275 lines
9.9 KiB
PHP
275 lines
9.9 KiB
PHP
<?php
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declare(strict_types=1);
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// SPDX-FileCopyrightText: 2026 Dillard Blom
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// SPDX-License-Identifier: AGPL-3.0-or-later
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namespace OCA\NgBackup\Repository;
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use OCA\NgBackup\Backend\BackendException;
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use OCA\NgBackup\Backend\IBackend;
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use OCA\NgBackup\Crypto\StreamCipher;
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/**
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* Which blob lives in which pack. Every uploaded pack gets its own small encrypted index file
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* (index/<packId>), written right after the pack, so an interrupted run leaves a consistent
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* repository and the next run can reuse what was already uploaded.
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*
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* Phase 0 keeps the whole index in memory. For large repositories this becomes a table in the
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* Nextcloud database (a cache that can always be rebuilt from index/ and the pack headers).
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*/
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final class BlobIndex {
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/** @var array<string, array{0:string, 1:int, 2:int, 3:int, 4:int}> id => [pack, offset, length, raw, flags] */
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private array $blobs = [];
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/** @var array<string, true> blobs added in this run but whose pack is not uploaded yet */
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private array $pending = [];
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private ?IIndexCache $cache = null;
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/** @var list<\Closure():void>|null cache writes held back by holdCache(), or null when writing directly */
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private ?array $heldCacheWrites = null;
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private string $repositoryId = '';
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/** Index files written to the cache per database transaction while loading. */
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private const CACHE_LOT = 256;
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/** @var int index files downloaded by the last load() (for tests and diagnostics) */
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public int $downloaded = 0;
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public function __construct(
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private IBackend $backend,
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private StreamCipher $cipher,
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) {
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}
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public function setCache(IIndexCache $cache, string $repositoryId): void {
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$this->cache = $cache;
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$this->repositoryId = $repositoryId;
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}
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/**
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* Hold back cache writes until releaseCache(). The database dump reads inside a read-only
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* transaction on the same connection that the cache writes to: a write there fails on
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* PostgreSQL and would be rolled back with the dump transaction elsewhere.
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*/
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public function holdCache(): void {
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$this->heldCacheWrites ??= [];
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}
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/** Write the cache changes held back since holdCache(). */
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public function releaseCache(): void {
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$writes = $this->heldCacheWrites ?? [];
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$this->heldCacheWrites = null;
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foreach ($writes as $write) {
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$write();
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}
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}
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/** @param list<array{id:string, offset:int, length:int, raw:int, flags:int}> $entries */
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private function cachePut(string $packId, array $entries): void {
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if ($this->heldCacheWrites !== null) {
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$this->heldCacheWrites[] = function () use ($packId, $entries): void {
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$this->cache?->put($this->repositoryId, $packId, $entries);
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};
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return;
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}
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$this->cache?->put($this->repositoryId, $packId, $entries);
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}
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/** @param list<string> $packIds */
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private function cacheRemove(array $packIds): void {
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if ($this->heldCacheWrites !== null) {
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$this->heldCacheWrites[] = function () use ($packIds): void {
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$this->cache?->remove($this->repositoryId, $packIds);
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};
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return;
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}
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$this->cache?->remove($this->repositoryId, $packIds);
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}
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/**
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* Load the index: one listing of index/, entries from the local cache where available,
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* and only the index files that are not cached yet are downloaded. Cached packs that no
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* longer exist on the backend are dropped from the cache.
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*/
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public function load(bool $verify = false, ?callable $progress = null): void {
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$this->blobs = [];
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$cached = $verify ? [] : ($this->cache?->all($this->repositoryId) ?? []);
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$present = [];
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$this->downloaded = 0;
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$order = []; // pack ids in listing order: where a blob is in two packs, the last listed wins
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$fetch = [];
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foreach ($this->backend->listFiles('index') as $path) {
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$packId = basename($path);
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$present[$packId] = true;
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$order[] = $packId;
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if (!isset($cached[$packId])) {
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$fetch[] = $path;
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}
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}
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if ($present === [] && $cached !== []) {
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// A repository never loses all its index files: an empty listing is a connection that
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// failed quietly. Taken as is, it would empty the index and the cache.
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throw new BackendException('The location listed no index files, while ' . count($cached) . ' are known: not trusting that listing');
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}
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// The rest is downloaded several at a time where the location allows it: on a large
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// repository these are tens of thousands of small files. getMany() keeps their order, so
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// the cached packs listed before each one are added first.
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$next = 0;
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$total = count($fetch);
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$toCache = []; // written to the cache a few hundred at a time, each lot in one transaction
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foreach ($this->backend->getMany($fetch) as $path => $data) {
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$packId = basename($path);
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$entries = json_decode($this->cipher->decryptString($data, 'index:' . $packId), true, 512, JSON_THROW_ON_ERROR);
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$this->downloaded++;
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if ($this->cache !== null) {
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$toCache[$packId] = $entries;
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// a check writes the whole cache afresh at the end
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if (!$verify && count($toCache) >= self::CACHE_LOT) {
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$this->cache->putMany($this->repositoryId, $toCache);
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$toCache = [];
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}
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}
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for (; $next < count($order) && $order[$next] !== $packId; $next++) {
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$this->add($order[$next], $cached[$order[$next]] ?? []);
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}
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$this->add($packId, $entries);
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$next++;
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if ($progress !== null) {
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$progress($this->downloaded, $total);
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}
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}
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for (; $next < count($order); $next++) {
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$this->add($order[$next], $cached[$order[$next]] ?? []);
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}
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if ($verify && $this->cache !== null) {
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// Refresh the cache from what was just verified, as the index files list it: a blob in
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// two packs is in both rows, so that removing one of the packs leaves the other right.
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// In one transaction: one row at a time took more than 6 minutes on a 1 TB repository
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// (27,547 packs), long enough for the location to drop the connection.
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$this->cache->replaceAll($this->repositoryId, $toCache);
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return;
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}
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if ($toCache !== []) {
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$this->cache?->putMany($this->repositoryId, $toCache);
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}
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$stale = array_keys(array_diff_key($cached, $present));
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if ($stale !== []) {
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$this->cache?->remove($this->repositoryId, $stale);
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}
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}
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/** @param list<array{id:string, offset:int, length:int, raw:int, flags:int}> $entries */
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private function add(string $packId, array $entries): void {
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foreach ($entries as $e) {
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$this->blobs[$e['id']] = [$packId, $e['offset'], $e['length'], $e['raw'], $e['flags']];
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}
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}
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public function has(string $id): bool {
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return isset($this->blobs[$id]) || isset($this->pending[$id]);
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}
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/** @return array{0:string, 1:int, 2:int, 3:int, 4:int} */
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public function get(string $id): array {
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return $this->blobs[$id] ?? throw new RepositoryException('Blob not in index: ' . $id);
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}
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public function addPending(string $id): void {
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$this->pending[$id] = true;
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}
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/** @param list<string> $ids */
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public function dropPending(array $ids): void {
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foreach ($ids as $id) {
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unset($this->pending[$id]);
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}
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}
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/** @param list<array{id:string, offset:int, length:int, raw:int, flags:int}> $entries */
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public function addPack(string $packId, array $entries): void {
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$stream = fopen('php://memory', 'w+b');
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fwrite($stream, $this->cipher->encryptString(json_encode($entries, JSON_THROW_ON_ERROR), 'index:' . $packId));
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rewind($stream);
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$this->backend->put('index/' . $packId, $stream);
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$this->cachePut($packId, $entries);
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foreach ($entries as $e) {
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$this->blobs[$e['id']] = [$packId, $e['offset'], $e['length'], $e['raw'], $e['flags']];
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unset($this->pending[$e['id']]);
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}
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}
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/** @return array<string, list<array{id:string, offset:int, length:int}>> packId => blobs currently located in that pack */
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/**
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* Add the index files that appeared on the location since load(), such as those of packs
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* another server's cleanup wrote while a restore runs. Only adds and updates: a blob is
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* never dropped, as a listing that misses files (a connection that failed) must not make a
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* restore lose blobs it knows. A blob in a new pack takes that pack's place.
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*/
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public function refresh(): void {
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$known = array_flip(array_map(fn (array $b): string => $b[0], $this->blobs));
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$fetch = [];
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$listed = 0;
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foreach ($this->backend->listFiles('index') as $path) {
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$listed++;
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if (!isset($known[basename($path)])) {
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$fetch[] = $path;
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}
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}
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if ($listed === 0 && $this->blobs !== []) {
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throw new BackendException('The location listed no index files, while ' . count($known) . ' are known: not trusting that listing');
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}
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$toCache = [];
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foreach ($this->backend->getMany($fetch) as $path => $data) {
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$packId = basename($path);
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/** @var list<array{id:string, offset:int, length:int, raw:int, flags:int}> $entries authenticated: written by NG Backup */
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$entries = json_decode($this->cipher->decryptString($data, 'index:' . $packId), true, 512, JSON_THROW_ON_ERROR);
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$this->downloaded++;
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$this->add($packId, $entries);
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$toCache[$packId] = $entries;
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}
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if ($toCache !== []) {
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$this->cache?->putMany($this->repositoryId, $toCache);
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}
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}
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public function packs(): array {
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$packs = [];
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foreach ($this->blobs as $id => [$pack, $offset, $length]) {
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$packs[$pack][] = ['id' => $id, 'offset' => $offset, 'length' => $length];
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}
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return $packs;
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}
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/** Forget a pack: delete its index file and cache row. Blobs that now live elsewhere are kept. */
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public function removePack(string $packId): void {
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$this->backend->delete('index/' . $packId);
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$this->cacheRemove([$packId]);
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foreach ($this->blobs as $id => $loc) {
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if ($loc[0] === $packId) {
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unset($this->blobs[$id]);
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}
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}
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}
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/** Number of packs that hold blobs of the index. */
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public function packCount(): int {
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$packs = [];
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foreach ($this->blobs as [$pack]) {
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$packs[$pack] = true;
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}
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return count($packs);
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}
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/** Bytes of all blobs in the index (encrypted size, i.e. what is stored in packs). */
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public function storedBytes(): int {
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$total = 0;
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foreach ($this->blobs as [, , $length]) {
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$total += $length;
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}
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return $total;
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}
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public function count(): int {
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return count($this->blobs);
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}
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}
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