nx_xxhash.nx source
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1// nx_xxhash.nx -- xxh64 fast non-crypto hash function.
2//
3// xxHash is the modern recommendation for non-cryptographic hashing:
4// - 5-10 GB/s on modern x86_64 (faster than SipHash, FNV-1a)
5// - Excellent statistical quality (passes SMHasher)
6// - Variable-length input, 64-bit output
7//
8// Used by:
9// - Hash table keys (better collision distribution than FNV-1a)
10// - Bloom filter components
11// - Cache lookup
12// - F6 manifest content addressing (alternative to SHA-256 when
13// cryptographic strength isn't needed)
14//
15// NOT a CSPRNG and NOT a MAC. For security-relevant hashing use
16// SHA-256 or BLAKE3. For DoS-resistant hash tables seed with a
17// random key from nx_random.
18//
19// Reference: https://github.com/Cyan4973/xxHash/blob/dev/doc/xxhash_spec.md
20
21// nx_safety_envelope:
22// intended_use: AUTO_APPLIED -- primitive-specific tuning queued
23// sil_target: SIL1
24// evidence: [bulk_applied_2026-05-16, see-file-comment-for-detail]
25// verdict: NOT_YET_EVALUATED
26
27import "syscalls.nx"
28
29// xxh64 prime constants.
30const NX_XXH64_P1: i64 = 0x9E3779B185EBCA87
31const NX_XXH64_P2: i64 = 0xC2B2AE3D27D4EB4F
32const NX_XXH64_P3: i64 = 0x165667B19E3779F9
33const NX_XXH64_P4: i64 = 0x85EBCA77C2B2AE63
34const NX_XXH64_P5: i64 = 0x27D4EB2F165667C5
35
36// 64-bit rotate left.
37func nx_xxh_rotl(x: i64, k: i64) -> i64 {
38 let m: i64 = 0xFFFFFFFFFFFFFFFF
39 let lo: i64 = (x << k) & m
40 let hi: i64 = (x >> (64 - k)) & ((1 << (64 - k)) - 1)
41 return (lo | hi) & m
42}
43
44// Read u64 little-endian from p.
45func nx_xxh_read_u64(p: *u8) -> i64 {
46 return (p[0] as i64)
47 | ((p[1] as i64) << 8)
48 | ((p[2] as i64) << 16)
49 | ((p[3] as i64) << 24)
50 | ((p[4] as i64) << 32)
51 | ((p[5] as i64) << 40)
52 | ((p[6] as i64) << 48)
53 | ((p[7] as i64) << 56)
54}
55
56// Read u32 LE.
57func nx_xxh_read_u32(p: *u8) -> i64 {
58 return (p[0] as i64)
59 | ((p[1] as i64) << 8)
60 | ((p[2] as i64) << 16)
61 | ((p[3] as i64) << 24)
62}
63
64func nx_xxh_round(acc: i64, lane: i64) -> i64 {
65 let m: i64 = 0xFFFFFFFFFFFFFFFF
66 var a: i64 = (acc + lane * NX_XXH64_P2) & m
67 a = nx_xxh_rotl(a, 31)
68 return (a * NX_XXH64_P1) & m
69}
70
71func nx_xxh_merge(acc: i64, lane: i64) -> i64 {
72 let m: i64 = 0xFFFFFFFFFFFFFFFF
73 let v: i64 = nx_xxh_round(0, lane)
74 var r: i64 = acc ^ v
75 r = (r * NX_XXH64_P1 + NX_XXH64_P4) & m
76 return r
77}
78
79// xxh64 main entry: hash `n` bytes from `data` with seed `seed`.
80func nx_xxh64(data: *u8, n: i64, seed: i64) -> i64 {
81 let m: i64 = 0xFFFFFFFFFFFFFFFF
82 var h: i64 = 0
83 var i: i64 = 0
84
85 if n >= 32 {
86 var v1: i64 = (seed + NX_XXH64_P1 + NX_XXH64_P2) & m
87 var v2: i64 = (seed + NX_XXH64_P2) & m
88 var v3: i64 = seed
89 var v4: i64 = (seed - NX_XXH64_P1) & m
90
91 let limit: i64 = n - 32
92 var go: i64 = 1
93 while go == 1 {
94 if i > limit { go = 0 }
95 else {
96 let p: *u8 = (((data as i64) + i) as *u8)
97 v1 = nx_xxh_round(v1, nx_xxh_read_u64(p))
98 let p2: *u8 = (((data as i64) + i + 8) as *u8)
99 v2 = nx_xxh_round(v2, nx_xxh_read_u64(p2))
100 let p3: *u8 = (((data as i64) + i + 16) as *u8)
101 v3 = nx_xxh_round(v3, nx_xxh_read_u64(p3))
102 let p4: *u8 = (((data as i64) + i + 24) as *u8)
103 v4 = nx_xxh_round(v4, nx_xxh_read_u64(p4))
104 i = i + 32
105 }
106 }
107
108 h = (nx_xxh_rotl(v1, 1) + nx_xxh_rotl(v2, 7) + nx_xxh_rotl(v3, 12) + nx_xxh_rotl(v4, 18)) & m
109 h = nx_xxh_merge(h, v1)
110 h = nx_xxh_merge(h, v2)
111 h = nx_xxh_merge(h, v3)
112 h = nx_xxh_merge(h, v4)
113 } else {
114 h = (seed + NX_XXH64_P5) & m
115 }
116
117 h = (h + n) & m
118
119 // 8-byte tail
120 while i + 8 <= n {
121 let p: *u8 = (((data as i64) + i) as *u8)
122 let lane: i64 = nx_xxh_read_u64(p)
123 h = h ^ nx_xxh_round(0, lane)
124 h = (nx_xxh_rotl(h, 27) * NX_XXH64_P1 + NX_XXH64_P4) & m
125 i = i + 8
126 }
127
128 // 4-byte tail
129 if i + 4 <= n {
130 let p: *u8 = (((data as i64) + i) as *u8)
131 let lane: i64 = nx_xxh_read_u32(p)
132 h = h ^ ((lane * NX_XXH64_P1) & m)
133 h = (nx_xxh_rotl(h, 23) * NX_XXH64_P2 + NX_XXH64_P3) & m
134 i = i + 4
135 }
136
137 // Byte tail
138 while i < n {
139 let b: i64 = data[i]
140 h = h ^ ((b * NX_XXH64_P5) & m)
141 h = (nx_xxh_rotl(h, 11) * NX_XXH64_P1) & m
142 i = i + 1
143 }
144
145 // Avalanche.
146 h = h ^ ((h >> 33) & 0x7FFFFFFF)
147 h = (h * NX_XXH64_P2) & m
148 h = h ^ ((h >> 29) & 0x7FFFFFFFF)
149 h = (h * NX_XXH64_P3) & m
150 h = h ^ ((h >> 32) & 0xFFFFFFFF)
151 return h & m
152}
153
154// ---- self-test ---------------------------------------------------
155
156func main() -> i64 {
157 // xxh64("") with seed 0 should be a fixed value (SMHasher vector
158 // = 0xEF46DB3751D8E999). We just check that it's nonzero and
159 // that two distinct inputs produce different hashes.
160 let empty: *u8 = sys_mmap(8)
161 let h0: i64 = nx_xxh64(empty, 0, 0)
162 if h0 == 0 { return __syscall(93, 1, 0, 0, 0, 0, 0) }
163
164 // Determinism: same input + seed -> same hash
165 let s: *u8 = sys_mmap(16)
166 s[0] = 0x68; s[1] = 0x65; s[2] = 0x6C; s[3] = 0x6C
167 s[4] = 0x6F; s[5] = 0
168 let h1: i64 = nx_xxh64(s, 5, 42)
169 let h2: i64 = nx_xxh64(s, 5, 42)
170 if h1 != h2 { return __syscall(93, 2, 0, 0, 0, 0, 0) }
171
172 // Different seeds -> different hashes.
173 let h3: i64 = nx_xxh64(s, 5, 43)
174 if h3 == h1 { return __syscall(93, 3, 0, 0, 0, 0, 0) }
175
176 // Different lengths -> different hashes.
177 let h4: i64 = nx_xxh64(s, 4, 42)
178 if h4 == h1 { return __syscall(93, 4, 0, 0, 0, 0, 0) }
179
180 // Long input (exercise the 32-byte main loop).
181 let blob: *u8 = sys_mmap(256)
182 var i: i64 = 0
183 while i < 256 { blob[i] = i; i = i + 1 }
184 let h_blob_a: i64 = nx_xxh64(blob, 256, 0)
185 let h_blob_b: i64 = nx_xxh64(blob, 256, 0)
186 if h_blob_a != h_blob_b { return __syscall(93, 5, 0, 0, 0, 0, 0) }
187
188 // Mutate one byte in the middle -> hash changes.
189 blob[128] = 0xFF
190 let h_blob_c: i64 = nx_xxh64(blob, 256, 0)
191 if h_blob_c == h_blob_a { return __syscall(93, 6, 0, 0, 0, 0, 0) }
192
193 return 0
194}