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b int signed byte
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B int unsigned byte
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h int signed 16-bit
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H int unsigned 16-bit
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i int signed 32-bit
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I int unsigned 32-bit
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l int signed 32-bit
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L int unsigned 32-bit
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q int signed 64-bit
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Q int unsigned 64-bit
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r int record number
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s str fixed-length string
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S str NUL-terminated string
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t int fixed-length bit field
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u str raw byte array
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"""
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from intpacking import pack_int, unpack_int
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def __get_type(fmt):
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if not fmt:
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return None, fmt
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# Variable-sized encoding is the default (and only supported format in v1)
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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
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def __unpack_iter_fmt(fmt):
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size = 0
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havesize = 0
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for offset, char in enumerate(fmt):
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if char.isdigit():
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size = (size * 10) + int(char)
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havesize = 1
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else:
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yield offset, havesize, size, char
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size = 0
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havesize = 0
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def unpack(fmt, s):
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tfmt, fmt = __get_type(fmt)
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if not fmt:
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return ()
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if tfmt != '.':
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raise ValueError('Only variable-length encoding is currently supported')
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result = []
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for offset, havesize, size, f in __unpack_iter_fmt(fmt):
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if f == 'x':
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if not havesize:
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size = 1
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s = s[size:]
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# Note: no value, don't increment i
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elif f in 'Ssu':
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if not havesize:
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if f == 's':
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size = 1
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elif f == 'S':
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size = s.find('\0')
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elif f == 'u':
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if offset == len(fmt) - 1:
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size = len(s)
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else:
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size, s = unpack_int(s)
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result.append(s[:size])
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if f == 'S' and not havesize:
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size += 1
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s = s[size:]
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elif f in 't':
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# bit type, size is number of bits
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if not havesize:
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size = 1
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result.append(ord(s[0:1]))
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s = s[1:]
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elif f in 'Bb':
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# byte type
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if not havesize:
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size = 1
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for i in xrange(size):
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v = ord(s[0:1])
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if f != 'B':
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v -= 0x80
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result.append(v)
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s = s[1:]
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else:
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# integral type
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if not havesize:
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size = 1
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for j in xrange(size):
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v, s = unpack_int(s)
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result.append(v)
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return result
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def __pack_iter_fmt(fmt, values):
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index = 0
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for offset, havesize, size, char in __unpack_iter_fmt(fmt):
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if char == 'x': # padding no value
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yield offset, havesize, size, char, None
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elif char in 'Ssut':
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yield offset, havesize, size, char, values[index]
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index += 1
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else: # integral type
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size = size if havesize else 1
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for i in xrange(size):
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value = values[index]
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yield offset, havesize, 1, char, value
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index = index + 1
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def pack(fmt, *values):
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tfmt, fmt = __get_type(fmt)
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if not fmt:
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return ()
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if tfmt != '.':
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raise ValueError('Only variable-length encoding is currently supported')
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result = ''
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i = 0
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for offset, havesize, size, f, val in __pack_iter_fmt(fmt, values):
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if f == 'x':
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if not havesize:
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result += '\0'
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else:
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result += '\0' * size
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# Note: no value, don't increment i
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elif f in 'Ssu':
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if f == 'S' and '\0' in val:
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l = val.find('\0')
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else:
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l = len(val)
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if havesize:
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if l > size:
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l = size
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elif f == 's':
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havesize = size = 1
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elif f == 'u' and offset != len(fmt) - 1:
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result += pack_int(l)
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if type(val) is unicode and f in 'Ss':
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result += str(val[:l])
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else:
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result += val[:l]
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if f == 'S' and not havesize:
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result += '\0'
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elif size > l:
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result += '\0' * (size - l)
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elif f in 't':
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# bit type, size is number of bits
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if not havesize:
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size = 1
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if size > 8:
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raise ValueError("bit count cannot be greater than 8 for 't' encoding")
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mask = (1 << size) - 1
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if (mask & val) != val:
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raise ValueError("value out of range for 't' encoding")
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result += chr(val)
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elif f in 'Bb':
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# byte type
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if not havesize:
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size = 1
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for i in xrange(size):
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if f == 'B':
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v = val
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else:
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# Translate to maintain ordering with the sign bit.
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v = val + 0x80
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if v > 255 or v < 0:
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raise ValueError("value out of range for 'B' encoding")
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result += chr(v)
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else:
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# integral type
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result += pack_int(val)
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return result
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