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4bec0ef03e
In some places the xcrc32 documentation refers to GDB's own crc32 implementation, but GDB no longer has its own crc32 implementation. It now uses libiberty's xcrc32 throughout. So this patch removes these references to GDB's now-nonexistent crc32 implementation. Also, there appears to be a bug in the table-generation program embedded within the documentation. When the variable "int i" is >= 128, the computation "i << 24" shifts a one bit into the sign bit (assuming a 32-bit int), which is UB. To avoid this UB, I think it is sufficient to make the induction variables i and j have type unsigned int. This bug seems latent, however. I ran the program before and after this change and the table output is the same.
180 lines
6.4 KiB
C
180 lines
6.4 KiB
C
/* crc32.c
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Copyright (C) 2009, 2011 Free Software Foundation, Inc.
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This file is part of the libiberty library.
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This file is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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In addition to the permissions in the GNU General Public License, the
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Free Software Foundation gives you unlimited permission to link the
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compiled version of this file into combinations with other programs,
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and to distribute those combinations without any restriction coming
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from the use of this file. (The General Public License restrictions
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do apply in other respects; for example, they cover modification of
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the file, and distribution when not linked into a combined
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executable.)
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "libiberty.h"
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/* This table was generated by the following program.
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#include <stdio.h>
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int
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main ()
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{
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unsigned int i, j;
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unsigned int c;
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int table[256];
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for (i = 0; i < 256; i++)
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{
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for (c = i << 24, j = 8; j > 0; --j)
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c = c & 0x80000000 ? (c << 1) ^ 0x04c11db7 : (c << 1);
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table[i] = c;
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}
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printf ("static const unsigned int crc32_table[] =\n{\n");
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for (i = 0; i < 256; i += 4)
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{
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printf (" 0x%08x, 0x%08x, 0x%08x, 0x%08x",
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table[i + 0], table[i + 1], table[i + 2], table[i + 3]);
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if (i + 4 < 256)
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putchar (',');
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putchar ('\n');
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}
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printf ("};\n");
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return 0;
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}
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For more information on CRC, see, e.g.,
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http://www.ross.net/crc/download/crc_v3.txt. */
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static const unsigned int crc32_table[] =
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{
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0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9,
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0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005,
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0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
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0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
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0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9,
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0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
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0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011,
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0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd,
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0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
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0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5,
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0xbe2b5b58, 0xbaea46ef, 0xb7a96036, 0xb3687d81,
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0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
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0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49,
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0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
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0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
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0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d,
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0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae,
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0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
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0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
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0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca,
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0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
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0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02,
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0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066,
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0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
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0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e,
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0xbfa1b04b, 0xbb60adfc, 0xb6238b25, 0xb2e29692,
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0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
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0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a,
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0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
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0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
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0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686,
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0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a,
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0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
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0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
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0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f,
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0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
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0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47,
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0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b,
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0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
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0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623,
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0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7,
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0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
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0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f,
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0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
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0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
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0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b,
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0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f,
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0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
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0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
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0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c,
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0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
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0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24,
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0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30,
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0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
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0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088,
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0x2497d08d, 0x2056cd3a, 0x2d15ebe3, 0x29d4f654,
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0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
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0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c,
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0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
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0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
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0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0,
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0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c,
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0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
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0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
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};
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/*
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@deftypefn Extension {unsigned int} crc32 (const unsigned char *@var{buf}, @
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int @var{len}, unsigned int @var{init})
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Compute the 32-bit CRC of @var{buf} which has length @var{len}. The
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starting value is @var{init}; this may be used to compute the CRC of
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data split across multiple buffers by passing the return value of each
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call as the @var{init} parameter of the next.
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This is used by the @command{gdb} remote protocol for the @samp{qCRC}
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command. In order to get the same results as gdb for a block of data,
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you must pass the first CRC parameter as @code{0xffffffff}.
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This CRC can be specified as:
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Width : 32
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Poly : 0x04c11db7
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Init : parameter, typically 0xffffffff
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RefIn : false
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RefOut : false
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XorOut : 0
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This differs from the "standard" CRC-32 algorithm in that the values
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are not reflected, and there is no final XOR value. These differences
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make it easy to compose the values of multiple blocks.
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@end deftypefn
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*/
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unsigned int
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xcrc32 (const unsigned char *buf, int len, unsigned int init)
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{
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unsigned int crc = init;
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while (len--)
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{
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crc = (crc << 8) ^ crc32_table[((crc >> 24) ^ *buf) & 255];
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buf++;
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}
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return crc;
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}
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