64 lines
2.1 KiB
Dart
64 lines
2.1 KiB
Dart
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import 'dart:collection';
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import 'parser.dart';
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import 'range_header_item.dart';
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import 'range_header_impl.dart';
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/// Represents the contents of a parsed `Range` header.
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abstract class RangeHeader {
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/// Returns an immutable list of the ranges that were parsed.
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UnmodifiableListView<RangeHeaderItem> get items;
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const factory RangeHeader(Iterable<RangeHeaderItem> items,
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{String rangeUnit}) = _ConstantRangeHeader;
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/// Eliminates any overlapping [items], sorts them, and folds them all into the most efficient representation possible.
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static UnmodifiableListView<RangeHeaderItem> foldItems(
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Iterable<RangeHeaderItem> items) {
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var out = new Set<RangeHeaderItem>();
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for (var item in items) {
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// Remove any overlapping items, consolidate them.
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while (out.any((x) => x.overlaps(item))) {
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var f = out.firstWhere((x) => x.overlaps(item));
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out.remove(f);
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item = item.consolidate(f);
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}
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out.add(item);
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}
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return new UnmodifiableListView(out.toList()..sort());
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}
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/// Attempts to parse a [RangeHeader] from its [text] representation.
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///
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/// You can optionally pass a custom list of [allowedRangeUnits].
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/// The default is `['bytes']`.
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///
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/// If [fold] is `true`, the items will be folded into the most compact
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/// possible representation.
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factory RangeHeader.parse(String text,
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{Iterable<String> allowedRangeUnits, bool fold: true}) {
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var tokens = scan(text, allowedRangeUnits?.toList() ?? ['bytes']);
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var parser = new Parser(tokens);
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var header = parser.parseRangeHeader();
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if (header == null) return null;
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var items = foldItems(header.items);
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return RangeHeaderImpl(header.rangeUnit, items);
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}
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/// Returns this header's range unit. Most commonly, this is `bytes`.
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String get rangeUnit;
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}
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class _ConstantRangeHeader implements RangeHeader {
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final Iterable<RangeHeaderItem> items_;
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final String rangeUnit;
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const _ConstantRangeHeader(this.items_, {this.rangeUnit: 'bytes'});
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@override
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UnmodifiableListView<RangeHeaderItem> get items =>
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new UnmodifiableListView(items_);
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}
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