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wyhash: support comptime usage

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Closes #16070.
This commit is contained in:
Marc Tiehuis 2023-06-17 20:22:16 +12:00 committed by Andrew Kelley
parent 6f766fbf00
commit 5baa05664e
1 changed files with 23 additions and 11 deletions
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34
lib/std/hash/wyhash.zig
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@ -68,18 +68,20 @@ pub const Wyhash = struct {
if (self.total_len <= 16) {
newSelf.smallKey(input);
} else {
var offset: usize = 0;
if (self.buf_len < 16) {
var scratch: [16]u8 = undefined;
const rem = 16 - self.buf_len;
@memcpy(scratch[0..rem], self.buf[self.buf.len - rem ..][0..rem]);
@memcpy(scratch[rem..][0..self.buf_len], self.buf[0..self.buf_len]);
// Same as input with lookbehind to pad to 16-bytes
input = scratch[rem..];
// Same as input but with additional bytes preceeding start in case of a short buffer
input = &scratch;
offset = rem;
}
newSelf.final0();
newSelf.final1(input);
newSelf.final1(input, offset);
}
return newSelf.final2();
@ -145,19 +147,21 @@ pub const Wyhash = struct {
self.state[0] ^= self.state[1] ^ self.state[2];
}
// Input must reside in a 16-byte buffer. The input slice passed be offset into it in which
// case this function will index in front of the slice.
inline fn final1(self: *Wyhash, input: []const u8) void {
std.debug.assert(input.len <= 48);
// input_lb must be at least 16-bytes long (in shorter key cases the smallKey function will be
// used instead). We use an index into a slice to for comptime processing as opposed to if we
// used pointers.
inline fn final1(self: *Wyhash, input_lb: []const u8, start_pos: usize) void {
std.debug.assert(input_lb.len >= 16);
std.debug.assert(input_lb.len - start_pos <= 48);
const input = input_lb[start_pos..];
var i: usize = 0;
while (i + 16 < input.len) : (i += 16) {
self.state[0] = mix(read(8, input[i..]) ^ secret[1], read(8, input[i + 8 ..]) ^ self.state[0]);
}
// Possible lookbehind past pointer start.
self.a = read(8, (input.ptr + input.len - 16)[0..8]);
self.b = read(8, (input.ptr + input.len - 8)[0..8]);
self.a = read(8, input_lb[input_lb.len - 16 ..][0..8]);
self.b = read(8, input_lb[input_lb.len - 8 ..][0..8]);
}
inline fn final2(self: *Wyhash) u64 {
@ -180,7 +184,7 @@ pub const Wyhash = struct {
}
self.final0();
}
self.final1(input[i..]);
self.final1(input, i);
}
self.total_len = input.len;
@ -213,6 +217,14 @@ test "test vectors" {
}
}
test "test vectors at comptime" {
comptime {
inline for (vectors) |e| {
try expectEqual(e.expected, Wyhash.hash(e.seed, e.input));
}
}
}
test "test vectors streaming" {
const step = 5;