Fix the handling of reserve-bytes so that the maximum value of 255 can be used.

FossilOrigin-Name: 99749d4fd4930ccf15227f67c732266af9e09dd3cabdc0834fb450ef98196441

src/backup.c

@@ -112,7 +112,7 @@ static Btree *findBtree(sqlite3 *pErrorDb, sqlite3 *pDb, const char *zDb){
 */
 static int setDestPgsz(sqlite3_backup *p){
   int rc;
-  rc = sqlite3BtreeSetPageSize(p->pDest,sqlite3BtreeGetPageSize(p->pSrc),-1,0);
+  rc = sqlite3BtreeSetPageSize(p->pDest,sqlite3BtreeGetPageSize(p->pSrc),0,0);
   return rc;
 }
 

src/btree.c

@@ -2856,19 +2856,17 @@ int sqlite3BtreeSetPagerFlags(
 */
 int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
   int rc = SQLITE_OK;
+  int x;
   BtShared *pBt = p->pBt;
-  assert( nReserve>=-1 && nReserve<=254 );
+  assert( nReserve>=0 && nReserve<=255 );
   sqlite3BtreeEnter(p);
-  if( nReserve>=0 ){
-    pBt->nReserveWanted = nReserve + 1;
-  }
+  pBt->nReserveWanted = nReserve;
+  x = pBt->pageSize - pBt->usableSize;
+  if( nReserve<x ) nReserve = x;
   if( pBt->btsFlags & BTS_PAGESIZE_FIXED ){
     sqlite3BtreeLeave(p);
     return SQLITE_READONLY;
   }
-  if( nReserve<0 ){
-    nReserve = pBt->pageSize - pBt->usableSize;
-  }
   assert( nReserve>=0 && nReserve<=255 );
   if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
         ((pageSize-1)&pageSize)==0 ){
@@ -2919,12 +2917,12 @@ int sqlite3BtreeGetReserveNoMutex(Btree *p){
 ** The amount of reserve can only grow - never shrink.
 */
 int sqlite3BtreeGetRequestedReserve(Btree *p){
-  int n;
+  int n1, n2;
   sqlite3BtreeEnter(p);
-  n = ((int)p->pBt->nReserveWanted) - 1;
-  if( n<0 ) n = sqlite3BtreeGetReserveNoMutex(p);
+  n1 = (int)p->pBt->nReserveWanted;
+  n2 = sqlite3BtreeGetReserveNoMutex(p);
   sqlite3BtreeLeave(p);
-  return n;
+  return n1>n2 ? n1 : n2;
 }
 
 

src/btreeInt.h

@@ -417,7 +417,7 @@ struct BtShared {
 #endif
   u8 inTransaction;     /* Transaction state */
   u8 max1bytePayload;   /* Maximum first byte of cell for a 1-byte payload */
-  u8 nReserveWanted;    /* 1 more than desired number of extra bytes per page */
+  u8 nReserveWanted;    /* Desired number of extra bytes per page */
   u16 btsFlags;         /* Boolean parameters.  See BTS_* macros below */
   u16 maxLocal;         /* Maximum local payload in non-LEAFDATA tables */
   u16 minLocal;         /* Minimum local payload in non-LEAFDATA tables */

src/build.c

@@ -4630,7 +4630,7 @@ int sqlite3OpenTempDatabase(Parse *pParse){
     }
     db->aDb[1].pBt = pBt;
     assert( db->aDb[1].pSchema );
-    if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, -1, 0) ){
+    if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, 0, 0) ){
       sqlite3OomFault(db);
       return 1;
     }

src/main.c

@@ -3854,7 +3854,7 @@ int sqlite3_file_control(sqlite3 *db, const char *zDbName, int op, void *pArg){
     }else if( op==SQLITE_FCNTL_RESERVE_BYTES ){
       int iNew = *(int*)pArg;
       *(int*)pArg = sqlite3BtreeGetRequestedReserve(pBtree);
-      if( iNew>=0 && iNew<=254 ){
+      if( iNew>=0 && iNew<=255 ){
         sqlite3BtreeSetPageSize(pBtree, 0, iNew, 0);
       }
       rc = SQLITE_OK;

src/pragma.c

@@ -555,7 +555,7 @@ void sqlite3Pragma(
       ** buffer that the pager module resizes using sqlite3_realloc().
       */
       db->nextPagesize = sqlite3Atoi(zRight);
-      if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize,-1,0) ){
+      if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize,0,0) ){
         sqlite3OomFault(db);
       }
     }

src/vacuum.c

@@ -377,7 +377,7 @@ end_of_vacuum:
   db->nChange = saved_nChange;
   db->nTotalChange = saved_nTotalChange;
   db->mTrace = saved_mTrace;
-  sqlite3BtreeSetPageSize(pMain, -1, -1, 1);
+  sqlite3BtreeSetPageSize(pMain, -1, 0, 1);
 
   /* Currently there is an SQL level transaction open on the vacuum
   ** database. No locks are held on any other files (since the main file