cpython/Objects/dictobject.c at doc-link-https · 180909/cpython · GitHub

History

5794 lines (5213 loc) · 171 KB

Raw

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

620

621

622

623

624

625

626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

647

648

649

650

651

652

653

654

655

656

657

658

659

660

661

662

663

664

665

666

667

668

669

670

671

672

673

674

675

676

677

678

679

680

681

682

683

684

685

686

687

688

689

690

691

692

693

694

695

696

697

698

699

700

701

702

703

704

705

706

707

708

709

710

711

712

713

714

715

716

717

718

719

720

721

722

723

724

725

726

727

728

729

730

731

732

733

734

735

736

737

738

739

740

741

742

743

744

745

746

747

748

749

750

751

752

753

754

755

756

757

758

759

760

761

762

763

764

765

766

767

768

769

770

771

772

773

774

775

776

777

778

779

780

781

782

783

784

785

786

787

788

789

790

791

792

793

794

795

796

797

798

799

800

801

802

803

804

805

806

807

808

809

810

811

812

813

814

815

816

817

818

819

820

821

822

823

824

825

826

827

828

829

830

831

832

833

834

835

836

837

838

839

840

841

842

843

844

845

846

847

848

849

850

851

852

853

854

855

856

857

858

859

860

861

862

863

864

865

866

867

868

869

870

871

872

873

874

875

876

877

878

879

880

881

882

883

884

885

886

887

888

889

890

891

892

893

894

895

896

897

898

899

900

901

902

903

904

905

906

907

908

909

910

911

912

913

914

915

916

917

918

919

920

921

922

923

924

925

926

927

928

929

930

931

932

933

934

935

936

937

938

939

940

941

942

943

944

945

946

947

948

949

950

951

952

953

954

955

956

957

958

959

960

961

962

963

964

965

966

967

968

969

970

971

972

973

974

975

976

977

978

979

980

981

982

983

984

985

986

987

988

989

990

991

992

993

994

995

996

997

998

999

1000

/* Dictionary object implementation using a hash table */

/* The distribution includes a separate file, Objects/dictnotes.txt,

describing explorations into dictionary design and optimization.

It covers typical dictionary use patterns, the parameters for

tuning dictionaries, and several ideas for possible optimizations.

/* PyDictKeysObject

This implements the dictionary's hashtable.

As of Python 3.6, this is compact and ordered. Basic idea is described here:

* https://mail.python.org/pipermail/python-dev/2012-December/123028.html

* https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html

layout:

+---------------------+

| dk_refcnt |

| dk_log2_size |

| dk_log2_index_bytes |

| dk_kind |

| dk_usable |

| dk_nentries |

+---------------------+

| dk_indices[] |

| |

+---------------------+

| dk_entries[] |

| |

+---------------------+

dk_indices is actual hashtable. It holds index in entries, or DKIX_EMPTY(-1)

or DKIX_DUMMY(-2).

Size of indices is dk_size. Type of each index in indices is vary on dk_size:

* int8 for dk_size <= 128

* int16 for 256 <= dk_size <= 2**15

* int32 for 2**16 <= dk_size <= 2**31

* int64 for 2**32 <= dk_size

dk_entries is array of PyDictKeyEntry when dk_kind == DICT_KEYS_GENERAL or

PyDictUnicodeEntry otherwise. Its length is USABLE_FRACTION(dk_size).

NOTE: Since negative value is used for DKIX_EMPTY and DKIX_DUMMY, type of

dk_indices entry is signed integer and int16 is used for table which

dk_size == 256.

The DictObject can be in one of two forms.

Either:

A combined table:

ma_values == NULL, dk_refcnt == 1.

Values are stored in the me_value field of the PyDictKeysObject.

Or:

A split table:

ma_values != NULL, dk_refcnt >= 1

Values are stored in the ma_values array.

Only string (unicode) keys are allowed.

There are four kinds of slots in the table (slot is index, and

DK_ENTRIES(keys)[index] if index >= 0):

1. Unused. index == DKIX_EMPTY

Does not hold an active (key, value) pair now and never did. Unused can

transition to Active upon key insertion. This is each slot's initial state.

2. Active. index >= 0, me_key != NULL and me_value != NULL

Holds an active (key, value) pair. Active can transition to Dummy or

Pending upon key deletion (for combined and split tables respectively).

This is the only case in which me_value != NULL.

3. Dummy. index == DKIX_DUMMY (combined only)

Previously held an active (key, value) pair, but that was deleted and an

active pair has not yet overwritten the slot. Dummy can transition to

Active upon key insertion. Dummy slots cannot be made Unused again

else the probe sequence in case of collision would have no way to know

they were once active.

4. Pending. index >= 0, key != NULL, and value == NULL (split only)

Not yet inserted in split-table.

Preserving insertion order

It's simple for combined table. Since dk_entries is mostly append only, we can

get insertion order by just iterating dk_entries.

One exception is .popitem(). It removes last item in dk_entries and decrement

dk_nentries to achieve amortized O(1). Since there are DKIX_DUMMY remains in

dk_indices, we can't increment dk_usable even though dk_nentries is

decremented.

To preserve the order in a split table, a bit vector is used to record the

insertion order. When a key is inserted the bit vector is shifted up by 4 bits

and the index of the key is stored in the low 4 bits.

As a consequence of this, split keys have a maximum size of 16.

/* PyDict_MINSIZE is the starting size for any new dict.

* 8 allows dicts with no more than 5 active entries; experiments suggested

* this suffices for the majority of dicts (consisting mostly of usually-small

* dicts created to pass keyword arguments).

* Making this 8, rather than 4 reduces the number of resizes for most

* dictionaries, without any significant extra memory use.

#define PyDict_LOG_MINSIZE 3

#define PyDict_MINSIZE 8

#include "Python.h"

#include "pycore_bitutils.h" // _Py_bit_length

#include "pycore_call.h" // _PyObject_CallNoArgs()

#include "pycore_code.h" // stats

#include "pycore_dict.h" // PyDictKeysObject

#include "pycore_gc.h" // _PyObject_GC_IS_TRACKED()

#include "pycore_object.h" // _PyObject_GC_TRACK()

#include "pycore_pyerrors.h" // _PyErr_Fetch()

#include "pycore_pystate.h" // _PyThreadState_GET()

#include "stringlib/eq.h" // unicode_eq()

#include <stdbool.h>

/*[clinic input]

class dict "PyDictObject *" "&PyDict_Type"

[clinic start generated code]*/

/*[clinic end generated code: output=da39a3ee5e6b4b0d input=f157a5a0ce9589d6]*/

To ensure the lookup algorithm terminates, there must be at least one Unused

slot (NULL key) in the table.

To avoid slowing down lookups on a near-full table, we resize the table when

it's USABLE_FRACTION (currently two-thirds) full.

#define PERTURB_SHIFT 5

Major subtleties ahead: Most hash schemes depend on having a "good" hash

function, in the sense of simulating randomness. Python doesn't: its most

important hash functions (for ints) are very regular in common

cases:

>>>[hash(i) for i in range(4)]

[0, 1, 2, 3]

This isn't necessarily bad! To the contrary, in a table of size 2**i, taking

the low-order i bits as the initial table index is extremely fast, and there

are no collisions at all for dicts indexed by a contiguous range of ints. So

this gives better-than-random behavior in common cases, and that's very

desirable.

OTOH, when collisions occur, the tendency to fill contiguous slices of the

hash table makes a good collision resolution strategy crucial. Taking only

the last i bits of the hash code is also vulnerable: for example, consider

the list [i << 16 for i in range(20000)] as a set of keys. Since ints are

their own hash codes, and this fits in a dict of size 2**15, the last 15 bits

of every hash code are all 0: they *all* map to the same table index.

But catering to unusual cases should not slow the usual ones, so we just take

the last i bits anyway. It's up to collision resolution to do the rest. If

we *usually* find the key we're looking for on the first try (and, it turns

out, we usually do -- the table load factor is kept under 2/3, so the odds

are solidly in our favor), then it makes best sense to keep the initial index

computation dirt cheap.

The first half of collision resolution is to visit table indices via this

recurrence:

j = ((5*j) + 1) mod 2**i

For any initial j in range(2**i), repeating that 2**i times generates each

int in range(2**i) exactly once (see any text on random-number generation for

proof). By itself, this doesn't help much: like linear probing (setting

j += 1, or j -= 1, on each loop trip), it scans the table entries in a fixed

order. This would be bad, except that's not the only thing we do, and it's

actually *good* in the common cases where hash keys are consecutive. In an

example that's really too small to make this entirely clear, for a table of

size 2**3 the order of indices is:

0 -> 1 -> 6 -> 7 -> 4 -> 5 -> 2 -> 3 -> 0 [and here it's repeating]

If two things come in at index 5, the first place we look after is index 2,

not 6, so if another comes in at index 6 the collision at 5 didn't hurt it.

Linear probing is deadly in this case because there the fixed probe order

is the *same* as the order consecutive keys are likely to arrive. But it's

extremely unlikely hash codes will follow a 5*j+1 recurrence by accident,

and certain that consecutive hash codes do not.

The other half of the strategy is to get the other bits of the hash code

into play. This is done by initializing a (unsigned) vrbl "perturb" to the

full hash code, and changing the recurrence to:

perturb >>= PERTURB_SHIFT;

j = (5*j) + 1 + perturb;

use j % 2**i as the next table index;

Now the probe sequence depends (eventually) on every bit in the hash code,

and the pseudo-scrambling property of recurring on 5*j+1 is more valuable,

because it quickly magnifies small differences in the bits that didn't affect

the initial index. Note that because perturb is unsigned, if the recurrence

is executed often enough perturb eventually becomes and remains 0. At that

point (very rarely reached) the recurrence is on (just) 5*j+1 again, and

that's certain to find an empty slot eventually (since it generates every int

in range(2**i), and we make sure there's always at least one empty slot).

Selecting a good value for PERTURB_SHIFT is a balancing act. You want it

small so that the high bits of the hash code continue to affect the probe

sequence across iterations; but you want it large so that in really bad cases

the high-order hash bits have an effect on early iterations. 5 was "the

best" in minimizing total collisions across experiments Tim Peters ran (on

both normal and pathological cases), but 4 and 6 weren't significantly worse.

Historical: Reimer Behrends contributed the idea of using a polynomial-based

approach, using repeated multiplication by x in GF(2**n) where an irreducible

polynomial for each table size was chosen such that x was a primitive root.

Christian Tismer later extended that to use division by x instead, as an

efficient way to get the high bits of the hash code into play. This scheme

also gave excellent collision statistics, but was more expensive: two

if-tests were required inside the loop; computing "the next" index took about

the same number of operations but without as much potential parallelism

(e.g., computing 5*j can go on at the same time as computing 1+perturb in the

above, and then shifting perturb can be done while the table index is being

masked); and the PyDictObject struct required a member to hold the table's

polynomial. In Tim's experiments the current scheme ran faster, produced

equally good collision statistics, needed less code & used less memory.

static int dictresize(PyDictObject *mp, uint8_t log_newsize, int unicode);

static PyObject* dict_iter(PyDictObject *dict);

/*Global counter used to set ma_version_tag field of dictionary.

* It is incremented each time that a dictionary is created and each

* time that a dictionary is modified. */

uint64_t _pydict_global_version = 0;

#include "clinic/dictobject.c.h"

#if PyDict_MAXFREELIST > 0

static struct _Py_dict_state *

get_dict_state(void)

{

PyInterpreterState *interp = _PyInterpreterState_GET();

return &interp->dict_state;

}

#endif

void

_PyDict_ClearFreeList(PyInterpreterState *interp)

{

#if PyDict_MAXFREELIST > 0

struct _Py_dict_state *state = &interp->dict_state;

while (state->numfree) {

PyDictObject *op = state->free_list[--state->numfree];

assert(PyDict_CheckExact(op));

PyObject_GC_Del(op);

}

while (state->keys_numfree) {

PyObject_Free(state->keys_free_list[--state->keys_numfree]);

}

#endif

}

void

_PyDict_Fini(PyInterpreterState *interp)

{

_PyDict_ClearFreeList(interp);

#if defined(Py_DEBUG) && PyDict_MAXFREELIST > 0

struct _Py_dict_state *state = &interp->dict_state;

state->numfree = -1;

state->keys_numfree = -1;

#endif

}

static inline Py_hash_t

unicode_get_hash(PyObject *o)

{

assert(PyUnicode_CheckExact(o));

return _PyASCIIObject_CAST(o)->hash;

}

/* Print summary info about the state of the optimized allocator */

void

_PyDict_DebugMallocStats(FILE *out)

{

#if PyDict_MAXFREELIST > 0

struct _Py_dict_state *state = get_dict_state();

_PyDebugAllocatorStats(out, "free PyDictObject",

state->numfree, sizeof(PyDictObject));

#endif

}

#define DK_MASK(dk) (DK_SIZE(dk)-1)

static void free_keys_object(PyDictKeysObject *keys);

static inline void

dictkeys_incref(PyDictKeysObject *dk)

{

#ifdef Py_REF_DEBUG

_Py_RefTotal++;

#endif

dk->dk_refcnt++;

}

static inline void

dictkeys_decref(PyDictKeysObject *dk)

{

assert(dk->dk_refcnt > 0);

#ifdef Py_REF_DEBUG

_Py_RefTotal--;

#endif

if (--dk->dk_refcnt == 0) {

free_keys_object(dk);

}

/* lookup indices. returns DKIX_EMPTY, DKIX_DUMMY, or ix >=0 */

static inline Py_ssize_t

dictkeys_get_index(const PyDictKeysObject *keys, Py_ssize_t i)

{

int log2size = DK_LOG_SIZE(keys);

Py_ssize_t ix;

if (log2size < 8) {

const int8_t *indices = (const int8_t*)(keys->dk_indices);

ix = indices[i];

}

else if (log2size < 16) {

const int16_t *indices = (const int16_t*)(keys->dk_indices);

ix = indices[i];

}

#if SIZEOF_VOID_P > 4

else if (log2size >= 32) {

const int64_t *indices = (const int64_t*)(keys->dk_indices);

ix = indices[i];

}

#endif

else {

const int32_t *indices = (const int32_t*)(keys->dk_indices);

ix = indices[i];

}

assert(ix >= DKIX_DUMMY);

return ix;

}

/* write to indices. */

static inline void

dictkeys_set_index(PyDictKeysObject *keys, Py_ssize_t i, Py_ssize_t ix)

{

int log2size = DK_LOG_SIZE(keys);

assert(ix >= DKIX_DUMMY);

assert(keys->dk_version == 0);

if (log2size < 8) {

int8_t *indices = (int8_t*)(keys->dk_indices);

assert(ix <= 0x7f);

indices[i] = (char)ix;

}

else if (log2size < 16) {

int16_t *indices = (int16_t*)(keys->dk_indices);

assert(ix <= 0x7fff);

indices[i] = (int16_t)ix;

}

#if SIZEOF_VOID_P > 4

else if (log2size >= 32) {

int64_t *indices = (int64_t*)(keys->dk_indices);

indices[i] = ix;

}

#endif

else {

int32_t *indices = (int32_t*)(keys->dk_indices);

assert(ix <= 0x7fffffff);

indices[i] = (int32_t)ix;

}

/* USABLE_FRACTION is the maximum dictionary load.

* Increasing this ratio makes dictionaries more dense resulting in more

* collisions. Decreasing it improves sparseness at the expense of spreading

* indices over more cache lines and at the cost of total memory consumed.

* USABLE_FRACTION must obey the following:

* (0 < USABLE_FRACTION(n) < n) for all n >= 2

* USABLE_FRACTION should be quick to calculate.

* Fractions around 1/2 to 2/3 seem to work well in practice.

#define USABLE_FRACTION(n) (((n) << 1)/3)

/* Find the smallest dk_size >= minsize. */

static inline uint8_t

calculate_log2_keysize(Py_ssize_t minsize)

{

#if SIZEOF_LONG == SIZEOF_SIZE_T

minsize = (minsize | PyDict_MINSIZE) - 1;

return _Py_bit_length(minsize | (PyDict_MINSIZE-1));

#elif defined(_MSC_VER)

// On 64bit Windows, sizeof(long) == 4.

minsize = (minsize | PyDict_MINSIZE) - 1;

unsigned long msb;

_BitScanReverse64(&msb, (uint64_t)minsize);

return (uint8_t)(msb + 1);

#else

uint8_t log2_size;

for (log2_size = PyDict_LOG_MINSIZE;

(((Py_ssize_t)1) << log2_size) < minsize;

log2_size++)

;

return log2_size;

#endif

}

/* estimate_keysize is reverse function of USABLE_FRACTION.

* This can be used to reserve enough size to insert n entries without

* resizing.

static inline uint8_t

estimate_log2_keysize(Py_ssize_t n)

{

return calculate_log2_keysize((n*3 + 1) / 2);

}

/* GROWTH_RATE. Growth rate upon hitting maximum load.

* Currently set to used*3.

* This means that dicts double in size when growing without deletions,

* but have more head room when the number of deletions is on a par with the

* number of insertions. See also bpo-17563 and bpo-33205.

* GROWTH_RATE was set to used*4 up to version 3.2.

* GROWTH_RATE was set to used*2 in version 3.3.0

* GROWTH_RATE was set to used*2 + capacity/2 in 3.4.0-3.6.0.

#define GROWTH_RATE(d) ((d)->ma_used*3)

/* This immutable, empty PyDictKeysObject is used for PyDict_Clear()

* (which cannot fail and thus can do no allocation).

static PyDictKeysObject empty_keys_struct = {

1, /* dk_refcnt */

0, /* dk_log2_size */

0, /* dk_log2_index_bytes */

DICT_KEYS_UNICODE, /* dk_kind */

1, /* dk_version */

0, /* dk_usable (immutable) */

0, /* dk_nentries */

{DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY,

DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY, DKIX_EMPTY}, /* dk_indices */

};

#define Py_EMPTY_KEYS &empty_keys_struct

/* Uncomment to check the dict content in _PyDict_CheckConsistency() */

// #define DEBUG_PYDICT

#ifdef DEBUG_PYDICT

# define ASSERT_CONSISTENT(op) assert(_PyDict_CheckConsistency((PyObject *)(op), 1))

#else

# define ASSERT_CONSISTENT(op) assert(_PyDict_CheckConsistency((PyObject *)(op), 0))

#endif

static inline int

get_index_from_order(PyDictObject *mp, Py_ssize_t i)

{

assert(mp->ma_used <= SHARED_KEYS_MAX_SIZE);

assert(i < (((char *)mp->ma_values)[-2]));

return ((char *)mp->ma_values)[-3-i];

}

#ifdef DEBUG_PYDICT

static void

dump_entries(PyDictKeysObject *dk)

{

for (Py_ssize_t i = 0; i < dk->dk_nentries; i++) {

if (DK_IS_UNICODE(dk)) {

PyDictUnicodeEntry *ep = &DK_UNICODE_ENTRIES(dk)[i];

printf("key=%p value=%p\n", ep->me_key, ep->me_value);

}

else {

PyDictKeyEntry *ep = &DK_ENTRIES(dk)[i];

printf("key=%p hash=%lx value=%p\n", ep->me_key, ep->me_hash, ep->me_value);

}

#endif

int

_PyDict_CheckConsistency(PyObject *op, int check_content)

{

#define CHECK(expr) \

do { if (!(expr)) { _PyObject_ASSERT_FAILED_MSG(op, Py_STRINGIFY(expr)); } } while (0)

assert(op != NULL);

CHECK(PyDict_Check(op));

PyDictObject *mp = (PyDictObject *)op;

PyDictKeysObject *keys = mp->ma_keys;

int splitted = _PyDict_HasSplitTable(mp);

Py_ssize_t usable = USABLE_FRACTION(DK_SIZE(keys));

CHECK(0 <= mp->ma_used && mp->ma_used <= usable);

CHECK(0 <= keys->dk_usable && keys->dk_usable <= usable);

CHECK(0 <= keys->dk_nentries && keys->dk_nentries <= usable);

CHECK(keys->dk_usable + keys->dk_nentries <= usable);

if (!splitted) {

/* combined table */

CHECK(keys->dk_kind != DICT_KEYS_SPLIT);

CHECK(keys->dk_refcnt == 1 || keys == Py_EMPTY_KEYS);

}

else {

CHECK(keys->dk_kind == DICT_KEYS_SPLIT);

CHECK(mp->ma_used <= SHARED_KEYS_MAX_SIZE);

}

if (check_content) {

for (Py_ssize_t i=0; i < DK_SIZE(keys); i++) {

Py_ssize_t ix = dictkeys_get_index(keys, i);

CHECK(DKIX_DUMMY <= ix && ix <= usable);

}

if (keys->dk_kind == DICT_KEYS_GENERAL) {

PyDictKeyEntry *entries = DK_ENTRIES(keys);

for (Py_ssize_t i=0; i < usable; i++) {

PyDictKeyEntry *entry = &entries[i];

PyObject *key = entry->me_key;

if (key != NULL) {

/* test_dict fails if PyObject_Hash() is called again */

CHECK(entry->me_hash != -1);

CHECK(entry->me_value != NULL);

if (PyUnicode_CheckExact(key)) {

Py_hash_t hash = unicode_get_hash(key);

CHECK(entry->me_hash == hash);

}

else {

PyDictUnicodeEntry *entries = DK_UNICODE_ENTRIES(keys);

for (Py_ssize_t i=0; i < usable; i++) {

PyDictUnicodeEntry *entry = &entries[i];

PyObject *key = entry->me_key;

if (key != NULL) {

CHECK(PyUnicode_CheckExact(key));

Py_hash_t hash = unicode_get_hash(key);

CHECK(hash != -1);

if (!splitted) {

CHECK(entry->me_value != NULL);

}

if (splitted) {

CHECK(entry->me_value == NULL);

}

if (splitted) {

CHECK(mp->ma_used <= SHARED_KEYS_MAX_SIZE);

/* splitted table */

int duplicate_check = 0;

for (Py_ssize_t i=0; i < mp->ma_used; i++) {

int index = get_index_from_order(mp, i);

CHECK((duplicate_check & (1<<index)) == 0);

duplicate_check |= (1<<index);

CHECK(mp->ma_values->values[index] != NULL);

}

return 1;

#undef CHECK

}

static PyDictKeysObject*

new_keys_object(uint8_t log2_size, bool unicode)

{

PyDictKeysObject *dk;

Py_ssize_t usable;

int log2_bytes;

size_t entry_size = unicode ? sizeof(PyDictUnicodeEntry) : sizeof(PyDictKeyEntry);

assert(log2_size >= PyDict_LOG_MINSIZE);

usable = USABLE_FRACTION(1<<log2_size);

if (log2_size < 8) {

log2_bytes = log2_size;

}

else if (log2_size < 16) {

log2_bytes = log2_size + 1;

}

#if SIZEOF_VOID_P > 4

else if (log2_size >= 32) {

log2_bytes = log2_size + 3;

}

#endif

else {

log2_bytes = log2_size + 2;

}

#if PyDict_MAXFREELIST > 0

struct _Py_dict_state *state = get_dict_state();

#ifdef Py_DEBUG

// new_keys_object() must not be called after _PyDict_Fini()

assert(state->keys_numfree != -1);

#endif

if (log2_size == PyDict_LOG_MINSIZE && unicode && state->keys_numfree > 0) {

dk = state->keys_free_list[--state->keys_numfree];

OBJECT_STAT_INC(from_freelist);

}

else

#endif

{

dk = PyObject_Malloc(sizeof(PyDictKeysObject)

+ ((size_t)1 << log2_bytes)

+ entry_size * usable);

if (dk == NULL) {

PyErr_NoMemory();

return NULL;

}

#ifdef Py_REF_DEBUG

_Py_RefTotal++;

#endif

dk->dk_refcnt = 1;

dk->dk_log2_size = log2_size;

dk->dk_log2_index_bytes = log2_bytes;

dk->dk_kind = unicode ? DICT_KEYS_UNICODE : DICT_KEYS_GENERAL;

dk->dk_nentries = 0;

dk->dk_usable = usable;

dk->dk_version = 0;

memset(&dk->dk_indices[0], 0xff, ((size_t)1 << log2_bytes));

memset(&dk->dk_indices[(size_t)1 << log2_bytes], 0, entry_size * usable);

return dk;

}

static void

free_keys_object(PyDictKeysObject *keys)

{

assert(keys != Py_EMPTY_KEYS);

if (DK_IS_UNICODE(keys)) {

PyDictUnicodeEntry *entries = DK_UNICODE_ENTRIES(keys);

Py_ssize_t i, n;

for (i = 0, n = keys->dk_nentries; i < n; i++) {

Py_XDECREF(entries[i].me_key);

Py_XDECREF(entries[i].me_value);

}

else {

PyDictKeyEntry *entries = DK_ENTRIES(keys);

Py_ssize_t i, n;

for (i = 0, n = keys->dk_nentries; i < n; i++) {

Py_XDECREF(entries[i].me_key);

Py_XDECREF(entries[i].me_value);

}

#if PyDict_MAXFREELIST > 0

struct _Py_dict_state *state = get_dict_state();

#ifdef Py_DEBUG

// free_keys_object() must not be called after _PyDict_Fini()

assert(state->keys_numfree != -1);

#endif

if (DK_LOG_SIZE(keys) == PyDict_LOG_MINSIZE

&& state->keys_numfree < PyDict_MAXFREELIST

&& DK_IS_UNICODE(keys)) {

state->keys_free_list[state->keys_numfree++] = keys;

OBJECT_STAT_INC(to_freelist);

return;

}

#endif

PyObject_Free(keys);

}

static inline PyDictValues*

new_values(Py_ssize_t size)

{

assert(size > 0);

size_t prefix_size = _Py_SIZE_ROUND_UP(size+2, sizeof(PyObject *));

assert(prefix_size < 256);

size_t n = prefix_size + size * sizeof(PyObject *);

uint8_t *mem = PyMem_Malloc(n);

if (mem == NULL) {

return NULL;

}

assert(prefix_size % sizeof(PyObject *) == 0);

mem[prefix_size-1] = (uint8_t)prefix_size;

return (PyDictValues*)(mem + prefix_size);

}

static inline void

free_values(PyDictValues *values)

{

int prefix_size = ((uint8_t *)values)[-1];

PyMem_Free(((char *)values)-prefix_size);

}

/* Consumes a reference to the keys object */

static PyObject *

new_dict(PyDictKeysObject *keys, PyDictValues *values, Py_ssize_t used, int free_values_on_failure)

{

PyDictObject *mp;

assert(keys != NULL);

#if PyDict_MAXFREELIST > 0

struct _Py_dict_state *state = get_dict_state();

#ifdef Py_DEBUG

// new_dict() must not be called after _PyDict_Fini()

assert(state->numfree != -1);

#endif

if (state->numfree) {

mp = state->free_list[--state->numfree];

assert (mp != NULL);

assert (Py_IS_TYPE(mp, &PyDict_Type));

OBJECT_STAT_INC(from_freelist);

_Py_NewReference((PyObject *)mp);

}

else

#endif

{

mp = PyObject_GC_New(PyDictObject, &PyDict_Type);

if (mp == NULL) {

dictkeys_decref(keys);

if (free_values_on_failure) {

free_values(values);

}

return NULL;

}

mp->ma_keys = keys;

mp->ma_values = values;

mp->ma_used = used;

mp->ma_version_tag = DICT_NEXT_VERSION();

ASSERT_CONSISTENT(mp);

return (PyObject *)mp;

}

static inline Py_ssize_t

shared_keys_usable_size(PyDictKeysObject *keys)

{

return keys->dk_nentries + keys->dk_usable;

}

/* Consumes a reference to the keys object */

static PyObject *

new_dict_with_shared_keys(PyDictKeysObject *keys)

{

PyDictValues *values;

Py_ssize_t i, size;

size = shared_keys_usable_size(keys);

values = new_values(size);

if (values == NULL) {

dictkeys_decref(keys);

return PyErr_NoMemory();

}

((char *)values)[-2] = 0;

for (i = 0; i < size; i++) {

values->values[i] = NULL;

}

return new_dict(keys, values, 0, 1);

}

static PyDictKeysObject *

clone_combined_dict_keys(PyDictObject *orig)

{

assert(PyDict_Check(orig));

assert(Py_TYPE(orig)->tp_iter == (getiterfunc)dict_iter);

assert(orig->ma_values == NULL);

assert(orig->ma_keys->dk_refcnt == 1);

Py_ssize_t keys_size = _PyDict_KeysSize(orig->ma_keys);

PyDictKeysObject *keys = PyObject_Malloc(keys_size);

if (keys == NULL) {

PyErr_NoMemory();

return NULL;

}

memcpy(keys, orig->ma_keys, keys_size);

/* After copying key/value pairs, we need to incref all

keys and values and they are about to be co-owned by a

new dict object. */

PyObject **pkey, **pvalue;

size_t offs;

if (DK_IS_UNICODE(orig->ma_keys)) {

PyDictUnicodeEntry *ep0 = DK_UNICODE_ENTRIES(keys);

pkey = &ep0->me_key;

pvalue = &ep0->me_value;

offs = sizeof(PyDictUnicodeEntry) / sizeof(PyObject*);

}

else {

PyDictKeyEntry *ep0 = DK_ENTRIES(keys);

pkey = &ep0->me_key;

pvalue = &ep0->me_value;

offs = sizeof(PyDictKeyEntry) / sizeof(PyObject*);

}

Py_ssize_t n = keys->dk_nentries;

for (Py_ssize_t i = 0; i < n; i++) {

PyObject *value = *pvalue;

if (value != NULL) {

Py_INCREF(value);

Py_INCREF(*pkey);

}

pvalue += offs;

pkey += offs;

}

/* Since we copied the keys table we now have an extra reference

in the system. Manually call increment _Py_RefTotal to signal that

we have it now; calling dictkeys_incref would be an error as

keys->dk_refcnt is already set to 1 (after memcpy). */

#ifdef Py_REF_DEBUG

_Py_RefTotal++;

#endif

return keys;

}

PyObject *

PyDict_New(void)

{

dictkeys_incref(Py_EMPTY_KEYS);

return new_dict(Py_EMPTY_KEYS, NULL, 0, 0);

}

/* Search index of hash table from offset of entry table */

static Py_ssize_t

lookdict_index(PyDictKeysObject *k, Py_hash_t hash, Py_ssize_t index)

{

size_t mask = DK_MASK(k);

size_t perturb = (size_t)hash;

size_t i = (size_t)hash & mask;

for (;;) {

Py_ssize_t ix = dictkeys_get_index(k, i);

if (ix == index) {

return i;

}

if (ix == DKIX_EMPTY) {

return DKIX_EMPTY;

}

perturb >>= PERTURB_SHIFT;

i = mask & (i*5 + perturb + 1);

}

Py_UNREACHABLE();

}

// Search non-Unicode key from Unicode table

static Py_ssize_t

unicodekeys_lookup_generic(PyDictObject *mp, PyDictKeysObject* dk, PyObject *key, Py_hash_t hash)

{

PyDictUnicodeEntry *ep0 = DK_UNICODE_ENTRIES(dk);

size_t mask = DK_MASK(dk);

size_t perturb = hash;

size_t i = (size_t)hash & mask;

Py_ssize_t ix;

for (;;) {

ix = dictkeys_get_index(dk, i);

if (ix >= 0) {

PyDictUnicodeEntry *ep = &ep0[ix];

assert(ep->me_key != NULL);

assert(PyUnicode_CheckExact(ep->me_key));

if (ep->me_key == key) {

return ix;

}

if (unicode_get_hash(ep->me_key) == hash) {

PyObject *startkey = ep->me_key;

Py_INCREF(startkey);

int cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);

Py_DECREF(startkey);

if (cmp < 0) {

return DKIX_ERROR;

}

if (dk == mp->ma_keys && ep->me_key == startkey) {

if (cmp > 0) {

return ix;

}

else {

/* The dict was mutated, restart */

return DKIX_KEY_CHANGED;

}

else if (ix == DKIX_EMPTY) {

return DKIX_EMPTY;

}

perturb >>= PERTURB_SHIFT;

i = mask & (i*5 + perturb + 1);

}

Py_UNREACHABLE();

}

// Search Unicode key from Unicode table.

static Py_ssize_t _Py_HOT_FUNCTION

unicodekeys_lookup_unicode(PyDictKeysObject* dk, PyObject *key, Py_hash_t hash)

{

PyDictUnicodeEntry *ep0 = DK_UNICODE_ENTRIES(dk);

size_t mask = DK_MASK(dk);

size_t perturb = hash;

size_t i = (size_t)hash & mask;

Py_ssize_t ix;

for (;;) {

ix = dictkeys_get_index(dk, i);

if (ix >= 0) {

PyDictUnicodeEntry *ep = &ep0[ix];

assert(ep->me_key != NULL);

assert(PyUnicode_CheckExact(ep->me_key));

if (ep->me_key == key ||

(unicode_get_hash(ep->me_key) == hash && unicode_eq(ep->me_key, key))) {

return ix;

}

else if (ix == DKIX_EMPTY) {

return DKIX_EMPTY;

}

perturb >>= PERTURB_SHIFT;

i = mask & (i*5 + perturb + 1);

ix = dictkeys_get_index(dk, i);

if (ix >= 0) {

PyDictUnicodeEntry *ep = &ep0[ix];

assert(ep->me_key != NULL);

assert(PyUnicode_CheckExact(ep->me_key));

if (ep->me_key == key ||

(unicode_get_hash(ep->me_key) == hash && unicode_eq(ep->me_key, key))) {

return ix;

}

else if (ix == DKIX_EMPTY) {

return DKIX_EMPTY;

}

perturb >>= PERTURB_SHIFT;

i = mask & (i*5 + perturb + 1);

}

Py_UNREACHABLE();

}

// Search key from Generic table.

static Py_ssize_t

dictkeys_generic_lookup(PyDictObject *mp, PyDictKeysObject* dk, PyObject *key, Py_hash_t hash)

{

PyDictKeyEntry *ep0 = DK_ENTRIES(dk);

size_t mask = DK_MASK(dk);

size_t perturb = hash;

size_t i = (size_t)hash & mask;

Py_ssize_t ix;

for (;;) {

ix = dictkeys_get_index(dk, i);

if (ix >= 0) {

PyDictKeyEntry *ep = &ep0[ix];

assert(ep->me_key != NULL);

if (ep->me_key == key) {

return ix;

}

if (ep->me_hash == hash) {

PyObject *startkey = ep->me_key;

Py_INCREF(startkey);

int cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);

Py_DECREF(startkey);

if (cmp < 0) {

return DKIX_ERROR;

}

if (dk == mp->ma_keys && ep->me_key == startkey) {

if (cmp > 0) {

return ix;

}

else {

/* The dict was mutated, restart */

return DKIX_KEY_CHANGED;

}

else if (ix == DKIX_EMPTY) {

return DKIX_EMPTY;

}

perturb >>= PERTURB_SHIFT;

i = mask & (i*5 + perturb + 1);

}

Py_UNREACHABLE();

}

View remainder of file in raw view

cpython/Objects/dictobject.c at doc-link-https · 180909/cpython · GitHub

Navigation Menu

Expand file tree

Breadcrumbs

dictobject.c

Latest commit

History

Breadcrumbs

dictobject.c

File metadata and controls

Footer

Footer navigation