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annotate paraspace/tools.py @ 68:b7432d6f7e93

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adler32
author Thinker K.F. Li <thinker@codemud.net>
date Wed, 29 Jun 2011 19:56:24 +0800
parents
children ff6f869273b7
rev   line source
68
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
parents:
diff changeset
1 base = 65521
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
parents:
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2
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
parents:
diff changeset
3 def adler32(adler, buf, offset, sz):
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
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4 sum1 = adler & 0xffff
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
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5 sum2 = (adler >> 16) & 0xffff
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
parents:
diff changeset
6 for off in range(offset, offset + sz):
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
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7 sum1 = (sum1 + ord(buf[off])) % base
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
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8 sum2 = (sum2 + sum1) % base
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
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9 pass
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
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10 r = (sum2 << 16) | sum1
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
parents:
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11 return r
b7432d6f7e93 adler32
Thinker K.F. Li <thinker@codemud.net>
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diff changeset
12