mirror of
https://github.com/octoleo/syncthing.git
synced 2024-12-23 11:28:59 +00:00
132 lines
3.3 KiB
Go
132 lines
3.3 KiB
Go
// Copyright (C) 2014 The Syncthing Authors.
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//
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// This program is free software: you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by the Free
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// Software Foundation, either version 3 of the License, or (at your option)
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// any later version.
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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// more details.
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//
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// You should have received a copy of the GNU General Public License along
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// with this program. If not, see <http://www.gnu.org/licenses/>.
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package scanner
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import (
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"bytes"
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"crypto/sha256"
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"fmt"
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"io"
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"github.com/syncthing/syncthing/internal/protocol"
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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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// Blocks returns the blockwise hash of the reader.
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func Blocks(r io.Reader, blocksize int, sizehint int64) ([]protocol.BlockInfo, error) {
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var blocks []protocol.BlockInfo
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if sizehint > 0 {
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blocks = make([]protocol.BlockInfo, 0, int(sizehint/int64(blocksize)))
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}
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var offset int64
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hf := sha256.New()
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for {
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lr := &io.LimitedReader{R: r, N: int64(blocksize)}
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n, err := io.Copy(hf, lr)
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if err != nil {
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return nil, err
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}
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if n == 0 {
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break
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}
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b := protocol.BlockInfo{
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Size: uint32(n),
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Offset: offset,
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Hash: hf.Sum(nil),
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}
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blocks = append(blocks, b)
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offset += int64(n)
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hf.Reset()
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}
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if len(blocks) == 0 {
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// Empty file
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blocks = append(blocks, protocol.BlockInfo{
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Offset: 0,
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Size: 0,
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Hash: SHA256OfNothing,
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})
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}
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return blocks, nil
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}
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// Set the Offset field on each block
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func PopulateOffsets(blocks []protocol.BlockInfo) {
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var offset int64
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for i := range blocks {
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blocks[i].Offset = offset
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offset += int64(blocks[i].Size)
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}
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}
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// BlockDiff returns lists of common and missing (to transform src into tgt)
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// blocks. Both block lists must have been created with the same block size.
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func BlockDiff(src, tgt []protocol.BlockInfo) (have, need []protocol.BlockInfo) {
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if len(tgt) == 0 && len(src) != 0 {
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return nil, nil
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}
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if len(tgt) != 0 && len(src) == 0 {
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// Copy the entire file
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return nil, tgt
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}
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for i := range tgt {
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if i >= len(src) || bytes.Compare(tgt[i].Hash, src[i].Hash) != 0 {
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// Copy differing block
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need = append(need, tgt[i])
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} else {
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have = append(have, tgt[i])
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}
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}
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return have, need
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}
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// Verify returns nil or an error describing the mismatch between the block
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// list and actual reader contents
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func Verify(r io.Reader, blocksize int, blocks []protocol.BlockInfo) error {
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hf := sha256.New()
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for i, block := range blocks {
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lr := &io.LimitedReader{R: r, N: int64(blocksize)}
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_, err := io.Copy(hf, lr)
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if err != nil {
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return err
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}
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hash := hf.Sum(nil)
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hf.Reset()
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if bytes.Compare(hash, block.Hash) != 0 {
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return fmt.Errorf("hash mismatch %x != %x for block %d", hash, block.Hash, i)
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}
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}
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// We should have reached the end now
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bs := make([]byte, 1)
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n, err := r.Read(bs)
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if n != 0 || err != io.EOF {
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return fmt.Errorf("file continues past end of blocks")
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}
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return nil
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}
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