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getpagesize.c
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C/C++ Source or Header
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1995-05-23
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2KB
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90 lines
/* Emulation of getpagesize() for systems that need it. */
/*
NAME
getpagesize -- return the number of bytes in page of memory
SYNOPSIS
int getpagesize (void)
DESCRIPTION
Returns the number of bytes in a page of memory. This is the
granularity of many of the system memory management routines.
No guarantee is made as to whether or not it is the same as the
basic memory management hardware page size.
BUGS
Is intended as a reasonable replacement for systems where this
is not provided as a system call. The value of 4096 may or may
not be correct for the systems where it is returned as the default
value.
*/
#ifndef VMS
#include <sys/types.h>
#ifndef NO_SYS_PARAM_H
#include <sys/param.h>
#endif
#ifdef HAVE_SYSCONF
#include <unistd.h>
#define GNU_OUR_PAGESIZE sysconf(_SC_PAGESIZE)
#else
#ifdef PAGESIZE
#define GNU_OUR_PAGESIZE PAGESIZE
#else /* no PAGESIZE */
#ifdef EXEC_PAGESIZE
#define GNU_OUR_PAGESIZE EXEC_PAGESIZE
#else /* no EXEC_PAGESIZE */
#ifdef NBPG
#define GNU_OUR_PAGESIZE (NBPG * CLSIZE)
#ifndef CLSIZE
#define CLSIZE 1
#endif /* CLSIZE */
#else /* no NBPG */
#ifdef NBPC
#define GNU_OUR_PAGESIZE NBPC
#else /* no NBPC */
#define GNU_OUR_PAGESIZE 4096 /* Just punt and use reasonable value */
#endif /* NBPC */
#endif /* NBPG */
#endif /* EXEC_PAGESIZE */
#endif /* PAGESIZE */
#endif /* HAVE_SYSCONF */
int
getpagesize ()
{
return (GNU_OUR_PAGESIZE);
}
#else /* VMS */
#if 0 /* older distributions of gcc-vms are missing <syidef.h> */
#include <syidef.h>
#endif
#ifndef SYI$_PAGE_SIZE /* VMS V5.4 and earlier didn't have this yet */
#define SYI$_PAGE_SIZE 4452
#endif
extern unsigned long lib$getsyi(const unsigned short *,...);
int getpagesize ()
{
long pagsiz = 0L;
unsigned short itmcod = SYI$_PAGE_SIZE;
(void) lib$getsyi (&itmcod, (void *) &pagsiz);
if (pagsiz == 0L)
pagsiz = 512L; /* VAX default */
return (int) pagsiz;
}
#endif /* VMS */