Minor optimization to allocateSpace().

FossilOrigin-Name: d007bc339b9ea6d59a3dd2b0c5e77e9c801b16f6

manifest

@@ -1,5 +1,5 @@
-C Enhance\sthe\sBtree\sobject\sto\sremember\swhether\sor\snot\sit\sis\sholding\san\nIncrblob\scursor.\s\sUse\sthis\sknowledge\sto\simprove\sperformance\sin\sthe\scommon\ncase\swhere\sit\sdoes\snot.
-D 2015-06-25T13:03:10.554
+C Minor\soptimization\sto\sallocateSpace().
+D 2015-06-25T15:04:56.778
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 1063c58075b7400d93326b0eb332b48a54f53025
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -192,7 +192,7 @@ F src/auth.c b56c78ebe40a2110fd361379f7e8162d23f92240
 F src/backup.c ff743689c4d6c5cb55ad42ed9d174b2b3e71f1e3
 F src/bitvec.c 5eb7958c3bf65210211cbcfc44eff86d0ded7c9d
 F src/btmutex.c 45a968cc85afed9b5e6cf55bf1f42f8d18107f79
-F src/btree.c 8a4109bdc6993507e95e3b377917a51a33b47027
+F src/btree.c 8910b2a624c7fcf06060442155ba81ed673f28fa
 F src/btree.h 969adc948e89e449220ff0ff724c94bb2a52e9f1
 F src/btreeInt.h fdd1aff02fb2a63812bd95716e7f579fc3759107
 F src/build.c b3f15255d5b16e42dafeaa638fd4f8a47c94ed70
@@ -1286,7 +1286,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 3ee888beb974e015bd11ae79381b208eaa310f6f
-R 0fbef3ab0e1cedf4de8407e78df7b662
+P 476b11563c08c6d9c0abd69e4d865c4edcdd45f5
+R 839b3c203557349d49b4237a455fedf1
 U drh
-Z 765ae28d6062dc43145a9a4098bd20e0
+Z 4ce9d033e6697dcd53f95c95d2de46fc

manifest.uuid

@@ -1 +1 @@
-476b11563c08c6d9c0abd69e4d865c4edcdd45f5
+d007bc339b9ea6d59a3dd2b0c5e77e9c801b16f6

src/btree.c

@@ -1440,9 +1440,14 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
   ** then the cell content offset of an empty page wants to be 65536.
   ** However, that integer is too large to be stored in a 2-byte unsigned
   ** integer, so a value of 0 is used in its place. */
-  top = get2byteNotZero(&data[hdr+5]);
-  if( gap>top || (u32)top>pPage->pBt->usableSize ){
-    return SQLITE_CORRUPT_BKPT;
+  top = get2byte(&data[hdr+5]);
+  assert( top<=pPage->pBt->usableSize ); /* Prevent by getAndInitPage() */
+  if( gap>top ){
+    if( top==0 && pPage->pBt->usableSize==65536 ){
+      top = 65536;
+    }else{
+      return SQLITE_CORRUPT_BKPT;
+    }
   }
 
   /* If there is enough space between gap and top for one more cell pointer