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