v1.4.4

source/core/StarLockFile_unix.cpp

@@ -0,0 +1,94 @@
+#include "StarLockFile.hpp"
+#include "StarTime.hpp"
+#include "StarThread.hpp"
+
+#include <sys/file.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+
+namespace Star {
+
+int64_t const LockFile::MaximumSleepMillis;
+
+Maybe<LockFile> LockFile::acquireLock(String const& filename, int64_t lockTimeout) {
+  LockFile lock(move(filename));
+  if (lock.lock(lockTimeout))
+    return move(lock);
+  return {};
+}
+
+LockFile::LockFile(String const& filename) : m_filename(move(filename)) {}
+
+LockFile::LockFile(LockFile&& lockFile) {
+  operator=(move(lockFile));
+}
+
+LockFile::~LockFile() {
+  unlock();
+}
+
+LockFile& LockFile::operator=(LockFile&& lockFile) {
+  m_filename = move(lockFile.m_filename);
+  m_handle = move(lockFile.m_handle);
+
+  return *this;
+}
+
+bool LockFile::lock(int64_t timeout) {
+  auto doFLock = [](String const& filename, bool block) -> shared_ptr<int> {
+    int fd = open(filename.utf8Ptr(), O_RDONLY | O_CREAT, 0644);
+    if (fd < 0)
+      throw StarException(strf("Could not open lock file %s, %s\n", filename, strerror(errno)));
+
+    int ret;
+    if (block)
+      ret = flock(fd, LOCK_EX);
+    else
+      ret = flock(fd, LOCK_EX | LOCK_NB);
+
+    if (ret != 0) {
+      close(fd);
+      if (errno != EWOULDBLOCK)
+        throw StarException(strf("Could not lock file %s, %s\n", filename, strerror(errno)));
+      return {};
+    }
+
+    return make_shared<int>(fd);
+  };
+
+  if (timeout < 0) {
+    m_handle = doFLock(m_filename, true);
+    return true;
+  } else if (timeout == 0) {
+    m_handle = doFLock(m_filename, false);
+    return (bool)m_handle;
+  } else {
+    int64_t startTime = Time::monotonicMilliseconds();
+    while (true) {
+      m_handle = doFLock(m_filename, false);
+      if (m_handle)
+        return true;
+
+      if (Time::monotonicMilliseconds() - startTime > timeout)
+        return false;
+
+      Thread::sleep(min(timeout / 4, MaximumSleepMillis));
+    }
+  }
+}
+
+void LockFile::unlock() {
+  if (m_handle) {
+    int fd = *(int*)m_handle.get();
+    unlink(m_filename.utf8Ptr());
+    close(fd);
+    m_handle.reset();
+  }
+}
+
+bool LockFile::isLocked() const {
+  return (bool)m_handle;
+}
+
+}