#
# Copyright (c) 2004 Dug Song <dugsong@monkey.org>
# All rights reserved, all wrongs reversed.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 3. The names of the authors and copyright holders may not be used to
#    endorse or promote products derived from this software without
#    specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
# INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
# AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
# THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
# OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
# OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
# ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# $Id: crc32c.py 23 2006-11-08 15:45:33Z dugsong $
#

import array

# CRC-32C Checksum
# http://tools.ietf.org/html/rfc3309

crc32c_table = (
    0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L, 0xC79A971FL,
    0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL, 0x8AD958CFL, 0x78B2DBCCL,
    0x6BE22838L, 0x9989AB3BL, 0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L,
    0x5E133C24L, 0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL,
    0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L, 0x9A879FA0L,
    0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L, 0x5D1D08BFL, 0xAF768BBCL,
    0xBC267848L, 0x4E4DFB4BL, 0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L,
    0x33ED7D2AL, 0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L,
    0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L, 0x6DFE410EL,
    0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL, 0x30E349B1L, 0xC288CAB2L,
    0xD1D83946L, 0x23B3BA45L, 0xF779DEAEL, 0x05125DADL, 0x1642AE59L,
    0xE4292D5AL, 0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL,
    0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L, 0x417B1DBCL,
    0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L, 0x86E18AA3L, 0x748A09A0L,
    0x67DAFA54L, 0x95B17957L, 0xCBA24573L, 0x39C9C670L, 0x2A993584L,
    0xD8F2B687L, 0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L,
    0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L, 0x96BF4DCCL,
    0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L, 0xDBFC821CL, 0x2997011FL,
    0x3AC7F2EBL, 0xC8AC71E8L, 0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L,
    0x0F36E6F7L, 0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L,
    0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L, 0xEB1FCBADL,
    0x197448AEL, 0x0A24BB5AL, 0xF84F3859L, 0x2C855CB2L, 0xDEEEDFB1L,
    0xCDBE2C45L, 0x3FD5AF46L, 0x7198540DL, 0x83F3D70EL, 0x90A324FAL,
    0x62C8A7F9L, 0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L,
    0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L, 0x3CDB9BDDL,
    0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L, 0x82F63B78L, 0x709DB87BL,
    0x63CD4B8FL, 0x91A6C88CL, 0x456CAC67L, 0xB7072F64L, 0xA457DC90L,
    0x563C5F93L, 0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L,
    0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL, 0x92A8FC17L,
    0x60C37F14L, 0x73938CE0L, 0x81F80FE3L, 0x55326B08L, 0xA759E80BL,
    0xB4091BFFL, 0x466298FCL, 0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL,
    0x0B21572CL, 0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L,
    0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L, 0x65D122B9L,
    0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL, 0x2892ED69L, 0xDAF96E6AL,
    0xC9A99D9EL, 0x3BC21E9DL, 0xEF087A76L, 0x1D63F975L, 0x0E330A81L,
    0xFC588982L, 0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL,
    0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L, 0x38CC2A06L,
    0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L, 0xFF56BD19L, 0x0D3D3E1AL,
    0x1E6DCDEEL, 0xEC064EEDL, 0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L,
    0xD0DDD530L, 0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL,
    0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL, 0x8ECEE914L,
    0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L, 0xD3D3E1ABL, 0x21B862A8L,
    0x32E8915CL, 0xC083125FL, 0x144976B4L, 0xE622F5B7L, 0xF5720643L,
    0x07198540L, 0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L,
    0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL, 0xE330A81AL,
    0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL, 0x24AA3F05L, 0xD6C1BC06L,
    0xC5914FF2L, 0x37FACCF1L, 0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L,
    0x7AB90321L, 0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL,
    0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L, 0x34F4F86AL,
    0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL, 0x79B737BAL, 0x8BDCB4B9L,
    0x988C474DL, 0x6AE7C44EL, 0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L,
    0xAD7D5351L
    )

def add(crc, buf):
    buf = array.array('B', buf)
    for b in buf:
        crc = (crc >> 8) ^ crc32c_table[(crc ^ b) & 0xff]
    return crc

def done(crc):
    tmp = ~crc & 0xffffffffL
    b0 = tmp & 0xff
    b1 = (tmp >> 8) & 0xff
    b2 = (tmp >> 16) & 0xff
    b3 = (tmp >> 24) & 0xff
    crc = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3
    return crc

def cksum(buf):
    """Return computed CRC-32c checksum."""
    return done(add(0xffffffffL, buf))
