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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 (
"errors"
"github.com/ethereum/go-ethereum/core/types"
)
// errSectionOutOfBounds is returned if the user tried to add more bloom filters
// to the batch than available space, or if tries to retrieve above the capacity,
var errSectionOutOfBounds = errors.New("section out of bounds")
// Generator takes a number of bloom filters and generates the rotated bloom bits
// to be used for batched filtering.
type Generator struct {
blooms [types.BloomBitLength][]byte // Rotated blooms for per-bit matching
sections uint // Number of sections to batch together
nextBit uint // Next bit to set when adding a bloom
}
// NewGenerator creates a rotated bloom generator that can iteratively fill a
// batched bloom filter's bits.
func NewGenerator(sections uint) (*Generator, error) {
if sections%8 != 0 {
return nil, errors.New("section count not multiple of 8")
}
b := &Generator{sections: sections}
for i := 0; i < types.BloomBitLength; i++ {
b.blooms[i] = make([]byte, sections/8)
}
return b, nil
}
// AddBloom takes a single bloom filter and sets the corresponding bit column
// in memory accordingly.
func (b *Generator) AddBloom(index uint, bloom types.Bloom) error {
// Make sure we're not adding more bloom filters than our capacity
if b.nextBit >= b.sections {
return errSectionOutOfBounds
}
if b.nextBit != index {
return errors.New("bloom filter with unexpected index")
}
// Rotate the bloom and insert into our collection
byteIndex := b.nextBit / 8
bitMask := byte(1) << byte(7-b.nextBit%8)
for i := 0; i < types.BloomBitLength; i++ {
bloomByteIndex := types.BloomByteLength - 1 - i/8
bloomBitMask := byte(1) << byte(i%8)
if (bloom[bloomByteIndex] & bloomBitMask) != 0 {
b.blooms[i][byteIndex] |= bitMask
}
}
b.nextBit++
return nil
}
// Bitset returns the bit vector belonging to the given bit index after all
// blooms have been added.
func (b *Generator) Bitset(idx uint) ([]byte, error) {
if b.nextBit != b.sections {
return nil, errors.New("bloom not fully generated yet")
}
if idx >= b.sections {
return nil, errSectionOutOfBounds
}
return b.blooms[idx], nil
}
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