# HG changeset patch
# User Mike Becker <universe@uap-core.de>
# Date 1764947499 -3600
# Node ID 2cbdb482d325dec3c8e0fec2eaa34690c6b9be5b
# Parent  fd948e5af26eb82763a5ccc9aca1642e8fbc8a44
add cx_system_page_size() to allocator.h

resolves #763

diff -r fd948e5af26e -r 2cbdb482d325 CHANGELOG
--- a/CHANGELOG	Thu Dec 04 18:57:54 2025 +0100
+++ b/CHANGELOG	Fri Dec 05 16:11:39 2025 +0100
@@ -1,3 +1,8 @@
+Version 4.0 - tbd
+------------------------
+
+* adds cx_system_page_size() to allocator.h
+
 Version 3.2 - 2025-11-30
 ------------------------
 
diff -r fd948e5af26e -r 2cbdb482d325 docs/Writerside/topics/about.md
--- a/docs/Writerside/topics/about.md	Thu Dec 04 18:57:54 2025 +0100
+++ b/docs/Writerside/topics/about.md	Fri Dec 05 16:11:39 2025 +0100
@@ -26,6 +26,10 @@
 
 ## Changelog
 
+### Version 4.0 - preview {collapsible="true"}
+
+* adds cx_system_page_size() to allocator.h
+
 ### Version 3.2 - 2025-11-30 {collapsible="true"}
 
 * adds cxMempoolTransfer() and cxMempoolTransferObject()
diff -r fd948e5af26e -r 2cbdb482d325 docs/Writerside/topics/allocator.h.md
--- a/docs/Writerside/topics/allocator.h.md	Thu Dec 04 18:57:54 2025 +0100
+++ b/docs/Writerside/topics/allocator.h.md	Fri Dec 05 16:11:39 2025 +0100
@@ -40,6 +40,8 @@
     
 void cxFree(const CxAllocator *allocator, void *mem);
 
+void cx_system_page_size(void);
+
 void *cx_zalloc(size_t n);
 
 int cx_reallocate(void **mem, size_t n);
@@ -105,6 +107,9 @@
 > with the **same** allocator that was used to allocate the memory.
 {style="warning"}
 
+The function `cx_system_page_size()` offers a cross-platform way to retrieve the memory page size in bytes.
+If, for some reason, the page size cannot be determined, a default of 4096 bytes is returned.
+
 ## Custom Allocator
 
 If you want to define your own allocator, you need to initialize the `CxAllocator` structure
diff -r fd948e5af26e -r 2cbdb482d325 docs/Writerside/writerside.cfg
--- a/docs/Writerside/writerside.cfg	Thu Dec 04 18:57:54 2025 +0100
+++ b/docs/Writerside/writerside.cfg	Fri Dec 05 16:11:39 2025 +0100
@@ -5,5 +5,5 @@
     <topics dir="topics" web-path="topics"/>
     <categories src="c.list"/>
     <images dir="images" web-path="images"/>
-    <instance src="ucx.tree" version="3.2"/>
+    <instance src="ucx.tree" version="4.0"/>
 </ihp>
\ No newline at end of file
diff -r fd948e5af26e -r 2cbdb482d325 src/allocator.c
--- a/src/allocator.c	Thu Dec 04 18:57:54 2025 +0100
+++ b/src/allocator.c	Fri Dec 05 16:11:39 2025 +0100
@@ -31,6 +31,35 @@
 #include <errno.h>
 #include <string.h>
 
+#ifdef _WIN32
+#include <Windows.h>
+#include <sysinfoapi.h>
+unsigned long system_page_size(void) {
+    static unsigned long ps = 0;
+    if (ps == 0) {
+        SYSTEM_INFO sysinfo;
+        GetSystemInfo(&sysinfo);
+        ps = (unsigned long) sysinfo.dwPageSize;
+    }
+    return ps;
+}
+#else
+#include <unistd.h>
+unsigned long system_page_size(void) {
+    static unsigned long ps = 0;
+    if (ps == 0) {
+        long sc = sysconf(_SC_PAGESIZE);
+        if (sc < 0) {
+            // fallback for systems which do not report a value here
+            ps = 4096; // LCOV_EXCL_LINE
+        } else {
+            ps = (unsigned long) sc;
+        }
+    }
+    return ps;
+}
+#endif
+
 static void *cx_malloc_stdlib(
         cx_attr_unused void *d,
         size_t n
diff -r fd948e5af26e -r 2cbdb482d325 src/buffer.c
--- a/src/buffer.c	Thu Dec 04 18:57:54 2025 +0100
+++ b/src/buffer.c	Fri Dec 05 16:11:39 2025 +0100
@@ -32,35 +32,6 @@
 #include <string.h>
 #include <errno.h>
 
-#ifdef _WIN32
-#include <Windows.h>
-#include <sysinfoapi.h>
-static unsigned long system_page_size(void) {
-    static unsigned long ps = 0;
-    if (ps == 0) {
-        SYSTEM_INFO sysinfo;
-        GetSystemInfo(&sysinfo);
-        ps = sysinfo.dwPageSize;
-    }
-    return ps;
-}
-#else
-#include <unistd.h>
-static unsigned long system_page_size(void) {
-    static unsigned long ps = 0;
-    if (ps == 0) {
-        long sc = sysconf(_SC_PAGESIZE);
-        if (sc < 0) {
-            // fallback for systems which do not report a value here
-            ps = 4096; // LCOV_EXCL_LINE
-        } else {
-            ps = (unsigned long) sc;
-        }
-    }
-    return ps;
-}
-#endif
-
 static int buffer_copy_on_write(CxBuffer* buffer) {
     if (0 == (buffer->flags & CX_BUFFER_COPY_ON_WRITE)) return 0;
     void *newspace = cxMalloc(buffer->allocator, buffer->capacity);
@@ -262,7 +233,7 @@
 }
 
 static size_t cx_buffer_calculate_minimum_capacity(size_t mincap) {
-    unsigned long pagesize = system_page_size();
+    unsigned long pagesize = cx_system_page_size();
     // if page size is larger than 64 KB - for some reason - truncate to 64 KB
     if (pagesize > 65536) pagesize = 65536;
     if (mincap < pagesize) {
diff -r fd948e5af26e -r 2cbdb482d325 src/cx/allocator.h
--- a/src/cx/allocator.h	Thu Dec 04 18:57:54 2025 +0100
+++ b/src/cx/allocator.h	Fri Dec 05 16:11:39 2025 +0100
@@ -146,6 +146,17 @@
                              const CxAllocator *allocator, void *data);
 
 /**
+ * Returns the system's memory page size.
+ *
+ * If the page size cannot be retrieved from the system,
+ * a default of 4096 bytes is assumed.
+ *
+ * @return the system's memory page size in bytes
+ */
+cx_attr_nodiscard
+CX_EXPORT unsigned long cx_system_page_size(void);
+
+/**
  * Reallocate a previously allocated block and changes the pointer in-place,
  * if necessary.
  *
diff -r fd948e5af26e -r 2cbdb482d325 tests/test_buffer.c
--- a/tests/test_buffer.c	Thu Dec 04 18:57:54 2025 +0100
+++ b/tests/test_buffer.c	Fri Dec 05 16:11:39 2025 +0100
@@ -32,35 +32,6 @@
 
 #include "cx/buffer.h"
 
-#ifdef _WIN32
-#include <Windows.h>
-#include <sysinfoapi.h>
-static unsigned long system_page_size(void) {
-    static unsigned long ps = 0;
-    if (ps == 0) {
-        SYSTEM_INFO sysinfo;
-        GetSystemInfo(&sysinfo);
-        ps = sysinfo.dwPageSize;
-    }
-    return ps;
-}
-#else
-#include <unistd.h>
-static unsigned long system_page_size(void) {
-    static unsigned long ps = 0;
-    if (ps == 0) {
-        long sc = sysconf(_SC_PAGESIZE);
-        if (sc < 0) {
-            // fallback for systems which do not report a value here
-            ps = 4096; // LCOV_EXCL_LINE
-        } else {
-            ps = (unsigned long) sc;
-        }
-    }
-    return ps;
-}
-#endif
-
 CX_TEST(test_buffer_init_wrap_space) {
     CxTestingAllocator talloc;
     cx_testing_allocator_init(&talloc);
@@ -234,8 +205,8 @@
         CX_TEST_ASSERT(buf.capacity == 256);
 
         // greater than page size, new capacity should be multiple of pagesize
-        cxBufferMinimumCapacity(&buf, system_page_size() + 200);
-        CX_TEST_ASSERT(buf.capacity == system_page_size()*2);
+        cxBufferMinimumCapacity(&buf, cx_system_page_size() + 200);
+        CX_TEST_ASSERT(buf.capacity == cx_system_page_size()*2);
 
         cxBufferDestroy(&buf);
         CX_TEST_ASSERT(cx_testing_allocator_verify(&talloc));