Line data Source code
1 : /*
2 : * Based on file found here:
3 : *
4 : * https://svnweb.freebsd.org/base/stable/10/sys/libkern/crc32.c?revision=256281
5 : */
6 :
7 : /*-
8 : * COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or
9 : * code or tables extracted from it, as desired without restriction.
10 : */
11 :
12 : /*
13 : * First, the polynomial itself and its table of feedback terms. The
14 : * polynomial is
15 : * X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0
16 : *
17 : * Note that we take it "backwards" and put the highest-order term in
18 : * the lowest-order bit. The X^32 term is "implied"; the LSB is the
19 : * X^31 term, etc. The X^0 term (usually shown as "+1") results in
20 : * the MSB being 1
21 : *
22 : * Note that the usual hardware shift register implementation, which
23 : * is what we're using (we're merely optimizing it by doing eight-bit
24 : * chunks at a time) shifts bits into the lowest-order term. In our
25 : * implementation, that means shifting towards the right. Why do we
26 : * do it this way? Because the calculated CRC must be transmitted in
27 : * order from highest-order term to lowest-order term. UARTs transmit
28 : * characters in order from LSB to MSB. By storing the CRC this way
29 : * we hand it to the UART in the order low-byte to high-byte; the UART
30 : * sends each low-bit to hight-bit; and the result is transmission bit
31 : * by bit from highest- to lowest-order term without requiring any bit
32 : * shuffling on our part. Reception works similarly
33 : *
34 : * The feedback terms table consists of 256, 32-bit entries. Notes
35 : *
36 : * The table can be generated at runtime if desired; code to do so
37 : * is shown later. It might not be obvious, but the feedback
38 : * terms simply represent the results of eight shift/xor opera
39 : * tions for all combinations of data and CRC register values
40 : *
41 : * The values must be right-shifted by eight bits by the "updcrc
42 : * logic; the shift must be unsigned (bring in zeroes). On some
43 : * hardware you could probably optimize the shift in assembler by
44 : * using byte-swap instructions
45 : * polynomial $edb88320
46 : *
47 : *
48 : * CRC32 code derived from work by Gary S. Brown.
49 : */
50 :
51 : #include "crc32c.h"
52 :
53 : /* CRC32C routines, these use a different polynomial */
54 : /*****************************************************************/
55 : /* */
56 : /* CRC LOOKUP TABLE */
57 : /* ================ */
58 : /* The following CRC lookup table was generated automagically */
59 : /* by the Rocksoft^tm Model CRC Algorithm Table Generation */
60 : /* Program V1.0 using the following model parameters: */
61 : /* */
62 : /* Width : 4 bytes. */
63 : /* Poly : 0x1EDC6F41L */
64 : /* Reverse : TRUE. */
65 : /* */
66 : /* For more information on the Rocksoft^tm Model CRC Algorithm, */
67 : /* see the document titled "A Painless Guide to CRC Error */
68 : /* Detection Algorithms" by Ross Williams */
69 : /* (ross@guest.adelaide.edu.au.). This document is likely to be */
70 : /* in the FTP archive "ftp.adelaide.edu.au/pub/rocksoft". */
71 : /* */
72 : /*****************************************************************/
73 :
74 : static const uint32_t crc32Table[256] = {
75 : 0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L,
76 : 0xC79A971FL, 0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL,
77 : 0x8AD958CFL, 0x78B2DBCCL, 0x6BE22838L, 0x9989AB3BL,
78 : 0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L, 0x5E133C24L,
79 : 0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL,
80 : 0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L,
81 : 0x9A879FA0L, 0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L,
82 : 0x5D1D08BFL, 0xAF768BBCL, 0xBC267848L, 0x4E4DFB4BL,
83 : 0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L, 0x33ED7D2AL,
84 : 0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L,
85 : 0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L,
86 : 0x6DFE410EL, 0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL,
87 : 0x30E349B1L, 0xC288CAB2L, 0xD1D83946L, 0x23B3BA45L,
88 : 0xF779DEAEL, 0x05125DADL, 0x1642AE59L, 0xE4292D5AL,
89 : 0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL,
90 : 0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L,
91 : 0x417B1DBCL, 0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L,
92 : 0x86E18AA3L, 0x748A09A0L, 0x67DAFA54L, 0x95B17957L,
93 : 0xCBA24573L, 0x39C9C670L, 0x2A993584L, 0xD8F2B687L,
94 : 0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L,
95 : 0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L,
96 : 0x96BF4DCCL, 0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L,
97 : 0xDBFC821CL, 0x2997011FL, 0x3AC7F2EBL, 0xC8AC71E8L,
98 : 0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L, 0x0F36E6F7L,
99 : 0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L,
100 : 0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L,
101 : 0xEB1FCBADL, 0x197448AEL, 0x0A24BB5AL, 0xF84F3859L,
102 : 0x2C855CB2L, 0xDEEEDFB1L, 0xCDBE2C45L, 0x3FD5AF46L,
103 : 0x7198540DL, 0x83F3D70EL, 0x90A324FAL, 0x62C8A7F9L,
104 : 0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L,
105 : 0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L,
106 : 0x3CDB9BDDL, 0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L,
107 : 0x82F63B78L, 0x709DB87BL, 0x63CD4B8FL, 0x91A6C88CL,
108 : 0x456CAC67L, 0xB7072F64L, 0xA457DC90L, 0x563C5F93L,
109 : 0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L,
110 : 0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL,
111 : 0x92A8FC17L, 0x60C37F14L, 0x73938CE0L, 0x81F80FE3L,
112 : 0x55326B08L, 0xA759E80BL, 0xB4091BFFL, 0x466298FCL,
113 : 0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL, 0x0B21572CL,
114 : 0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L,
115 : 0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L,
116 : 0x65D122B9L, 0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL,
117 : 0x2892ED69L, 0xDAF96E6AL, 0xC9A99D9EL, 0x3BC21E9DL,
118 : 0xEF087A76L, 0x1D63F975L, 0x0E330A81L, 0xFC588982L,
119 : 0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL,
120 : 0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L,
121 : 0x38CC2A06L, 0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L,
122 : 0xFF56BD19L, 0x0D3D3E1AL, 0x1E6DCDEEL, 0xEC064EEDL,
123 : 0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L, 0xD0DDD530L,
124 : 0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL,
125 : 0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL,
126 : 0x8ECEE914L, 0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L,
127 : 0xD3D3E1ABL, 0x21B862A8L, 0x32E8915CL, 0xC083125FL,
128 : 0x144976B4L, 0xE622F5B7L, 0xF5720643L, 0x07198540L,
129 : 0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L,
130 : 0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL,
131 : 0xE330A81AL, 0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL,
132 : 0x24AA3F05L, 0xD6C1BC06L, 0xC5914FF2L, 0x37FACCF1L,
133 : 0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L, 0x7AB90321L,
134 : 0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL,
135 : 0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L,
136 : 0x34F4F86AL, 0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL,
137 : 0x79B737BAL, 0x8BDCB4B9L, 0x988C474DL, 0x6AE7C44EL,
138 : 0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L, 0xAD7D5351L
139 : };
140 :
141 : // NOTE: See source URL at top of this file for multitable implementation which
142 : // offers a performance boost at the cost of ~8KB of static tables.
143 :
144 : uint32_t
145 0 : ComputeCrc32c(uint32_t crc, const void *buf, size_t size)
146 : {
147 0 : const uint8_t *p = buf;
148 :
149 :
150 0 : while (size--)
151 0 : crc = crc32Table[(crc ^ *p++) & 0xff] ^ (crc >> 8);
152 :
153 0 : return crc;
154 : }
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