shared: switch our hash table implementation over to SipHash

SipHash appears to be the new gold standard for hashing smaller strings
for hashtables these days, so let's make use of it.

1 files changed, 135 insertions, 0 deletions

diff --git a/src/shared/siphash24.c b/src/shared/siphash24.c
new file mode 100644
index 0000000000..f68bd283a1
--- /dev/null
+++ b/src/shared/siphash24.c
@@ -0,0 +1,135 @@
+/*
+   SipHash reference C implementation
+
+   Written in 2012 by
+   Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
+   Daniel J. Bernstein <djb@cr.yp.to>
+
+   To the extent possible under law, the author(s) have dedicated all copyright
+   and related and neighboring rights to this software to the public domain
+   worldwide. This software is distributed without any warranty.
+
+   You should have received a copy of the CC0 Public Domain Dedication along with
+   this software. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+
+   (Minimal changes made by Lennart Poettering, to make clean for inclusion in systemd)
+*/
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "siphash24.h"
+
+typedef uint64_t u64;
+typedef uint32_t u32;
+typedef uint8_t u8;
+
+#define ROTL(x,b) (u64)( ((x) << (b)) | ( (x) >> (64 - (b))) )
+
+#define U32TO8_LE(p, v)         \
+    (p)[0] = (u8)((v)      ); (p)[1] = (u8)((v) >>  8); \
+    (p)[2] = (u8)((v) >> 16); (p)[3] = (u8)((v) >> 24);
+
+#define U64TO8_LE(p, v)         \
+  U32TO8_LE((p),     (u32)((v)      ));   \
+  U32TO8_LE((p) + 4, (u32)((v) >> 32));
+
+#define U8TO64_LE(p) \
+  (((u64)((p)[0])      ) | \
+   ((u64)((p)[1]) <<  8) | \
+   ((u64)((p)[2]) << 16) | \
+   ((u64)((p)[3]) << 24) | \
+   ((u64)((p)[4]) << 32) | \
+   ((u64)((p)[5]) << 40) | \
+   ((u64)((p)[6]) << 48) | \
+   ((u64)((p)[7]) << 56))
+
+#define SIPROUND            \
+  do {              \
+    v0 += v1; v1=ROTL(v1,13); v1 ^= v0; v0=ROTL(v0,32); \
+    v2 += v3; v3=ROTL(v3,16); v3 ^= v2;     \
+    v0 += v3; v3=ROTL(v3,21); v3 ^= v0;     \
+    v2 += v1; v1=ROTL(v1,17); v1 ^= v2; v2=ROTL(v2,32); \
+  } while(0)
+
+/* SipHash-2-4 */
+void siphash24(uint8_t out[8], const void *_in, size_t inlen, const uint8_t k[16])
+{
+  /* "somepseudorandomlygeneratedbytes" */
+  u64 v0 = 0x736f6d6570736575ULL;
+  u64 v1 = 0x646f72616e646f6dULL;
+  u64 v2 = 0x6c7967656e657261ULL;
+  u64 v3 = 0x7465646279746573ULL;
+  u64 b;
+  u64 k0 = U8TO64_LE( k );
+  u64 k1 = U8TO64_LE( k + 8 );
+  u64 m;
+  const u8 *in = _in;
+  const u8 *end = in + inlen - ( inlen % sizeof( u64 ) );
+  const int left = inlen & 7;
+  b = ( ( u64 )inlen ) << 56;
+  v3 ^= k1;
+  v2 ^= k0;
+  v1 ^= k1;
+  v0 ^= k0;
+
+  for ( ; in != end; in += 8 )
+  {
+    m = U8TO64_LE( in );
+#ifdef DEBUG
+    printf( "(%3d) v0 %08x %08x\n", ( int )inlen, ( u32 )( v0 >> 32 ), ( u32 )v0 );
+    printf( "(%3d) v1 %08x %08x\n", ( int )inlen, ( u32 )( v1 >> 32 ), ( u32 )v1 );
+    printf( "(%3d) v2 %08x %08x\n", ( int )inlen, ( u32 )( v2 >> 32 ), ( u32 )v2 );
+    printf( "(%3d) v3 %08x %08x\n", ( int )inlen, ( u32 )( v3 >> 32 ), ( u32 )v3 );
+    printf( "(%3d) compress %08x %08x\n", ( int )inlen, ( u32 )( m >> 32 ), ( u32 )m );
+#endif
+    v3 ^= m;
+    SIPROUND;
+    SIPROUND;
+    v0 ^= m;
+  }
+
+  switch( left )
+  {
+  case 7: b |= ( ( u64 )in[ 6] )  << 48;
+
+  case 6: b |= ( ( u64 )in[ 5] )  << 40;
+
+  case 5: b |= ( ( u64 )in[ 4] )  << 32;
+
+  case 4: b |= ( ( u64 )in[ 3] )  << 24;
+
+  case 3: b |= ( ( u64 )in[ 2] )  << 16;
+
+  case 2: b |= ( ( u64 )in[ 1] )  <<  8;
+
+  case 1: b |= ( ( u64 )in[ 0] ); break;
+
+  case 0: break;
+  }
+
+#ifdef DEBUG
+  printf( "(%3d) v0 %08x %08x\n", ( int )inlen, ( u32 )( v0 >> 32 ), ( u32 )v0 );
+  printf( "(%3d) v1 %08x %08x\n", ( int )inlen, ( u32 )( v1 >> 32 ), ( u32 )v1 );
+  printf( "(%3d) v2 %08x %08x\n", ( int )inlen, ( u32 )( v2 >> 32 ), ( u32 )v2 );
+  printf( "(%3d) v3 %08x %08x\n", ( int )inlen, ( u32 )( v3 >> 32 ), ( u32 )v3 );
+  printf( "(%3d) padding   %08x %08x\n", ( int )inlen, ( u32 )( b >> 32 ), ( u32 )b );
+#endif
+  v3 ^= b;
+  SIPROUND;
+  SIPROUND;
+  v0 ^= b;
+#ifdef DEBUG
+  printf( "(%3d) v0 %08x %08x\n", ( int )inlen, ( u32 )( v0 >> 32 ), ( u32 )v0 );
+  printf( "(%3d) v1 %08x %08x\n", ( int )inlen, ( u32 )( v1 >> 32 ), ( u32 )v1 );
+  printf( "(%3d) v2 %08x %08x\n", ( int )inlen, ( u32 )( v2 >> 32 ), ( u32 )v2 );
+  printf( "(%3d) v3 %08x %08x\n", ( int )inlen, ( u32 )( v3 >> 32 ), ( u32 )v3 );
+#endif
+  v2 ^= 0xff;
+  SIPROUND;
+  SIPROUND;
+  SIPROUND;
+  SIPROUND;
+  b = v0 ^ v1 ^ v2  ^ v3;
+  U64TO8_LE( out, b );
+}