path: root/pow/ar/pow.go

package ar

import (
    "math/big"

    "github.com/ethereum/go-ethereum/ethutil"
)

type Entry struct {
    op   OpsFunc
    i, j *big.Int
}

type Tape struct {
    tape  []Entry
    block Block
}

func NewTape(block Block) *Tape {
    return &Tape{nil, block}
}

func (self *Tape) gen(w, h int64, gen NumberGenerator) {
    self.tape = nil

    for v := int64(0); v < h; v++ {
        op := ops[gen.rand64(lenops).Int64()]
        r := gen.rand64(100).Uint64()

        var j *big.Int
        if r < 20 && v > 20 {
            j = self.tape[len(self.tape)-1].i
        } else {
            j = gen.rand64(w)
        }

        i := gen.rand64(w)
        self.tape = append(self.tape, Entry{op, i, j})
    }
}

func (self *Tape) runTape(w, h int64, gen NumberGenerator) *big.Int {
    var mem []*big.Int
    for i := int64(0); i < w; i++ {
        mem = append(mem, gen.rand(ethutil.BigPow(2, 64)))
    }

    set := func(i, j int) Entry {
        entry := self.tape[i*100+j]
        mem[entry.i.Uint64()] = entry.op(entry.i, entry.j)

        return entry
    }

    dir := true
    for i := 0; i < int(h)/100; i++ {
        var entry Entry
        if dir {
            for j := 0; j < 100; j++ {
                entry = set(i, j)
            }
        } else {
            for j := 99; i >= 0; j-- {
                entry = set(i, j)
            }
        }

        t := mem[entry.i.Uint64()]
        if big.NewInt(2).Cmp(new(big.Int).Mod(t, big.NewInt(37))) < 0 {
            dir = !dir
        }
    }

    return Sha3(mem)
}

func (self *Tape) Verify(header, nonce []byte) bool {
    n := ethutil.BigD(nonce)

    var w int64 = 10000
    var h int64 = 150000
    gen := Rnd(Sha3([]interface{}{header, new(big.Int).Div(n, big.NewInt(1000))}))
    self.gen(w, h, gen)

    gen = Rnd(Sha3([]interface{}{header, new(big.Int).Mod(n, big.NewInt(1000))}))
    hash := self.runTape(w, h, gen)

    it := self.block.Trie().Iterator()
    next := it.Next(string(new(big.Int).Mod(hash, ethutil.BigPow(2, 160)).Bytes()))

    req := ethutil.BigPow(2, 256)
    req.Div(req, self.block.Diff())
    return Sha3([]interface{}{hash, next}).Cmp(req) < 0
}

func (self *Tape) Run(header []byte) []byte {
    nonce := big.NewInt(0)
    var w int64 = 10000
    var h int64 = 150000

    req := ethutil.BigPow(2, 256)
    req.Div(req, self.block.Diff())

    for {
        if new(big.Int).Mod(nonce, b(1000)).Cmp(b(0)) == 0 {
            gen := Rnd(Sha3([]interface{}{header, new(big.Int).Div(nonce, big.NewInt(1000))}))
            self.gen(w, h, gen)
        }

        gen := Rnd(Sha3([]interface{}{header, new(big.Int).Mod(nonce, big.NewInt(1000))}))
        hash := self.runTape(w, h, gen)

        it := self.block.Trie().Iterator()
        next := it.Next(string(new(big.Int).Mod(hash, ethutil.BigPow(2, 160)).Bytes()))

        if Sha3([]interface{}{hash, next}).Cmp(req) < 0 {
            return nonce.Bytes()
        } else {
            nonce.Add(nonce, ethutil.Big1)
        }
    }
}