Move byte_store.dart and file_byte_store.dart to their own subdirectory.

pkg/front_end/lib/src/incremental/byte_store.dart

-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import 'dart:collection';
-
-/**
- * Store of bytes associated with string keys.
- *
- * Each key must be not longer than 100 characters and consist of only `[a-z]`,
- * `[0-9]`, `.` and `_` characters. The key cannot be an empty string, the
- * literal `.`, or contain the sequence `..`.
- *
- * Note that associations are not guaranteed to be persistent. The value
- * associated with a key can change or become `null` at any point in time.
- *
- * TODO(scheglov) Research using asynchronous API.
- */
-abstract class ByteStore {
-  /**
-   * Return the bytes associated with the given [key].
-   * Return `null` if the association does not exist.
-   */
-  List<int> get(String key);
-
-  /**
-   * Associate the given [bytes] with the [key].
-   */
-  void put(String key, List<int> bytes);
-}
-
-/**
- * [ByteStore] which stores data only in memory.
- */
-class MemoryByteStore implements ByteStore {
-  final Map<String, List<int>> _map = {};
-
-  @override
-  List<int> get(String key) {
-    return _map[key];
-  }
-
-  @override
-  void put(String key, List<int> bytes) {
-    _map[key] = bytes;
-  }
-}
-
-/**
- * A wrapper around [ByteStore] which adds an in-memory LRU cache to it.
- */
-class MemoryCachingByteStore implements ByteStore {
-  final ByteStore _store;
-  final int _maxSizeBytes;
-
-  final _map = new LinkedHashMap<String, List<int>>();
-  int _currentSizeBytes = 0;
-
-  MemoryCachingByteStore(this._store, this._maxSizeBytes);
-
-  @override
-  List<int> get(String key) {
-    List<int> bytes = _map.remove(key);
-    if (bytes == null) {
-      bytes = _store.get(key);
-      if (bytes != null) {
-        _map[key] = bytes;
-        _currentSizeBytes += bytes.length;
-        _evict();
-      }
-    } else {
-      _map[key] = bytes;
-    }
-    return bytes;
-  }
-
-  @override
-  void put(String key, List<int> bytes) {
-    _store.put(key, bytes);
-    _currentSizeBytes -= _map[key]?.length ?? 0;
-    _map[key] = bytes;
-    _currentSizeBytes += bytes.length;
-    _evict();
-  }
-
-  void _evict() {
-    while (_currentSizeBytes > _maxSizeBytes) {
-      if (_map.isEmpty) {
-        // Should be impossible, since _currentSizeBytes should always match
-        // _map.  But recover anyway.
-        assert(false);
-        _currentSizeBytes = 0;
-        break;
-      }
-      String key = _map.keys.first;
-      List<int> bytes = _map.remove(key);
-      _currentSizeBytes -= bytes.length;
-    }
-  }
-}
-
-/**
- * [ByteStore] which does not store any data.
- */
-class NullByteStore implements ByteStore {
-  @override
-  List<int> get(String key) => null;
-
-  @override
-  void put(String key, List<int> bytes) {}
-}