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[LZ4] Slightly optimize xxHash32

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This commit is contained in:
Timofey Solomko
2021-10-02 13:49:29 +03:00
parent 932153541d
commit 68e46728af
1 changed files with 11 additions and 11 deletions
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Sources/LZ4/XxHash32.swift
+11 -11
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@@ -32,18 +32,18 @@ enum XxHash32 {
@inline(__always)
private static func hashSmall(_ data: Data, _ seed: UInt32) -> UInt32 {
let acc = seed &+ prime5
return finalize(data, 0, acc)
return finalize(data, data.startIndex, acc)
}
@inline(__always)
private static func hashBig(_ data: Data, _ seed: UInt32) -> UInt32 {
var accs = [seed &+ prime1 &+ prime2, seed &+ prime2, seed &+ 0, seed &- prime1]
var i = 0
while data.count - i >= 16 { // Loop over stripes.
var i = data.startIndex
while data.endIndex - i >= 16 { // Loop over stripes.
for j in 0..<4 { // Loop over lanes.
var lane = 0 as UInt32
for k: UInt32 in 0..<4 {
lane &+= UInt32(truncatingIfNeeded: data[data.startIndex + i + j * 4 + k.toInt()]) << (k * 8)
lane &+= UInt32(truncatingIfNeeded: data[i + j * 4 + k.toInt()]) << (k * 8)
}
accs[j] &+= lane &* prime2
accs[j] = accs[j] <<< 13
@@ -58,19 +58,19 @@ enum XxHash32 {
private static func finalize(_ data: Data, _ ptr: Int, _ acc: UInt32) -> UInt32 {
var acc = acc &+ UInt32(truncatingIfNeeded: data.count)
var ptr = ptr
while data.count - ptr >= 4 {
var i = ptr
while data.endIndex - i >= 4 {
var lane = 0 as UInt32
for k: UInt32 in 0..<4 {
lane &+= UInt32(truncatingIfNeeded: data[data.startIndex + ptr]) << (k * 8)
ptr += 1
lane &+= UInt32(truncatingIfNeeded: data[i]) << (k * 8)
i += 1
}
acc &+= lane &* prime3
acc = (acc <<< 17) &* prime4
}
while data.count - ptr >= 1 {
let lane = UInt32(truncatingIfNeeded: data[data.startIndex + ptr])
ptr += 1
while data.endIndex - i >= 1 {
let lane = UInt32(truncatingIfNeeded: data[i])
i += 1
acc &+= lane &* prime5
acc = (acc <<< 11) &* prime1
}