Include/pyport.h

/***********************************************************
Copyright (c) 2000, BeOpen.com.
All rights reserved.

See the file "Misc/COPYRIGHT" for information on usage and
redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
******************************************************************/

#ifndef Py_PYPORT_H
#define Py_PYPORT_H

/**************************************************************************
Symbols and macros to supply platform-independent interfaces to basic
C language & library operations whose spellings vary across platforms.

Please try to make documentation here as clear as possible:  by definition,
the stuff here is trying to illuminate C's darkest corners.

Config #defines referenced here:

SIGNED_RIGHT_SHIFT_ZERO_FILLS
Meaning:  To be defined iff i>>j does not extend the sign bit when i is a
          signed integral type and i < 0.
Used in:  Py_ARITHMETIC_RIGHT_SHIFT

Py_DEBUG
Meaning:  Extra checks compiled in for debug mode.
Used in:  Py_SAFE_DOWNCAST
**************************************************************************/


#ifdef __cplusplus
extern "C" {
#endif

/* Py_ARITHMETIC_RIGHT_SHIFT
 * C doesn't define whether a right-shift of a signed integer sign-extends
 * or zero-fills.  Here a macro to force sign extension:
 * Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J)
 *    Return I >> J, forcing sign extension.
 * Requirements:
 *    I is of basic signed type TYPE (char, short, int, long, or long long).
 *    TYPE is one of char, short, int, long, or long long, although long long
 *    must not be used except on platforms that support it.
 *    J is an integer >= 0 and strictly less than the number of bits in TYPE
 *    (because C doesn't define what happens for J outside that range either).
 * Caution:
 *    I may be evaluated more than once.
 */
#ifdef SIGNED_RIGHT_SHIFT_ZERO_FILLS
#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) \
	((I) < 0 ? ~((~(unsigned TYPE)(I)) >> (J)) : (I) >> (J))
#else
#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) ((I) >> (J))
#endif

/* Py_FORCE_EXPANSION
 * "Simply" returns its argument.  However, macro expansions within the
 * argument are evaluated.  This unfortunate trickery is needed to get
 * token-pasting to work as desired in some cases.
 */
#define Py_FORCE_EXPANSION(X) X

/* Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW)
 * Cast VALUE to type NARROW from type WIDE.  In Py_DEBUG mode, this
 * assert-fails if any information is lost.
 * Caution:
 *    VALUE may be evaluated more than once.
 */
#ifdef Py_DEBUG
#define Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW) \
	(assert((WIDE)(NARROW)(VALUE) == (VALUE)), (NARROW)(VALUE))
#else
#define Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW) (NARROW)(VALUE)
#endif



/**************************************************************************
Prototypes that are missing from the standard include files on some systems
(and possibly only some versions of such systems.)

Please be conservative with adding new ones, document them and enclose them
in platform-specific #ifdefs.
**************************************************************************/

#ifdef SOLARIS
/* Unchecked */
extern int gethostname(char *, int);
#endif

#ifdef __BEOS__
/* Unchecked */
/* It's in the libs, but not the headers... - [cjh] */
int shutdown( int, int ); 
#endif

#ifdef HAVE__GETPTY
/* Unchecked */
extern char * _getpty(int *, int, mode_t, int);
#endif

#if defined(HAVE_OPENPTY) || defined(HAVE_FORKPTY)
#if !defined(HAVE_PTY_H) && !defined(HAVE_LIBUTIL_H)
/* BSDI does not supply a prototype for the 'openpty' and 'forkpty'
   functions, even though they are included in libutil. */
#include <termios.h>
extern int openpty(int *, int *, char *, struct termios *, struct winsize *);
extern int forkpty(int *, char *, struct termios *, struct winsize *);
#endif /* !defined(HAVE_PTY_H) && !defined(HAVE_LIBUTIL_H) */
#endif /* defined(HAVE_OPENPTY) || defined(HAVE_FORKPTY) */


/* These are pulled from various places. It isn't obvious on what platforms
   they are necessary, nor what the exact prototype should look like (which
   is likely to vary between platforms!) If you find you need one of these
   declarations, please move them to a platform-specific block and include
   proper prototypes. */
#if 0

/* From Modules/resource.c */
extern int getrusage();
extern int getpagesize();

/* From Python/sysmodule.c and Modules/posixmodule.c */
extern int fclose(FILE *);

/* From Modules/posixmodule.c */
extern int fdatasync(int);
/* XXX These are supposedly for SunOS4.1.3 but "shouldn't hurt elsewhere" */
extern int rename(const char *, const char *);
extern int pclose(FILE *);
extern int lstat(const char *, struct stat *);
extern int symlink(const char *, const char *);
extern int fsync(int fd);

#endif /* 0 */

#ifdef __cplusplus
}
#endif

#endif /* Py_PYPORT_H */