110 lines
3.0 KiB
C++
110 lines
3.0 KiB
C++
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// gKeyMapper daemon - watches the mappings file for changes (inotify).
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#include "config_watch.h"
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#include <cerrno>
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#include <cstdint>
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#include <cstdio>
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#include <cstring>
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#include <sys/inotify.h>
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#include <sys/stat.h>
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#include <unistd.h>
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namespace gkeymapper::daemon {
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namespace {
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// IN_CLOSE_WRITE is the useful one (the writer closed the file); IN_MODIFY
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// covers writers that hold the file open, IN_MOVED_TO/CREATE the atomic save.
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constexpr uint32_t kMask = IN_CLOSE_WRITE | IN_MODIFY | IN_MOVED_TO | IN_CREATE;
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std::string directory_of(const std::string& path) {
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size_t slash = path.find_last_of('/');
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if (slash == std::string::npos) {
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return ".";
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}
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return slash == 0 ? std::string("/") : path.substr(0, slash);
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}
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std::string basename_of(const std::string& path) {
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size_t slash = path.find_last_of('/');
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return slash == std::string::npos ? path : path.substr(slash + 1);
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}
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} // namespace
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ConfigWatcher::~ConfigWatcher() {
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if (fd_ >= 0) {
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::close(fd_);
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}
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}
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bool ConfigWatcher::init(const std::string& path) {
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name_ = basename_of(path);
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directory_ = directory_of(path);
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fd_ = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
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if (fd_ < 0) {
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std::fprintf(stderr,
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"gkeymapper-daemon: inotify unavailable (%s); "
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"use SIGHUP to reload\n",
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std::strerror(errno));
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return false;
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}
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int watch = inotify_add_watch(fd_, directory_.c_str(), kMask);
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if (watch < 0 && errno == ENOENT) {
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// First start before anything was ever saved: create the directory the
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// GUI would create and try once more.
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::mkdir(directory_.c_str(), 0755);
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watch = inotify_add_watch(fd_, directory_.c_str(), kMask);
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}
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if (watch < 0) {
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std::fprintf(stderr,
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"gkeymapper-daemon: cannot watch %s (%s); "
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"use SIGHUP to reload\n",
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directory_.c_str(), std::strerror(errno));
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::close(fd_);
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fd_ = -1;
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return false;
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}
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std::fprintf(stderr, "gkeymapper-daemon: watching %s for changes\n",
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directory_.c_str());
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return true;
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}
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void ConfigWatcher::poll_events() {
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if (fd_ < 0) {
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return;
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}
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alignas(inotify_event) char buffer[4096];
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for (;;) {
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ssize_t length = ::read(fd_, buffer, sizeof(buffer));
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if (length <= 0) {
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return; // nothing queued (EAGAIN) or a read error
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}
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for (ssize_t offset = 0; offset < length;) {
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const auto* event = reinterpret_cast<const inotify_event*>(buffer + offset);
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offset += static_cast<ssize_t>(sizeof(inotify_event)) + event->len;
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// Only the configured file matters; the directory may hold others.
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if (event->len == 0 || name_ == event->name) {
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pending_ = true;
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}
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}
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}
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}
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bool ConfigWatcher::take_change() {
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if (!pending_) {
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return false;
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}
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pending_ = false;
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return true;
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}
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} // namespace gkeymapper::daemon
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