Cleanup SQLite 3.6.18 import.

third_party/sqlite/sqlite-poison.patch

-Index: src/btree.c
-===================================================================
---- src/btree.c 2009-09-09 06:45:19.000000000 -0700
-+++ src/btree.c 2009-09-14 18:17:53.000000000 -0700
-@@ -24,6 +24,12 @@
- static const char zMagicHeader[] = SQLITE_FILE_HEADER;
- 
- /*
-+** The header string that appears at the beginning of a SQLite
-+** database which has been poisoned.
-+*/
-+static const char zPoisonHeader[] = "SQLite poison 3";
-+
-+/*
- ** Set this global variable to 1 to enable tracing using the TRACE
- ** macro.
- */
-@@ -2337,6 +2343,7 @@
-   if( rc ) return rc;
-   memcpy(data, zMagicHeader, sizeof(zMagicHeader));
-   assert( sizeof(zMagicHeader)==16 );
-+  assert( sizeof(zMagicHeader)==sizeof(zPoisonHeader) );
-   put2byte(&data[16], pBt->pageSize);
-   data[18] = 1;
-   data[19] = 1;
-@@ -7804,4 +7811,72 @@
-   assert(!pCur->aOverflow);
-   pCur->isIncrblobHandle = 1;
- }
-+
-+/* Poison the db so that other clients error out as quickly as
-+** possible.
-+*/
-+int sqlite3Poison(sqlite3 *db){
-+  int rc;
-+  Btree *p;
-+  BtShared *pBt;
-+  unsigned char *pP1;
-+
-+  if( db == NULL) return SQLITE_OK;
-+
-+  /* Database 0 corrosponds to the main database. */
-+  if( db->nDb<1 ) return SQLITE_OK;
-+  p = db->aDb[0].pBt;
-+  pBt = p->pBt;
-+
-+  /* If in a transaction, roll it back.  Committing any changes to a
-+  ** corrupt database may mess up evidence, we definitely don't want
-+  ** to allow poisoning to be rolled back, and the database is anyhow
-+  ** going bye-bye RSN.
-+  */
-+  /* TODO(shess): Figure out if this might release the lock and let
-+  ** someone else get in there, which might deny us the lock a couple
-+  ** lines down.
-+  */
-+  if( sqlite3BtreeIsInTrans(p) ) sqlite3BtreeRollback(p);
-+
-+  /* Start an exclusive transaction.  This will check the headers, so
-+  ** if someone else poisoned the database we should get an error.
-+  */
-+  rc = sqlite3BtreeBeginTrans(p, 2);
-+  /* TODO(shess): Handle SQLITE_BUSY? */
-+  if( rc!=SQLITE_OK ) return rc;
-+
-+  /* Copied from sqlite3BtreeUpdateMeta().  Writing the old version of
-+  ** the page to the journal may be overkill, but it probably won't
-+  ** hurt.
-+  */
-+  assert( pBt->inTrans==TRANS_WRITE );
-+  assert( pBt->pPage1!=0 );
-+  rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
-+  if( rc ) goto err;
-+
-+  /* "SQLite format 3" changes to
-+  ** "SQLite poison 3".  Be extra paranoid about making this change.
-+  */
-+  if( sizeof(zMagicHeader)!=16 ||
-+      sizeof(zPoisonHeader)!=sizeof(zMagicHeader) ){
-+    rc = SQLITE_ERROR;
-+    goto err;
-+  }
-+  pP1 = pBt->pPage1->aData;
-+  if( memcmp(pP1, zMagicHeader, 16)!=0 ){
-+    rc = SQLITE_CORRUPT;
-+    goto err;
-+  }
-+  memcpy(pP1, zPoisonHeader, 16);
-+
-+  /* Push it to the database file. */
-+  return sqlite3BtreeCommit(p);
-+
-+ err:
-+  /* TODO(shess): What about errors, here? */
-+  sqlite3BtreeRollback(p);
-+  return rc;
-+}
-+
- #endif