crc32.c

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/*
 * Copyright (c) 2020 Bitdefender
 * SPDX-License-Identifier: Apache-2.0
 */
//
//  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
//  code or tables extracted from it, as desired without restriction.
//
//  First, the polynomial itself and its table of feedback terms.  The
//  polynomial is
//  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
//
//  Note that we take it "backwards" and put the highest-order term in
//  the lowest-order bit.  The X^32 term is "implied"; the LSB is the
//  X^31 term, etc.  The X^0 term (usually shown as "+1") results in
//  the MSB being 1
//
//  Note that the usual hardware shift register implementation, which
//  is what we're using (we're merely optimizing it by doing eight-bit
//  chunks at a time) shifts bits into the lowest-order term.  In our
//  implementation, that means shifting towards the right.  Why do we
//  do it this way?  Because the calculated CRC must be transmitted in
//  order from highest-order term to lowest-order term.  UARTs transmit
//  characters in order from LSB to MSB.  By storing the CRC this way
//  we hand it to the UART in the order low-byte to high-byte; the UART
//  sends each low-bit to hight-bit; and the result is transmission bit
//  by bit from highest- to lowest-order term without requiring any bit
//  shuffling on our part.  Reception works similarly
//
//  The feedback terms table consists of 256, 32-bit entries.  Notes
//
//      The table can be generated at runtime if desired; code to do so
//      is shown later.  It might not be obvious, but the feedback
//      terms simply represent the results of eight shift/xor opera
//      tions for all combinations of data and CRC register values
//
//      The values must be right-shifted by eight bits by the "updcrc
//      logic; the shift must be unsigned (bring in zeroes).  On some
//      hardware you could probably optimize the shift in assembler by
//      using byte-swap instructions
//      polynomial $edb88320
//
//
// CRC32 code derived from work by Gary S. Brown.
//
// https://opensource.apple.com/source/xnu/xnu-4903.241.1/bsd/libkern/crc32.c.auto.html
//
#include "crc32.h"
#include "introcrt.h"

static const DWORD gCrc32Table[] =
{
    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
};


BOOLEAN gSse42Supported = FALSE;


DWORD
Crc32Compute(
    _In_ const void *Buffer,
    _In_ size_t Size,
    _In_ DWORD InitialCrc
    )
{
    const BYTE *p = Buffer;
    DWORD crc = InitialCrc ^ ~0;

    if (0 == Size)
    {
        return 0xFFFFFFFF;
    }

    for (DWORD i = 0; i < 16; i++)
    {
        _mm_prefetch((const BYTE *)gCrc32Table + 64ull * i, 1);
    }

    for (size_t i = 0; i < Size; i++)
    {
        crc = gCrc32Table[(crc ^ p[i]) & 0xFF] ^ (crc >> 8);
    }

    return crc ^ ~0U;
}


__attribute__((target("sse4.2")))
DWORD
Crc32ComputeFast(
    _In_ const void *Buffer,
    _In_ size_t Size,
    _In_ DWORD InitialCrc
    )
//
// Use this when Size >= PAGE_SIZE, for faster calculation.
// For more info see:
// https://www-ssl.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-paper.pdf
// The parallel version is too much trouble to implement and for what we use it for (usually swapped pages),
// it's fast enough (20x faster than Crc32Compute).
//
{
    const QWORD *p = Buffer;
    size_t qwords = Size / 8;
    const BYTE *pBytes = (const BYTE *)Buffer + qwords * 8;

#ifdef INT_COMPILER_MSVC
    QWORD crc = InitialCrc;
#else
    DWORD crc = InitialCrc;
#endif

    if (__unlikely(!gSse42Supported))
    {
        return Crc32Compute(Buffer, Size, InitialCrc);
    }

    if (Size < 8)
    {
        goto _remaining;
    }

    // Remaining size
    Size -= qwords * 8;

    for (size_t i = 0; i < qwords; i++)
    {
#ifdef INT_COMPILER_MSVC
        crc = _mm_crc32_u64(crc, p[i]);
#else
        crc = __builtin_ia32_crc32di(crc, p[i]);
#endif
    }

    //
    // Remaining bytes (max 7) will be done byte-by-byte
    // NOTE: pBytes already points to the right area
    //
_remaining:
    for (size_t i = 0; i < Size; i++)
    {
#ifdef INT_COMPILER_MSVC
        crc = _mm_crc32_u8((DWORD)crc, pBytes[i]);
#else
        crc = __builtin_ia32_crc32qi(crc, pBytes[i]);
#endif
    }

    return (DWORD)crc;
}


DWORD
Crc32String(
    _In_ const char *String,
    _In_ DWORD InitialCrc
    )
{
    DWORD crc = InitialCrc ^ ~0;

    for (DWORD i = 0; i < 16; i++)
    {
        _mm_prefetch((const BYTE *)gCrc32Table + 64ull * i, 1);
    }

    while (*String)
    {
        crc = gCrc32Table[(crc ^ *String) & 0xFF] ^ (crc >> 8);
        String++;
    }

    return crc ^ ~0U;
}


DWORD
Crc32Wstring(
    _In_ const WCHAR *String,
    _In_ DWORD InitialCrc
    )
{
    DWORD crc = InitialCrc ^ ~0;

    for (DWORD i = 0; i < 16; i++)
    {
        _mm_prefetch((const BYTE *)gCrc32Table + 64ull * i, 1);
    }

    while (*String)
    {
        const BYTE *p = (const BYTE *)String;

        crc = gCrc32Table[(crc ^ p[0]) & 0xFF] ^ (crc >> 8);
        crc = gCrc32Table[(crc ^ p[1]) & 0xFF] ^ (crc >> 8);

        String++;
    }

    return crc ^ ~0U;
}


//
// Crc32WstringLength
//
DWORD
Crc32WstringLen(
    _In_ const WCHAR *String,
    _In_ DWORD InitialCrc,
    _In_ size_t MaxLength,
    _Out_ BOOLEAN *Valid
    )
{
    DWORD crc = InitialCrc ^ ~0;

    for (DWORD i = 0; i < 16; i++)
    {
        _mm_prefetch((const BYTE *)gCrc32Table + 64ull * i, 1);
    }

    while (MaxLength > 0 && *String)
    {
        const BYTE *p = (const BYTE *)String;

        crc = gCrc32Table[(crc ^ p[0]) & 0xFF] ^ (crc >> 8);
        crc = gCrc32Table[(crc ^ p[1]) & 0xFF] ^ (crc >> 8);

        String++;
        MaxLength--;
    }

    if (Valid)
    {
        *Valid = MaxLength > 0;
    }

    return crc ^ ~0U;
}


//
// Crc32StringLength
//
DWORD
Crc32StringLen(
    _In_ const char *String,
    _In_ DWORD InitialCrc,
    _In_ size_t MaxLength,
    _Out_ BOOLEAN *Valid
    )
{
    DWORD crc = InitialCrc ^ ~0;

    for (DWORD i = 0; i < 16; i++)
    {
        _mm_prefetch((const BYTE *)gCrc32Table + 64ull * i, 1);
    }

    while (MaxLength > 0 && *String)
    {
        crc = gCrc32Table[(crc ^ *String) & 0xFF] ^ (crc >> 8);
        String++;
        MaxLength--;
    }

    if (Valid)
    {
        *Valid = MaxLength > 0;
    }

    return crc ^ ~0U;
}