Compatibility Macros

Macros
#define	MDB_DEVEL   0
#define	mdb_func_   "<mdb_unknown>"
#define	MDB_NO_ROOT   (MDB_LAST_ERRCODE + 10)
#define	MDB_USE_ROBUST   1
#define	THREAD_RET   void *
#define	THREAD_CREATE(thr, start, arg)   pthread_create(&thr,NULL,start,arg)
#define	THREAD_FINISH(thr)   pthread_join(thr,NULL)
#define	Z   "z"
#define	MDB_PIDLOCK   1
#define	LOCK_MUTEX0(mutex)   pthread_mutex_lock(mutex)
#define	UNLOCK_MUTEX(mutex)   pthread_mutex_unlock(mutex)
#define	mdb_mutex_consistent(mutex)   pthread_mutex_consistent(mutex)
#define	ErrCode()   errno
#define	HANDLE   int
#define	INVALID_HANDLE_VALUE   (-1)
#define	GET_PAGESIZE(x)   ((x) = sysconf(_SC_PAGE_SIZE))
#define	MNAME_LEN   (sizeof(pthread_mutex_t))
typedef pthread_mutex_t	mdb_mutex_t [1]
typedef pthread_mutex_t *	mdb_mutexref_t

Detailed Description

A bunch of macros to minimize the amount of platform-specific ifdefs needed throughout the rest of the code. When the features this library needs are similar enough to POSIX to be hidden in a one-or-two line replacement, this macro approach is used.

Macro Definition Documentation

#define MDB_DEVEL   0

Features under development

#define mdb_func_   "<mdb_unknown>"

Wrapper around func, which is a C99 feature

#define MDB_USE_ROBUST   1

Some platforms define the EOWNERDEAD error code even though they don't support Robust Mutexes. Compile with -DMDB_USE_ROBUST=0, or use some other mechanism like -DMDB_USE_SYSV_SEM instead of -DMDB_USE_POSIX_MUTEX. (SysV semaphores are also Robust, but some systems don't support them either.)

#define Z   "z"

printf format modifier for size_t

#define MDB_PIDLOCK   1

For MDB_LOCK_FORMAT: True if readers take a pid lock in the lockfile

#define LOCK_MUTEX0

(

mutex

)

pthread_mutex_lock(mutex)

Lock the reader or writer mutex. Returns 0 or a code to give mdb_mutex_failed(), as in LOCK_MUTEX().

#define UNLOCK_MUTEX

(

mutex

)

pthread_mutex_unlock(mutex)

Unlock the reader or writer mutex.

#define mdb_mutex_consistent

(

mutex

)

pthread_mutex_consistent(mutex)

Mark mutex-protected data as repaired, after death of previous owner.

#define ErrCode

(

)

errno

Get the error code for the last failed system function.

#define HANDLE   int

An abstraction for a file handle. On POSIX systems file handles are small integers. On Windows they're opaque pointers.

#define INVALID_HANDLE_VALUE   (-1)

A value for an invalid file handle. Mainly used to initialize file variables and signify that they are unused.

#define GET_PAGESIZE

(

x

)

((x) = sysconf(_SC_PAGE_SIZE))

Get the size of a memory page for the system. This is the basic size that the platform's memory manager uses, and is fundamental to the use of memory-mapped files.

Typedef Documentation

typedef pthread_mutex_t mdb_mutex_t[1]

Shared mutex/semaphore as it is stored (mdb_mutex_t), and as local variables keep it (mdb_mutexref_t).

When #mdb_mutexref_t is a pointer declaration and mdb_mutex_t is not, then it is array[size 1] so it can be assigned to a pointer.