syncthing/lib/scanner/blocks.go

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// Copyright (C) 2014 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
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package scanner
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import (
"bytes"
"context"
"hash"
lib/scanner: Use standard adler32 when we don't need rolling (#5556) * lib/scanner: Use standard adler32 when we don't need rolling Seems the rolling adler32 implementation is super slow when executed on large blocks, even tho I can't explain why. BenchmarkFind1MFile-16 100 18991667 ns/op 55.21 MB/s 398844 B/op 20 allocs/op BenchmarkBlock/adler32-131072/#00-16 200 9726519 ns/op 1078.06 MB/s 2654936 B/op 163 allocs/op BenchmarkBlock/bozo32-131072/#00-16 20 73435540 ns/op 142.79 MB/s 2654928 B/op 163 allocs/op BenchmarkBlock/buzhash32-131072/#00-16 20 61482005 ns/op 170.55 MB/s 2654928 B/op 163 allocs/op BenchmarkBlock/buzhash64-131072/#00-16 20 61673660 ns/op 170.02 MB/s 2654928 B/op 163 allocs/op BenchmarkBlock/vanilla-adler32-131072/#00-16 300 4377307 ns/op 2395.48 MB/s 2654935 B/op 163 allocs/op BenchmarkBlock/adler32-16777216/#00-16 2 544010100 ns/op 19.27 MB/s 65624 B/op 5 allocs/op BenchmarkBlock/bozo32-16777216/#00-16 1 4678108500 ns/op 2.24 MB/s 51970144 B/op 24 allocs/op BenchmarkBlock/buzhash32-16777216/#00-16 1 3880370700 ns/op 2.70 MB/s 51970144 B/op 24 allocs/op BenchmarkBlock/buzhash64-16777216/#00-16 1 3875911700 ns/op 2.71 MB/s 51970144 B/op 24 allocs/op BenchmarkBlock/vanilla-adler32-16777216/#00-16 300 4010279 ns/op 2614.72 MB/s 65624 B/op 5 allocs/op BenchmarkRoll/adler32-131072/#00-16 2000 974279 ns/op 134.53 MB/s 270 B/op 0 allocs/op BenchmarkRoll/bozo32-131072/#00-16 2000 791770 ns/op 165.54 MB/s 270 B/op 0 allocs/op BenchmarkRoll/buzhash32-131072/#00-16 2000 917409 ns/op 142.87 MB/s 270 B/op 0 allocs/op BenchmarkRoll/buzhash64-131072/#00-16 2000 881125 ns/op 148.76 MB/s 270 B/op 0 allocs/op BenchmarkRoll/adler32-16777216/#00-16 10 124000400 ns/op 135.30 MB/s 7548937 B/op 0 allocs/op BenchmarkRoll/bozo32-16777216/#00-16 10 118008080 ns/op 142.17 MB/s 7548928 B/op 0 allocs/op BenchmarkRoll/buzhash32-16777216/#00-16 10 126794440 ns/op 132.32 MB/s 7548928 B/op 0 allocs/op BenchmarkRoll/buzhash64-16777216/#00-16 10 126631960 ns/op 132.49 MB/s 7548928 B/op 0 allocs/op * Update benchmark_test.go * gofmt * fixup benchmark
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"hash/adler32"
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"io"
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"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/sha256"
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)
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var SHA256OfNothing = []uint8{0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14, 0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24, 0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c, 0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55}
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type Counter interface {
Update(bytes int64)
}
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// Blocks returns the blockwise hash of the reader.
func Blocks(ctx context.Context, r io.Reader, blocksize int, sizehint int64, counter Counter, useWeakHashes bool) ([]protocol.BlockInfo, error) {
if counter == nil {
counter = &noopCounter{}
}
hf := sha256.New()
hashLength := hf.Size()
var weakHf hash.Hash32 = noopHash{}
var multiHf io.Writer = hf
if useWeakHashes {
// Use an actual weak hash function, make the multiHf
// write to both hash functions.
weakHf = adler32.New()
multiHf = io.MultiWriter(hf, weakHf)
}
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var blocks []protocol.BlockInfo
var hashes, thisHash []byte
if sizehint >= 0 {
// Allocate contiguous blocks for the BlockInfo structures and their
// hashes once and for all, and stick to the specified size.
r = io.LimitReader(r, sizehint)
numBlocks := int(sizehint / int64(blocksize))
blocks = make([]protocol.BlockInfo, 0, numBlocks)
hashes = make([]byte, 0, hashLength*numBlocks)
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}
// A 32k buffer is used for copying into the hash function.
buf := make([]byte, 32<<10)
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var offset int64
lr := io.LimitReader(r, int64(blocksize)).(*io.LimitedReader)
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for {
select {
case <-ctx.Done():
return nil, ctx.Err()
default:
}
lr.N = int64(blocksize)
n, err := io.CopyBuffer(multiHf, lr, buf)
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if err != nil {
return nil, err
}
if n == 0 {
break
}
counter.Update(n)
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// Carve out a hash-sized chunk of "hashes" to store the hash for this
// block.
hashes = hf.Sum(hashes)
thisHash, hashes = hashes[:hashLength], hashes[hashLength:]
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b := protocol.BlockInfo{
Size: int32(n),
Offset: offset,
Hash: thisHash,
WeakHash: weakHf.Sum32(),
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}
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blocks = append(blocks, b)
offset += n
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hf.Reset()
weakHf.Reset()
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}
if len(blocks) == 0 {
// Empty file
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blocks = append(blocks, protocol.BlockInfo{
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Offset: 0,
Size: 0,
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Hash: SHA256OfNothing,
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})
}
return blocks, nil
}
// Validate quickly validates buf against the 32-bit weakHash, if not zero,
// else against the cryptohash hash, if len(hash)>0. It is satisfied if
// either hash matches or neither hash is given.
func Validate(buf, hash []byte, weakHash uint32) bool {
if weakHash != 0 && adler32.Checksum(buf) == weakHash {
return true
}
if len(hash) > 0 {
hbuf := sha256.Sum256(buf)
return bytes.Equal(hbuf[:], hash)
}
return true
}
type noopHash struct{}
func (noopHash) Sum32() uint32 { return 0 }
func (noopHash) BlockSize() int { return 0 }
func (noopHash) Size() int { return 0 }
func (noopHash) Reset() {}
func (noopHash) Sum([]byte) []byte { return nil }
func (noopHash) Write([]byte) (int, error) { return 0, nil }
type noopCounter struct{}
func (c *noopCounter) Update(bytes int64) {}