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58 lines
2.4 KiB
C
58 lines
2.4 KiB
C
#ifndef XXHASH_BPF_H
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#define XXHASH_BPF_H
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#define PRIME1 0x9E3779B1U
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#define PRIME2 0x85EBCA77U
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#define PRIME3 0xC2B2AE3DU
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#define PRIME4 0x27D4EB2FU
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#define PRIME5 0x165667B1U
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static __always_inline unsigned int rotl (unsigned int x, int r) {
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return ((x << r) | (x >> (32 - r)));
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}
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// Normal stripe processing routine.
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static __always_inline unsigned int round_xxhash(unsigned int acc, const unsigned int input) {
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return rotl(acc + (input * PRIME2), 13) * PRIME1;
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}
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static __always_inline unsigned int avalanche_step (const unsigned int h, const int rshift, const unsigned int prime) {
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return (h ^ (h >> rshift)) * prime;
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}
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// Mixes all bits to finalize the hash.
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static __always_inline unsigned int avalanche (const unsigned int h) {
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return avalanche_step(avalanche_step(avalanche_step(h, 15, PRIME2), 13, PRIME3), 16, 1);
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}
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static __always_inline unsigned int endian32 (const char *v) {
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return (unsigned int)((unsigned char)(v[0]))|((unsigned int)((unsigned char)(v[1])) << 8)
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|((unsigned int)((unsigned char)(v[2])) << 16)|((unsigned int)((unsigned char)(v[3])) << 24);
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}
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static __always_inline unsigned int fetch32 (const char *p, const unsigned int v) {
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return round_xxhash(v, endian32(p));
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}
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// Processes the last 0-15 bytes of p.
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static __always_inline unsigned int finalize (const unsigned int h, const char *p, unsigned int len) {
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return
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(len >= 4) ? finalize(rotl(h + (endian32(p) * PRIME3), 17) * PRIME4, p + 4, len - 4) :
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(len > 0) ? finalize(rotl(h + ((unsigned char)(*p) * PRIME5), 11) * PRIME1, p + 1, len - 1) :
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avalanche(h);
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}
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static __always_inline unsigned int h16bytes_4 (const char *p, unsigned int len, const unsigned int v1, const unsigned int v2, const unsigned int v3, const unsigned int v4) {
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return
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(len >= 16) ? h16bytes_4(p + 16, len - 16, fetch32(p, v1), fetch32(p+4, v2), fetch32(p+8, v3), fetch32(p+12, v4)) :
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rotl(v1, 1) + rotl(v2, 7) + rotl(v3, 12) + rotl(v4, 18);
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}
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static __always_inline unsigned int h16bytes_3 (const char *p, unsigned int len, const unsigned int seed) {
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return h16bytes_4(p, len, seed + PRIME1 + PRIME2, seed + PRIME2, seed, seed - PRIME1);
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}
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static __always_inline unsigned int xxhash32 (const char *input, unsigned int len, unsigned int seed) {
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return finalize((len >= 16 ? h16bytes_3(input, len, seed) : seed + PRIME5) + len, (input) + (len & ~0xF), len & 0xF);
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}
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#endif
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