72 lines
1.6 KiB
C
72 lines
1.6 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2019 Facebook
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#include <features.h>
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typedef unsigned int u32;
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static __always_inline u32 rol32(u32 word, unsigned int shift)
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{
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return (word << shift) | (word >> ((-shift) & 31));
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}
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#define __jhash_mix(a, b, c) \
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{ \
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a -= c; a ^= rol32(c, 4); c += b; \
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b -= a; b ^= rol32(a, 6); a += c; \
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c -= b; c ^= rol32(b, 8); b += a; \
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a -= c; a ^= rol32(c, 16); c += b; \
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b -= a; b ^= rol32(a, 19); a += c; \
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c -= b; c ^= rol32(b, 4); b += a; \
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}
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#define __jhash_final(a, b, c) \
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{ \
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c ^= b; c -= rol32(b, 14); \
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a ^= c; a -= rol32(c, 11); \
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b ^= a; b -= rol32(a, 25); \
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c ^= b; c -= rol32(b, 16); \
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a ^= c; a -= rol32(c, 4); \
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b ^= a; b -= rol32(a, 14); \
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c ^= b; c -= rol32(b, 24); \
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}
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#define JHASH_INITVAL 0xdeadbeef
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static ATTR
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u32 jhash(const void *key, u32 length, u32 initval)
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{
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u32 a, b, c;
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const unsigned char *k = key;
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a = b = c = JHASH_INITVAL + length + initval;
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while (length > 12) {
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a += *(volatile u32 *)(k);
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b += *(volatile u32 *)(k + 4);
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c += *(volatile u32 *)(k + 8);
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__jhash_mix(a, b, c);
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length -= 12;
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k += 12;
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}
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switch (length) {
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case 12: c += (u32)k[11]<<24;
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case 11: c += (u32)k[10]<<16;
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case 10: c += (u32)k[9]<<8;
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case 9: c += k[8];
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case 8: b += (u32)k[7]<<24;
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case 7: b += (u32)k[6]<<16;
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case 6: b += (u32)k[5]<<8;
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case 5: b += k[4];
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case 4: a += (u32)k[3]<<24;
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case 3: a += (u32)k[2]<<16;
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case 2: a += (u32)k[1]<<8;
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case 1: a += k[0];
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c ^= a;
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__jhash_final(a, b, c);
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case 0: /* Nothing left to add */
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break;
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}
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return c;
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}
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