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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/file.h>
#include <cstring>
#include <unistd.h>
#include <limits.h>
#include <cstdio>
#include "log.h"
LOG_SETUP_INDIRECT(".log.lock", "$Id$");
#include "lock.h"
#include "internal.h"
#undef LOG
#define LOG LOG_INDIRECT
namespace ns_log {
Lock::Lock(int arg_fd)
: _fd(dup(arg_fd)),
_isLocked(false)
{
if (_fd == -1) {
throwInvalid("Cannot duplicate fd %d for lock: %s", arg_fd,
strerror(errno));
}
}
Lock::Lock(const char *filename, int mode)
: _fd(open(filename, mode, 0666)),
_isLocked(false)
{
if (_fd == -1) {
if (mode & O_CREAT) {
unlink(filename);
_fd = open(filename, mode, 0666);
}
if (_fd == -1) {
throwInvalid("Cannot open lockfile '%s': %s", filename,
strerror(errno));
}
}
fcntl(_fd, F_SETFD, FD_CLOEXEC);
}
void
Lock::lock(bool exclusive)
{
// Early escape to avoid double locking which would of course block forever
if (_isLocked) return;
if (flock(_fd, exclusive ? LOCK_EX : LOCK_SH) == -1) {
int err = errno;
close(_fd);
LOG(error, "Cannot lock fd %d: %s", _fd, strerror(err));
throwInvalid("Cannot lock fd %d: %s", _fd, strerror(err));
}
_isLocked = true;
}
void
Lock::unlock() {
if (_isLocked) {
flock(_fd, LOCK_UN);
_isLocked = false;
}
}
int Lock::size()
{
struct stat st;
int err = fstat(_fd, &st);
if (err == -1) {
return -1;
}
return st.st_size;
}
Lock::~Lock()
{
unlock();
close(_fd);
}
} // end namespace ns_log
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