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erofs: Add xxh32 hash function
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This is a copy of the upstream bsd-2 licences code
which is also used by the kernel.

Signed-off-by: Alexander Larsson <[email protected]>
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alexlarsson committed Aug 29, 2023
1 parent 8e3d434 commit ff00dac
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115 changes: 115 additions & 0 deletions libcomposefs/lcfs-writer-erofs.c
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#include <assert.h>
#include <linux/fsverity.h>

/* The xxh32 hash function is copied from xxhash with this copyright:
*
* xxHash - Extremely Fast Hash algorithm
* Copyright (C) 2012-2016, Yann Collet.
*
* BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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 COPYRIGHT
* OWNER OR CONTRIBUTORS 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.
*
* This program is free software; you can redistribute it and/or modify it under
* the terms of the GNU General Public License version 2 as published by the
* Free Software Foundation. This program is dual-licensed; you may select
* either version 2 of the GNU General Public License ("GPL") or BSD license
* ("BSD").
*
* You can contact the author at:
* - xxHash homepage: https://cyan4973.github.io/xxHash/
* - xxHash source repository: https://github.com/Cyan4973/xxHash
*/

static const uint32_t PRIME32_1 = 2654435761U;
static const uint32_t PRIME32_2 = 2246822519U;
static const uint32_t PRIME32_3 = 3266489917U;
static const uint32_t PRIME32_4 = 668265263U;
static const uint32_t PRIME32_5 = 374761393U;

static inline uint32_t get_unaligned_le32(const uint8_t *p)
{
return p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
}

#define xxh_rotl32(x, r) ((x << r) | (x >> (32 - r)))

static uint32_t xxh32_round(uint32_t seed, const uint32_t input)
{
seed += input * PRIME32_2;
seed = xxh_rotl32(seed, 13);
seed *= PRIME32_1;
return seed;
}

static uint32_t xxh32(const void *input, const size_t len, const uint32_t seed)
{
const uint8_t *p = (const uint8_t *)input;
const uint8_t *b_end = p + len;
uint32_t h32;

if (len >= 16) {
const uint8_t *const limit = b_end - 16;
uint32_t v1 = seed + PRIME32_1 + PRIME32_2;
uint32_t v2 = seed + PRIME32_2;
uint32_t v3 = seed + 0;
uint32_t v4 = seed - PRIME32_1;

do {
v1 = xxh32_round(v1, get_unaligned_le32(p));
p += 4;
v2 = xxh32_round(v2, get_unaligned_le32(p));
p += 4;
v3 = xxh32_round(v3, get_unaligned_le32(p));
p += 4;
v4 = xxh32_round(v4, get_unaligned_le32(p));
p += 4;
} while (p <= limit);

h32 = xxh_rotl32(v1, 1) + xxh_rotl32(v2, 7) +
xxh_rotl32(v3, 12) + xxh_rotl32(v4, 18);
} else {
h32 = seed + PRIME32_5;
}

h32 += (uint32_t)len;

while (p + 4 <= b_end) {
h32 += get_unaligned_le32(p) * PRIME32_3;
h32 = xxh_rotl32(h32, 17) * PRIME32_4;
p += 4;
}

while (p < b_end) {
h32 += (*p) * PRIME32_5;
h32 = xxh_rotl32(h32, 11) * PRIME32_1;
p++;
}

h32 ^= h32 >> 15;
h32 *= PRIME32_2;
h32 ^= h32 >> 13;
h32 *= PRIME32_3;
h32 ^= h32 >> 16;

return h32;
}

struct lcfs_ctx_erofs_s {
struct lcfs_ctx_s base;

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