/*
** 2020-04-20
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file implements a VFS shim that writes a checksum on each page
** of an SQLite database file. When reading pages, the checksum is verified
** and an error is raised if the checksum is incorrect.
**
** COMPILING
**
** This extension requires SQLite 3.32.0 or later. It uses the
** sqlite3_database_file_object() interface which was added in
** version 3.32.0, so it will not link with an earlier version of
** SQLite.
**
** To build this extension as a separately loaded shared library or
** DLL, use compiler command-lines similar to the following:
**
** (linux) gcc -fPIC -shared cksumvfs.c -o cksumvfs.so
** (mac) clang -fPIC -dynamiclib cksumvfs.c -o cksumvfs.dylib
** (windows) cl cksumvfs.c -link -dll -out:cksumvfs.dll
**
** You may want to add additional compiler options, of course,
** according to the needs of your project.
**
** If you want to statically link this extension with your product,
** then compile it like any other C-language module but add the
** "-DSQLITE_CKSUMVFS_STATIC" option so that this module knows that
** it is being statically linked rather than dynamically linked
**
** LOADING
**
** To load this extension as a shared library, you first have to
** bring up a dummy SQLite database connection to use as the argument
** to the sqlite3_load_extension() API call. Then you invoke the
** sqlite3_load_extension() API and shutdown the dummy database
** connection. All subsequent database connections that are opened
** will include this extension. For example:
**
** sqlite3 *db;
** sqlite3_open(":memory:", &db);
** sqlite3_load_extention(db, "./cksumvfs");
** sqlite3_close(db);
**
** If this extension is compiled with -DSQLITE_CKSUMVFS_STATIC and
** statically linked against the application, initialize it using
** a single API call as follows:
**
** sqlite3_register_cksumvfs();
**
** Cksumvfs is a VFS Shim. When loaded, "cksmvfs" becomes the new
** default VFS and it uses the prior default VFS as the next VFS
** down in the stack. This is normally what you want. However, in
** complex situations where multiple VFS shims are being loaded,
** it might be important to ensure that cksumvfs is loaded in the
** correct order so that it sequences itself into the default VFS
** Shim stack in the right order.
**
** USING
**
** Open database connections using the sqlite3_open() or
** sqlite3_open_v2() interfaces, as normal. Ordinary database files
** (without a checksum) will operate normally. Databases with
** checksums will return an SQLITE_IOERR_DATA error if a page is
** encountered that contains an invalid checksum.
**
** Checksumming only works on databases that have a reserve-bytes
** value of exactly 8. The default value for reserve-bytes is 0.
** Hence, newly created database files will omit the checksum by
** default. To create a database that includes a checksum, change
** the reserve-bytes value to 8 by runing:
**
** int n = 8;
** sqlite3_file_control(db, 0, SQLITE_FCNTL_RESERVE_BYTES, &n);
**
** If you do this immediately after creating a new database file,
** before anything else has been written into the file, then that
** might be all that you need to do. Otherwise, the API call
** above should be followed by:
**
** sqlite3_exec(db, "VACUUM", 0, 0, 0);
**
** It never hurts to run the VACUUM, even if you don't need it.
** If the database is in WAL mode, you should shutdown and
** reopen all database connections before continuing.
**
** From the CLI, use the ".filectrl reserve_bytes 8" command,
** followed by "VACUUM;".
**
** Note that SQLite allows the number of reserve-bytes to be
** increased but not decreased. So if a database file already
** has a reserve-bytes value greater than 8, there is no way to
** activate checksumming on that database, other than to dump
** and restore the database file. Note also that other extensions
** might also make use of the reserve-bytes. Checksumming will
** be incompatible with those other extensions.
**
** VERIFICATION OF CHECKSUMS
**
** If any checksum is incorrect, the "PRAGMA quick_check" command
** will find it. To verify that checksums are actually enabled
** and running, use the following query:
**
** SELECT count(*), verify_checksum(data)
** FROM sqlite_dbpage
** GROUP BY 2;
**
** There are three possible outputs form the verify_checksum()
** function: 1, 0, and NULL. 1 is returned if the checksum is
** correct. 0 is returned if the checksum is incorrect. NULL
** is returned if the page is unreadable. If checksumming is
** enabled, the read will fail if the checksum is wrong, so the
** usual result from verify_checksum() on a bad checksum is NULL.
**
** If everything is OK, the query above should return a single
** row where the second column is 1. Any other result indicates
** either that there is a checksum error, or checksum validation
** is disabled.
**
** CONTROLLING CHECKSUM VERIFICATION
**
** The cksumvfs extension implements a new PRAGMA statement that can
** be used to disable, re-enable, or query the status of checksum
** verification:
**
** PRAGMA checksum_verification; -- query status
** PRAGMA checksum_verification=OFF; -- disable verification
** PRAGMA checksum_verification=ON; -- re-enable verification
**
** The "checksum_verification" pragma will return "1" (true) or "0"
** (false) if checksum verification is enabled or disabled, respectively.
** "Verification" in this context means the feature that causes
** SQLITE_IOERR_DATA errors if a checksum mismatch is detected while
** reading. Checksums are always kept up-to-date as long as the
** reserve-bytes value of the database is 8, regardless of the setting
** of this pragma. Checksum verification can be disabled (for example)
** to do forensic analysis of a database that has previously reported
** a checksum error.
**
** The "checksum_verification" pragma will always respond with "0" if
** the database file does not have a reserve-bytes value of 8. The
** pragma will return no rows at all if the cksumvfs extension is
** not loaded.
**
** IMPLEMENTATION NOTES
**
** The checksum is stored in the last 8 bytes of each page. This
** module only operates if the "bytes of reserved space on each page"
** value at offset 20 the SQLite database header is exactly 8. If
** the reserved-space value is not 8, this module is a no-op.
*/
#if defined(SQLITE_AMALGAMATION) && !defined(SQLITE_CKSUMVFS_STATIC)
# define SQLITE_CKSUMVFS_STATIC
#endif
#ifdef SQLITE_CKSUMVFS_STATIC
# include "sqlite3.h"
#else
# include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#endif
#include <string.h>
#include <assert.h>
/*
** Forward declaration of objects used by this utility
*/
typedef struct sqlite3_vfs CksmVfs;
typedef struct CksmFile CksmFile;
/*
** Useful datatype abbreviations
*/
#if !defined(SQLITE_AMALGAMATION)
typedef unsigned char u8;
typedef unsigned int u32;
#endif
/* Access to a lower-level VFS that (might) implement dynamic loading,
** access to randomness, etc.
*/
#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))
#define ORIGFILE(p) ((sqlite3_file*)(((CksmFile*)(p))+1))
/* An open file */
struct CksmFile {
sqlite3_file base; /* IO methods */
const char *zFName; /* Original name of the file */
char computeCksm; /* True to compute checksums.
** Always true if reserve size is 8. */
char verifyCksm; /* True to verify checksums */
char isWal; /* True if processing a WAL file */
char inCkpt; /* Currently doing a checkpoint */
CksmFile *pPartner; /* Ptr from WAL to main-db, or from main-db to WAL */
};
/*
** Methods for CksmFile
*/
static int cksmClose(sqlite3_file*);
static int cksmRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
static int cksmWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
static int cksmTruncate(sqlite3_file*, sqlite3_int64 size);
static int cksmSync(sqlite3_file*, int flags);
static int cksmFileSize(sqlite3_file*, sqlite3_int64 *pSize);
static int cksmLock(sqlite3_file*, int);
static int cksmUnlock(sqlite3_file*, int);
static int cksmCheckReservedLock(sqlite3_file*, int *pResOut);
static int cksmFileControl(sqlite3_file*, int op, void *pArg);
static int cksmSectorSize(sqlite3_file*);
static int cksmDeviceCharacteristics(sqlite3_file*);
static int cksmShmMap(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
static int cksmShmLock(sqlite3_file*, int offset, int n, int flags);
static void cksmShmBarrier(sqlite3_file*);
static int cksmShmUnmap(sqlite3_file*, int deleteFlag);
static int cksmFetch(sqlite3_file*, sqlite3_int64 iOfst, int iAmt, void **pp);
static int cksmUnfetch(sqlite3_file*, sqlite3_int64 iOfst, void *p);
/*
** Methods for CksmVfs
*/
static int cksmOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int cksmDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int cksmAccess(sqlite3_vfs*, const char *zName, int flags, int *);
static int cksmFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
static void *cksmDlOpen(sqlite3_vfs*, const char *zFilename);
static void cksmDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
static void (*cksmDlSym(sqlite3_vfs *pVfs, void *p, const char*zSym))(void);
static void cksmDlClose(sqlite3_vfs*, void*);
static int cksmRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int cksmSleep(sqlite3_vfs*, int microseconds);
static int cksmCurrentTime(sqlite3_vfs*, double*);
static int cksmGetLastError(sqlite3_vfs*, int, char *);
static int cksmCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
static int cksmSetSystemCall(sqlite3_vfs*, const char*,sqlite3_syscall_ptr);
static sqlite3_syscall_ptr cksmGetSystemCall(sqlite3_vfs*, const char *z);
static const char *cksmNextSystemCall(sqlite3_vfs*, const char *zName);
static sqlite3_vfs cksm_vfs = {
3, /* iVersion (set when registered) */
0, /* szOsFile (set when registered) */
1024, /* mxPathname */
0, /* pNext */
"cksmvfs", /* zName */
0, /* pAppData (set when registered) */
cksmOpen, /* xOpen */
cksmDelete, /* xDelete */
cksmAccess, /* xAccess */
cksmFullPathname, /* xFullPathname */
cksmDlOpen, /* xDlOpen */
cksmDlError, /* xDlError */
cksmDlSym, /* xDlSym */
cksmDlClose, /* xDlClose */
cksmRandomness, /* xRandomness */
cksmSleep, /* xSleep */
cksmCurrentTime, /* xCurrentTime */
cksmGetLastError, /* xGetLastError */
cksmCurrentTimeInt64, /* xCurrentTimeInt64 */
cksmSetSystemCall, /* xSetSystemCall */
cksmGetSystemCall, /* xGetSystemCall */
cksmNextSystemCall /* xNextSystemCall */
};
static const sqlite3_io_methods cksm_io_methods = {
3, /* iVersion */
cksmClose, /* xClose */
cksmRead, /* xRead */
cksmWrite, /* xWrite */
cksmTruncate, /* xTruncate */
cksmSync, /* xSync */
cksmFileSize, /* xFileSize */
cksmLock, /* xLock */
cksmUnlock, /* xUnlock */
cksmCheckReservedLock, /* xCheckReservedLock */
cksmFileControl, /* xFileControl */
cksmSectorSize, /* xSectorSize */
cksmDeviceCharacteristics, /* xDeviceCharacteristics */
cksmShmMap, /* xShmMap */
cksmShmLock, /* xShmLock */
cksmShmBarrier, /* xShmBarrier */
cksmShmUnmap, /* xShmUnmap */
cksmFetch, /* xFetch */
cksmUnfetch /* xUnfetch */
};
/* Do byte swapping on a unsigned 32-bit integer */
#define BYTESWAP32(x) ( \
(((x)&0x000000FF)<<24) + (((x)&0x0000FF00)<<8) \
+ (((x)&0x00FF0000)>>8) + (((x)&0xFF000000)>>24) \
)
/* Compute a checksum on a buffer */
static void cksmCompute(
u8 *a, /* Content to be checksummed */
int nByte, /* Bytes of content in a[]. Must be a multiple of 8. */
u8 *aOut /* OUT: Final 8-byte checksum value output */
){
u32 s1 = 0, s2 = 0;
u32 *aData = (u32*)a;
u32 *aEnd = (u32*)&a[nByte];
u32 x = 1;
assert( nByte>=8 );
assert( (nByte&0x00000007)==0 );
assert( nByte<=65536 );
if( 1 == *(u8*)&x ){
/* Little-endian */
do {
s1 += *aData++ + s2;
s2 += *aData++ + s1;
}while( aData<aEnd );
}else{
/* Big-endian */
do {
s1 += BYTESWAP32(aData[0]) + s2;
s2 += BYTESWAP32(aData[1]) + s1;
aData += 2;
}while( aData<aEnd );
s1 = BYTESWAP32(s1);
s2 = BYTESWAP32(s2);
}
memcpy(aOut, &s1, 4);
memcpy(aOut+4, &s2, 4);
}
/*
** SQL function: verify_checksum(BLOB)
**
** Return 0 or 1 if the checksum is invalid or valid. Or return
** NULL if the input is not a BLOB that is the right size for a
** database page.
*/
static void cksmVerifyFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
int nByte;
u8 *data;
u8 cksum[8];
data = (u8*)sqlite3_value_blob(argv[0]);
if( data==0 ) return;
if( sqlite3_value_type(argv[0])!=SQLITE_BLOB ) return;
nByte = sqlite3_value_bytes(argv[0]);
if( nByte<512 || nByte>65536 || (nByte & (nByte-1))!=0 ) return;
cksmCompute(data, nByte-8, cksum);
sqlite3_result_int(context, memcmp(data+nByte-8,cksum,8)==0);
}
#ifdef SQLITE_CKSUMVFS_INIT_FUNCNAME
/*
** SQL function: initialize_cksumvfs(SCHEMANAME)
**
** This SQL functions (whose name is actually determined at compile-time
** by the value of the SQLITE_CKSUMVFS_INIT_FUNCNAME macro) invokes:
**
** sqlite3_file_control(db, SCHEMANAME, SQLITE_FCNTL_RESERVE_BYTE, &n);
**
** In order to set the reserve bytes value to 8, so that cksumvfs will
** operation. This feature is provided (if and only if the
** SQLITE_CKSUMVFS_INIT_FUNCNAME compile-time option is set to a string
** which is the name of the SQL function) so as to provide the ability
** to invoke the file-control in programming languages that lack
** direct access to the sqlite3_file_control() interface (ex: Java).
**
** This interface is undocumented, apart from this comment. Usage
** example:
**
** 1. Compile with -DSQLITE_CKSUMVFS_INIT_FUNCNAME="ckvfs_init"
** 2. Run: "SELECT cksum_init('main'); VACUUM;"
*/
static void cksmInitFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
int nByte = 8;
const char *zSchemaName = (const char*)sqlite3_value_text(argv[0]);
sqlite3 *db = sqlite3_context_db_handle(context);
sqlite3_file_control(db, zSchemaName, SQLITE_FCNTL_RESERVE_BYTES, &nByte);
/* Return NULL */
}
#endif /* SQLITE_CKSUMBFS_INIT_FUNCNAME */
/*
** Close a cksm-file.
*/
static int cksmClose(sqlite3_file *pFile){
CksmFile *p = (CksmFile *)pFile;
if( p->pPartner ){
assert( p->pPartner->pPartner==p );
p->pPartner->pPartner = 0;
p->pPartner = 0;
}
pFile = ORIGFILE(pFile);
return pFile->pMethods->xClose(pFile);
}
/*
** Set the computeCkSm and verifyCksm flags, if they need to be
** changed.
*/
static void cksmSetFlags(CksmFile *p, int hasCorrectReserveSize){
if( hasCorrectReserveSize!=p->computeCksm ){
p->computeCksm = p->verifyCksm = hasCorrectReserveSize;
if( p->pPartner ){
p->pPartner->verifyCksm = hasCorrectReserveSize;
p->pPartner->computeCksm = hasCorrectReserveSize;
}
}
}
/*
** Read data from a cksm-file.
*/
static int cksmRead(
sqlite3_file *pFile,
void *zBuf,
int iAmt,
sqlite_int64 iOfst
){
int rc;
CksmFile *p = (CksmFile *)pFile;
pFile = ORIGFILE(pFile);
rc = pFile->pMethods->xRead(pFile, zBuf, iAmt, iOfst);
if( rc==SQLITE_OK ){
if( iOfst==0 && iAmt>=100 && (
memcmp(zBuf,"SQLite format 3",16)==0 || memcmp(zBuf,"ZV-",3)==0
)){
u8 *d = (u8*)zBuf;
char hasCorrectReserveSize = (d[20]==8);
cksmSetFlags(p, hasCorrectReserveSize);
}
/* Verify the checksum if
** (1) the size indicates that we are dealing with a complete
** database page
** (2) checksum verification is enabled
** (3) we are not in the middle of checkpoint
*/
if( iAmt>=512 /* (1) */
&& p->verifyCksm /* (2) */
&& !p->inCkpt /* (3) */
){
u8 cksum[8];
cksmCompute((u8*)zBuf, iAmt-8, cksum);
if( memcmp((u8*)zBuf+iAmt-8, cksum, 8)!=0 ){
sqlite3_log(SQLITE_IOERR_DATA,
"checksum fault offset %lld of \"%s\"",
iOfst, p->zFName);
rc = SQLITE_IOERR_DATA;
}
}
}
return rc;
}
/*
** Write data to a cksm-file.
*/
static int cksmWrite(
sqlite3_file *pFile,
const void *zBuf,
int iAmt,
sqlite_int64 iOfst
){
CksmFile *p = (CksmFile *)pFile;
pFile = ORIGFILE(pFile);
if( iOfst==0 && iAmt>=100 && (
memcmp(zBuf,"SQLite format 3",16)==0 || memcmp(zBuf,"ZV-",3)==0
)){
u8 *d = (u8*)zBuf;
char hasCorrectReserveSize = (d[20]==8);
cksmSetFlags(p, hasCorrectReserveSize);
}
/* If the write size is appropriate for a database page and if
** checksums where ever enabled, then it will be safe to compute
** the checksums. The reserve byte size might have increased, but
** it will never decrease. And because it cannot decrease, the
** checksum will not overwrite anything.
*/
if( iAmt>=512
&& p->computeCksm
&& !p->inCkpt
){
cksmCompute((u8*)zBuf, iAmt-8, ((u8*)zBuf)+iAmt-8);
}
return pFile->pMethods->xWrite(pFile, zBuf, iAmt, iOfst);
}
/*
** Truncate a cksm-file.
*/
static int cksmTruncate(sqlite3_file *pFile, sqlite_int64 size){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xTruncate(pFile, size);
}
/*
** Sync a cksm-file.
*/
static int cksmSync(sqlite3_file *pFile, int flags){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xSync(pFile, flags);
}
/*
** Return the current file-size of a cksm-file.
*/
static int cksmFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
CksmFile *p = (CksmFile *)pFile;
pFile = ORIGFILE(p);
return pFile->pMethods->xFileSize(pFile, pSize);
}
/*
** Lock a cksm-file.
*/
static int cksmLock(sqlite3_file *pFile, int eLock){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xLock(pFile, eLock);
}
/*
** Unlock a cksm-file.
*/
static int cksmUnlock(sqlite3_file *pFile, int eLock){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xUnlock(pFile, eLock);
}
/*
** Check if another file-handle holds a RESERVED lock on a cksm-file.
*/
static int cksmCheckReservedLock(sqlite3_file *pFile, int *pResOut){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xCheckReservedLock(pFile, pResOut);
}
/*
** File control method. For custom operations on a cksm-file.
*/
static int cksmFileControl(sqlite3_file *pFile, int op, void *pArg){
int rc;
CksmFile *p = (CksmFile*)pFile;
pFile = ORIGFILE(pFile);
if( op==SQLITE_FCNTL_PRAGMA ){
char **azArg = (char**)pArg;
assert( azArg[1]!=0 );
if( sqlite3_stricmp(azArg[1],"checksum_verification")==0 ){
char *zArg = azArg[2];
if( zArg!=0 ){
if( (zArg[0]>='1' && zArg[0]<='9')
|| sqlite3_strlike("enable%",zArg,0)==0
|| sqlite3_stricmp("yes",zArg)==0
|| sqlite3_stricmp("on",zArg)==0
){
p->verifyCksm = p->computeCksm;
}else{
p->verifyCksm = 0;
}
if( p->pPartner ) p->pPartner->verifyCksm = p->verifyCksm;
}
azArg[0] = sqlite3_mprintf("%d",p->verifyCksm);
return SQLITE_OK;
}else if( p->computeCksm && azArg[2]!=0
&& sqlite3_stricmp(azArg[1], "page_size")==0 ){
/* Do not allow page size changes on a checksum database */
return SQLITE_OK;
}
}else if( op==SQLITE_FCNTL_CKPT_START || op==SQLITE_FCNTL_CKPT_DONE ){
p->inCkpt = op==SQLITE_FCNTL_CKPT_START;
if( p->pPartner ) p->pPartner->inCkpt = p->inCkpt;
}else if( op==SQLITE_FCNTL_CKSM_FILE ){
/* This VFS needs to obtain a pointer to the corresponding database
** file handle from within xOpen() calls to open wal files. To do this,
** it uses the sqlite3_database_file_object() API to obtain a pointer
** to the file-handle used by SQLite to access the db file. This is
** fine if cksmvfs happens to be the top-level VFS, but not if there
** are one or more wrapper VFS. To handle this case, this file-control
** is used to extract the cksmvfs file-handle from any wrapper file
** handle. */
sqlite3_file **ppFile = (sqlite3_file**)pArg;
*ppFile = (sqlite3_file*)p;
return SQLITE_OK;
}
rc = pFile->pMethods->xFileControl(pFile, op, pArg);
if( rc==SQLITE_OK && op==SQLITE_FCNTL_VFSNAME ){
*(char**)pArg = sqlite3_mprintf("cksm/%z", *(char**)pArg);
}
return rc;
}
/*
** Return the sector-size in bytes for a cksm-file.
*/
static int cksmSectorSize(sqlite3_file *pFile){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xSectorSize(pFile);
}
/*
** Return the device characteristic flags supported by a cksm-file.
*/
static int cksmDeviceCharacteristics(sqlite3_file *pFile){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xDeviceCharacteristics(pFile);
}
/* Create a shared memory file mapping */
static int cksmShmMap(
sqlite3_file *pFile,
int iPg,
int pgsz,
int bExtend,
void volatile **pp
){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xShmMap(pFile,iPg,pgsz,bExtend,pp);
}
/* Perform locking on a shared-memory segment */
static int cksmShmLock(sqlite3_file *pFile, int offset, int n, int flags){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xShmLock(pFile,offset,n,flags);
}
/* Memory barrier operation on shared memory */
static void cksmShmBarrier(sqlite3_file *pFile){
pFile = ORIGFILE(pFile);
pFile->pMethods->xShmBarrier(pFile);
}
/* Unmap a shared memory segment */
static int cksmShmUnmap(sqlite3_file *pFile, int deleteFlag){
pFile = ORIGFILE(pFile);
return pFile->pMethods->xShmUnmap(pFile,deleteFlag);
}
/* Fetch a page of a memory-mapped file */
static int cksmFetch(
sqlite3_file *pFile,
sqlite3_int64 iOfst,
int iAmt,
void **pp
){
CksmFile *p = (CksmFile *)pFile;
if( p->computeCksm ){
*pp = 0;
return SQLITE_OK;
}
pFile = ORIGFILE(pFile);
if( pFile->pMethods->iVersion>2 && pFile->pMethods->xFetch ){
return pFile->pMethods->xFetch(pFile, iOfst, iAmt, pp);
}
*pp = 0;
return SQLITE_OK;
}
/* Release a memory-mapped page */
static int cksmUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *pPage){
pFile = ORIGFILE(pFile);
if( pFile->pMethods->iVersion>2 && pFile->pMethods->xUnfetch ){
return pFile->pMethods->xUnfetch(pFile, iOfst, pPage);
}
return SQLITE_OK;
}
/*
** Open a cksm file handle.
*/
static int cksmOpen(
sqlite3_vfs *pVfs,
const char *zName,
sqlite3_file *pFile,
int flags,
int *pOutFlags
){
CksmFile *p;
sqlite3_file *pSubFile;
sqlite3_vfs *pSubVfs;
int rc;
pSubVfs = ORIGVFS(pVfs);
if( (flags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_WAL))==0 ){
return pSubVfs->xOpen(pSubVfs, zName, pFile, flags, pOutFlags);
}
p = (CksmFile*)pFile;
memset(p, 0, sizeof(*p));
pSubFile = ORIGFILE(pFile);
pFile->pMethods = &cksm_io_methods;
rc = pSubVfs->xOpen(pSubVfs, zName, pSubFile, flags, pOutFlags);
if( rc ) goto cksm_open_done;
if( flags & SQLITE_OPEN_WAL ){
sqlite3_file *pDb = sqlite3_database_file_object(zName);
rc = pDb->pMethods->xFileControl(pDb, SQLITE_FCNTL_CKSM_FILE, (void*)&pDb);
assert( rc==SQLITE_OK );
p->pPartner = (CksmFile*)pDb;
assert( p->pPartner->pPartner==0 );
p->pPartner->pPartner = p;
p->isWal = 1;
p->computeCksm = p->pPartner->computeCksm;
}else{
p->isWal = 0;
p->computeCksm = 0;
}
p->zFName = zName;
cksm_open_done:
if( rc ) pFile->pMethods = 0;
return rc;
}
/*
** All other VFS methods are pass-thrus.
*/
static int cksmDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
return ORIGVFS(pVfs)->xDelete(ORIGVFS(pVfs), zPath, dirSync);
}
static int cksmAccess(
sqlite3_vfs *pVfs,
const char *zPath,
int flags,
int *pResOut
){
return ORIGVFS(pVfs)->xAccess(ORIGVFS(pVfs), zPath, flags, pResOut);
}
static int cksmFullPathname(
sqlite3_vfs *pVfs,
const char *zPath,
int nOut,
char *zOut
){
return ORIGVFS(pVfs)->xFullPathname(ORIGVFS(pVfs),zPath,nOut,zOut);
}
static void *cksmDlOpen(sqlite3_vfs *pVfs, const char *zPath){
return ORIGVFS(pVfs)->xDlOpen(ORIGVFS(pVfs), zPath);
}
static void cksmDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
ORIGVFS(pVfs)->xDlError(ORIGVFS(pVfs), nByte, zErrMsg);
}
static void (*cksmDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
return ORIGVFS(pVfs)->xDlSym(ORIGVFS(pVfs), p, zSym);
}
static void cksmDlClose(sqlite3_vfs *pVfs, void *pHandle){
ORIGVFS(pVfs)->xDlClose(ORIGVFS(pVfs), pHandle);
}
static int cksmRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
return ORIGVFS(pVfs)->xRandomness(ORIGVFS(pVfs), nByte, zBufOut);
}
static int cksmSleep(sqlite3_vfs *pVfs, int nMicro){
return ORIGVFS(pVfs)->xSleep(ORIGVFS(pVfs), nMicro);
}
static int cksmCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
return ORIGVFS(pVfs)->xCurrentTime(ORIGVFS(pVfs), pTimeOut);
}
static int cksmGetLastError(sqlite3_vfs *pVfs, int a, char *b){
return ORIGVFS(pVfs)->xGetLastError(ORIGVFS(pVfs), a, b);
}
static int cksmCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){
sqlite3_vfs *pOrig = ORIGVFS(pVfs);
int rc;
assert( pOrig->iVersion>=2 );
if( pOrig->xCurrentTimeInt64 ){
rc = pOrig->xCurrentTimeInt64(pOrig, p);
}else{
double r;
rc = pOrig->xCurrentTime(pOrig, &r);
*p = (sqlite3_int64)(r*86400000.0);
}
return rc;
}
static int cksmSetSystemCall(
sqlite3_vfs *pVfs,
const char *zName,
sqlite3_syscall_ptr pCall
){
return ORIGVFS(pVfs)->xSetSystemCall(ORIGVFS(pVfs),zName,pCall);
}
static sqlite3_syscall_ptr cksmGetSystemCall(
sqlite3_vfs *pVfs,
const char *zName
){
return ORIGVFS(pVfs)->xGetSystemCall(ORIGVFS(pVfs),zName);
}
static const char *cksmNextSystemCall(sqlite3_vfs *pVfs, const char *zName){
return ORIGVFS(pVfs)->xNextSystemCall(ORIGVFS(pVfs), zName);
}
/* Register the verify_checksum() SQL function.
*/
static int cksmRegisterFunc(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc;
if( db==0 ) return SQLITE_OK;
rc = sqlite3_create_function(db, "verify_checksum", 1,
SQLITE_UTF8|SQLITE_INNOCUOUS|SQLITE_DETERMINISTIC,
0, cksmVerifyFunc, 0, 0);
#ifdef SQLITE_CKSUMVFS_INIT_FUNCNAME
(void)sqlite3_create_function(db, SQLITE_CKSUMVFS_INIT_FUNCNAME, 1,
SQLITE_UTF8|SQLITE_DIRECTONLY,
0, cksmInitFunc, 0, 0);
#endif
return rc;
}
/*
** Register the cksum VFS as the default VFS for the system.
** Also make arrangements to automatically register the "verify_checksum()"
** SQL function on each new database connection.
*/
static int cksmRegisterVfs(void){
int rc = SQLITE_OK;
sqlite3_vfs *pOrig;
if( sqlite3_vfs_find("cksmvfs")!=0 ) return SQLITE_OK;
pOrig = sqlite3_vfs_find(0);
if( pOrig==0 ) return SQLITE_ERROR;
cksm_vfs.iVersion = pOrig->iVersion;
cksm_vfs.pAppData = pOrig;
cksm_vfs.szOsFile = pOrig->szOsFile + sizeof(CksmFile);
rc = sqlite3_vfs_register(&cksm_vfs, 1);
if( rc==SQLITE_OK ){
rc = sqlite3_auto_extension((void(*)(void))cksmRegisterFunc);
}
return rc;
}
#if defined(SQLITE_CKSUMVFS_STATIC)
/* This variant of the initializer runs when the extension is
** statically linked.
*/
int sqlite3_register_cksumvfs(const char *NotUsed){
(void)NotUsed;
return cksmRegisterVfs();
}
int sqlite3_unregister_cksumvfs(void){
if( sqlite3_vfs_find("cksmvfs") ){
sqlite3_vfs_unregister(&cksm_vfs);
sqlite3_cancel_auto_extension((void(*)(void))cksmRegisterFunc);
}
return SQLITE_OK;
}
#endif /* defined(SQLITE_CKSUMVFS_STATIC */
#if !defined(SQLITE_CKSUMVFS_STATIC)
/* This variant of the initializer function is used when the
** extension is shared library to be loaded at run-time.
*/
#ifdef _WIN32
__declspec(dllexport)
#endif
/*
** This routine is called by sqlite3_load_extension() when the
** extension is first loaded.
***/
int sqlite3_cksumvfs_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc;
SQLITE_EXTENSION_INIT2(pApi);
(void)pzErrMsg; /* not used */
rc = cksmRegisterFunc(db, 0, 0);
if( rc==SQLITE_OK ){
rc = cksmRegisterVfs();
}
if( rc==SQLITE_OK ) rc = SQLITE_OK_LOAD_PERMANENTLY;
return rc;
}
#endif /* !defined(SQLITE_CKSUMVFS_STATIC) */