114 lines
3.2 KiB
Dart
114 lines
3.2 KiB
Dart
// Copyright (c) 2021, Erik C. Thauvin. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be found
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// in the LICENSE file.
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library dcat;
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import 'dart:convert';
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import 'dart:io';
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const libName = 'dcat';
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const exitFailure = 1;
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const exitSuccess = 0;
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/// Concatenates files in [paths] to [stdout]
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///
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/// The parameters are similar to the [GNU cat utility](https://www.gnu.org/software/coreutils/manual/html_node/cat-invocation.html#cat-invocation).
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/// Specify a [log] for debugging purpose.
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Future<int> cat(List<String> paths,
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{List<String>? log,
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bool showEnds = false,
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bool numberNonBlank = false,
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bool showLineNumbers = false,
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bool showTabs = false,
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bool squeezeBlank = false}) async {
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var lineNumber = 1;
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var returnCode = 0;
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log?.clear();
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if (paths.isEmpty) {
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final lines = await _readStdin();
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await _writeLines(lines, lineNumber, log, showEnds, showLineNumbers,
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numberNonBlank, showTabs, squeezeBlank);
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} else {
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for (final path in paths) {
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try {
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final Stream<String> lines;
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if (path == '-') {
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lines = await _readStdin();
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} else {
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lines = utf8.decoder
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.bind(File(path).openRead())
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.transform(const LineSplitter());
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}
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lineNumber = await _writeLines(lines, lineNumber, log, showEnds,
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showLineNumbers, numberNonBlank, showTabs, squeezeBlank);
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} on FileSystemException catch (e) {
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final String? osMessage = e.osError?.message;
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final String message;
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if (osMessage != null && osMessage.isNotEmpty) {
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message = osMessage;
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} else {
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message = e.message;
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}
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returnCode = await printError(message, path: path);
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} on FormatException {
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returnCode = await printError('Binary file not supported.', path: path);
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} catch (e) {
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returnCode = await printError(e.toString(), path: path);
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}
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}
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}
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return returnCode;
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}
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/// Prints the [appName], [path] and error [message] to [stderr].
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Future<int> printError(String message,
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{String appName = libName, String path = ''}) async {
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if (path.isNotEmpty) {
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stderr.writeln('$libName: $path: $message');
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} else {
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stderr.write('$libName: $message');
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}
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return exitFailure;
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}
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/// Reads from stdin.
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Future<Stream<String>> _readStdin() async =>
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stdin.transform(utf8.decoder).transform(const LineSplitter());
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/// Writes lines to stdout.
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Future<int> _writeLines(Stream<String> lines, int lineNumber,
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[List<String>? log,
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bool showEnds = false,
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bool showLineNumbers = false,
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bool showNonBlank = false,
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bool showTabs = false,
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bool squeezeBlank = false]) async {
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var emptyLine = 0;
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final sb = StringBuffer();
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await for (final line in lines) {
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sb.clear();
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if (squeezeBlank && line.isEmpty) {
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if (++emptyLine >= 2) {
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continue;
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}
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} else {
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emptyLine = 0;
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}
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if (showNonBlank || showLineNumbers) {
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sb.write('${lineNumber++}: ');
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}
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if (showTabs) {
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sb.write(line.replaceAll('\t', '^I'));
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} else {
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sb.write(line);
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}
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if (showEnds) {
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sb.write('\$');
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}
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log?.add(sb.toString());
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stdout.writeln(sb);
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}
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return lineNumber;
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}
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