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Issue #22341: Merge CRC doc from 3.5

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Martin Panter 2015-12-11 05:41:48 +00:00
commit 70fe09bc67
6 changed files with 39 additions and 58 deletions
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Doc/library/binascii.rst
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@ -115,15 +115,16 @@ The :mod:`binascii` module defines the following functions:
possibly the last fragment).
.. function:: crc_hqx(data, crc)
.. function:: crc_hqx(data, value)
Compute the binhex4 crc value of *data*, starting with an initial *crc* and
returning the result.
Compute the binhex4 crc value of *data*, starting with *value* as the
initial crc, and return the result.
.. function:: crc32(data[, crc])
.. function:: crc32(data[, value])
Compute CRC-32, the 32-bit checksum of data, starting with an initial crc. This
Compute CRC-32, the 32-bit checksum of *data*, starting with an
initial CRC of *value*. The default initial CRC is zero. The algorithm
is consistent with the ZIP file checksum. Since the algorithm is designed for
use as a checksum algorithm, it is not suitable for use as a general hash
algorithm. Use as follows::
@ -131,15 +132,13 @@ The :mod:`binascii` module defines the following functions:
print(binascii.crc32(b"hello world"))
# Or, in two pieces:
crc = binascii.crc32(b"hello")
crc = binascii.crc32(b" world", crc) & 0xffffffff
crc = binascii.crc32(b" world", crc)
print('crc32 = {:#010x}'.format(crc))
.. note::
To generate the same numeric value across all Python versions and
platforms use crc32(data) & 0xffffffff. If you are only using
the checksum in packed binary format this is not necessary as the
return value is the correct 32bit binary representation
regardless of sign.
.. versionchanged:: 3.0
The result is always unsigned.
To generate the same numeric value across all Python versions and
platforms, use ``crc32(data) & 0xffffffff``.
.. function:: b2a_hex(data)