mirror of
https://github.com/LadybirdBrowser/ladybird.git
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135 lines
4.6 KiB
C++
135 lines
4.6 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibCore/ArgsParser.h>
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#include <LibCore/EventLoop.h>
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#include <LibCore/File.h>
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#include <LibCore/FileWatcher.h>
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#include <LibCore/System.h>
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#define DEFAULT_LINE_COUNT 10
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static ErrorOr<void> tail_from_pos(Core::File& file, off_t startline)
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{
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TRY(file.seek(startline + 1, SeekMode::SetPosition));
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auto buffer = TRY(file.read_until_eof());
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out("{}", StringView { buffer });
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return {};
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}
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static ErrorOr<off_t> find_seek_pos(Core::File& file, int wanted_lines)
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{
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// Rather than reading the whole file, start at the end and work backwards,
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// stopping when we've found the number of lines we want.
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off_t pos = TRY(file.seek(0, SeekMode::FromEndPosition));
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off_t end = pos;
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int lines = 0;
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for (; pos >= 0; pos--) {
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TRY(file.seek(pos, SeekMode::SetPosition));
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if (file.is_eof())
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break;
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Array<u8, 1> buffer;
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auto ch = TRY(file.read(buffer));
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if (*ch.data() == '\n' && (end - pos) > 1) {
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lines++;
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if (lines == wanted_lines)
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break;
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}
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}
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return pos;
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}
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ErrorOr<int> serenity_main(Main::Arguments arguments)
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{
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TRY(Core::System::pledge("stdio rpath"));
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bool follow = false;
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size_t wanted_line_count = DEFAULT_LINE_COUNT;
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StringView file;
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Core::ArgsParser args_parser;
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args_parser.set_general_help("Print the end ('tail') of a file.");
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args_parser.add_option(follow, "Output data as it is written to the file", "follow", 'f');
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args_parser.add_option(wanted_line_count, "Fetch the specified number of lines", "lines", 'n', "number");
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args_parser.add_positional_argument(file, "File path", "file", Core::ArgsParser::Required::No);
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args_parser.parse(arguments);
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auto f = TRY(Core::File::open_file_or_standard_stream(file, Core::File::OpenMode::Read));
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if (!follow)
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TRY(Core::System::pledge("stdio"));
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auto file_is_seekable = !f->tell().is_error();
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if (!file_is_seekable) {
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do {
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// FIXME: If f is the standard input, f->read_all() does not block
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// anymore after sending EOF (^D), despite f->is_open() returning true.
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auto buffer = TRY(f->read_until_eof(PAGE_SIZE));
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auto line_count = StringView(buffer).count("\n"sv);
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auto bytes = buffer.bytes();
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size_t line_index = 0;
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StringBuilder line;
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if (!line_count && wanted_line_count) {
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out("{}", StringView { bytes });
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continue;
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}
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for (size_t i = 0; i < bytes.size(); i++) {
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auto ch = bytes.at(i);
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line.append(ch);
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if (ch == '\n') {
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if (wanted_line_count > line_count || line_index >= line_count - wanted_line_count)
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out("{}", line.to_deprecated_string());
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line_index++;
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line.clear();
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}
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}
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// Since we can't have FileWatchers on the standard input either,
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// we just loop forever if the -f option was passed.
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} while (follow);
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return 0;
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}
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auto pos = TRY(find_seek_pos(*f, wanted_line_count));
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TRY(tail_from_pos(*f, pos));
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if (follow) {
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TRY(f->seek(0, SeekMode::FromEndPosition));
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Core::EventLoop event_loop;
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auto watcher = TRY(Core::FileWatcher::create());
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watcher->on_change = [&](Core::FileWatcherEvent const& event) {
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if (event.type == Core::FileWatcherEvent::Type::ContentModified) {
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auto buffer_or_error = f->read_until_eof();
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if (buffer_or_error.is_error()) {
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auto error = buffer_or_error.release_error();
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warnln(error.string_literal());
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event_loop.quit(error.code());
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return;
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}
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auto bytes = buffer_or_error.value().bytes();
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out("{}", StringView { bytes });
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auto potential_error = f->seek(0, SeekMode::FromEndPosition);
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if (potential_error.is_error()) {
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auto error = potential_error.release_error();
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warnln(error.string_literal());
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event_loop.quit(error.code());
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return;
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}
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}
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};
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TRY(watcher->add_watch(file, Core::FileWatcherEvent::Type::ContentModified));
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TRY(Core::System::pledge("stdio"));
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return event_loop.exec();
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}
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return 0;
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}
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