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+/*
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+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
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+ * Copyright (c) 2021, the SerenityOS developers.
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+ * All rights reserved.
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions are met:
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+ *
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+ * 1. Redistributions of source code must retain the above copyright notice, this
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+ * list of conditions and the following disclaimer.
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+ *
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+ * 2. Redistributions in binary form must reproduce the above copyright notice,
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+ * this list of conditions and the following disclaimer in the documentation
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+ * and/or other materials provided with the distribution.
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+ *
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+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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+ */
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+
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+#include "FileWatcher.h"
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+#include <AK/Debug.h>
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+#include <AK/Function.h>
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+#include <AK/LexicalPath.h>
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+#include <AK/Noncopyable.h>
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+#include <AK/NonnullRefPtr.h>
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+#include <AK/RefCounted.h>
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+#include <AK/Result.h>
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+#include <AK/String.h>
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+#include <Kernel/API/InodeWatcherEvent.h>
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+#include <LibCore/DirIterator.h>
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+#include <LibCore/Notifier.h>
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+#include <fcntl.h>
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+#include <string.h>
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+#include <sys/stat.h>
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+
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+namespace Core {
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+
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+// Only supported in serenity mode because we use `watch_file`
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+#ifdef __serenity__
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+
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+static String get_child_path_from_inode_index(const String& path, unsigned child_inode_index)
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+{
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+ DirIterator iterator(path, Core::DirIterator::SkipDots);
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+ if (iterator.has_error()) {
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+ return {};
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+ }
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+
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+ while (iterator.has_next()) {
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+ auto child_full_path = String::formatted("{}/{}", path, iterator.next_path());
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+ struct stat st;
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+
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+ if (lstat(child_full_path.characters(), &st)) {
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+ return {};
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+ }
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+
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+ if (st.st_ino == child_inode_index) {
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+ return child_full_path;
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+ }
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+ }
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+ return {};
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+}
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+
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+BlockingFileWatcher::BlockingFileWatcher(const String& path)
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+ : m_path(path)
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+{
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+ m_watcher_fd = watch_file(path.characters(), path.length());
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+ ASSERT(m_watcher_fd != -1);
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+}
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+
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+BlockingFileWatcher::~BlockingFileWatcher()
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+{
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+ close(m_watcher_fd);
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+}
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+
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+Optional<FileWatcherEvent> BlockingFileWatcher::wait_for_event()
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+{
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+ InodeWatcherEvent event {};
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+ int rc = read(m_watcher_fd, &event, sizeof(event));
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+ if (rc <= 0)
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+ return {};
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+
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+ FileWatcherEvent result;
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+ if (event.type == InodeWatcherEvent::Type::ChildAdded)
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+ result.type = FileWatcherEvent::Type::ChildAdded;
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+ else if (event.type == InodeWatcherEvent::Type::ChildRemoved)
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+ result.type = FileWatcherEvent::Type::ChildRemoved;
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+ else if (event.type == InodeWatcherEvent::Type::Modified)
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+ result.type = FileWatcherEvent::Type::Modified;
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+ else
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+ return {};
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+
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+ if (result.type == FileWatcherEvent::Type::ChildAdded || result.type == FileWatcherEvent::Type::ChildRemoved) {
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+ auto child_path = get_child_path_from_inode_index(m_path, event.inode_index);
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+ if (!LexicalPath(child_path).is_valid())
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+ return {};
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+
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+ result.child_path = child_path;
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+ }
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+
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+ return result;
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+}
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+
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+Result<NonnullRefPtr<FileWatcher>, String> FileWatcher::watch(const String& path)
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+{
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+ auto watch_fd = watch_file(path.characters(), path.length());
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+ if (watch_fd < 0) {
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+ return String::formatted("Could not watch file '{}' : {}", path.characters(), strerror(errno));
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+ }
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+
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+ fcntl(watch_fd, F_SETFD, FD_CLOEXEC);
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+ if (watch_fd < 0) {
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+ return String::formatted("Could not watch file '{}' : {}", path.characters(), strerror(errno));
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+ }
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+
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+ dbgln_if(FILE_WATCHER_DEBUG, "Started watcher for file '{}'", path.characters());
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+ auto notifier = Notifier::construct(watch_fd, Notifier::Event::Read);
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+ return adopt(*new FileWatcher(move(notifier), move(path)));
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+}
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+
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+FileWatcher::FileWatcher(NonnullRefPtr<Notifier> notifier, const String& path)
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+ : m_notifier(move(notifier))
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+ , m_path(path)
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+{
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+ m_notifier->on_ready_to_read = [this] {
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+ InodeWatcherEvent event {};
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+ int rc = read(m_notifier->fd(), &event, sizeof(event));
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+ if (rc <= 0)
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+ return;
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+
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+ FileWatcherEvent result;
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+ if (event.type == InodeWatcherEvent::Type::ChildAdded) {
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+ result.type = FileWatcherEvent::Type::ChildAdded;
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+ } else if (event.type == InodeWatcherEvent::Type::ChildRemoved) {
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+ result.type = FileWatcherEvent::Type::ChildRemoved;
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+ } else if (event.type == InodeWatcherEvent::Type::Modified) {
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+ result.type = FileWatcherEvent::Type::Modified;
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+ } else {
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+ warnln("Unknown event type {} returned by the watch_file descriptor for {}", (unsigned)event.type, m_path.characters());
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+ return;
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+ }
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+
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+ if (result.type == FileWatcherEvent::Type::ChildAdded || result.type == FileWatcherEvent::Type::ChildRemoved) {
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+ auto child_path = get_child_path_from_inode_index(m_path, event.inode_index);
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+ if (!LexicalPath(child_path).is_valid())
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+ return;
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+
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+ result.child_path = child_path;
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+ }
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+
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+ on_change(result);
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+ };
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+}
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+
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+FileWatcher::~FileWatcher()
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+{
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+ m_notifier->on_ready_to_read = nullptr;
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+ close(m_notifier->fd());
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+ dbgln_if(FILE_WATCHER_DEBUG, "Ended watcher for file '{}'", m_path.characters());
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+}
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+
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+#endif
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+
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+}
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