/*
  Copyright 2020 David Anderson. All Rights Reserved.

  This program is free software; you can redistribute it
  and/or modify it under the terms of version 2.1 of the
  GNU Lesser General Public License as published by the Free
  Software Foundation.

  This program is distributed in the hope that it would be
  useful, but WITHOUT ANY WARRANTY; without even the implied
  warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
  PURPOSE.

  Further, this software is distributed without any warranty
  that it is free of the rightful claim of any third person
  regarding infringement or the like.  Any license provided
  herein, whether implied or otherwise, applies only to this
  software file.  Patent licenses, if any, provided herein
  do not apply to combinations of this program with other
  software, or any other product whatsoever.

  You should have received a copy of the GNU Lesser General
  Public License along with this program; if not, write the
  Free Software Foundation, Inc., 51 Franklin Street - Fifth
  Floor, Boston MA 02110-1301, USA.
*/

#include <config.h>

#include <stddef.h> /* size_t */

#include "dwarf.h"
#include "libdwarf.h"
#include "dwarf_local_malloc.h"
#include "libdwarf_private.h"
#include "dwarf_base_types.h"
#include "dwarf_opaque.h" /* For the function prototype */

#define uint32_t unsigned int

/*  Table computed by David Anderson
    with Mark Adler's table builder
    logic on October 20,2020
    with pattern from polynomial (0xedb88320) */
static const uint32_t crc32_table[256] =
{
0x00000000,0x77073096,0xee0e612c,0x990951ba,
0x076dc419,0x706af48f,0xe963a535,0x9e6495a3,
0x0edb8832,0x79dcb8a4,0xe0d5e91e,0x97d2d988,
0x09b64c2b,0x7eb17cbd,0xe7b82d07,0x90bf1d91,
0x1db71064,0x6ab020f2,0xf3b97148,0x84be41de,
0x1adad47d,0x6ddde4eb,0xf4d4b551,0x83d385c7,
0x136c9856,0x646ba8c0,0xfd62f97a,0x8a65c9ec,
0x14015c4f,0x63066cd9,0xfa0f3d63,0x8d080df5,
0x3b6e20c8,0x4c69105e,0xd56041e4,0xa2677172,
0x3c03e4d1,0x4b04d447,0xd20d85fd,0xa50ab56b,
0x35b5a8fa,0x42b2986c,0xdbbbc9d6,0xacbcf940,
0x32d86ce3,0x45df5c75,0xdcd60dcf,0xabd13d59,
0x26d930ac,0x51de003a,0xc8d75180,0xbfd06116,
0x21b4f4b5,0x56b3c423,0xcfba9599,0xb8bda50f,
0x2802b89e,0x5f058808,0xc60cd9b2,0xb10be924,
0x2f6f7c87,0x58684c11,0xc1611dab,0xb6662d3d,
0x76dc4190,0x01db7106,0x98d220bc,0xefd5102a,
0x71b18589,0x06b6b51f,0x9fbfe4a5,0xe8b8d433,
0x7807c9a2,0x0f00f934,0x9609a88e,0xe10e9818,
0x7f6a0dbb,0x086d3d2d,0x91646c97,0xe6635c01,
0x6b6b51f4,0x1c6c6162,0x856530d8,0xf262004e,
0x6c0695ed,0x1b01a57b,0x8208f4c1,0xf50fc457,
0x65b0d9c6,0x12b7e950,0x8bbeb8ea,0xfcb9887c,
0x62dd1ddf,0x15da2d49,0x8cd37cf3,0xfbd44c65,
0x4db26158,0x3ab551ce,0xa3bc0074,0xd4bb30e2,
0x4adfa541,0x3dd895d7,0xa4d1c46d,0xd3d6f4fb,
0x4369e96a,0x346ed9fc,0xad678846,0xda60b8d0,
0x44042d73,0x33031de5,0xaa0a4c5f,0xdd0d7cc9,
0x5005713c,0x270241aa,0xbe0b1010,0xc90c2086,
0x5768b525,0x206f85b3,0xb966d409,0xce61e49f,
0x5edef90e,0x29d9c998,0xb0d09822,0xc7d7a8b4,
0x59b33d17,0x2eb40d81,0xb7bd5c3b,0xc0ba6cad,
0xedb88320,0x9abfb3b6,0x03b6e20c,0x74b1d29a,
0xead54739,0x9dd277af,0x04db2615,0x73dc1683,
0xe3630b12,0x94643b84,0x0d6d6a3e,0x7a6a5aa8,
0xe40ecf0b,0x9309ff9d,0x0a00ae27,0x7d079eb1,
0xf00f9344,0x8708a3d2,0x1e01f268,0x6906c2fe,
0xf762575d,0x806567cb,0x196c3671,0x6e6b06e7,
0xfed41b76,0x89d32be0,0x10da7a5a,0x67dd4acc,
0xf9b9df6f,0x8ebeeff9,0x17b7be43,0x60b08ed5,
0xd6d6a3e8,0xa1d1937e,0x38d8c2c4,0x4fdff252,
0xd1bb67f1,0xa6bc5767,0x3fb506dd,0x48b2364b,
0xd80d2bda,0xaf0a1b4c,0x36034af6,0x41047a60,
0xdf60efc3,0xa867df55,0x316e8eef,0x4669be79,
0xcb61b38c,0xbc66831a,0x256fd2a0,0x5268e236,
0xcc0c7795,0xbb0b4703,0x220216b9,0x5505262f,
0xc5ba3bbe,0xb2bd0b28,0x2bb45a92,0x5cb36a04,
0xc2d7ffa7,0xb5d0cf31,0x2cd99e8b,0x5bdeae1d,
0x9b64c2b0,0xec63f226,0x756aa39c,0x026d930a,
0x9c0906a9,0xeb0e363f,0x72076785,0x05005713,
0x95bf4a82,0xe2b87a14,0x7bb12bae,0x0cb61b38,
0x92d28e9b,0xe5d5be0d,0x7cdcefb7,0x0bdbdf21,
0x86d3d2d4,0xf1d4e242,0x68ddb3f8,0x1fda836e,
0x81be16cd,0xf6b9265b,0x6fb077e1,0x18b74777,
0x88085ae6,0xff0f6a70,0x66063bca,0x11010b5c,
0x8f659eff,0xf862ae69,0x616bffd3,0x166ccf45,
0xa00ae278,0xd70dd2ee,0x4e048354,0x3903b3c2,
0xa7672661,0xd06016f7,0x4969474d,0x3e6e77db,
0xaed16a4a,0xd9d65adc,0x40df0b66,0x37d83bf0,
0xa9bcae53,0xdebb9ec5,0x47b2cf7f,0x30b5ffe9,
0xbdbdf21c,0xcabac28a,0x53b39330,0x24b4a3a6,
0xbad03605,0xcdd70693,0x54de5729,0x23d967bf,
0xb3667a2e,0xc4614ab8,0x5d681b02,0x2a6f2b94,
0xb40bbe37,0xc30c8ea1,0x5a05df1b,0x2d02ef8d
};

/*  The following is essentially identical
    to every crc32 anyone uses up to trivial
    differences in starting conditions.
    The algorithm appears on
    https://en.wikipedia.org/wiki/Cyclic_redundancy_check
    in a simple logic loop (written in no actual
    language but English) and the following is a translation
    into C. Just like every other crc calculation.

    There is no error indicated if buf does not point
    to a readable area of memory at least len bytes long!

    The unsigned int return will not get the same CRC as
    Linux/Macos if int/unsigned-int is 16 bits (Windows),
    but there the crc does not matter in practice.
    The results on big-endian are not the same
    as little-endian machines.*/
unsigned int
dwarf_basic_crc32 (const unsigned char *buf,
    unsigned long len,
    unsigned int crc)
{
    const unsigned char *end = 0;

    if (!buf) {
        return 0;
    }
    crc = ~crc;
    for (end = buf + len; buf < end; ++buf)
        crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
    return ~crc;
}
