Change the way checksums are calculated.

FossilOrigin-Name: 84955c2e9ce526c5a3ed479aa09f093a7e37c7d0

diff --git a/manifest b/manifest
index d7f5bd5c6c4e0780ac1e7e9ce7d45d01d5870eac..4dcbaf750eacc8bec39cb61b7c7e1dc12842f0a6 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,8 +1,5 @@
------BEGIN PGP SIGNED MESSAGE-----
-Hash: SHA1
-
-C Bring\sover\sthe\srecent\squery\splanner\senhancements\sfrom\sthe\strunk.
-D 2010-04-15T02:37:11
+C Change\sthe\sway\schecksums\sare\scalculated.
+D 2010-04-15T10:58:52
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 4f2f967b7e58a35bb74fb7ec8ae90e0f4ca7868b
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -134,7 +131,7 @@ F src/journal.c b0ea6b70b532961118ab70301c00a33089f9315c
 F src/legacy.c a199d7683d60cef73089e892409113e69c23a99f
 F src/lempar.c 7f026423f4d71d989e719a743f98a1cbd4e6d99e
 F src/loadext.c 1c7a61ce1281041f437333f366a96aa0d29bb581
-F src/log.c 165addfd51fa9581936ec04914b17a3b274c49bd
+F src/log.c bf7ce56249b2a08d26b4029430c32a01efc4a64e
 F src/log.h a2654af46ce7b5732f4d5a731abfdd180f0a06d9
 F src/main.c c0e7192bad5b90544508b241eb2487ac661de890
 F src/malloc.c a08f16d134f0bfab6b20c3cd142ebf3e58235a6a
@@ -807,14 +804,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P c18077f2465fc34830f11c9832e76be5746eaeea defaf0d99a807027f8883bf821b6482025f9f54e
-R 5f5abc6d19fbeba7fb34263a5662faa7
-U drh
-Z 9dfe9b346dd22ca03d0d17a2ddbb8a3c
------BEGIN PGP SIGNATURE-----
-Version: GnuPG v1.4.6 (GNU/Linux)
-
-iD8DBQFLxnvaoxKgR168RlERAkpHAJ9umCCf7Sfy2xa1T3mJ1bqzrPY7tgCgjEA2
-oN5S7m+hWn0GMbvXKOIs1cY=
-=ADT1
------END PGP SIGNATURE-----
+P 82969f27e5ea843cb379666d8a02e4a3fddc03b2
+R b356f412a9c351edeb3f07a632ecce9f
+U dan
+Z 01a21dba5524ff578c531f4245d5f626

diff --git a/manifest.uuid b/manifest.uuid
index 232556f3c5adcc5eb51b0fc062a7354e019ccb3d..c8288d828e080165459767486409bed6b13b8a64 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-82969f27e5ea843cb379666d8a02e4a3fddc03b2
\ No newline at end of file
+84955c2e9ce526c5a3ed479aa09f093a7e37c7d0
\ No newline at end of file

diff --git a/src/log.c b/src/log.c
index 30d9d8ded6600d21701e4126cc87c61ca4839a3d..112b907f4c6ff593f2ac09d71ba518a3085e0f50 100644 (file)
--- a/src/log.c
+++ b/src/log.c
@@ -141,23 +141,21 @@ static LogSummary *pLogSummary = 0;
 */
 #define LOG_CKSM_BYTES 8
 static void logChecksumBytes(u8 *aByte, int nByte, u32 *aCksum){
-  u32 *z32 = (u32 *)aByte;
-  int n32 = nByte / sizeof(u32);
-  int i;
+  u64 sum1 = aCksum[0];
+  u64 sum2 = aCksum[1];
+  u32 *a32 = (u32 *)aByte;
+  u32 *aEnd = (u32 *)&aByte[nByte];
 
   assert( LOG_CKSM_BYTES==2*sizeof(u32) );
   assert( (nByte&0x00000003)==0 );
 
-  u32 cksum0 = aCksum[0];
-  u32 cksum1 = aCksum[1];
-
-  for(i=0; i<n32; i++){
-    cksum0 = (cksum0 >> 8) + (cksum0 ^ z32[i]);
-    cksum1 = (cksum1 >> 8) + (cksum1 ^ z32[i]);
-  }
+  do {
+    sum1 += (*a32++);
+    sum2 += sum1;
+  } while( a32<aEnd );
 
-  aCksum[0] = cksum0;
-  aCksum[1] = cksum1;
+  aCksum[0] = sum1 + (sum1>>24);
+  aCksum[1] = sum2 + (sum2>>24);
 }
 
 /*
@@ -1259,8 +1257,6 @@ void sqlite3LogCloseSnapshot(Log *pLog){
   pLog->isLocked = 0;
 }
 
-
-
 /* 
 ** Read a page from the log, if it is present. 
 */
@@ -1269,6 +1265,8 @@ int sqlite3LogRead(Log *pLog, Pgno pgno, int *pInLog, u8 *pOut){
   u32 *aData = pLog->pSummary->aData;
   int iFrame = (pLog->hdr.iLastPg & 0xFFFFFF00);
 
+  assert( pLog->isLocked );
+
   /* Do a linear search of the unindexed block of page-numbers (if any) 
   ** at the end of the log-summary. An alternative to this would be to
   ** build an index in private memory each time a read transaction is
@@ -1349,11 +1347,11 @@ int sqlite3LogWriteLock(Log *pLog, int op){
       return rc;
     }
 
-    /* If this is connection is a region D, then the SHARED lock on region
-    ** D has just been upgraded to EXCLUSIVE. But no lock at all is held on
-    ** region A. This means that if the write-transaction is committed
+    /* If this is connection is a region D reader, then the SHARED lock on 
+    ** region D has just been upgraded to EXCLUSIVE. But no lock at all is 
+    ** held on region A. This means that if the write-transaction is committed
     ** and this connection downgrades to a reader, it will be left with no
-    ** lock at all. And its snapshot could get clobbered by a checkpoint
+    ** lock at all. And so its snapshot could get clobbered by a checkpoint
     ** operation. 
     **
     ** To stop this from happening, grab a SHARED lock on region A now.
@@ -1367,6 +1365,10 @@ int sqlite3LogWriteLock(Log *pLog, int op){
       pLog->isLocked = LOG_REGION_A;
     }
 
+    /* If this connection is not reading the most recent database snapshot,
+    ** it is not possible to write to the database. In this case release
+    ** the write locks and return SQLITE_BUSY.
+    */
     if( memcmp(&pLog->hdr, pLog->pSummary->aData, sizeof(pLog->hdr)) ){
       logLockRegion(pLog, LOG_REGION_C|LOG_REGION_D, LOG_UNLOCK);
       return SQLITE_BUSY;
@@ -1535,13 +1537,15 @@ int sqlite3LogCheckpoint(
 ){
   int rc;                         /* Return code */
 
-  /* Wait for a write-lock on regions B and C. */
+  assert( !pLog->isLocked );
+
+  /* Wait for an EXCLUSIVE lock on regions B and C. */
   do {
     rc = logLockRegion(pLog, LOG_REGION_B|LOG_REGION_C, LOG_WRLOCK);
   }while( rc==SQLITE_BUSY && xBusyHandler(pBusyHandlerArg) );
   if( rc!=SQLITE_OK ) return rc;
 
-  /* Wait for a write-lock on region A. */
+  /* Wait for an EXCLUSIVE lock on region A. */
   do {
     rc = logLockRegion(pLog, LOG_REGION_A, LOG_WRLOCK);
   }while( rc==SQLITE_BUSY && xBusyHandler(pBusyHandlerArg) );