Add const qualifiers to bufpage.h

This makes use of the new PageData type.

PageGetSpecialPointer() had to be turned back into a macro, because it
is used in a way that sometimes it takes const and returns const and
sometimes takes non-const and returns non-const.

Discussion: https://www.postgresql.org/message-id/flat/692ee0da-49da-4d32-8dca-da224cc2800e@eisentraut.org

1 files changed, 37 insertions, 38 deletions

diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h
index c28ec1fb1d7..d06208b7ce6 100644
--- a/src/include/storage/bufpage.h
+++ b/src/include/storage/bufpage.h
@@ -222,9 +222,9 @@ typedef PageHeaderData *PageHeader;
  *		returns true iff no itemid has been allocated on the page
  */
 static inline bool
-PageIsEmpty(Page page)
+PageIsEmpty(const PageData *page)
 {
-	return ((PageHeader) page)->pd_lower <= SizeOfPageHeaderData;
+	return ((const PageHeaderData *) page)->pd_lower <= SizeOfPageHeaderData;
 }
 
 /*
@@ -232,9 +232,9 @@ PageIsEmpty(Page page)
  *		returns true iff page has not been initialized (by PageInit)
  */
 static inline bool
-PageIsNew(Page page)
+PageIsNew(const PageData *page)
 {
-	return ((PageHeader) page)->pd_upper == 0;
+	return ((const PageHeaderData *) page)->pd_upper == 0;
 }
 
 /*
@@ -275,9 +275,9 @@ PageGetContents(Page page)
  * however, it can be called on a page that is not stored in a buffer.
  */
 static inline Size
-PageGetPageSize(Page page)
+PageGetPageSize(const PageData *page)
 {
-	return (Size) (((PageHeader) page)->pd_pagesize_version & (uint16) 0xFF00);
+	return (Size) (((const PageHeaderData *) page)->pd_pagesize_version & (uint16) 0xFF00);
 }
 
 /*
@@ -285,9 +285,9 @@ PageGetPageSize(Page page)
  *		Returns the page layout version of a page.
  */
 static inline uint8
-PageGetPageLayoutVersion(Page page)
+PageGetPageLayoutVersion(const PageData *page)
 {
-	return (((PageHeader) page)->pd_pagesize_version & 0x00FF);
+	return (((const PageHeaderData *) page)->pd_pagesize_version & 0x00FF);
 }
 
 /*
@@ -315,9 +315,9 @@ PageSetPageSizeAndVersion(Page page, Size size, uint8 version)
  *		Returns size of special space on a page.
  */
 static inline uint16
-PageGetSpecialSize(Page page)
+PageGetSpecialSize(const PageData *page)
 {
-	return (PageGetPageSize(page) - ((PageHeader) page)->pd_special);
+	return (PageGetPageSize(page) - ((const PageHeaderData *) page)->pd_special);
 }
 
 /*
@@ -326,23 +326,22 @@ PageGetSpecialSize(Page page)
  * This is intended to catch use of the pointer before page initialization.
  */
 static inline void
-PageValidateSpecialPointer(Page page)
+PageValidateSpecialPointer(const PageData *page)
 {
 	Assert(page);
-	Assert(((PageHeader) page)->pd_special <= BLCKSZ);
-	Assert(((PageHeader) page)->pd_special >= SizeOfPageHeaderData);
+	Assert(((const PageHeaderData *) page)->pd_special <= BLCKSZ);
+	Assert(((const PageHeaderData *) page)->pd_special >= SizeOfPageHeaderData);
 }
 
 /*
  * PageGetSpecialPointer
  *		Returns pointer to special space on a page.
  */
-static inline char *
-PageGetSpecialPointer(Page page)
-{
-	PageValidateSpecialPointer(page);
-	return (char *) page + ((PageHeader) page)->pd_special;
-}
+#define PageGetSpecialPointer(page) \
+( \
+	PageValidateSpecialPointer(page), \
+	((page) + ((PageHeader) (page))->pd_special) \
+)
 
 /*
  * PageGetItem
@@ -353,12 +352,12 @@ PageGetSpecialPointer(Page page)
  *		The semantics may change in the future.
  */
 static inline Item
-PageGetItem(Page page, ItemId itemId)
+PageGetItem(const PageData *page, const ItemIdData *itemId)
 {
 	Assert(page);
 	Assert(ItemIdHasStorage(itemId));
 
-	return (Item) (((char *) page) + ItemIdGetOffset(itemId));
+	return (Item) (((const char *) page) + ItemIdGetOffset(itemId));
 }
 
 /*
@@ -371,9 +370,9 @@ PageGetItem(Page page, ItemId itemId)
  *		return zero to ensure sane behavior.
  */
 static inline OffsetNumber
-PageGetMaxOffsetNumber(Page page)
+PageGetMaxOffsetNumber(const PageData *page)
 {
-	PageHeader	pageheader = (PageHeader) page;
+	const PageHeaderData *pageheader = (const PageHeaderData *) page;
 
 	if (pageheader->pd_lower <= SizeOfPageHeaderData)
 		return 0;
@@ -385,7 +384,7 @@ PageGetMaxOffsetNumber(Page page)
  * Additional functions for access to page headers.
  */
 static inline XLogRecPtr
-PageGetLSN(const char *page)
+PageGetLSN(const PageData *page)
 {
 	return PageXLogRecPtrGet(((const PageHeaderData *) page)->pd_lsn);
 }
@@ -396,9 +395,9 @@ PageSetLSN(Page page, XLogRecPtr lsn)
 }
 
 static inline bool
-PageHasFreeLinePointers(Page page)
+PageHasFreeLinePointers(const PageData *page)
 {
-	return ((PageHeader) page)->pd_flags & PD_HAS_FREE_LINES;
+	return ((const PageHeaderData *) page)->pd_flags & PD_HAS_FREE_LINES;
 }
 static inline void
 PageSetHasFreeLinePointers(Page page)
@@ -412,9 +411,9 @@ PageClearHasFreeLinePointers(Page page)
 }
 
 static inline bool
-PageIsFull(Page page)
+PageIsFull(const PageData *page)
 {
-	return ((PageHeader) page)->pd_flags & PD_PAGE_FULL;
+	return ((const PageHeaderData *) page)->pd_flags & PD_PAGE_FULL;
 }
 static inline void
 PageSetFull(Page page)
@@ -428,9 +427,9 @@ PageClearFull(Page page)
 }
 
 static inline bool
-PageIsAllVisible(Page page)
+PageIsAllVisible(const PageData *page)
 {
-	return ((PageHeader) page)->pd_flags & PD_ALL_VISIBLE;
+	return ((const PageHeaderData *) page)->pd_flags & PD_ALL_VISIBLE;
 }
 static inline void
 PageSetAllVisible(Page page)
@@ -490,19 +489,19 @@ StaticAssertDecl(BLCKSZ == ((BLCKSZ / sizeof(size_t)) * sizeof(size_t)),
 				 "BLCKSZ has to be a multiple of sizeof(size_t)");
 
 extern void PageInit(Page page, Size pageSize, Size specialSize);
-extern bool PageIsVerifiedExtended(Page page, BlockNumber blkno, int flags);
+extern bool PageIsVerifiedExtended(const PageData *page, BlockNumber blkno, int flags);
 extern OffsetNumber PageAddItemExtended(Page page, Item item, Size size,
 										OffsetNumber offsetNumber, int flags);
-extern Page PageGetTempPage(Page page);
-extern Page PageGetTempPageCopy(Page page);
-extern Page PageGetTempPageCopySpecial(Page page);
+extern Page PageGetTempPage(const PageData *page);
+extern Page PageGetTempPageCopy(const PageData *page);
+extern Page PageGetTempPageCopySpecial(const PageData *page);
 extern void PageRestoreTempPage(Page tempPage, Page oldPage);
 extern void PageRepairFragmentation(Page page);
 extern void PageTruncateLinePointerArray(Page page);
-extern Size PageGetFreeSpace(Page page);
-extern Size PageGetFreeSpaceForMultipleTuples(Page page, int ntups);
-extern Size PageGetExactFreeSpace(Page page);
-extern Size PageGetHeapFreeSpace(Page page);
+extern Size PageGetFreeSpace(const PageData *page);
+extern Size PageGetFreeSpaceForMultipleTuples(const PageData *page, int ntups);
+extern Size PageGetExactFreeSpace(const PageData *page);
+extern Size PageGetHeapFreeSpace(const PageData *page);
 extern void PageIndexTupleDelete(Page page, OffsetNumber offnum);
 extern void PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems);
 extern void PageIndexTupleDeleteNoCompact(Page page, OffsetNumber offnum);