pkg/analyzer/lib/src/dart/micro/cider_byte_store.dart

// Copyright (c) 2020, 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:typed_data';

import 'package:meta/meta.dart';

class CacheData {
  final int id;
  final Uint8List bytes;

  CacheData(this.id, this.bytes);
}

/// Store of bytes associated with string keys and a hash.
///
/// 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.
abstract class CiderByteStore {
  /// Return the bytes associated with the [key], and increment the reference
  /// count.
  ///
  /// Return `null` if the association does not exist.
  Uint8List? get2(String key);

  /// Associate [bytes] with [key].
  /// Return an internalized version of [bytes], the reference count is `1`.
  ///
  /// This method will throw an exception if there is already an association
  /// for the [key]. The client should either use [get2] to access data,
  /// or first [release2] it.
  Uint8List putGet2(String key, Uint8List bytes);

  ///  Decrement the reference count for every key in [keys].
  void release2(Iterable<String> keys);
}

class CiderByteStoreTestView {
  int length = 0;
}

/// [CiderByteStore] that keeps all data in local memory.
class MemoryCiderByteStore implements CiderByteStore {
  @visibleForTesting
  final Map<String, MemoryCiderByteStoreEntry> map = {};

  /// This field gets value only during testing.
  CiderByteStoreTestView? testView;

  @override
  Uint8List? get2(String key) {
    final entry = map[key];
    if (entry == null) {
      return null;
    }

    entry.refCount++;
    return entry.bytes;
  }

  @override
  Uint8List putGet2(String key, Uint8List bytes) {
    if (map.containsKey(key)) {
      throw StateError('Overwriting is not allowed: $key');
    }

    testView?.length++;
    map[key] = MemoryCiderByteStoreEntry._(bytes);
    return bytes;
  }

  @override
  void release2(Iterable<String> keys) {
    for (final key in keys) {
      final entry = map[key];
      if (entry != null) {
        entry.refCount--;
        if (entry.refCount == 0) {
          map.remove(key);
        }
      }
    }
  }
}

@visibleForTesting
class MemoryCiderByteStoreEntry {
  final Uint8List bytes;
  int refCount = 1;

  MemoryCiderByteStoreEntry._(this.bytes);

  @override
  String toString() {
    return '(length: ${bytes.length}, refCount: $refCount)';
  }
}