static int openDatabase(
const char *zFilename, /* Database filename UTF-8 encoded */
sqlite3 **ppDb, /* OUT: Returned database handle */
sqlite3_area_info *area,/* db area info */
int wal_cnt, /* db max wal cnt */
unsigned int flags, /* Operational flags */
const char *zVfs /* Name of the VFS to use */
){
sqlite3 *db; /* Store allocated handle here */
int rc; /* Return code */
int isThreadsafe; /* True for threadsafe connections */
char *zOpen = 0; /* Filename argument to pass to BtreeOpen() */
char *zErrMsg = 0; /* Error message from sqlite3ParseUri() */
#ifdef SQLITE_ENABLE_API_ARMOR
if( ppDb==0 ) return SQLITE_MISUSE_BKPT;
#endif
*ppDb = 0;
#ifndef SQLITE_OMIT_AUTOINIT
rc = sqlite3_initialize();
if( rc ) return rc;
#endif
/* Only allow sensible combinations of bits in the flags argument.
** Throw an error if any non-sense combination is used. If we
** do not block illegal combinations here, it could trigger
** assert() statements in deeper layers. Sensible combinations
** are:
**
** 1: SQLITE_OPEN_READONLY
** 2: SQLITE_OPEN_READWRITE
** 6: SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE
*/
assert( SQLITE_OPEN_READONLY == 0x01 );
assert( SQLITE_OPEN_READWRITE == 0x02 );
assert( SQLITE_OPEN_CREATE == 0x04 );
testcase( (1<<(flags&7))==0x02 ); /* READONLY */
testcase( (1<<(flags&7))==0x04 ); /* READWRITE */
testcase( (1<<(flags&7))==0x40 ); /* READWRITE | CREATE */
if( ((1<<(flags&7)) & 0x46)==0 ){
return SQLITE_MISUSE_BKPT; /* IMP: R-65497-44594 */
}
if( sqlite3GlobalConfig.bCoreMutex==0 ){
isThreadsafe = 0;
}else if( flags & SQLITE_OPEN_NOMUTEX ){
isThreadsafe = 0;
}else if( flags & SQLITE_OPEN_FULLMUTEX ){
isThreadsafe = 1;
}else{
isThreadsafe = sqlite3GlobalConfig.bFullMutex;
}
if( flags & SQLITE_OPEN_PRIVATECACHE ){
flags &= ~SQLITE_OPEN_SHAREDCACHE;
}else if( sqlite3GlobalConfig.sharedCacheEnabled ){
flags |= SQLITE_OPEN_SHAREDCACHE;
}
/* Remove harmful bits from the flags parameter
**
** The SQLITE_OPEN_NOMUTEX and SQLITE_OPEN_FULLMUTEX flags were
** dealt with in the previous code block. Besides these, the only
** valid input flags for sqlite3_open_v2() are SQLITE_OPEN_READONLY,
** SQLITE_OPEN_READWRITE, SQLITE_OPEN_CREATE, SQLITE_OPEN_SHAREDCACHE,
** SQLITE_OPEN_PRIVATECACHE, and some reserved bits. Silently mask
** off all other flags.
*/
flags &= ~( SQLITE_OPEN_DELETEONCLOSE |
SQLITE_OPEN_EXCLUSIVE |
SQLITE_OPEN_MAIN_DB |
SQLITE_OPEN_TEMP_DB |
SQLITE_OPEN_TRANSIENT_DB |
SQLITE_OPEN_MAIN_JOURNAL |
SQLITE_OPEN_TEMP_JOURNAL |
SQLITE_OPEN_SUBJOURNAL |
SQLITE_OPEN_MASTER_JOURNAL |
SQLITE_OPEN_NOMUTEX |
SQLITE_OPEN_FULLMUTEX |
SQLITE_OPEN_WAL
);
/* Allocate the sqlite data structure */
db = sqlite3MallocZero( sizeof(sqlite3) );
if( db==0 ) goto opendb_out;
if( isThreadsafe ){
db->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
if( db->mutex==0 ){
sqlite3_free(db);
db = 0;
goto opendb_out;
}
}
sqlite3_mutex_enter(db->mutex);
db->errMask = 0xff;
db->nDb = 2;
db->magic = SQLITE_MAGIC_BUSY;
db->aDb = db->aDbStatic;
assert( sizeof(db->aLimit)==sizeof(aHardLimit) );
memcpy(db->aLimit, aHardLimit, sizeof(db->aLimit));
db->aLimit[SQLITE_LIMIT_WORKER_THREADS] = SQLITE_DEFAULT_WORKER_THREADS;
db->autoCommit = 1;
db->nextAutovac = -1;
db->szMmap = sqlite3GlobalConfig.szMmap;
db->nextPagesize = 0;
db->nMaxSorterMmap = 0x7FFFFFFF;
db->flags |= SQLITE_ShortColNames | SQLITE_EnableTrigger | SQLITE_CacheSpill
#if !defined(SQLITE_DEFAULT_AUTOMATIC_INDEX) || SQLITE_DEFAULT_AUTOMATIC_INDEX
| SQLITE_AutoIndex
#endif
#if SQLITE_DEFAULT_CKPTFULLFSYNC
| SQLITE_CkptFullFSync
#endif
#if SQLITE_DEFAULT_FILE_FORMAT<4
| SQLITE_LegacyFileFmt
#endif
#ifdef SQLITE_ENABLE_LOAD_EXTENSION
| SQLITE_LoadExtension
#endif
#if SQLITE_DEFAULT_RECURSIVE_TRIGGERS
| SQLITE_RecTriggers
#endif
#if defined(SQLITE_DEFAULT_FOREIGN_KEYS) && SQLITE_DEFAULT_FOREIGN_KEYS
| SQLITE_ForeignKeys
#endif
#if defined(SQLITE_REVERSE_UNORDERED_SELECTS)
| SQLITE_ReverseOrder
#endif
#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
| SQLITE_CellSizeCk
#endif
#if defined(SQLITE_ENABLE_FTS3_TOKENIZER)
| SQLITE_Fts3Tokenizer
#endif
;
sqlite3HashInit(&db->aCollSeq);
#ifndef SQLITE_OMIT_VIRTUALTABLE
sqlite3HashInit(&db->aModule);
#endif
/* Add the default collation sequence BINARY. BINARY works for both UTF-8
** and UTF-16, so add a version for each to avoid any unnecessary
** conversions. The only error that can occur here is a malloc() failure.
**
** EVIDENCE-OF: R-52786-44878 SQLite defines three built-in collating
** functions:
*/
createCollation(db, sqlite3StrBINARY, SQLITE_UTF8, 0, binCollFunc, 0);
createCollation(db, sqlite3StrBINARY, SQLITE_UTF16BE, 0, binCollFunc, 0);
createCollation(db, sqlite3StrBINARY, SQLITE_UTF16LE, 0, binCollFunc, 0);
createCollation(db, "NOCASE", SQLITE_UTF8, 0, nocaseCollatingFunc, 0);
createCollation(db, "RTRIM", SQLITE_UTF8, (void*)1, binCollFunc, 0);
if( db->mallocFailed ){
goto opendb_out;
}
/* EVIDENCE-OF: R-08308-17224 The default collating function for all
** strings is BINARY.
*/
db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, sqlite3StrBINARY, 0);
assert( db->pDfltColl!=0 );
/* Parse the filename/URI argument. */
db->openFlags = flags;
rc = sqlite3ParseUri(zVfs, zFilename, &flags, &db->pVfs, &zOpen, &zErrMsg);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM ) sqlite3OomFault(db);
sqlite3ErrorWithMsg(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
sqlite3_free(zErrMsg);
goto opendb_out;
}
/* Open the backend database driver */
rc = sqlite3BtreeOpen(db->pVfs, zOpen, db, &db->aDb[0].pBt, area, wal_cnt, 0,
flags | SQLITE_OPEN_MAIN_DB);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_IOERR_NOMEM ){
rc = SQLITE_NOMEM_BKPT;
}
sqlite3Error(db, rc);
goto opendb_out;
}
sqlite3BtreeEnter(db->aDb[0].pBt);
db->aDb[0].pSchema = sqlite3SchemaGet(db, db->aDb[0].pBt);
if( !db->mallocFailed ) ENC(db) = SCHEMA_ENC(db);
sqlite3BtreeLeave(db->aDb[0].pBt);
db->aDb[1].pSchema = sqlite3SchemaGet(db, 0);
/* The default safety_level for the main database is FULL; for the temp
** database it is OFF. This matches the pager layer defaults.
*/
db->aDb[0].zDbSName = "main";
db->aDb[0].safety_level = SQLITE_DEFAULT_SYNCHRONOUS+1;
db->aDb[1].zDbSName = "temp";
db->aDb[1].safety_level = PAGER_SYNCHRONOUS_OFF;
db->magic = SQLITE_MAGIC_OPEN;
if( db->mallocFailed ){
goto opendb_out;
}
/* Register all built-in functions, but do not attempt to read the
** database schema yet. This is delayed until the first time the database
** is accessed.
*/
sqlite3Error(db, SQLITE_OK);
sqlite3RegisterPerConnectionBuiltinFunctions(db);
rc = sqlite3_errcode(db);代码太长，先给你一部分，给我详细解释一下
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本文介绍如何在Windows环境下通过编译选项启用SQLite3数据库的R-tree特性。具体操作是在编译SQLite3时添加宏定义/DSQLITE_ENABLE_RTREE=1。
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