From d235e2c6a5788ec4a6cff15a16f56b38a3876a0d Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Sun, 28 Jun 2020 14:47:41 -0400
Subject: ...

---
 core/bloombits/generator.go | 93 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 core/bloombits/generator.go

(limited to 'core/bloombits/generator.go')

diff --git a/core/bloombits/generator.go b/core/bloombits/generator.go
new file mode 100644
index 0000000..3dd54b6
--- /dev/null
+++ b/core/bloombits/generator.go
@@ -0,0 +1,93 @@
+// 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/ava-labs/coreth/core/types"
+)
+
+var (
+	// 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.
+	errSectionOutOfBounds = errors.New("section out of bounds")
+
+	// errBloomBitOutOfBounds is returned if the user tried to retrieve specified
+	// bit bloom above the capacity.
+	errBloomBitOutOfBounds = errors.New("bloom bit 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
+	nextSec  uint                         // Next section 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.nextSec >= b.sections {
+		return errSectionOutOfBounds
+	}
+	if b.nextSec != index {
+		return errors.New("bloom filter with unexpected index")
+	}
+	// Rotate the bloom and insert into our collection
+	byteIndex := b.nextSec / 8
+	bitMask := byte(1) << byte(7-b.nextSec%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.nextSec++
+
+	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.nextSec != b.sections {
+		return nil, errors.New("bloom not fully generated yet")
+	}
+	if idx >= types.BloomBitLength {
+		return nil, errBloomBitOutOfBounds
+	}
+	return b.blooms[idx], nil
+}
-- 
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