Sandbox::https://github.com/ashed/sqlcipher/blob/Xcode5/src/pcache.c

Repository navigation

History

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

** 2008 August 05

** The author disclaims copyright to this source code. In place of

** a legal notice, here is a blessing:

** May you do good and not evil.

** May you find forgiveness for yourself and forgive others.

** May you share freely, never taking more than you give.

*************************************************************************

** This file implements that page cache.

#include "sqliteInt.h"

** A complete page cache is an instance of this structure.

struct PCache {

PgHdr *pDirty, *pDirtyTail; /* List of dirty pages in LRU order */

PgHdr *pSynced; /* Last synced page in dirty page list */

int nRef; /* Number of referenced pages */

int szCache; /* Configured cache size */

int szPage; /* Size of every page in this cache */

int szExtra; /* Size of extra space for each page */

int bPurgeable; /* True if pages are on backing store */

int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */

void *pStress; /* Argument to xStress */

sqlite3_pcache *pCache; /* Pluggable cache module */

PgHdr *pPage1; /* Reference to page 1 */

};

** Some of the assert() macros in this code are too expensive to run

** even during normal debugging. Use them only rarely on long-running

** tests. Enable the expensive asserts using the

** -DSQLITE_ENABLE_EXPENSIVE_ASSERT=1 compile-time option.

#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT

# define expensive_assert(X) assert(X)

#else

# define expensive_assert(X)

#endif

/********************************** Linked List Management ********************/

#if !defined(NDEBUG) && defined(SQLITE_ENABLE_EXPENSIVE_ASSERT)

** Check that the pCache->pSynced variable is set correctly. If it

** is not, either fail an assert or return zero. Otherwise, return

** non-zero. This is only used in debugging builds, as follows:

** expensive_assert( pcacheCheckSynced(pCache) );

static int pcacheCheckSynced(PCache *pCache){

PgHdr *p;

for(p=pCache->pDirtyTail; p!=pCache->pSynced; p=p->pDirtyPrev){

assert( p->nRef || (p->flags&PGHDR_NEED_SYNC) );

}

return (p==0 || p->nRef || (p->flags&PGHDR_NEED_SYNC)==0);

}

#endif /* !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT */

** Remove page pPage from the list of dirty pages.

static void pcacheRemoveFromDirtyList(PgHdr *pPage){

PCache *p = pPage->pCache;

assert( pPage->pDirtyNext || pPage==p->pDirtyTail );

assert( pPage->pDirtyPrev || pPage==p->pDirty );

/* Update the PCache1.pSynced variable if necessary. */

if( p->pSynced==pPage ){

PgHdr *pSynced = pPage->pDirtyPrev;

while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){

pSynced = pSynced->pDirtyPrev;

}

p->pSynced = pSynced;

}

if( pPage->pDirtyNext ){

pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev;

}else{

assert( pPage==p->pDirtyTail );

p->pDirtyTail = pPage->pDirtyPrev;

}

if( pPage->pDirtyPrev ){

pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;

}else{

assert( pPage==p->pDirty );

p->pDirty = pPage->pDirtyNext;

}

pPage->pDirtyNext = 0;

pPage->pDirtyPrev = 0;

expensive_assert( pcacheCheckSynced(p) );

}

** Add page pPage to the head of the dirty list (PCache1.pDirty is set to

** pPage).

static void pcacheAddToDirtyList(PgHdr *pPage){

PCache *p = pPage->pCache;

assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );

pPage->pDirtyNext = p->pDirty;

if( pPage->pDirtyNext ){

assert( pPage->pDirtyNext->pDirtyPrev==0 );

pPage->pDirtyNext->pDirtyPrev = pPage;

}

p->pDirty = pPage;

if( !p->pDirtyTail ){

p->pDirtyTail = pPage;

}

if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){

p->pSynced = pPage;

}

expensive_assert( pcacheCheckSynced(p) );

}

** Wrapper around the pluggable caches xUnpin method. If the cache is

** being used for an in-memory database, this function is a no-op.

static void pcacheUnpin(PgHdr *p){

PCache *pCache = p->pCache;

if( pCache->bPurgeable ){

if( p->pgno==1 ){

pCache->pPage1 = 0;

}

sqlite3GlobalConfig.pcache2.xUnpin(pCache->pCache, p->pPage, 0);

}

/*************************************************** General Interfaces ******

** Initialize and shutdown the page cache subsystem. Neither of these

** functions are threadsafe.

int sqlite3PcacheInitialize(void){

if( sqlite3GlobalConfig.pcache2.xInit==0 ){

/* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the

** built-in default page cache is used instead of the application defined

** page cache. */

sqlite3PCacheSetDefault();

}

return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg);

}

void sqlite3PcacheShutdown(void){

if( sqlite3GlobalConfig.pcache2.xShutdown ){

/* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */

sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg);

}

** Return the size in bytes of a PCache object.

int sqlite3PcacheSize(void){ return sizeof(PCache); }

** Create a new PCache object. Storage space to hold the object

** has already been allocated and is passed in as the p pointer.

** The caller discovers how much space needs to be allocated by

** calling sqlite3PcacheSize().

void sqlite3PcacheOpen(

int szPage, /* Size of every page */

int szExtra, /* Extra space associated with each page */

int bPurgeable, /* True if pages are on backing store */

int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */

void *pStress, /* Argument to xStress */

PCache *p /* Preallocated space for the PCache */

){

memset(p, 0, sizeof(PCache));

p->szPage = szPage;

p->szExtra = szExtra;

p->bPurgeable = bPurgeable;

p->xStress = xStress;

p->pStress = pStress;

p->szCache = 100;

}

** Change the page size for PCache object. The caller must ensure that there

** are no outstanding page references when this function is called.

void sqlite3PcacheSetPageSize(PCache *pCache, int szPage){

assert( pCache->nRef==0 && pCache->pDirty==0 );

if( pCache->pCache ){

sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);

pCache->pCache = 0;

pCache->pPage1 = 0;

}

pCache->szPage = szPage;

}

** Compute the number of pages of cache requested.

static int numberOfCachePages(PCache *p){

if( p->szCache>=0 ){

return p->szCache;

}else{

return (int)((-1024*(i64)p->szCache)/(p->szPage+p->szExtra));

}

** Try to obtain a page from the cache.

int sqlite3PcacheFetch(

PCache *pCache, /* Obtain the page from this cache */

Pgno pgno, /* Page number to obtain */

int createFlag, /* If true, create page if it does not exist already */

PgHdr **ppPage /* Write the page here */

){

sqlite3_pcache_page *pPage = 0;

PgHdr *pPgHdr = 0;

int eCreate;

assert( pCache!=0 );

assert( createFlag==1 || createFlag==0 );

assert( pgno>0 );

/* If the pluggable cache (sqlite3_pcache*) has not been allocated,

** allocate it now.

if( !pCache->pCache && createFlag ){

sqlite3_pcache *p;

p = sqlite3GlobalConfig.pcache2.xCreate(

pCache->szPage, pCache->szExtra + sizeof(PgHdr), pCache->bPurgeable

);

if( !p ){

return SQLITE_NOMEM;

}

sqlite3GlobalConfig.pcache2.xCachesize(p, numberOfCachePages(pCache));

pCache->pCache = p;

}

eCreate = createFlag * (1 + (!pCache->bPurgeable || !pCache->pDirty));

if( pCache->pCache ){

pPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);

}

if( !pPage && eCreate==1 ){

PgHdr *pPg;

/* Find a dirty page to write-out and recycle. First try to find a

** page that does not require a journal-sync (one with PGHDR_NEED_SYNC

** cleared), but if that is not possible settle for any other

** unreferenced dirty page.

expensive_assert( pcacheCheckSynced(pCache) );

for(pPg=pCache->pSynced;

pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC));

pPg=pPg->pDirtyPrev

);

pCache->pSynced = pPg;

if( !pPg ){

for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev);

}

if( pPg ){

int rc;

#ifdef SQLITE_LOG_CACHE_SPILL

sqlite3_log(SQLITE_FULL,

"spill page %d making room for %d - cache used: %d/%d",

pPg->pgno, pgno,

sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache),

numberOfCachePages(pCache));

#endif

rc = pCache->xStress(pCache->pStress, pPg);

if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){

return rc;

}

pPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2);

}

if( pPage ){

pPgHdr = (PgHdr *)pPage->pExtra;

if( !pPgHdr->pPage ){

memset(pPgHdr, 0, sizeof(PgHdr));

pPgHdr->pPage = pPage;

pPgHdr->pData = pPage->pBuf;

pPgHdr->pExtra = (void *)&pPgHdr[1];

memset(pPgHdr->pExtra, 0, pCache->szExtra);

pPgHdr->pCache = pCache;

pPgHdr->pgno = pgno;

}

assert( pPgHdr->pCache==pCache );

assert( pPgHdr->pgno==pgno );

assert( pPgHdr->pData==pPage->pBuf );

assert( pPgHdr->pExtra==(void *)&pPgHdr[1] );

if( 0==pPgHdr->nRef ){

pCache->nRef++;

}

pPgHdr->nRef++;

if( pgno==1 ){

pCache->pPage1 = pPgHdr;

}

*ppPage = pPgHdr;

return (pPgHdr==0 && eCreate) ? SQLITE_NOMEM : SQLITE_OK;

}

** Decrement the reference count on a page. If the page is clean and the

** reference count drops to 0, then it is made elible for recycling.

void sqlite3PcacheRelease(PgHdr *p){

assert( p->nRef>0 );

p->nRef--;

if( p->nRef==0 ){

PCache *pCache = p->pCache;

pCache->nRef--;

if( (p->flags&PGHDR_DIRTY)==0 ){

pcacheUnpin(p);

}else{

/* Move the page to the head of the dirty list. */

pcacheRemoveFromDirtyList(p);

pcacheAddToDirtyList(p);

}

** Increase the reference count of a supplied page by 1.

void sqlite3PcacheRef(PgHdr *p){

assert(p->nRef>0);

p->nRef++;

}

** Drop a page from the cache. There must be exactly one reference to the

** page. This function deletes that reference, so after it returns the

** page pointed to by p is invalid.

void sqlite3PcacheDrop(PgHdr *p){

PCache *pCache;

assert( p->nRef==1 );

if( p->flags&PGHDR_DIRTY ){

pcacheRemoveFromDirtyList(p);

}

pCache = p->pCache;

pCache->nRef--;

if( p->pgno==1 ){

pCache->pPage1 = 0;

}

sqlite3GlobalConfig.pcache2.xUnpin(pCache->pCache, p->pPage, 1);

}

** Make sure the page is marked as dirty. If it isn't dirty already,

** make it so.

void sqlite3PcacheMakeDirty(PgHdr *p){

p->flags &= ~PGHDR_DONT_WRITE;

assert( p->nRef>0 );

if( 0==(p->flags & PGHDR_DIRTY) ){

p->flags |= PGHDR_DIRTY;

pcacheAddToDirtyList( p);

}

** Make sure the page is marked as clean. If it isn't clean already,

** make it so.

void sqlite3PcacheMakeClean(PgHdr *p){

if( (p->flags & PGHDR_DIRTY) ){

pcacheRemoveFromDirtyList(p);

p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC);

if( p->nRef==0 ){

pcacheUnpin(p);

}

** Make every page in the cache clean.

void sqlite3PcacheCleanAll(PCache *pCache){

PgHdr *p;

while( (p = pCache->pDirty)!=0 ){

sqlite3PcacheMakeClean(p);

}

** Clear the PGHDR_NEED_SYNC flag from all dirty pages.

void sqlite3PcacheClearSyncFlags(PCache *pCache){

PgHdr *p;

for(p=pCache->pDirty; p; p=p->pDirtyNext){

p->flags &= ~PGHDR_NEED_SYNC;

}

pCache->pSynced = pCache->pDirtyTail;

}

** Change the page number of page p to newPgno.

void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){

PCache *pCache = p->pCache;

assert( p->nRef>0 );

assert( newPgno>0 );

sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno);

p->pgno = newPgno;

if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){

pcacheRemoveFromDirtyList(p);

pcacheAddToDirtyList(p);

}

** Drop every cache entry whose page number is greater than "pgno". The

** caller must ensure that there are no outstanding references to any pages

** other than page 1 with a page number greater than pgno.

** If there is a reference to page 1 and the pgno parameter passed to this

** function is 0, then the data area associated with page 1 is zeroed, but

** the page object is not dropped.

void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){

if( pCache->pCache ){

PgHdr *p;

PgHdr *pNext;

for(p=pCache->pDirty; p; p=pNext){

pNext = p->pDirtyNext;

/* This routine never gets call with a positive pgno except right

** after sqlite3PcacheCleanAll(). So if there are dirty pages,

** it must be that pgno==0.

assert( p->pgno>0 );

if( ALWAYS(p->pgno>pgno) ){

assert( p->flags&PGHDR_DIRTY );

sqlite3PcacheMakeClean(p);

}

if( pgno==0 && pCache->pPage1 ){

memset(pCache->pPage1->pData, 0, pCache->szPage);

pgno = 1;

}

sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);

}

** Close a cache.

void sqlite3PcacheClose(PCache *pCache){

if( pCache->pCache ){

sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);

}

** Discard the contents of the cache.

void sqlite3PcacheClear(PCache *pCache){

sqlite3PcacheTruncate(pCache, 0);

}

** Merge two lists of pages connected by pDirty and in pgno order.

** Do not both fixing the pDirtyPrev pointers.

static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){

PgHdr result, *pTail;

pTail = &result;

while( pA && pB ){

if( pA->pgno<pB->pgno ){

pTail->pDirty = pA;

pTail = pA;

pA = pA->pDirty;

}else{

pTail->pDirty = pB;

pTail = pB;

pB = pB->pDirty;

}

if( pA ){

pTail->pDirty = pA;

}else if( pB ){

pTail->pDirty = pB;

}else{

pTail->pDirty = 0;

}

return result.pDirty;

}

** Sort the list of pages in accending order by pgno. Pages are

** connected by pDirty pointers. The pDirtyPrev pointers are

** corrupted by this sort.

** Since there cannot be more than 2^31 distinct pages in a database,

** there cannot be more than 31 buckets required by the merge sorter.

** One extra bucket is added to catch overflow in case something

** ever changes to make the previous sentence incorrect.

#define N_SORT_BUCKET 32

static PgHdr *pcacheSortDirtyList(PgHdr *pIn){

PgHdr *a[N_SORT_BUCKET], *p;

int i;

memset(a, 0, sizeof(a));

while( pIn ){

p = pIn;

pIn = p->pDirty;

p->pDirty = 0;

for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){

if( a[i]==0 ){

a[i] = p;

break;

}else{

p = pcacheMergeDirtyList(a[i], p);

a[i] = 0;

}

if( NEVER(i==N_SORT_BUCKET-1) ){

/* To get here, there need to be 2^(N_SORT_BUCKET) elements in

** the input list. But that is impossible.

a[i] = pcacheMergeDirtyList(a[i], p);

}

p = a[0];

for(i=1; i<N_SORT_BUCKET; i++){

p = pcacheMergeDirtyList(p, a[i]);

}

return p;

}

** Return a list of all dirty pages in the cache, sorted by page number.

PgHdr *sqlite3PcacheDirtyList(PCache *pCache){

PgHdr *p;

for(p=pCache->pDirty; p; p=p->pDirtyNext){

p->pDirty = p->pDirtyNext;

}

return pcacheSortDirtyList(pCache->pDirty);

}

** Return the total number of referenced pages held by the cache.

int sqlite3PcacheRefCount(PCache *pCache){

return pCache->nRef;

}

** Return the number of references to the page supplied as an argument.

int sqlite3PcachePageRefcount(PgHdr *p){

return p->nRef;

}

** Return the total number of pages in the cache.

int sqlite3PcachePagecount(PCache *pCache){

int nPage = 0;

if( pCache->pCache ){

nPage = sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache);

}

return nPage;

}

#ifdef SQLITE_TEST

** Get the suggested cache-size value.

int sqlite3PcacheGetCachesize(PCache *pCache){

return numberOfCachePages(pCache);

}

#endif

** Set the suggested cache-size value.

void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){

pCache->szCache = mxPage;

if( pCache->pCache ){

sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache,

numberOfCachePages(pCache));

}

** Free up as much memory as possible from the page cache.

void sqlite3PcacheShrink(PCache *pCache){

if( pCache->pCache ){

sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache);

}

#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)

** For all dirty pages currently in the cache, invoke the specified

** callback. This is only used if the SQLITE_CHECK_PAGES macro is

** defined.

void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){

PgHdr *pDirty;

for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){

xIter(pDirty);

}

#endif

FilesExpand file tree

pcache.c

Latest commit

History

pcache.c

File metadata and controls