seahash/
stream.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
use std::hash::Hasher;
use std::slice;

use helper;

/// The streaming version of the algorithm.
#[derive(Clone, Copy)]
pub struct SeaHasher {
    /// The state of the hasher.
    state: (u64, u64, u64, u64),
    /// The number of bytes we have written in total
    written: u64,
    /// Our tail
    tail: u64,
    /// The number of bytes in the tail
    ntail: usize,
}

impl Default for SeaHasher {
    fn default() -> SeaHasher {
        SeaHasher::with_seeds(
            0x16f11fe89b0d677c,
            0xb480a793d8e6c86c,
            0x6fe2e5aaf078ebc9,
            0x14f994a4c5259381,
        )
    }
}

impl SeaHasher {
    /// Create a new `SeaHasher` with default state.
    pub fn new() -> SeaHasher {
        SeaHasher::default()
    }

    /// Construct a new `SeaHasher` given some seed.
    ///
    /// For maximum quality, these seeds should be chosen at random.
    pub fn with_seeds(k1: u64, k2: u64, k3: u64, k4: u64) -> SeaHasher {
        SeaHasher {
            state: (k1, k2, k3, k4),
            written: 0,
            tail: 0,
            ntail: 0,
        }
    }

    #[inline(always)]
    fn push(&mut self, x: u64) {
        let a = helper::diffuse(self.state.0 ^ x);
        self.state.0 = self.state.1;
        self.state.1 = self.state.2;
        self.state.2 = self.state.3;
        self.state.3 = a;
        self.written += 8;
    }

    #[inline(always)]
    fn push_bytes(&mut self, bytes: &[u8]) {
        // The start of the bytes that aren't in the tail
        let copied = core::cmp::min(8 - self.ntail, bytes.len());
        unsafe {
            let mut this = self.tail.to_le_bytes();
            let mut ptr = bytes.as_ptr();
            ptr.copy_to_nonoverlapping(this.as_mut_ptr().add(self.ntail), copied);
            // It will be at most 8
            if copied + self.ntail != 8 {
                self.ntail += copied;
                self.tail = u64::from_le_bytes(this);
            } else {
                self.push(u64::from_le_bytes(this));
                self.ntail = 0;
                self.tail = 0;

                // We've done the existing tail, now just do the rest in chunks of 4 x u64.
                ptr = ptr.offset(copied as isize);
                let end_ptr = ptr.offset((bytes.len() - copied) as isize & !0x1F);
                while end_ptr > ptr {
                    self.state.0 = helper::diffuse(self.state.0 ^ helper::read_u64(ptr));
                    self.state.1 = helper::diffuse(self.state.1 ^ helper::read_u64(ptr.offset(8)));
                    self.state.2 = helper::diffuse(self.state.2 ^ helper::read_u64(ptr.offset(16)));
                    self.state.3 = helper::diffuse(self.state.3 ^ helper::read_u64(ptr.offset(24)));

                    ptr = ptr.offset(32);
                    self.written += 32;
                }
                let mut excessive = bytes.len() + bytes.as_ptr() as usize - ptr as usize;
                match excessive {
                    0 => {
                        // input was a multiple of 4 x u64 bytes long; no new tail bytes.
                    }
                    1..=7 => {
                        self.tail =
                            helper::read_int(slice::from_raw_parts(ptr as *const u8, excessive));
                        self.ntail = excessive;
                        // self.written does not need to be updated as we only gathered self.tail
                        // bytes after larger chunks.
                    }
                    8 => {
                        self.push(helper::read_u64(ptr));
                        // self.written is updated by self.push
                    }
                    9..=15 => {
                        self.push(helper::read_u64(ptr));
                        excessive -= 8;
                        self.tail =
                            helper::read_int(slice::from_raw_parts(ptr.offset(8), excessive));
                        self.ntail = excessive;
                        // self.written is updated by self.push
                    }
                    16 => {
                        let a = helper::diffuse(self.state.0 ^ helper::read_u64(ptr));
                        let b = helper::diffuse(self.state.1 ^ helper::read_u64(ptr.offset(8)));
                        // rotate
                        self.state.0 = self.state.2;
                        self.state.1 = self.state.3;
                        self.state.2 = a;
                        self.state.3 = b;
                        self.written += 16;
                    }
                    17..=23 => {
                        let a = helper::diffuse(self.state.0 ^ helper::read_u64(ptr));
                        let b = helper::diffuse(self.state.1 ^ helper::read_u64(ptr.offset(8)));
                        // rotate
                        self.state.0 = self.state.2;
                        self.state.1 = self.state.3;
                        self.state.2 = a;
                        self.state.3 = b;
                        excessive -= 16;
                        self.tail =
                            helper::read_int(slice::from_raw_parts(ptr.offset(16), excessive));
                        self.ntail = excessive;
                        self.written += 16;
                    }
                    24 => {
                        let a = helper::diffuse(self.state.0 ^ helper::read_u64(ptr));
                        let b = helper::diffuse(self.state.1 ^ helper::read_u64(ptr.offset(8)));
                        let c = helper::diffuse(self.state.2 ^ helper::read_u64(ptr.offset(16)));
                        self.state.0 = self.state.3;
                        self.state.1 = a;
                        self.state.2 = b;
                        self.state.3 = c;
                        self.written += 24;
                    }
                    _ => {
                        let a = helper::diffuse(self.state.0 ^ helper::read_u64(ptr));
                        let b = helper::diffuse(self.state.1 ^ helper::read_u64(ptr.offset(8)));
                        let c = helper::diffuse(self.state.2 ^ helper::read_u64(ptr.offset(16)));
                        self.state.0 = self.state.3;
                        self.state.1 = a;
                        self.state.2 = b;
                        self.state.3 = c;
                        excessive -= 24;
                        self.tail =
                            helper::read_int(slice::from_raw_parts(ptr.offset(24), excessive));
                        self.ntail = excessive;
                        self.written += 24;
                    }
                }
            }
        }
    }
}

impl Hasher for SeaHasher {
    fn finish(&self) -> u64 {
        let a = if self.ntail > 0 {
            let tail = helper::read_int(&self.tail.to_le_bytes()[..self.ntail]);
            helper::diffuse(self.state.0 ^ tail)
        } else {
            self.state.0
        };
        helper::diffuse(
            a ^ self.state.1 ^ self.state.2 ^ self.state.3 ^ self.written + self.ntail as u64,
        )
    }

    fn write(&mut self, bytes: &[u8]) {
        self.push_bytes(bytes)
    }

    fn write_u64(&mut self, n: u64) {
        self.write(&n.to_le_bytes())
    }

    fn write_u8(&mut self, n: u8) {
        self.write(&n.to_le_bytes())
    }

    fn write_u16(&mut self, n: u16) {
        self.write(&n.to_le_bytes())
    }

    fn write_u32(&mut self, n: u32) {
        self.write(&n.to_le_bytes())
    }

    fn write_usize(&mut self, n: usize) {
        self.write(&n.to_le_bytes())
    }

    fn write_i64(&mut self, n: i64) {
        self.write(&n.to_le_bytes())
    }

    fn write_i8(&mut self, n: i8) {
        self.write(&n.to_le_bytes())
    }

    fn write_i16(&mut self, n: i16) {
        self.write(&n.to_le_bytes())
    }

    fn write_i32(&mut self, n: i32) {
        self.write(&n.to_le_bytes())
    }

    fn write_isize(&mut self, n: isize) {
        self.write(&n.to_le_bytes())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::hash_seeded;
    use std::hash::Hasher;

    #[test]
    fn chunked_equiv() {
        let test_buf: &[u8] = &[
            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00,
        ];

        let mut stream_hasher1 = SeaHasher::default();
        Hasher::write(&mut stream_hasher1, test_buf);

        let mut stream_hasher2 = SeaHasher::default();
        Hasher::write(&mut stream_hasher2, &test_buf[..8]);
        Hasher::write(&mut stream_hasher2, &test_buf[8..]);

        let mut stream_hasher3 = SeaHasher::default();
        Hasher::write(&mut stream_hasher3, &test_buf[..3]);
        Hasher::write(&mut stream_hasher3, &test_buf[3..]);

        let mut stream_hasher4 = SeaHasher::default();
        Hasher::write_u16(&mut stream_hasher4, 0xffff);
        Hasher::write_u16(&mut stream_hasher4, 0xffff);
        Hasher::write_u32(&mut stream_hasher4, 0xffffffff);
        Hasher::write_u64(&mut stream_hasher4, 0);

        assert_eq!(stream_hasher1.finish(), stream_hasher2.finish());
        assert_eq!(stream_hasher1.finish(), stream_hasher3.finish());
        assert_eq!(stream_hasher1.finish(), stream_hasher4.finish());
    }

    #[test]
    fn match_optimized() {
        let test_buf: &[u8] = &[
            0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00,
        ];

        let mut sea_hasher = SeaHasher::with_seeds(
            0xe7b0c93ca8525013,
            0x011d02b854ae8182,
            0x7bcc5cf9c39cec76,
            0xfa336285d102d083,
        );
        sea_hasher.write(test_buf);
        let stream_hash = sea_hasher.finish();

        let buffer_hash = hash_seeded(
            test_buf,
            0xe7b0c93ca8525013,
            0x011d02b854ae8182,
            0x7bcc5cf9c39cec76,
            0xfa336285d102d083,
        );

        assert_eq!(buffer_hash, stream_hash)
    }
}