sqlite: safely move pointer values through SQL.

This lands https://www.sqlite.org/src/timeline?c=d6a44b35 in
third_party/sqlite/src/ and
third_party/sqlite/patches/0013-Add-new-interfaces-sqlite3_bind_pointer-sqlite3_resu.patch
and re-generates third_party/sqlite/amalgamation/* using the script at
third_party/sqlite/google_generate_amalgamation.sh.

The CL also adds a layout test that verifies the patch works as intended.

BUG=742407

Change-Id: I2e1a457459cd2e975e6241b630e7b79c82545981
Reviewed-on: https://chromium-review.googlesource.com/572976
Reviewed-by: Chris Mumford <cmumford@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487275}
static int blobReadWrite(
  sqlite3_blob *pBlob, 
  void *z, 
  int n, 
  int iOffset, 
  int (*xCall)(BtCursor*, u32, u32, void*)
){
  int rc;
  Incrblob *p = (Incrblob *)pBlob;
  Vdbe *v;
  sqlite3 *db;

  if( p==0 ) return SQLITE_MISUSE_BKPT;
  db = p->db;
  sqlite3_mutex_enter(db->mutex);
  v = (Vdbe*)p->pStmt;

  if( n<0 || iOffset<0 || ((sqlite3_int64)iOffset+n)>p->nByte ){
    /* Request is out of range. Return a transient error. */
    rc = SQLITE_ERROR;
  }else if( v==0 ){
    /* If there is no statement handle, then the blob-handle has
    ** already been invalidated. Return SQLITE_ABORT in this case.
    */
    rc = SQLITE_ABORT;
  }else{
    /* Call either BtreeData() or BtreePutData(). If SQLITE_ABORT is
    ** returned, clean-up the statement handle.
    */
    assert( db == v->db );
    sqlite3BtreeEnterCursor(p->pCsr);

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
    if( xCall==sqlite3BtreePutData && db->xPreUpdateCallback ){
      /* If a pre-update hook is registered and this is a write cursor, 
      ** invoke it here. 
      ** 
      ** TODO: The preupdate-hook is passed SQLITE_DELETE, even though this
      ** operation should really be an SQLITE_UPDATE. This is probably
      ** incorrect, but is convenient because at this point the new.* values 
      ** are not easily obtainable. And for the sessions module, an 
      ** SQLITE_UPDATE where the PK columns do not change is handled in the 
      ** same way as an SQLITE_DELETE (the SQLITE_DELETE code is actually
      ** slightly more efficient). Since you cannot write to a PK column
      ** using the incremental-blob API, this works. For the sessions module
      ** anyhow.
      */
      sqlite3_int64 iKey;
      iKey = sqlite3BtreeIntegerKey(p->pCsr);
      sqlite3VdbePreUpdateHook(
          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1
      );
    }
#endif

    rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
    sqlite3BtreeLeaveCursor(p->pCsr);
    if( rc==SQLITE_ABORT ){
      sqlite3VdbeFinalize(v);
      p->pStmt = 0;
    }else{
      v->rc = rc;
    }
  }
  sqlite3Error(db, rc);
  rc = sqlite3ApiExit(db, rc);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

static int blobReadWrite(
  sqlite3_blob *pBlob, 
  void *z, 
  int n, 
  int iOffset, 
  int (*xCall)(BtCursor*, u32, u32, void*)
){
  int rc;
  Incrblob *p = (Incrblob *)pBlob;
  Vdbe *v;
  sqlite3 *db;

  if( p==0 ) return SQLITE_MISUSE_BKPT;
  db = p->db;
  sqlite3_mutex_enter(db->mutex);
  v = (Vdbe*)p->pStmt;

  if( n<0 || iOffset<0 || ((sqlite3_int64)iOffset+n)>p->nByte ){
    /* Request is out of range. Return a transient error. */
    rc = SQLITE_ERROR;
  }else if( v==0 ){
    /* If there is no statement handle, then the blob-handle has
    ** already been invalidated. Return SQLITE_ABORT in this case.
    */
    rc = SQLITE_ABORT;
  }else{
    /* Call either BtreeData() or BtreePutData(). If SQLITE_ABORT is
    ** returned, clean-up the statement handle.
    */
    assert( db == v->db );
    sqlite3BtreeEnterCursor(p->pCsr);

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
    if( xCall==sqlite3BtreePutData && db->xPreUpdateCallback ){
      /* If a pre-update hook is registered and this is a write cursor, 
      ** invoke it here. 
      ** 
      ** TODO: The preupdate-hook is passed SQLITE_DELETE, even though this
      ** operation should really be an SQLITE_UPDATE. This is probably
      ** incorrect, but is convenient because at this point the new.* values 
      ** are not easily obtainable. And for the sessions module, an 
      ** SQLITE_UPDATE where the PK columns do not change is handled in the 
      ** same way as an SQLITE_DELETE (the SQLITE_DELETE code is actually
      ** slightly more efficient). Since you cannot write to a PK column
      ** using the incremental-blob API, this works. For the sessions module
      ** anyhow.
      */
      sqlite3_int64 iKey;
      iKey = sqlite3BtreeIntegerKey(p->pCsr);
      sqlite3VdbePreUpdateHook(
          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1
      );
    }
#endif

    rc = xCall(p->pCsr, iOffset+p->iOffset, n, z);
    sqlite3BtreeLeaveCursor(p->pCsr);
    if( rc==SQLITE_ABORT ){
      sqlite3VdbeFinalize(v);
      p->pStmt = 0;
    }else{
      v->rc = rc;
    }
  }
  sqlite3Error(db, rc);
  rc = sqlite3ApiExit(db, rc);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}
