github.com/jiajun1992/watercarver@v0.0.0-20191031150618-dfc2b17c0c4a/go-ethereum/core/bloombits/generator.go (about)

     1  // Copyright 2017 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package bloombits
    18  
    19  import (
    20  	"errors"
    21  
    22  	"github.com/ethereum/go-ethereum/core/types"
    23  )
    24  
    25  var (
    26  	// errSectionOutOfBounds is returned if the user tried to add more bloom filters
    27  	// to the batch than available space, or if tries to retrieve above the capacity.
    28  	errSectionOutOfBounds = errors.New("section out of bounds")
    29  
    30  	// errBloomBitOutOfBounds is returned if the user tried to retrieve specified
    31  	// bit bloom above the capacity.
    32  	errBloomBitOutOfBounds = errors.New("bloom bit out of bounds")
    33  )
    34  
    35  // Generator takes a number of bloom filters and generates the rotated bloom bits
    36  // to be used for batched filtering.
    37  type Generator struct {
    38  	blooms   [types.BloomBitLength][]byte // Rotated blooms for per-bit matching
    39  	sections uint                         // Number of sections to batch together
    40  	nextSec  uint                         // Next section to set when adding a bloom
    41  }
    42  
    43  // NewGenerator creates a rotated bloom generator that can iteratively fill a
    44  // batched bloom filter's bits.
    45  func NewGenerator(sections uint) (*Generator, error) {
    46  	if sections%8 != 0 {
    47  		return nil, errors.New("section count not multiple of 8")
    48  	}
    49  	b := &Generator{sections: sections}
    50  	for i := 0; i < types.BloomBitLength; i++ {
    51  		b.blooms[i] = make([]byte, sections/8)
    52  	}
    53  	return b, nil
    54  }
    55  
    56  // AddBloom takes a single bloom filter and sets the corresponding bit column
    57  // in memory accordingly.
    58  func (b *Generator) AddBloom(index uint, bloom types.Bloom) error {
    59  	// Make sure we're not adding more bloom filters than our capacity
    60  	if b.nextSec >= b.sections {
    61  		return errSectionOutOfBounds
    62  	}
    63  	if b.nextSec != index {
    64  		return errors.New("bloom filter with unexpected index")
    65  	}
    66  	// Rotate the bloom and insert into our collection
    67  	byteIndex := b.nextSec / 8
    68  	bitMask := byte(1) << byte(7-b.nextSec%8)
    69  
    70  	for i := 0; i < types.BloomBitLength; i++ {
    71  		bloomByteIndex := types.BloomByteLength - 1 - i/8
    72  		bloomBitMask := byte(1) << byte(i%8)
    73  
    74  		if (bloom[bloomByteIndex] & bloomBitMask) != 0 {
    75  			b.blooms[i][byteIndex] |= bitMask
    76  		}
    77  	}
    78  	b.nextSec++
    79  
    80  	return nil
    81  }
    82  
    83  // Bitset returns the bit vector belonging to the given bit index after all
    84  // blooms have been added.
    85  func (b *Generator) Bitset(idx uint) ([]byte, error) {
    86  	if b.nextSec != b.sections {
    87  		return nil, errors.New("bloom not fully generated yet")
    88  	}
    89  	if idx >= types.BloomBitLength {
    90  		return nil, errBloomBitOutOfBounds
    91  	}
    92  	return b.blooms[idx], nil
    93  }