string_readers #

Implementation of random access string readers for reading data from various data sources in various encodings through a single StringReader interface.

Version: 0.1.0

About this software #

Implementation of random access string readers for reading data from various data sources in various encodings through a single StringReader interface.

Possible application of this is the organization of access operations to data located in large files, as well as the organization of access to data from various sources through a single StringReader interface.

The current version includes the following implementations:

• ByteReader
• FileReader
• StringReader
• Utf8Reader

These implementations allow random read access to string input data from the following sources:

• String data encoded in Utf-16 encoding
• Byte data encoded in Utf-8 encoding
• String data located in files

Example #

An example of accessing data from various sources through a single StringReader interface.

import 'dart:convert';
import 'dart:io';

import 'package:string_reader/file_reader.dart';
import 'package:string_reader/string_reader.dart';
import 'package:string_reader/utf8_reader.dart';

void main(List<String> args) {
  const source = 'Hello';
  File? file;
  RandomAccessFile? fp;
  try {
    const filename = 'example/temp.txt';
    file = File(filename);
    _writeToFile(file, source);
    fp = file.openSync();
    final result = _readUsingFileReader(fp);
    print(result);
  } catch (e) {
    rethrow;
  } finally {
    if (fp != null) {
      fp.closeSync();
    }

    if (file != null) {
      if (file.existsSync()) {
        file.deleteSync();
      }
    }
  }

  final stringReader = StringReader(source);
  final result = _readUsingStringReader(stringReader);
  print(result);
}

String _readUsingFileReader(RandomAccessFile fp) {
  const bufferSize = 8;
  final fileReader = FileReader(fp, bufferSize: bufferSize);
  final utf8Reader = Utf8Reader(fileReader);
  return _readUsingStringReader(utf8Reader);
}

String _readUsingStringReader(StringReader reader) {
  final charCodes = <int>[];
  var position = 0;
  while (position < reader.length) {
    final char = reader.readChar(position);
    position += reader.count;
    charCodes.add(char);
  }

  return String.fromCharCodes(charCodes);
}

void _writeToFile(File file, String string) {
  if (file.existsSync()) {
    file.deleteSync();
  }

  final bytes = Utf8Encoder().convert('Hello');
  file.writeAsBytesSync(bytes);
}