core/bloombits/utils.go


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// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package bloombits

import (
    "github.com/ethereum/go-ethereum/core/types"
)

const BloomLength = 2048

// BloomBitsCreator takes SectionSize number of header bloom filters and calculates the bloomBits vectors of the section
type BloomBitsCreator struct {
    blooms              [BloomLength][]byte
    sectionSize, bitIndex uint64
}

func NewBloomBitsCreator(sectionSize uint64) *BloomBitsCreator {
    b := &BloomBitsCreator{sectionSize: sectionSize}
    for i, _ := range b.blooms {
        b.blooms[i] = make([]byte, sectionSize/8)
    }
    return b
}

// AddHeaderBloom takes a single bloom filter and sets the corresponding bit column in memory accordingly
func (b *BloomBitsCreator) AddHeaderBloom(bloom types.Bloom) {
    if b.bitIndex >= b.sectionSize {
        panic("too many header blooms added")
    }

    byteIdx := b.bitIndex / 8
    bitMask := byte(1) << byte(7-b.bitIndex%8)
    for bloomBitIdx, _ := range b.blooms {
        bloomByteIdx := BloomLength/8 - 1 - bloomBitIdx/8
        bloomBitMask := byte(1) << byte(bloomBitIdx%8)
        if (bloom[bloomByteIdx] & bloomBitMask) != 0 {
            b.blooms[bloomBitIdx][byteIdx] |= bitMask
        }
    }
    b.bitIndex++
}

// GetBitVector returns the bit vector belonging to the given bit index after header blooms have been added
func (b *BloomBitsCreator) GetBitVector(idx uint) []byte {
    if b.bitIndex != b.sectionSize {
        panic("not enough header blooms added")
    }

    return b.blooms[idx][:]
}