From: Matthew Fernandez <matthew.fernandez@gmail.com>
Date: Sun, 16 Oct 2022 21:48:06 +0000 (-0700)
Subject: sfio: use a more portable way of determining page size
X-Git-Tag: 7.0.2~19^2~1
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fc890507da4c25ceb0493c5cccbd1648fe0338c8;p=graphviz

sfio: use a more portable way of determining page size

This code was using a legacy API, `getpagesize`, to opportunistically find the
system virtual memory page size. This change updates to the newer POSIX
`sysconf` API that is available almost everywhere, and adds a workaround for
Windows. This code now has an accurate understanding of the page size on
platforms that did not have `getpagesize` (of which, Windows was one), rather
than falling back on 8192.
---

diff --git a/cmake/config_checks.cmake b/cmake/config_checks.cmake
index 135df6b5e..ab4150d95 100644
--- a/cmake/config_checks.cmake
+++ b/cmake/config_checks.cmake
@@ -20,7 +20,6 @@ include(CheckFunctionExists)
 
 check_function_exists( dl_iterate_phdr  HAVE_DL_ITERATE_PHDR )
 check_function_exists( drand48          HAVE_DRAND48         )
-check_function_exists( getpagesize      HAVE_GETPAGESIZE     )
 check_function_exists( lrand48          HAVE_LRAND48         )
 check_function_exists( setenv           HAVE_SETENV          )
 check_function_exists( setmode          HAVE_SETMODE         )
diff --git a/config-cmake.h.in b/config-cmake.h.in
index 485450354..af276ecac 100644
--- a/config-cmake.h.in
+++ b/config-cmake.h.in
@@ -16,7 +16,6 @@
 // Functions
 #cmakedefine HAVE_DL_ITERATE_PHDR
 #cmakedefine HAVE_DRAND48
-#cmakedefine HAVE_GETPAGESIZE
 #cmakedefine HAVE_LRAND48
 #cmakedefine HAVE_SETENV
 #cmakedefine HAVE_SETMODE
diff --git a/configure.ac b/configure.ac
index 9c667e714..82f7e4a15 100644
--- a/configure.ac
+++ b/configure.ac
@@ -465,7 +465,6 @@ LIBS=$save_LIBS
 
 # Checks for library functions
 AC_CHECK_FUNCS([lrand48 drand48 srand48 setmode setenv \
-	getpagesize \
   ftruncate lseek64 stat64 select dl_iterate_phdr])
 
 AC_REPLACE_FUNCS([strcasestr])
diff --git a/lib/sfio/sfhdr.h b/lib/sfio/sfhdr.h
index 8c80b1b95..0ca76f3f0 100644
--- a/lib/sfio/sfhdr.h
+++ b/lib/sfio/sfhdr.h
@@ -313,7 +313,6 @@ extern "C" {
 
 /* grain size for buffer increment */
 #define SF_GRAIN	1024
-#define SF_PAGE		((ssize_t)(SF_GRAIN*sizeof(int)*2))
 
 /* when the buffer is empty, certain io requests may be better done directly
    on the given application buffers. The below condition determines when.
diff --git a/lib/sfio/sfsetbuf.c b/lib/sfio/sfsetbuf.c
index a4dceb0af..2e219b9f2 100644
--- a/lib/sfio/sfsetbuf.c
+++ b/lib/sfio/sfsetbuf.c
@@ -10,10 +10,23 @@
 
 #include <stddef.h>
 #include	<sfio/sfhdr.h>
+#include <unistd.h>
 
-#ifdef HAVE_GETPAGESIZE
-	extern int getpagesize(void);
+#ifdef _WIN32
+#include <windows.h>
+#include <sysinfoapi.h>
 #endif
+
+static ssize_t get_page_size(void) {
+#ifdef _WIN32
+  SYSTEM_INFO info;
+  GetSystemInfo(&info);
+  return (ssize_t)info.dwPageSize;
+#else
+  return (ssize_t)sysconf(_SC_PAGESIZE);
+#endif
+}
+
 /*	Set a (new) buffer for a stream.
 **	If size < 0, it is assigned a suitable value depending on the
 **	kind of stream. The actual buffer size allocated is dependent
@@ -185,10 +198,7 @@ void *sfsetbuf(Sfio_t * f, void * buf, size_t size)
 
 	/* set page size, this is also the desired default buffer size */
 	if (_Sfpage <= 0) {
-#ifdef HAVE_GETPAGESIZE
-	    if ((_Sfpage = (size_t) getpagesize()) <= 0)
-#endif
-		_Sfpage = SF_PAGE;
+		_Sfpage = get_page_size();
 	}
     }