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Add a checksum to the master journal name stored at the end of a journal

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file. (CVS 1692)

FossilOrigin-Name: 4905e74925a4e9d467c51dc174f265b9395ae9fa
This commit is contained in:
danielk1977
2004-06-25 11:11:54 +00:00
parent 4cb1607bc0
commit cafadbac02
3 changed files with 46 additions and 13 deletions
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45
src/pager.c
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@@ -18,7 +18,7 @@
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.141 2004/06/25 08:32:26 danielk1977 Exp $
** @(#) $Id: pager.c,v 1.142 2004/06/25 11:11:54 danielk1977 Exp $
*/
#include "os.h" /* Must be first to enable large file support */
#include "sqliteInt.h"
@@ -402,19 +402,24 @@ static int readMasterJournal(OsFile *pJrnl, char **pzMaster){
int rc;
u32 len;
off_t szJ;
int cksum;
int i;
unsigned char aMagic[8]; /* A buffer to hold the magic header */
*pzMaster = 0;
rc = sqlite3OsFileSize(pJrnl, &szJ);
if( rc!=SQLITE_OK || szJ<12 ) return rc;
if( rc!=SQLITE_OK || szJ<16 ) return rc;
rc = sqlite3OsSeek(pJrnl, szJ-12);
rc = sqlite3OsSeek(pJrnl, szJ-16);
if( rc!=SQLITE_OK ) return rc;
rc = read32bits(pJrnl, &len);
if( rc!=SQLITE_OK ) return rc;
rc = read32bits(pJrnl, &cksum);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(pJrnl, aMagic, 8);
if( rc!=SQLITE_OK || memcmp(aMagic, aJournalMagic, 8) ) return rc;
@@ -431,6 +436,15 @@ static int readMasterJournal(OsFile *pJrnl, char **pzMaster){
*pzMaster = 0;
return rc;
}
/* See if the checksum matches the master journal name */
for(i=0; i<len; i++){
cksum -= *pzMaster[i];
}
if( !cksum ){
sqliteFree(*pzMaster);
*pzMaster = 0;
}
return SQLITE_OK;
}
@@ -591,16 +605,33 @@ static int readJournalHdr(
/*
** Write the supplied master journal name into the journal file for pager
** pPager at the current location.
** pPager at the current location. The master journal name must be the last
** thing written to a journal file. If the pager is in full-sync mode, the
** journal file descriptor is advanced to the next sector boundary before
** anything is written. The format is:
**
** + 4 bytes: PAGER_MJ_PGNO.
** + N bytes: length of master journal name.
** + 4 bytes: N
** + 4 bytes: Master journal name checksum.
** + 8 bytes: aJournalMagic[].
**
** The master journal page checksum is the sum of the bytes in the master
** journal name.
*/
static int writeMasterJournal(Pager *pPager, const char *zMaster){
int rc;
int len;
int i;
int cksum = 0;
if( !zMaster || pPager->setMaster) return SQLITE_OK;
pPager->setMaster = 1;
len = strlen(zMaster);
for(i=0; i<len; i++){
cksum += zMaster[i];
}
/* If in full-sync mode, advance to the next disk sector before writing
** the master journal name. This is in case the previous page written to
@@ -610,8 +641,7 @@ static int writeMasterJournal(Pager *pPager, const char *zMaster){
rc = seekJournalHdr(pPager);
if( rc!=SQLITE_OK ) return rc;
}
pPager->journalOff += (len+16);
pPager->journalOff += (len+20);
rc = write32bits(&pPager->jfd, PAGER_MJ_PGNO(pPager));
if( rc!=SQLITE_OK ) return rc;
@@ -622,6 +652,9 @@ static int writeMasterJournal(Pager *pPager, const char *zMaster){
rc = write32bits(&pPager->jfd, len);
if( rc!=SQLITE_OK ) return rc;
rc = write32bits(&pPager->jfd, cksum);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsWrite(&pPager->jfd, aJournalMagic, sizeof(aJournalMagic));
return rc;
}