63 lines
2.4 KiB
Dart
63 lines
2.4 KiB
Dart
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import 'dart:io';
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import 'dart:typed_data';
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import 'package:pure_zstd/pure_zstd.dart';
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import 'package:test/test.dart';
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/// The committed container was written by `hgtz.py`, so it is a
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/// real level-19 pyzstd frame rather than anything this package produced.
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///
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/// Every sample in it is `(northRow * 1000 + column) % 30000`, which makes the
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/// expected bytes of each block computable without a reference decompressor.
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void main() {
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group('a real .hgtz container', () {
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final bytes = File('test/fixtures/N51E000.hgtz').readAsBytesSync();
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final header = ByteData.sublistView(bytes);
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final rows = header.getUint16(6);
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final columns = header.getUint16(8);
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final block = header.getUint16(10);
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final blockColumns = (columns + block - 1) ~/ block;
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final blockRows = (rows + block - 1) ~/ block;
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test('has the shape its README documents', () {
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expect(rows, 1201);
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expect(columns, 121);
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expect(block, 256);
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expect(blockRows * blockColumns, 5);
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});
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test('decodes every block to the samples the generator wrote', () {
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final decoder = ZstdDecoder();
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for (var index = 0; index < blockRows * blockColumns; index++) {
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final entry = 12 + 8 * index;
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final offset = header.getUint32(entry);
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final length = header.getUint32(entry + 4);
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final blockRow = index ~/ blockColumns;
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final blockColumn = index % blockColumns;
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final top = blockRow * block;
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final left = blockColumn * block;
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final height = block < rows - top ? block : rows - top;
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final width = block < columns - left ? block : columns - left;
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final frame = Uint8List.sublistView(bytes, offset, offset + length);
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final out = decoder.decode(frame);
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expect(out.length, height * width * 2, reason: 'block $index size');
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final samples = ByteData.sublistView(out);
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for (var row = 0; row < height; row++) {
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for (var column = 0; column < width; column++) {
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// Row 0 of the container is the north edge, which is what the
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// generator counted from.
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final northRow = top + row;
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final expected = (northRow * 1000 + left + column) % 30000;
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expect(
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samples.getInt16((row * width + column) * 2),
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expected,
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reason: 'block $index at $row,$column',
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);
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}
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}
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}
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});
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});
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}
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