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Overview
Comment:Experimental changes toward making snapshots serializable.
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SHA1: b6a81fa1fc1fb78a65894129851a4ec3986640de
User & Date: drh 2016-11-15 17:37:56
Context
2016-11-18
14:38
Enhance existing snapshot tests to serialize/deserialize snapshots. No new tests. check-in: 16b9bf92 user: dan tags: serializable-snapshot
2016-11-15
17:37
Experimental changes toward making snapshots serializable. check-in: b6a81fa1 user: drh tags: serializable-snapshot
04:00
Change the OP_Last opcode so that it is a no-op if the cursor is already pointing at the end of the b-tree. check-in: 66347385 user: drh tags: trunk
Changes
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Changes to src/sqlite.h.in.

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** the most recent version.
**
** The constructor for this object is [sqlite3_snapshot_get()].  The
** [sqlite3_snapshot_open()] method causes a fresh read transaction to refer
** to an historical snapshot (if possible).  The destructor for 
** sqlite3_snapshot objects is [sqlite3_snapshot_free()].
*/
typedef struct sqlite3_snapshot sqlite3_snapshot;



/*
** CAPI3REF: Record A Database Snapshot
** EXPERIMENTAL
**
** ^The [sqlite3_snapshot_get(D,S,P)] interface attempts to make a
** new [sqlite3_snapshot] object that records the current state of







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** the most recent version.
**
** The constructor for this object is [sqlite3_snapshot_get()].  The
** [sqlite3_snapshot_open()] method causes a fresh read transaction to refer
** to an historical snapshot (if possible).  The destructor for 
** sqlite3_snapshot objects is [sqlite3_snapshot_free()].
*/
typedef struct sqlite3_snapshot {
  unsigned char hidden[48];
} sqlite3_snapshot;

/*
** CAPI3REF: Record A Database Snapshot
** EXPERIMENTAL
**
** ^The [sqlite3_snapshot_get(D,S,P)] interface attempts to make a
** new [sqlite3_snapshot] object that records the current state of

Changes to src/wal.c.

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/* Create a snapshot object.  The content of a snapshot is opaque to
** every other subsystem, so the WAL module can put whatever it needs
** in the object.
*/
int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot){
  int rc = SQLITE_OK;
  WalIndexHdr *pRet;


  assert( pWal->readLock>=0 && pWal->writeLock==0 );





  pRet = (WalIndexHdr*)sqlite3_malloc(sizeof(WalIndexHdr));
  if( pRet==0 ){
    rc = SQLITE_NOMEM_BKPT;
  }else{
    memcpy(pRet, &pWal->hdr, sizeof(WalIndexHdr));
    *ppSnapshot = (sqlite3_snapshot*)pRet;
  }







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/* Create a snapshot object.  The content of a snapshot is opaque to
** every other subsystem, so the WAL module can put whatever it needs
** in the object.
*/
int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot){
  int rc = SQLITE_OK;
  WalIndexHdr *pRet;
  static const u32 aZero[4] = { 0, 0, 0, 0 };

  assert( pWal->readLock>=0 && pWal->writeLock==0 );

  if( memcmp(&pWal->hdr.aFrameCksum[0],aZero,16)==0 ){
    *ppSnapshot = 0;
    return SQLITE_ERROR;
  }
  pRet = (WalIndexHdr*)sqlite3_malloc(sizeof(WalIndexHdr));
  if( pRet==0 ){
    rc = SQLITE_NOMEM_BKPT;
  }else{
    memcpy(pRet, &pWal->hdr, sizeof(WalIndexHdr));
    *ppSnapshot = (sqlite3_snapshot*)pRet;
  }