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1 files changed, 150 insertions, 0 deletions

diff --git a/halfsiphash.c b/halfsiphash.c
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+++ b/halfsiphash.c
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+
+/*
+   SipHash reference C implementation
+
+   Copyright (c) 2012-2014 Jean-Philippe Aumasson
+   <jeanphilippe.aumasson@gmail.com>
+   Copyright (c) 2012-2014 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/>.
+ */
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+/* default: SipHash-2-4 */
+#define cROUNDS 2
+#define dROUNDS 4
+
+#define ROTL(x, b) (uint32_t)(((x) << (b)) | ((x) >> (32 - (b))))
+
+#define U32TO8_LE(p, v)                                                     \
+    (p)[0] = (uint8_t)((v));                                                \
+    (p)[1] = (uint8_t)((v) >> 8);                                           \
+    (p)[2] = (uint8_t)((v) >> 16);                                          \
+    (p)[3] = (uint8_t)((v) >> 24);
+
+#define U32TO8_LE(p, v)                                                     \
+    (p)[0] = (uint8_t)((v));                                                \
+    (p)[1] = (uint8_t)((v) >> 8);                                           \
+    (p)[2] = (uint8_t)((v) >> 16);                                          \
+    (p)[3] = (uint8_t)((v) >> 24);
+
+#define U8TO32_LE(p)                                                        \
+    (((uint32_t)((p)[0])) | ((uint32_t)((p)[1]) << 8) |                     \
+     ((uint32_t)((p)[2]) << 16) | ((uint32_t)((p)[3]) << 24))               \
+
+#define SIPROUND                                                            \
+    do {                                                                    \
+        v0 += v1;                                                           \
+        v1 = ROTL(v1,  7);                                                  \
+        v1 ^= v0;                                                           \
+        v0 = ROTL(v0, 16);                                                  \
+        v2 += v3;                                                           \
+        v3 = ROTL(v3,  8);                                                  \
+        v3 ^= v2;                                                           \
+        v0 += v3;                                                           \
+        v3 = ROTL(v3, 11);                                                  \
+        v3 ^= v0;                                                           \
+        v2 += v1;                                                           \
+        v1 = ROTL(v1,  9);                                                  \
+        v1 ^= v2;                                                           \
+        v2 = ROTL(v2, 16);                                                  \
+    } while (0)
+
+#ifdef DEBUG
+#define TRACE                                                               \
+    do {                                                                    \
+        printf("(%3d) v0 %08x\n", (int)inlen, v0);                          \
+        printf("(%3d) v1 %08x\n", (int)inlen, v1);                          \
+        printf("(%3d) v2 %08x\n", (int)inlen, v2);                          \
+        printf("(%3d) v3 %08x\n", (int)inlen, v3);                          \
+    } while (0)
+#else
+#define TRACE
+#endif
+
+int halfsiphash(const uint8_t *in, const size_t inlen, const uint8_t *k, uint8_t *out, const size_t outlen) {
+
+    assert( (outlen == 4) || (outlen == 8));
+    uint32_t v0 = 0x736f6d65;
+    uint32_t v1 = 0x646f7261;
+    uint32_t v2 = 0x6c796765;
+    uint32_t v3 = 0x74656462;
+    uint32_t k0 = U8TO32_LE(k);
+    uint32_t k1 = U8TO32_LE(k + 4);
+    uint32_t m;
+    int i;
+    const uint8_t *end = in + inlen - (inlen % sizeof(uint32_t));
+    const int left = inlen & 7;
+    uint32_t b = ((uint32_t)inlen) << 24;
+    v3 ^= k1;
+    v2 ^= k0;
+    v1 ^= k1;
+    v0 ^= k0;
+
+    if (outlen == 8) v1 ^= 0xee;
+
+    for (; in != end; in += 4) {
+        m = U8TO32_LE(in);
+        v3 ^= m;
+
+        TRACE;
+        for (i = 0; i < cROUNDS; ++i)
+            SIPROUND;
+
+        v0 ^= m;
+    }
+
+    switch (left) {
+        case 3:
+            b |= ((uint32_t)in[2]) << 16;
+        case 2:
+            b |= ((uint32_t)in[1]) << 8;
+        case 1:
+            b |= ((uint32_t)in[0]);
+            break;
+        case 0:
+            break;
+    }
+
+    v3 ^= b;
+
+    TRACE;
+    for (i = 0; i < cROUNDS; ++i)
+        SIPROUND;
+
+    v0 ^= b;
+
+    if (outlen == 16) v2 ^= 0xee;
+    else v2 ^= 0xff;
+
+    TRACE;
+    for (i = 0; i < dROUNDS; ++i)
+        SIPROUND;
+
+    b = v0 ^ v1 ^ v2 ^ v3;
+    U32TO8_LE(out, b);
+
+    if (outlen == 4) return 0;
+
+    v1 ^= 0xdd;
+
+    TRACE;
+    for (i = 0; i < dROUNDS; ++i)
+        SIPROUND;
+
+    b = v0 ^ v1 ^ v2 ^ v3;
+    U32TO8_LE(out + 4, b);
+
+    return 0;
+}
+