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casacore
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#include <FileLocker.h>
Public Types | |
| enum | LockType { Read , Write } |
| Define the possible lock types. More... | |
Public Member Functions | |
| FileLocker () | |
| Default constructor creates an invalid fd. More... | |
| FileLocker (int fd, uInt start=0, uInt length=0) | |
| Construct the FileLocker object for the given file descriptor. More... | |
| ~FileLocker () | |
| Bool | acquire (LockType=Write, uInt nattempts=0) |
| Acquire a write or read lock. More... | |
| Bool | release () |
| Release a lock. More... | |
| Bool | canLock (LockType=Write) |
| Test if the file can be locked for read or write. More... | |
| Bool | canLock (uInt &pid, LockType=Write) |
| Bool | hasLock (LockType=Write) const |
| Test if the process has a lock for read or write on the file. More... | |
| int | fd () const |
| Get the fd in use. More... | |
| int | lastError () const |
| Get the last error. More... | |
| String | lastMessage () const |
| Get the message belonging to the last error. More... | |
Private Attributes | |
| int | itsFD |
| int | itsError |
| int | itsStart |
| int | itsLength |
| Bool | itsMsgShown |
| Bool | itsReadLocked |
| temporary for SUSE 6.1 More... | |
| Bool | itsWriteLocked |
Class to handle file locking.
Public interface
This class handles file locking by means of the fcntl SETLK function. Locking of files on NFS-mounted file systems works correctly as long as the NFS lockd and statd deamons are configured correctly. Otherwise lock requests may be granted incorrectly.
Acquiring a lock can be done for a read or a write lock. Multiple locks on a file can exist as long as they are all read locks. When a write lock is involved, no other lock can exist. It is possible to acquire a lock in 2 ways:
Make it possible to lock files in a standard way.
Definition at line 91 of file FileLocker.h.
Define the possible lock types.
| Enumerator | |
|---|---|
| Read | Acquire a read lock. |
| Write | Acquire a write lock. |
Definition at line 95 of file FileLocker.h.
| casacore::FileLocker::FileLocker | ( | ) |
Default constructor creates an invalid fd.
Construct the FileLocker object for the given file descriptor.
This can be used to lock a segment of the given file. The segment is given by start and length. Length=0 means till the end of the file.
| casacore::FileLocker::~FileLocker | ( | ) |
Acquire a write or read lock.
nattempts defines how often it tries to acquire the lock. A zero value indicates an infinite number of times (i.e. wait until the lock is acquired). A positive value means it waits 1 second between each attempt.
Test if the file can be locked for read or write.
Optionally the PID of the process holding the lock is returned.
Referenced by casacore::LockFile::canLock().
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Test if the process has a lock for read or write on the file.
Definition at line 154 of file FileLocker.h.
References itsReadLocked, itsWriteLocked, and Write.
Referenced by casacore::LockFile::hasLock().
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Get the last error.
Definition at line 162 of file FileLocker.h.
References itsError.
Referenced by casacore::LockFile::lastError().
| String casacore::FileLocker::lastMessage | ( | ) | const |
Get the message belonging to the last error.
Referenced by casacore::LockFile::lastMessage().
| Bool casacore::FileLocker::release | ( | ) |
Release a lock.
The return status indicates if an error occurred.
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private |
Definition at line 145 of file FileLocker.h.
Referenced by lastError().
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private |
Definition at line 144 of file FileLocker.h.
Referenced by fd().
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private |
Definition at line 147 of file FileLocker.h.
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private |
Definition at line 148 of file FileLocker.h.
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private |
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private |
Definition at line 146 of file FileLocker.h.
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private |
Definition at line 150 of file FileLocker.h.
Referenced by hasLock().
1.9.1