/*
** This function is exactly the same as sqlite3_create_function(), except
** that it is designed to be called by internal code. The difference is
** that if a malloc() fails in sqlite3_create_function(), an error code
** is returned and the mallocFailed flag cleared.
*/
int sqlite3CreateFunc(
sqlite3 *db,
const char *zFunctionName,
int nArg,
int enc,
void *pUserData,
void (*xFunc)(sqlite3_context*,int,sqlite3_value **),
void (*xStep)(sqlite3_context*,int,sqlite3_value **),
void (*xFinal)(sqlite3_context*)
){
FuncDef *p;
int nName;
assert( sqlite3_mutex_held(db->mutex) );
if( sqlite3SafetyCheck(db) ){
return SQLITE_MISUSE;
}
if( zFunctionName==0 ||
(xFunc && (xFinal || xStep)) ||
(!xFunc && (xFinal && !xStep)) ||
(!xFunc && (!xFinal && xStep)) ||
(nArg<-1 || nArg>127) ||
(255<(nName = strlen(zFunctionName))) ){
sqlite3Error(db, SQLITE_ERROR, "bad parameters");
return SQLITE_ERROR;
}
#ifndef SQLITE_OMIT_UTF16
/* If SQLITE_UTF16 is specified as the encoding type, transform this
** to one of SQLITE_UTF16LE or SQLITE_UTF16BE using the
** SQLITE_UTF16NATIVE macro. SQLITE_UTF16 is not used internally.
**
** If SQLITE_ANY is specified, add three versions of the function
** to the hash table.
*/
if( enc==SQLITE_UTF16 ){
enc = SQLITE_UTF16NATIVE;
}else if( enc==SQLITE_ANY ){
int rc;
rc = sqlite3CreateFunc(db, zFunctionName, nArg, SQLITE_UTF8,
pUserData, xFunc, xStep, xFinal);
if( rc==SQLITE_OK ){
rc = sqlite3CreateFunc(db, zFunctionName, nArg, SQLITE_UTF16LE,
pUserData, xFunc, xStep, xFinal);
}
if( rc!=SQLITE_OK ){
return rc;
}
enc = SQLITE_UTF16BE;
}
#else
enc = SQLITE_UTF8;
#endif
/* Check if an existing function is being overridden or deleted. If so,
** and there are active VMs, then return SQLITE_BUSY. If a function
** is being overridden/deleted but there are no active VMs, allow the
** operation to continue but invalidate all precompiled statements.
*/
p = sqlite3FindFunction(db, zFunctionName, nName, nArg, enc, 0);
if( p && p->iPrefEnc==enc && p->nArg==nArg ){
if( db->activeVdbeCnt ){
sqlite3Error(db, SQLITE_BUSY,
"Unable to delete/modify user-function due to active statements");
assert( !db->mallocFailed );
return SQLITE_BUSY;
}else{
sqlite3ExpirePreparedStatements(db);
}
}
p = sqlite3FindFunction(db, zFunctionName, nName, nArg, enc, 1);
assert(p || db->mallocFailed);
if( !p ){
return SQLITE_NOMEM;
}
p->flags = 0;
p->xFunc = xFunc;
p->xStep = xStep;
p->xFinalize = xFinal;
p->pUserData = pUserData;
p->nArg = nArg;
return SQLITE_OK;
}
SQLITE_API void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetInt64(&pCtx->s, iVal);
}
void sqlite3_result_zeroblob(sqlite3_context *pCtx, int n){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetZeroBlob(pCtx->pOut, n);
}
}
/*
** Discard all pages from cache pCache with a page number (key value)
** greater than or equal to iLimit. Any pinned pages that meet this
** criteria are unpinned before they are discarded.
**
** The PCache mutex must be held when this function is called.
*/
static void pcache1TruncateUnsafe(
PCache1 *pCache, /* The cache to truncate */
unsigned int iLimit /* Drop pages with this pgno or larger */
){
TESTONLY( unsigned int nPage = 0; ) /* To assert pCache->nPage is correct */
unsigned int h;
assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
for(h=0; h<pCache->nHash; h++){
PgHdr1 **pp = &pCache->apHash[h];
PgHdr1 *pPage;
while( (pPage = *pp)!=0 ){
if( pPage->iKey>=iLimit ){
pCache->nPage--;
*pp = pPage->pNext;
pcache1PinPage(pPage);
pcache1FreePage(pPage);
}else{
pp = &pPage->pNext;
TESTONLY( nPage++; )
}
}
}
void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
pCtx->isError = SQLITE_ERROR;
pCtx->fErrorOrAux = 1;
sqlite3VdbeMemSetStr(pCtx->pOut, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
}
void sqlite3_result_null(sqlite3_context *pCtx){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetNull(pCtx->pOut);
}
*/该函数返回至少n字节大小的block，没有则返回null。该函数假设所有必要的互斥锁都上了，所以不安全
static void *memsys3MallocUnsafe(int nByte){
u32 i;
u32 nBlock;
u32 toFree;
assert( sqlite3_mutex_held(mem3.mutex) ); //如果不能加锁，则终止程序
assert( sizeof(Mem3Block)==8 ); //若Mem3Block大小为8，继续往下执行
if( nByte<=12 ){ //给nBlock赋值
nBlock = 2;
}else{
nBlock = (nByte + 11)/8;
}
assert( nBlock>=2 );
/* STEP 1:
** Look for an entry of the correct size in either the small
** chunk table or in the large chunk hash table. This is
** successful most of the time (about 9 times out of 10).
*/ //首先在小chunk或者大chunk中寻找正确大小块的入口，一般都会成功
if( nBlock <= MX_SMALL ){ //nBlock小于MX_SMALL，则在小chunk中找
i = mem3.aiSmall[nBlock-2];
if( i>0 ){
memsys3UnlinkFromList(i, &mem3.aiSmall[nBlock-2]);
return memsys3Checkout(i, nBlock); //返回找到的满足的chunk
}
}else{ //若nBlock大于MX_SMALL，则在大chunk中找
int hash = nBlock % N_HASH;
for(i=mem3.aiHash[hash]; i>0; i=mem3.aPool[i].u.list.next){
if( mem3.aPool[i-1].u.hdr.size4x/4==nBlock ){
memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
return memsys3Checkout(i, nBlock); //返回找到的chunk
}
}
}
/* STEP 2:
** Try to satisfy the allocation by carving a piece off of the end
** of the master chunk. This step usually works if step 1 fails.
*/ //尝试从master chunk中分裂出合适的空间，第一步失败才执行
if( mem3.szMaster>=nBlock ){
return memsys3FromMaster(nBlock); //从master chunk中获取chunk
}
/* STEP 3:
** Loop through the entire memory pool. Coalesce adjacent free
** chunks. Recompute the master chunk as the largest free chunk.
** Then try again to satisfy the allocation by carving a piece off
** of the end of the master chunk. This step happens very
** rarely (we hope!)
*/遍历整个内存池，合并相邻空闲chunk，重新计算主要的chunk大小，再次尝试从master chunk中分裂出满足分配条件的chunk。前面都不行才执行该步骤。
for(toFree=nBlock*16; toFree<(mem3.nPool*16); toFree *= 2){ //遍历内存池
memsys3OutOfMemory(toFree); //不够分配则释放
if( mem3.iMaster ){ //master chunk存在，将其链接到相应块索引表中
memsys3Link(mem3.iMaster);
mem3.iMaster = 0;
mem3.szMaster = 0;
}
for(i=0; i<N_HASH; i++){
memsys3Merge(&mem3.aiHash[i]); //链接相邻空chunk到aiHash中
}
for(i=0; i<MX_SMALL-1; i++){
memsys3Merge(&mem3.aiSmall[i]); //链接相邻空chunk到aiSmall中
}
if( mem3.szMaster ){ //当前master chunk不为0，则从索引表中断开
memsys3Unlink(mem3.iMaster);
if( mem3.szMaster>=nBlock ){
return memsys3FromMaster(nBlock); //返回得到的内存空间
}
}
}
/* If none of the above worked, then we fail. */
return 0; //若上面三步都失败了，那就失败了，返回0
}
/*
** This is the callback routine for the code that initializes the
** database. See sqlite3Init() below for additional information.
** This routine is also called from the OP_ParseSchema opcode of the VDBE.
**
** Each callback contains the following information:
**
** argv[0] = name of thing being created
** argv[1] = root page number for table or index. 0 for trigger or view.
** argv[2] = SQL text for the CREATE statement.
**
*/
int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
InitData *pData = (InitData*)pInit;
sqlite3 *db = pData->db;
int iDb = pData->iDb;
assert( argc==3 );
UNUSED_PARAMETER2(NotUsed, argc);
assert( sqlite3_mutex_held(db->mutex) );
DbClearProperty(db, iDb, DB_Empty);
if( db->mallocFailed ){
corruptSchema(pData, argv[0], 0);
return 1;
}
assert( iDb>=0 && iDb<db->nDb );
if( argv==0 ) return 0; /* Might happen if EMPTY_RESULT_CALLBACKS are on */
if( argv[1]==0 ){
corruptSchema(pData, argv[0], 0);
}else if( argv[2] && argv[2][0] ){
/* Call the parser to process a CREATE TABLE, INDEX or VIEW.
** But because db->init.busy is set to 1, no VDBE code is generated
** or executed. All the parser does is build the internal data
** structures that describe the table, index, or view.
*/
char *zErr;
int rc;
assert( db->init.busy );
db->init.iDb = iDb;
db->init.newTnum = atoi(argv[1]);
db->init.orphanTrigger = 0;
rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);
db->init.iDb = 0;
assert( rc!=SQLITE_OK || zErr==0 );
if( SQLITE_OK!=rc ){
if( db->init.orphanTrigger ){
assert( iDb==1 );
}else{
pData->rc = rc;
if( rc==SQLITE_NOMEM ){
db->mallocFailed = 1;
}else if( rc!=SQLITE_INTERRUPT && rc!=SQLITE_LOCKED ){
corruptSchema(pData, argv[0], zErr);
}
}
sqlite3DbFree(db, zErr);
}
}else if( argv[0]==0 ){
corruptSchema(pData, 0, 0);
}else{
/* If the SQL column is blank it means this is an index that
** was created to be the PRIMARY KEY or to fulfill a UNIQUE
** constraint for a CREATE TABLE. The index should have already
** been created when we processed the CREATE TABLE. All we have
** to do here is record the root page number for that index.
*/
Index *pIndex;
pIndex = sqlite3FindIndex(db, argv[0], db->aDb[iDb].zName);
if( pIndex==0 ){
/* This can occur if there exists an index on a TEMP table which
** has the same name as another index on a permanent index. Since
** the permanent table is hidden by the TEMP table, we can also
** safely ignore the index on the permanent table.
*/
/* Do Nothing */;
}else if( sqlite3GetInt32(argv[1], &pIndex->tnum)==0 ){
corruptSchema(pData, argv[0], "invalid rootpage");
}
}
return 0;
}
}
/*
** Discard all pages from cache pCache with a page number (key value)
** greater than or equal to iLimit. Any pinned pages that meet this
** criteria are unpinned before they are discarded.
**
** The global mutex must be held when this function is called.
*/
static void pcache1TruncateUnsafe(
PCache1 *pCache,
unsigned int iLimit
){
TESTONLY( unsigned int nPage = 0; ) /* Used to assert pCache->nPage is correct */
unsigned int h;
assert( sqlite3_mutex_held(pcache1.mutex) );
for(h=0; h<pCache->nHash; h++){
PgHdr1 **pp = &pCache->apHash[h];
PgHdr1 *pPage;
while( (pPage = *pp)!=0 ){
if( pPage->iKey>=iLimit ){
pCache->nPage--;
*pp = pPage->pNext;
pcache1PinPage(pPage);
pcache1FreePage(pPage);
}else{
pp = &pPage->pNext;
TESTONLY( nPage++; )
}
}
}
/*
** This routine transforms the internal text encoding used by pMem to
** desiredEnc. It is an error if the string is already of the desired
** encoding, or if *pMem does not contain a string value.
*/
int sqlite3VdbeMemTranslate(Mem *pMem, u8 desiredEnc){
int len; /* Maximum length of output string in bytes */
unsigned char *zOut; /* Output buffer */
unsigned char *zIn; /* Input iterator */
unsigned char *zTerm; /* End of input */
unsigned char *z; /* Output iterator */
unsigned int c;
assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
assert( pMem->flags&MEM_Str );
assert( pMem->enc!=desiredEnc );
assert( pMem->enc!=0 );
assert( pMem->n>=0 );
#if defined(TRANSLATE_TRACE) && defined(SQLITE_DEBUG)
{
char zBuf[100];
sqlite3VdbeMemPrettyPrint(pMem, zBuf);
fprintf(stderr, "INPUT: %s\n", zBuf);
}
#endif
/* If the translation is between UTF-16 little and big endian, then
** all that is required is to swap the byte order. This case is handled
** differently from the others.
*/
if( pMem->enc!=SQLITE_UTF8 && desiredEnc!=SQLITE_UTF8 ){
u8 temp;
int rc;
rc = sqlite3VdbeMemMakeWriteable(pMem);
if( rc!=SQLITE_OK ){
assert( rc==SQLITE_NOMEM );
return SQLITE_NOMEM;
}
zIn = (u8*)pMem->z;
zTerm = &zIn[pMem->n&~1];
while( zIn<zTerm ){
temp = *zIn;
*zIn = *(zIn+1);
zIn++;
*zIn++ = temp;
}
pMem->enc = desiredEnc;
goto translate_out;
}
/* Set len to the maximum number of bytes required in the output buffer. */
if( desiredEnc==SQLITE_UTF8 ){
/* When converting from UTF-16, the maximum growth results from
** translating a 2-byte character to a 4-byte UTF-8 character.
** A single byte is required for the output string
** nul-terminator.
*/
pMem->n &= ~1;
len = pMem->n * 2 + 1;
}else{
/* When converting from UTF-8 to UTF-16 the maximum growth is caused
** when a 1-byte UTF-8 character is translated into a 2-byte UTF-16
** character. Two bytes are required in the output buffer for the
** nul-terminator.
*/
len = pMem->n * 2 + 2;
}
/* Set zIn to point at the start of the input buffer and zTerm to point 1
** byte past the end.
**
** Variable zOut is set to point at the output buffer, space obtained
** from sqlite3_malloc().
*/
zIn = (u8*)pMem->z;
zTerm = &zIn[pMem->n];
zOut = (unsigned char *) sqlite3DbMallocRaw(pMem->db, len);
if( !zOut ){
return SQLITE_NOMEM;
}
z = zOut;
if( pMem->enc==SQLITE_UTF8 ){
if( desiredEnc==SQLITE_UTF16LE ){
/* UTF-8 -> UTF-16 Little-endian */
while( zIn<zTerm ){
/* c = sqlite3Utf8Read(zIn, zTerm, (const u8**)&zIn); */
READ_UTF8(zIn, zTerm, c);
WRITE_UTF16LE(z, c);
}
}else{
assert( desiredEnc==SQLITE_UTF16BE );
/* UTF-8 -> UTF-16 Big-endian */
while( zIn<zTerm ){
/* c = sqlite3Utf8Read(zIn, zTerm, (const u8**)&zIn); */
READ_UTF8(zIn, zTerm, c);
WRITE_UTF16BE(z, c);
}
}
pMem->n = (int)(z - zOut);
*z++ = 0;
}else{
assert( desiredEnc==SQLITE_UTF8 );
if( pMem->enc==SQLITE_UTF16LE ){
/* UTF-16 Little-endian -> UTF-8 */
while( zIn<zTerm ){
READ_UTF16LE(zIn, zIn<zTerm, c);
WRITE_UTF8(z, c);
}
}else{
/* UTF-16 Big-endian -> UTF-8 */
while( zIn<zTerm ){
READ_UTF16BE(zIn, zIn<zTerm, c);
WRITE_UTF8(z, c);
}
}
pMem->n = (int)(z - zOut);
}
*z = 0;
assert( (pMem->n+(desiredEnc==SQLITE_UTF8?1:2))<=len );
sqlite3VdbeMemRelease(pMem);
pMem->flags &= ~(MEM_Static|MEM_Dyn|MEM_Ephem);
pMem->enc = desiredEnc;
pMem->flags |= (MEM_Term|MEM_Dyn);
pMem->z = (char*)zOut;
pMem->zMalloc = pMem->z;
translate_out:
#if defined(TRANSLATE_TRACE) && defined(SQLITE_DEBUG)
{
char zBuf[100];
sqlite3VdbeMemPrettyPrint(pMem, zBuf);
fprintf(stderr, "OUTPUT: %s\n", zBuf);
}
#endif
return SQLITE_OK;
}
SQLITE_API void sqlite3_result_zeroblob(sqlite3_context *pCtx, int n){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetZeroBlob(&pCtx->s, n);
}
/**************************** sqlite3_result_ *******************************
** The following routines are used by user-defined functions to specify
** the function result.
**
** The setStrOrError() funtion calls sqlite3VdbeMemSetStr() to store the
** result as a string or blob but if the string or blob is too large, it
** then sets the error code to SQLITE_TOOBIG
*/
static void setResultStrOrError(
sqlite3_context *pCtx, /* Function context */
const char *z, /* String pointer */
int n, /* Bytes in string, or negative */
u8 enc, /* Encoding of z. 0 for BLOBs */
void (*xDel)(void*) /* Destructor function */
){
if( sqlite3VdbeMemSetStr(&pCtx->s, z, n, enc, xDel)==SQLITE_TOOBIG ){
sqlite3_result_error_toobig(pCtx);
}
}
SQLITE_API void sqlite3_result_blob(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( n>=0 );
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
setResultStrOrError(pCtx, z, n, 0, xDel);
}
SQLITE_API void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetDouble(&pCtx->s, rVal);
}
SQLITE_API void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
pCtx->isError = SQLITE_ERROR;
pCtx->fErrorOrAux = 1;
sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
}
#ifndef SQLITE_OMIT_UTF16
SQLITE_API void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
pCtx->isError = SQLITE_ERROR;
pCtx->fErrorOrAux = 1;
sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
}
#endif
SQLITE_API void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetInt64(&pCtx->s, (i64)iVal);
}
SQLITE_API void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetInt64(&pCtx->s, iVal);
}
SQLITE_API void sqlite3_result_null(sqlite3_context *pCtx){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetNull(&pCtx->s);
}
SQLITE_API void sqlite3_result_text(
sqlite3_context *pCtx,
const char *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF8, xDel);
}
#ifndef SQLITE_OMIT_UTF16
SQLITE_API void sqlite3_result_text16(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF16NATIVE, xDel);
}
SQLITE_API void sqlite3_result_text16be(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF16BE, xDel);
}
SQLITE_API void sqlite3_result_text16le(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF16LE, xDel);
}
#endif /* SQLITE_OMIT_UTF16 */
SQLITE_API void sqlite3_result_value(sqlite3_context *pCtx, sqlite3_value *pValue){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemCopy(&pCtx->s, pValue);
}
SQLITE_API void sqlite3_result_null(sqlite3_context *pCtx){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetNull(&pCtx->s);
}
/*
** Attempt to read the database schema and initialize internal
** data structures for a single database file. The index of the
** database file is given by iDb. iDb==0 is used for the main
** database. iDb==1 should never be used. iDb>=2 is used for
** auxiliary databases. Return one of the SQLITE_ error codes to
** indicate success or failure.
*/
static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
int rc;
int i;
int size;
Table *pTab;
Db *pDb;
char const *azArg[4];
int meta[5];
InitData initData;
char const *zMasterSchema;
char const *zMasterName = SCHEMA_TABLE(iDb);
int openedTransaction = 0;
/*
** The master database table has a structure like this
*/
static const char master_schema[] =
"CREATE TABLE sqlite_master(\n"
" type text,\n"
" name text,\n"
" tbl_name text,\n"
" rootpage integer,\n"
" sql text\n"
")"
;
#ifndef SQLITE_OMIT_TEMPDB
static const char temp_master_schema[] =
"CREATE TEMP TABLE sqlite_temp_master(\n"
" type text,\n"
" name text,\n"
" tbl_name text,\n"
" rootpage integer,\n"
" sql text\n"
")"
;
#else
#define temp_master_schema 0
#endif
assert( iDb>=0 && iDb<db->nDb );
assert( db->aDb[iDb].pSchema );
assert( sqlite3_mutex_held(db->mutex) );
assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
/* zMasterSchema and zInitScript are set to point at the master schema
** and initialisation script appropriate for the database being
** initialised. zMasterName is the name of the master table.
*/
if( !OMIT_TEMPDB && iDb==1 ){
zMasterSchema = temp_master_schema;
}else{
zMasterSchema = master_schema;
}
zMasterName = SCHEMA_TABLE(iDb);
/* Construct the schema tables. */
azArg[0] = zMasterName;
azArg[1] = "1";
azArg[2] = zMasterSchema;
azArg[3] = 0;
initData.db = db;
initData.iDb = iDb;
initData.rc = SQLITE_OK;
initData.pzErrMsg = pzErrMsg;
(void)sqlite3SafetyOff(db);
sqlite3InitCallback(&initData, 3, (char **)azArg, 0);
(void)sqlite3SafetyOn(db);
if( initData.rc ){
rc = initData.rc;
goto error_out;
}
pTab = sqlite3FindTable(db, zMasterName, db->aDb[iDb].zName);
if( ALWAYS(pTab) ){
pTab->tabFlags |= TF_Readonly;
}
/* Create a cursor to hold the database open
*/
pDb = &db->aDb[iDb];
if( pDb->pBt==0 ){
if( !OMIT_TEMPDB && ALWAYS(iDb==1) ){
DbSetProperty(db, 1, DB_SchemaLoaded);
}
return SQLITE_OK;
}
/* If there is not already a read-only (or read-write) transaction opened
** on the b-tree database, open one now. If a transaction is opened, it
** will be closed before this function returns. */
sqlite3BtreeEnter(pDb->pBt);
if( !sqlite3BtreeIsInReadTrans(pDb->pBt) ){
rc = sqlite3BtreeBeginTrans(pDb->pBt, 0);
if( rc!=SQLITE_OK ){
sqlite3SetString(pzErrMsg, db, "%s", sqlite3ErrStr(rc));
goto initone_error_out;
}
openedTransaction = 1;
}
/* Get the database meta information.
**
** Meta values are as follows:
** meta[0] Schema cookie. Changes with each schema change.
** meta[1] File format of schema layer.
** meta[2] Size of the page cache.
** meta[3] Largest rootpage (auto/incr_vacuum mode)
** meta[4] Db text encoding. 1:UTF-8 2:UTF-16LE 3:UTF-16BE
** meta[5] User version
** meta[6] Incremental vacuum mode
** meta[7] unused
** meta[8] unused
** meta[9] unused
**
** Note: The #defined SQLITE_UTF* symbols in sqliteInt.h correspond to
** the possible values of meta[4].
*/
for(i=0; i<ArraySize(meta); i++){
sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
}
pDb->pSchema->schema_cookie = meta[BTREE_SCHEMA_VERSION-1];
/* If opening a non-empty database, check the text encoding. For the
** main database, set sqlite3.enc to the encoding of the main database.
** For an attached db, it is an error if the encoding is not the same
** as sqlite3.enc.
*/
if( meta[BTREE_TEXT_ENCODING-1] ){ /* text encoding */
if( iDb==0 ){
u8 encoding;
/* If opening the main database, set ENC(db). */
encoding = (u8)meta[BTREE_TEXT_ENCODING-1] & 3;
if( encoding==0 ) encoding = SQLITE_UTF8;
ENC(db) = encoding;
db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, "BINARY", 0);
}else{
/* If opening an attached database, the encoding much match ENC(db) */
if( meta[BTREE_TEXT_ENCODING-1]!=ENC(db) ){
sqlite3SetString(pzErrMsg, db, "attached databases must use the same"
" text encoding as main database");
rc = SQLITE_ERROR;
goto initone_error_out;
}
}
}else{
DbSetProperty(db, iDb, DB_Empty);
}
pDb->pSchema->enc = ENC(db);
if( pDb->pSchema->cache_size==0 ){
size = meta[BTREE_DEFAULT_CACHE_SIZE-1];
if( size==0 ){ size = SQLITE_DEFAULT_CACHE_SIZE; }
if( size<0 ) size = -size;
pDb->pSchema->cache_size = size;
sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
}
/*
** file_format==1 Version 3.0.0.
** file_format==2 Version 3.1.3. // ALTER TABLE ADD COLUMN
** file_format==3 Version 3.1.4. // ditto but with non-NULL defaults
** file_format==4 Version 3.3.0. // DESC indices. Boolean constants
*/
pDb->pSchema->file_format = (u8)meta[BTREE_FILE_FORMAT-1];
if( pDb->pSchema->file_format==0 ){
pDb->pSchema->file_format = 1;
}
if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){
sqlite3SetString(pzErrMsg, db, "unsupported file format");
rc = SQLITE_ERROR;
goto initone_error_out;
}
/* Ticket #2804: When we open a database in the newer file format,
** clear the legacy_file_format pragma flag so that a VACUUM will
** not downgrade the database and thus invalidate any descending
** indices that the user might have created.
*/
if( iDb==0 && meta[BTREE_FILE_FORMAT-1]>=4 ){
db->flags &= ~SQLITE_LegacyFileFmt;
}
/* Read the schema information out of the schema tables
*/
assert( db->init.busy );
{
char *zSql;
zSql = sqlite3MPrintf(db,
"SELECT name, rootpage, sql FROM '%q'.%s",
db->aDb[iDb].zName, zMasterName);
(void)sqlite3SafetyOff(db);
#ifndef SQLITE_OMIT_AUTHORIZATION
{
int (*xAuth)(void*,int,const char*,const char*,const char*,const char*);
xAuth = db->xAuth;
db->xAuth = 0;
#endif
rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
#ifndef SQLITE_OMIT_AUTHORIZATION
db->xAuth = xAuth;
}
#endif
if( rc==SQLITE_OK ) rc = initData.rc;
(void)sqlite3SafetyOn(db);
sqlite3DbFree(db, zSql);
#ifndef SQLITE_OMIT_ANALYZE
if( rc==SQLITE_OK ){
sqlite3AnalysisLoad(db, iDb);
}
#endif
}
if( db->mallocFailed ){
rc = SQLITE_NOMEM;
sqlite3ResetInternalSchema(db, 0);
}
if( rc==SQLITE_OK || (db->flags&SQLITE_RecoveryMode)){
/* Black magic: If the SQLITE_RecoveryMode flag is set, then consider
** the schema loaded, even if errors occurred. In this situation the
** current sqlite3_prepare() operation will fail, but the following one
** will attempt to compile the supplied statement against whatever subset
** of the schema was loaded before the error occurred. The primary
** purpose of this is to allow access to the sqlite_master table
** even when its contents have been corrupted.
*/
DbSetProperty(db, iDb, DB_SchemaLoaded);
rc = SQLITE_OK;
}
/* Jump here for an error that occurs after successfully allocating
** curMain and calling sqlite3BtreeEnter(). For an error that occurs
** before that point, jump to error_out.
*/
initone_error_out:
if( openedTransaction ){
sqlite3BtreeCommit(pDb->pBt);
}
sqlite3BtreeLeave(pDb->pBt);
error_out:
if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
db->mallocFailed = 1;
}
return rc;
}
void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
pCtx->isError = SQLITE_ERROR;
sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
}
/*
** Compile the UTF-8 encoded SQL statement zSql into a statement handle.
*/
static int sqlite3Prepare(
sqlite3 *db, /* Database handle. */
const char *zSql, /* UTF-8 encoded SQL statement. */
int nBytes, /* Length of zSql in bytes. */
int saveSqlFlag, /* True to copy SQL text into the sqlite3_stmt */
Vdbe *pReprepare, /* VM being reprepared */
sqlite3_stmt **ppStmt, /* OUT: A pointer to the prepared statement */
const char **pzTail /* OUT: End of parsed string */
){
Parse *pParse; /* Parsing context */
char *zErrMsg = 0; /* Error message */
int rc = SQLITE_OK; /* Result code */
int i; /* Loop counter */
/* Allocate the parsing context */
pParse = sqlite3StackAllocZero(db, sizeof(*pParse));
if( pParse==0 ){
rc = SQLITE_NOMEM;
goto end_prepare;
}
pParse->pReprepare = pReprepare;
if( sqlite3SafetyOn(db) ){
rc = SQLITE_MISUSE;
goto end_prepare;
}
assert( ppStmt && *ppStmt==0 );
assert( !db->mallocFailed );
assert( sqlite3_mutex_held(db->mutex) );
/* Check to verify that it is possible to get a read lock on all
** database schemas. The inability to get a read lock indicates that
** some other database connection is holding a write-lock, which in
** turn means that the other connection has made uncommitted changes
** to the schema.
**
** Were we to proceed and prepare the statement against the uncommitted
** schema changes and if those schema changes are subsequently rolled
** back and different changes are made in their place, then when this
** prepared statement goes to run the schema cookie would fail to detect
** the schema change. Disaster would follow.
**
** This thread is currently holding mutexes on all Btrees (because
** of the sqlite3BtreeEnterAll() in sqlite3LockAndPrepare()) so it
** is not possible for another thread to start a new schema change
** while this routine is running. Hence, we do not need to hold
** locks on the schema, we just need to make sure nobody else is
** holding them.
**
** Note that setting READ_UNCOMMITTED overrides most lock detection,
** but it does *not* override schema lock detection, so this all still
** works even if READ_UNCOMMITTED is set.
*/
for(i=0; i<db->nDb; i++) {
Btree *pBt = db->aDb[i].pBt;
if( pBt ){
assert( sqlite3BtreeHoldsMutex(pBt) );
rc = sqlite3BtreeSchemaLocked(pBt);
if( rc ){
const char *zDb = db->aDb[i].zName;
sqlite3Error(db, rc, "database schema is locked: %s", zDb);
(void)sqlite3SafetyOff(db);
testcase( db->flags & SQLITE_ReadUncommitted );
goto end_prepare;
}
}
}
sqlite3VtabUnlockList(db);
pParse->db = db;
if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){
char *zSqlCopy;
int mxLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
testcase( nBytes==mxLen );
testcase( nBytes==mxLen+1 );
if( nBytes>mxLen ){
sqlite3Error(db, SQLITE_TOOBIG, "statement too long");
(void)sqlite3SafetyOff(db);
rc = sqlite3ApiExit(db, SQLITE_TOOBIG);
goto end_prepare;
}
zSqlCopy = sqlite3DbStrNDup(db, zSql, nBytes);
if( zSqlCopy ){
sqlite3RunParser(pParse, zSqlCopy, &zErrMsg);
sqlite3DbFree(db, zSqlCopy);
pParse->zTail = &zSql[pParse->zTail-zSqlCopy];
}else{
pParse->zTail = &zSql[nBytes];
}
}else{
sqlite3RunParser(pParse, zSql, &zErrMsg);
}
if( db->mallocFailed ){
pParse->rc = SQLITE_NOMEM;
}
if( pParse->rc==SQLITE_DONE ) pParse->rc = SQLITE_OK;
if( pParse->checkSchema ){
schemaIsValid(pParse);
}
if( pParse->rc==SQLITE_SCHEMA ){
sqlite3ResetInternalSchema(db, 0);
}
if( db->mallocFailed ){
pParse->rc = SQLITE_NOMEM;
}
if( pzTail ){
*pzTail = pParse->zTail;
}
rc = pParse->rc;
#ifndef SQLITE_OMIT_EXPLAIN
if( rc==SQLITE_OK && pParse->pVdbe && pParse->explain ){
static const char * const azColName[] = {
"addr", "opcode", "p1", "p2", "p3", "p4", "p5", "comment",
"order", "from", "detail"
};
int iFirst, mx;
if( pParse->explain==2 ){
sqlite3VdbeSetNumCols(pParse->pVdbe, 3);
iFirst = 8;
mx = 11;
}else{
sqlite3VdbeSetNumCols(pParse->pVdbe, 8);
iFirst = 0;
mx = 8;
}
for(i=iFirst; i<mx; i++){
sqlite3VdbeSetColName(pParse->pVdbe, i-iFirst, COLNAME_NAME,
azColName[i], SQLITE_STATIC);
}
}
#endif
if( sqlite3SafetyOff(db) ){
rc = SQLITE_MISUSE;
}
assert( db->init.busy==0 || saveSqlFlag==0 );
if( db->init.busy==0 ){
Vdbe *pVdbe = pParse->pVdbe;
sqlite3VdbeSetSql(pVdbe, zSql, (int)(pParse->zTail-zSql), saveSqlFlag);
}
if( pParse->pVdbe && (rc!=SQLITE_OK || db->mallocFailed) ){
sqlite3VdbeFinalize(pParse->pVdbe);
assert(!(*ppStmt));
}else{
*ppStmt = (sqlite3_stmt*)pParse->pVdbe;
}
if( zErrMsg ){
sqlite3Error(db, rc, "%s", zErrMsg);
sqlite3DbFree(db, zErrMsg);
}else{
sqlite3Error(db, rc, 0);
}
/* Delete any TriggerPrg structures allocated while parsing this statement. */
while( pParse->pTriggerPrg ){
TriggerPrg *pT = pParse->pTriggerPrg;
pParse->pTriggerPrg = pT->pNext;
sqlite3VdbeProgramDelete(db, pT->pProgram, 0);
sqlite3DbFree(db, pT);
}
end_prepare:
sqlite3StackFree(db, pParse);
rc = sqlite3ApiExit(db, rc);
assert( (rc&db->errMask)==rc );
return rc;
}
void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetInt64(&pCtx->s, (i64)iVal);
}
void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetDouble(pCtx->pOut, rVal);
}
/* Force an SQLITE_TOOBIG error. */
void sqlite3_result_error_toobig(sqlite3_context *pCtx){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
pCtx->isError = SQLITE_TOOBIG;
sqlite3VdbeMemSetStr(&pCtx->s, "string or blob too big", -1,
SQLITE_UTF8, SQLITE_STATIC);
}
void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetInt64(pCtx->pOut, iVal);
}
/* An SQLITE_NOMEM error. */
void sqlite3_result_error_nomem(sqlite3_context *pCtx){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetNull(&pCtx->s);
pCtx->isError = SQLITE_NOMEM;
pCtx->s.db->mallocFailed = 1;
}
/* noop */
}else{
xDel((void*)p);
}
if( pCtx ) sqlite3_result_error_toobig(pCtx);
return SQLITE_TOOBIG;
}
void sqlite3_result_blob(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( n>=0 );
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
setResultStrOrError(pCtx, z, n, 0, xDel);
}
void sqlite3_result_blob64(
sqlite3_context *pCtx,
const void *z,
sqlite3_uint64 n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
assert( xDel!=SQLITE_DYNAMIC );
if( n>0x7fffffff ){
(void)invokeValueDestructor(z, xDel, pCtx);
}else{
setResultStrOrError(pCtx, z, (int)n, 0, xDel);
}
}
void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetDouble(pCtx->pOut, rVal);
}
void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
pCtx->isError = SQLITE_ERROR;
pCtx->fErrorOrAux = 1;
sqlite3VdbeMemSetStr(pCtx->pOut, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
}
#ifndef SQLITE_OMIT_UTF16
void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
pCtx->isError = SQLITE_ERROR;
pCtx->fErrorOrAux = 1;
sqlite3VdbeMemSetStr(pCtx->pOut, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
}
#endif
void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetInt64(pCtx->pOut, (i64)iVal);
}
void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetInt64(pCtx->pOut, iVal);
}
void sqlite3_result_null(sqlite3_context *pCtx){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemSetNull(pCtx->pOut);
}
void sqlite3_result_text(
sqlite3_context *pCtx,
const char *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF8, xDel);
}
void sqlite3_result_text64(
sqlite3_context *pCtx,
const char *z,
sqlite3_uint64 n,
void (*xDel)(void *),
unsigned char enc
){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
assert( xDel!=SQLITE_DYNAMIC );
if( enc==SQLITE_UTF16 ) enc = SQLITE_UTF16NATIVE;
if( n>0x7fffffff ){
(void)invokeValueDestructor(z, xDel, pCtx);
}else{
setResultStrOrError(pCtx, z, (int)n, enc, xDel);
}
}
#ifndef SQLITE_OMIT_UTF16
void sqlite3_result_text16(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF16NATIVE, xDel);
}
void sqlite3_result_text16be(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF16BE, xDel);
}
void sqlite3_result_text16le(
sqlite3_context *pCtx,
const void *z,
int n,
void (*xDel)(void *)
){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
setResultStrOrError(pCtx, z, n, SQLITE_UTF16LE, xDel);
}
#endif /* SQLITE_OMIT_UTF16 */
void sqlite3_result_value(sqlite3_context *pCtx, sqlite3_value *pValue){
assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
sqlite3VdbeMemCopy(pCtx->pOut, pValue);
}
/*
** Convert pMem to type integer. Invalidate any prior representations.
*/
int sqlite3VdbeMemIntegerify(Mem *pMem){
assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
pMem->u.i = sqlite3VdbeIntValue(pMem);
setTypeFlag(pMem, MEM_Int);
return SQLITE_OK;
}
/*
** Change the value of a Mem to be a string or a BLOB.
**
** The memory management strategy depends on the value of the xDel
** parameter. If the value passed is SQLITE_TRANSIENT, then the
** string is copied into a (possibly existing) buffer managed by the
** Mem structure. Otherwise, any existing buffer is freed and the
** pointer copied.
**
** If the string is too large (if it exceeds the SQLITE_LIMIT_LENGTH
** size limit) then no memory allocation occurs. If the string can be
** stored without allocating memory, then it is. If a memory allocation
** is required to store the string, then value of pMem is unchanged. In
** either case, SQLITE_TOOBIG is returned.
*/
SQLITE_PRIVATE int sqlite3VdbeMemSetStr(
Mem *pMem, /* Memory cell to set to string value */
const char *z, /* String pointer */
int n, /* Bytes in string, or negative */
u8 enc, /* Encoding of z. 0 for BLOBs */
void (*xDel)(void*) /* Destructor function */
){
int nByte = n; /* New value for pMem->n */
int iLimit; /* Maximum allowed string or blob size */
u16 flags = 0; /* New value for pMem->flags */
assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
assert( (pMem->flags & MEM_RowSet)==0 );
/* If z is a NULL pointer, set pMem to contain an SQL NULL. */
if( !z ){
sqlite3VdbeMemSetNull(pMem);
return SQLITE_OK;
}
if( pMem->db ){
iLimit = pMem->db->aLimit[SQLITE_LIMIT_LENGTH];
}else{
iLimit = SQLITE_MAX_LENGTH;
}
flags = (enc==0?MEM_Blob:MEM_Str);
if( nByte<0 ){
assert( enc!=0 );
if( enc==SQLITE_UTF8 ){
for(nByte=0; nByte<=iLimit && z[nByte]; nByte++){}
}else{
for(nByte=0; nByte<=iLimit && (z[nByte] | z[nByte+1]); nByte+=2){}
}
flags |= MEM_Term;
}
/* The following block sets the new values of Mem.z and Mem.xDel. It
** also sets a flag in local variable "flags" to indicate the memory
** management (one of MEM_Dyn or MEM_Static).
*/
if( xDel==SQLITE_TRANSIENT ){
int nAlloc = nByte;
if( flags&MEM_Term ){
nAlloc += (enc==SQLITE_UTF8?1:2);
}
if( nByte>iLimit ){
return SQLITE_TOOBIG;
}
if( sqlite3VdbeMemGrow(pMem, nAlloc, 0) ){
return SQLITE_NOMEM;
}
memcpy(pMem->z, z, nAlloc);
}else if( xDel==SQLITE_DYNAMIC ){
sqlite3VdbeMemRelease(pMem);
pMem->zMalloc = pMem->z = (char *)z;
pMem->xDel = 0;
}else{
sqlite3VdbeMemRelease(pMem);
pMem->z = (char *)z;
pMem->xDel = xDel;
flags |= ((xDel==SQLITE_STATIC)?MEM_Static:MEM_Dyn);
}
pMem->n = nByte;
pMem->flags = flags;
pMem->enc = (enc==0 ? SQLITE_UTF8 : enc);
pMem->type = (enc==0 ? SQLITE_BLOB : SQLITE_TEXT);
#ifndef SQLITE_OMIT_UTF16
if( pMem->enc!=SQLITE_UTF8 && sqlite3VdbeMemHandleBom(pMem) ){
return SQLITE_NOMEM;
}
#endif
if( nByte>iLimit ){
return SQLITE_TOOBIG;
}
return SQLITE_OK;
}
/*
** Convert pMem so that it is of type MEM_Real.
** Invalidate any prior representations.
*/
int sqlite3VdbeMemRealify(Mem *pMem){
assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
pMem->r = sqlite3VdbeRealValue(pMem);
setTypeFlag(pMem, MEM_Real);
return SQLITE_OK;
}
/*
** Enter a mutex on the given BTree object.
** 在给定的B树对象上输入一个互斥锁。
** If the object is not sharable, then no mutex is ever required
** and this routine is a no-op. The underlying mutex is non-recursive.
** But we keep a reference count in Btree.wantToLock so the behavior
** of this interface is recursive.
**
** To avoid deadlocks, multiple Btrees are locked in the same order
** by all database connections. The p->pNext is a list of other
** Btrees belonging to the same database connection as the p Btree
** which need to be locked after p. If we cannot get a lock on
** p, then first unlock all of the others on p->pNext, then wait
** for the lock to become available on p, then relock all of the
** subsequent Btrees that desire a lock.
** 如果对象不可共享，那么不需要互斥锁并且这个程序是无操作的。这个潜在的互斥锁是非递归的。
** 但是在Btree.wantToLock中保持对参数的计数，因此这歌接口的操作是递归的。
**
** 为了避免死锁，多个btree以相同的顺序被所有数据库连接锁定。p->pNext是其他属于相同数据库连接的B树列表
** 作为B树p，p->pNext需要在p后被锁。如果在p上不能的锁，那么首先在p->pNext上解除其他所有锁，然后等待
** 直到在p上的锁可用，接着对需要加锁的所有后续B树重新加锁。
*/
void sqlite3BtreeEnter(Btree *p){
Btree *pLater;
/* Some basic sanity checking on the Btree. The list of Btrees
** connected by pNext and pPrev should be in sorted order by
** Btree.pBt value. All elements of the list should belong to
** the same connection. Only shared Btrees are on the list.
** 在B树上进行基本的完整性检查。通过pNext和pPrev连接的B树列表应该
** 按Btree.pBt的值进行排序。列表的所有元素都应属于相同的连接。只有共享的B树在列表中。
*/
assert( p->pNext==0 || p->pNext->pBt>p->pBt );
assert( p->pPrev==0 || p->pPrev->pBt<p->pBt );
assert( p->pNext==0 || p->pNext->db==p->db );
assert( p->pPrev==0 || p->pPrev->db==p->db );
assert( p->sharable || (p->pNext==0 && p->pPrev==0) );
/* Check for locking consistency 检查锁的一致性*/
assert( !p->locked || p->wantToLock>0 );
assert( p->sharable || p->wantToLock==0 );
/* We should already hold a lock on the database connection 在数据库连接上应该已经持有一个锁*/
assert( sqlite3_mutex_held(p->db->mutex) );
/* Unless the database is sharable and unlocked, then BtShared.db
** should already be set correctly.
** 如果数据库是可共享的并且没有被锁，那么BtShared.db应该已经被正确设置。
*/
assert( (p->locked==0 && p->sharable) || p->pBt->db==p->db );
if( !p->sharable ) return;
p->wantToLock++;
if( p->locked ) return;
/* In most cases, we should be able to acquire the lock we
** want without having to go throught the ascending lock
** procedure that follows. Just be sure not to block.
** 在大多数情况下，我们应该能得到锁，我们想要的这个锁不必通过追溯在其后的锁进程。只是对块不确定。
*/
if( sqlite3_mutex_try(p->pBt->mutex)==SQLITE_OK ){
p->pBt->db = p->db;
p->locked = 1;
return;
}
/* To avoid deadlock, first release all locks with a larger
** BtShared address. Then acquire our lock. Then reacquire
** the other BtShared locks that we used to hold in ascending
** order.
** 为了避免死锁，首先释放所有更大BtShared地址的锁。然后获得我们的锁。
** 接着再次获取我们曾在提升顺序中持有的其他锁。
*/
for(pLater=p->pNext; pLater; pLater=pLater->pNext){
assert( pLater->sharable );
assert( pLater->pNext==0 || pLater->pNext->pBt>pLater->pBt );
assert( !pLater->locked || pLater->wantToLock>0 );
if( pLater->locked ){
unlockBtreeMutex(pLater);
}
}
lockBtreeMutex(p);
for(pLater=p->pNext; pLater; pLater=pLater->pNext){
if( pLater->wantToLock ){
lockBtreeMutex(pLater);
}
}
}
/*
** Return a block of memory of at least nBytes in size.
** Return NULL if unable.
*/
static void *memsys3Malloc(int nByte){
int i;
int nBlock;
int toFree;
assert( sqlite3_mutex_held(mem.mutex) );
assert( sizeof(Mem3Block)==8 );
if( nByte<=0 ){
nBlock = 2;
}else{
nBlock = (nByte + 15)/8;
}
assert( nBlock >= 2 );
/* STEP 1:
** Look for an entry of the correct size in either the small
** chunk table or in the large chunk hash table. This is
** successful most of the time (about 9 times out of 10).
*/
if( nBlock <= MX_SMALL ){
i = mem.aiSmall[nBlock-2];
if( i>0 ){
memsys3UnlinkFromList(i, &mem.aiSmall[nBlock-2]);
return memsys3Checkout(i, nBlock);
}
}else{
int hash = nBlock % N_HASH;
for(i=mem.aiHash[hash]; i>0; i=mem.aPool[i].u.list.next){
if( mem.aPool[i-1].u.hdr.size==nBlock ){
memsys3UnlinkFromList(i, &mem.aiHash[hash]);
return memsys3Checkout(i, nBlock);
}
}
}
/* STEP 2:
** Try to satisfy the allocation by carving a piece off of the end
** of the master chunk. This step usually works if step 1 fails.
*/
if( mem.szMaster>=nBlock ){
return memsys3FromMaster(nBlock);
}
/* STEP 3:
** Loop through the entire memory pool. Coalesce adjacent free
** chunks. Recompute the master chunk as the largest free chunk.
** Then try again to satisfy the allocation by carving a piece off
** of the end of the master chunk. This step happens very
** rarely (we hope!)
*/
for(toFree=nBlock*16; toFree<SQLITE_MEMORY_SIZE*2; toFree *= 2){
memsys3OutOfMemory(toFree);
if( mem.iMaster ){
memsys3Link(mem.iMaster);
mem.iMaster = 0;
mem.szMaster = 0;
}
for(i=0; i<N_HASH; i++){
memsys3Merge(&mem.aiHash[i]);
}
for(i=0; i<MX_SMALL-1; i++){
memsys3Merge(&mem.aiSmall[i]);
}
if( mem.szMaster ){
memsys3Unlink(mem.iMaster);
if( mem.szMaster>=nBlock ){
return memsys3FromMaster(nBlock);
}
}
}
/* If none of the above worked, then we fail. */
return 0;
}
/*
** Create a new collating function for database "db". The name is zName
** and the encoding is enc.
*/
static int createCollation(
sqlite3* db,
const char *zName,
int enc,
void* pCtx,
int(*xCompare)(void*,int,const void*,int,const void*),
void(*xDel)(void*)
){
CollSeq *pColl;
int enc2;
if( sqlite3SafetyCheck(db) ){
return SQLITE_MISUSE;
}
assert( sqlite3_mutex_held(db->mutex) );
/* If SQLITE_UTF16 is specified as the encoding type, transform this
** to one of SQLITE_UTF16LE or SQLITE_UTF16BE using the
** SQLITE_UTF16NATIVE macro. SQLITE_UTF16 is not used internally.
*/
enc2 = enc & ~SQLITE_UTF16_ALIGNED;
if( enc2==SQLITE_UTF16 ){
enc2 = SQLITE_UTF16NATIVE;
}
if( (enc2&~3)!=0 ){
sqlite3Error(db, SQLITE_ERROR, "unknown encoding");
return SQLITE_ERROR;
}
/* Check if this call is removing or replacing an existing collation
** sequence. If so, and there are active VMs, return busy. If there
** are no active VMs, invalidate any pre-compiled statements.
*/
pColl = sqlite3FindCollSeq(db, (u8)enc2, zName, strlen(zName), 0);
if( pColl && pColl->xCmp ){
if( db->activeVdbeCnt ){
sqlite3Error(db, SQLITE_BUSY,
"Unable to delete/modify collation sequence due to active statements");
return SQLITE_BUSY;
}
sqlite3ExpirePreparedStatements(db);
/* If collation sequence pColl was created directly by a call to
** sqlite3_create_collation, and not generated by synthCollSeq(),
** then any copies made by synthCollSeq() need to be invalidated.
** Also, collation destructor - CollSeq.xDel() - function may need
** to be called.
*/
if( (pColl->enc & ~SQLITE_UTF16_ALIGNED)==enc2 ){
CollSeq *aColl = (CollSeq*)sqlite3HashFind(&db->aCollSeq, zName, strlen(zName));
int j;
for(j=0; j<3; j++){
CollSeq *p = &aColl[j];
if( p->enc==pColl->enc ){
if( p->xDel ){
p->xDel(p->pUser);
}
p->xCmp = 0;
}
}
}
}
pColl = sqlite3FindCollSeq(db, (u8)enc2, zName, strlen(zName), 1);
if( pColl ){
pColl->xCmp = xCompare;
pColl->pUser = pCtx;
pColl->xDel = xDel;
pColl->enc = enc2 | (enc & SQLITE_UTF16_ALIGNED);
}
sqlite3Error(db, SQLITE_OK, 0);
return SQLITE_OK;
}
SQLITE_API void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
sqlite3VdbeMemSetDouble(&pCtx->s, rVal);
}
