1 files changed, 23 insertions, 5 deletions
diff --git a/ext/misc/cksumvfs.c b/ext/misc/cksumvfs.c
index dc2d35076..76a86ba41 100644
--- a/ext/misc/cksumvfs.c
+++ b/ext/misc/cksumvfs.c
@@ -176,7 +176,7 @@ typedef struct CksmFile CksmFile;
 /*
 ** Useful datatype abbreviations
 */
-#if !defined(SQLITE_CORE)
+#if !defined(SQLITE_AMALGAMATION)
   typedef unsigned char u8;
   typedef unsigned int u32;
 #endif
@@ -395,7 +395,9 @@ static int cksmRead(
   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 ){
+    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);
@@ -434,7 +436,9 @@ static int cksmWrite(
 ){
   CksmFile *p = (CksmFile *)pFile;
   pFile = ORIGFILE(pFile);
-  if( iOfst==0 && iAmt>=100 && memcmp(zBuf,"SQLite format 3",16)==0 ){
+  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);
@@ -604,13 +608,20 @@ static int cksmFetch(
     return SQLITE_OK;
   }
   pFile = ORIGFILE(pFile);
-  return pFile->pMethods->xFetch(pFile, iOfst, iAmt, pp);
+  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);
-  return pFile->pMethods->xUnfetch(pFile, iOfst, pPage);
+  if( pFile->pMethods->iVersion>2 && pFile->pMethods->xUnfetch ){
+    return pFile->pMethods->xUnfetch(pFile, iOfst, pPage);
+  }
+  return SQLITE_OK;
 }
 
 /*
@@ -763,6 +774,13 @@ 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)