stream_MT(3CC4)stream_MT(3CC4)NAMEstream_MT - base class to provide dynamic changing of iostream class
objects to and from MT safety.
SYNOPSIS
#include <rlocks.h>
typedef char stream_bool_t;
class stream_MT {
public:
enum { unsafe_object=0, safe_object=1 };
stream_MT();
stream_MT(stream_bool_t);
stream_bool_t test_safe_flag();
void set_safe_flag(stream_bool_t);
friend class stream_locker;
};
DESCRIPTION
Class stream_MT is a base class that allows the iostream classes in
libC to work correctly in a multi-threaded environment. The classes ios
and streambuf are derived from stream_MT.
The multi-thread (MT) safety of an iostream object can be dynamically
changed by setting a safe flag using the member function:
set_safe_flag(). An argument with the value of stream_MT::safe_object
sets the iostream object to be MT safe, an argument with the value of
stream_MT::unsafe_object sets the object to be MT-unsafe. The current
state of the iostream object can be determined by the member function:
test_safe_flag(). When an iostream object is MT safe there is a certain
amount of overhead associated with internal locking in the object. The
overhead can be avoided by setting the safe flag to zero which disables
internal locking.
Constructors
stream_MT();
By default the safe_flag of the class object is set to
stream_MT::safe_object
stream_MT(stream_bool_t);
The default can be changed by providing an explicit value for
the safe flag.
Member functions
stream_bool_t test_safe_flag();
Returns the current value of the safe flag. A value other than
stream_MT::unsafe_object indicates the iostream object is MT
safe and locking is enabled.
void set_safe_flag(stream_bool_t);
Sets the internal safe flag of the iostream object to the value
given as an argument. Setting the value to non-zero enables
locking and makes the object MT safe. Setting the value to zero
does the reverse.
SEE ALSO
C++ Library Reference
Chapter 4, "Using Classic iostream in a Multithreaded Environ‐
ment."
18 June 1998 stream_MT(3CC4)
