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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
public struct Mph {
public var bitArrays: [BitArray] = []
public var ranks: [[UInt16]] = []
init(gamma: Double, keys: [UInt64]) {
var size: Int
var a: BitArray
var collide: Set<Int>
var redoKeys: [UInt64] = keys
var i: UInt64 = 0
repeat {
size = Swift.max(64, Int(gamma * Double(redoKeys.count)))
a = BitArray(size: size)
collide = []
for key in redoKeys {
let idx = Int(hash(key, UInt64(size), seed: i))
if !collide.contains(idx), !a.insert(idx) {
collide.insert(idx)
}
}
var tmpRedo: [UInt64] = []
for key in redoKeys {
let idx = Int(hash(key, UInt64(size), seed: i))
if collide.contains(idx) {
a[idx] = false
tmpRedo.append(key)
}
}
bitArrays.append(a)
redoKeys = tmpRedo
i += 1
} while !redoKeys.isEmpty
computeRanks()
}
mutating func computeRanks() {
var pop: UInt16 = 0
for bitArray in bitArrays {
var rank: [UInt16] = []
for i in 0 ..< bitArray.words.count {
let v = bitArray.words[i]
if i % 8 == 0 {
rank.append(pop)
}
pop += UInt16(v.nonzeroBitCount)
}
ranks.append(rank)
}
}
public func index(for key: UInt64) -> Int {
for i in 0 ..< bitArrays.count {
let b = bitArrays[i]
let idx = Int(hash(key, UInt64(b.size), seed: UInt64(i)))
if b[idx] {
var rank = ranks[i][idx / 512]
for j in (idx / 64) & ~7 ..< idx / 64 {
rank += UInt16(b.words[j].nonzeroBitCount)
}
let finalWord = b.words[idx / 64]
if idx % 64 > 0 {
rank += UInt16((finalWord << (64 - (idx % 64))).nonzeroBitCount)
}
return Int(rank)
}
}
return -1
}
}
public func mph(for keys: [UInt64]) -> Mph {
Mph(gamma: 1, keys: keys)
}
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