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/*
* Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "FileWatcher.h"
#include <AK/Debug.h>
#include <AK/DeprecatedString.h>
#include <AK/LexicalPath.h>
#include <LibCore/Notifier.h>
#include <errno.h>
#include <limits.h>
#include <string.h>
#include <sys/inotify.h>
#include <sys/ioctl.h>
#include <unistd.h>
#if !defined(AK_OS_LINUX)
static_assert(false, "This file must only be used for Linux");
#endif
namespace Core {
static constexpr unsigned file_watcher_flags_to_inotify_flags(FileWatcherFlags flags)
{
unsigned result = 0;
if (has_flag(flags, FileWatcherFlags::Nonblock))
result |= IN_NONBLOCK;
if (has_flag(flags, FileWatcherFlags::CloseOnExec))
result |= IN_CLOEXEC;
return result;
}
static Optional<FileWatcherEvent> get_event_from_fd(int fd, HashMap<unsigned, DeprecatedString> const& wd_to_path)
{
static constexpr auto max_event_size = sizeof(inotify_event) + NAME_MAX + 1;
// Note from INOTIFY(7) man page:
//
// Some systems cannot read integer variables if they are not properly aligned. On other
// systems, incorrect alignment may decrease performance. Hence, the buffer used for reading
// from the inotify file descriptor should have the same alignment as inotify_event.
alignas(alignof(inotify_event)) Array<u8, max_event_size> buffer;
ssize_t rc = ::read(fd, buffer.data(), buffer.size());
if (rc == 0) {
return {};
} else if (rc < 0) {
dbgln_if(FILE_WATCHER_DEBUG, "get_event_from_fd: Reading from wd {} failed: {}", fd, strerror(errno));
return {};
}
auto const* event = reinterpret_cast<inotify_event const*>(buffer.data());
FileWatcherEvent result;
auto it = wd_to_path.find(event->wd);
if (it == wd_to_path.end()) {
dbgln_if(FILE_WATCHER_DEBUG, "get_event_from_fd: Got an event for a non-existent wd {}?!", event->wd);
return {};
}
auto const& path = it->value;
if ((event->mask & IN_CREATE) != 0)
result.type |= FileWatcherEvent::Type::ChildCreated;
if ((event->mask & IN_DELETE) != 0)
result.type |= FileWatcherEvent::Type::ChildDeleted;
if ((event->mask & IN_DELETE_SELF) != 0)
result.type |= FileWatcherEvent::Type::Deleted;
if ((event->mask & IN_MODIFY) != 0)
result.type |= FileWatcherEvent::Type::ContentModified;
if ((event->mask & IN_ATTRIB) != 0)
result.type |= FileWatcherEvent::Type::MetadataModified;
if (result.type == FileWatcherEvent::Type::Invalid) {
warnln("Unknown event type {:x} returned by the watch_file descriptor for {}", event->mask, path);
return {};
}
if (event->len > 0) {
StringView child_name { event->name, strlen(event->name) };
result.event_path = LexicalPath::join(path, child_name).string();
} else {
result.event_path = path;
}
dbgln_if(FILE_WATCHER_DEBUG, "get_event_from_fd: got event from wd {} on '{}' type {}", fd, result.event_path, result.type);
return result;
}
ErrorOr<NonnullRefPtr<FileWatcher>> FileWatcher::create(FileWatcherFlags flags)
{
auto watcher_fd = ::inotify_init1(file_watcher_flags_to_inotify_flags(flags | FileWatcherFlags::CloseOnExec));
if (watcher_fd < 0)
return Error::from_errno(errno);
auto notifier = TRY(Notifier::try_create(watcher_fd, Notifier::Event::Read));
return adopt_nonnull_ref_or_enomem(new (nothrow) FileWatcher(watcher_fd, move(notifier)));
}
FileWatcher::FileWatcher(int watcher_fd, NonnullRefPtr<Notifier> notifier)
: FileWatcherBase(watcher_fd)
, m_notifier(move(notifier))
{
m_notifier->on_ready_to_read = [this] {
auto maybe_event = get_event_from_fd(m_notifier->fd(), m_wd_to_path);
if (maybe_event.has_value()) {
auto event = maybe_event.value();
on_change(event);
if (has_flag(event.type, FileWatcherEvent::Type::Deleted)) {
auto result = remove_watch(event.event_path);
if (result.is_error()) {
dbgln_if(FILE_WATCHER_DEBUG, "on_ready_to_read: {}", result.error());
}
}
}
};
}
FileWatcher::~FileWatcher() = default;
ErrorOr<bool> FileWatcherBase::add_watch(DeprecatedString path, FileWatcherEvent::Type event_mask)
{
if (m_path_to_wd.find(path) != m_path_to_wd.end()) {
dbgln_if(FILE_WATCHER_DEBUG, "add_watch: path '{}' is already being watched", path);
return false;
}
unsigned inotify_mask = 0;
if (has_flag(event_mask, FileWatcherEvent::Type::ChildCreated))
inotify_mask |= IN_CREATE;
if (has_flag(event_mask, FileWatcherEvent::Type::ChildDeleted))
inotify_mask |= IN_DELETE;
if (has_flag(event_mask, FileWatcherEvent::Type::Deleted))
inotify_mask |= IN_DELETE_SELF;
if (has_flag(event_mask, FileWatcherEvent::Type::ContentModified))
inotify_mask |= IN_MODIFY;
if (has_flag(event_mask, FileWatcherEvent::Type::MetadataModified))
inotify_mask |= IN_ATTRIB;
int watch_descriptor = ::inotify_add_watch(m_watcher_fd, path.characters(), inotify_mask);
if (watch_descriptor < 0)
return Error::from_errno(errno);
m_path_to_wd.set(path, watch_descriptor);
m_wd_to_path.set(watch_descriptor, path);
dbgln_if(FILE_WATCHER_DEBUG, "add_watch: watching path '{}' on InodeWatcher {} wd {}", path, m_watcher_fd, watch_descriptor);
return true;
}
ErrorOr<bool> FileWatcherBase::remove_watch(DeprecatedString path)
{
auto it = m_path_to_wd.find(path);
if (it == m_path_to_wd.end()) {
dbgln_if(FILE_WATCHER_DEBUG, "remove_watch: path '{}' is not being watched", path);
return false;
}
if (::inotify_rm_watch(m_watcher_fd, it->value) < 0)
return Error::from_errno(errno);
m_path_to_wd.remove(it);
m_wd_to_path.remove(it->value);
dbgln_if(FILE_WATCHER_DEBUG, "remove_watch: stopped watching path '{}' on InodeWatcher {}", path, m_watcher_fd);
return true;
}
}
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