DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Implementation

Mercurial (4a108e94d3e2)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef vm_ArrayBufferObject_h
#define vm_ArrayBufferObject_h

#include "jsobj.h"

#include "builtin/TypedObjectConstants.h"
#include "vm/Runtime.h"

typedef struct JSProperty JSProperty;

namespace js {

class ArrayBufferViewObject;

// The inheritance hierarchy for the various classes relating to typed arrays
// is as follows.
//
// - JSObject
//   - ArrayBufferObjectMaybeShared
//     - ArrayBufferObject
//     - SharedArrayBufferObject
//   - ArrayBufferViewObject
//     - DataViewObject
//     - TypedArrayObject (declared in vm/TypedArrayObject.h)
//       - TypedArrayObjectTemplate
//         - Int8ArrayObject
//         - Uint8ArrayObject
//         - ...
//     - TypedObject (declared in builtin/TypedObject.h)
//   - SharedTypedArrayObject (declared in vm/SharedTypedArrayObject.h)
//     - SharedTypedArrayObjectTemplate
//       - SharedInt8ArrayObject
//       - SharedUint8ArrayObject
//       - ...
//
// Note that |TypedArrayObjectTemplate| is just an implementation
// detail that makes implementing its various subclasses easier.
// Note that |TypedArrayObjectTemplate| and |SharedTypedArrayObjectTemplate| are
// just implementation details that make implementing their various subclasses easier.
//
// ArrayBufferObject and SharedArrayBufferObject are unrelated data types:
// the racy memory of the latter cannot substitute for the non-racy memory of
// the former; the non-racy memory of the former cannot be used with the atomics;
// the former can be neutered and the latter not; and they have different
// method suites.  Hence they have been separated completely.
//
// Most APIs will only accept ArrayBufferObject.  ArrayBufferObjectMaybeShared exists
// as a join point to allow APIs that can take or use either, notably AsmJS.
//
// As ArrayBufferObject and SharedArrayBufferObject are separated, so are the
// TypedArray hierarchies below the two.  However, the TypedArrays have the
// same layout (see TypedArrayObject.h), so there is little code duplication.
//
// The possible data ownership and reference relationships with array buffers
// and related classes are enumerated below. These are the possible locations
// for typed data:
//
// (1) malloc'ed or mmap'ed data owned by an ArrayBufferObject.
// (2) Data allocated inline with an ArrayBufferObject.
// (3) Data allocated inline with a TypedArrayObject.
// (4) Data allocated inline with an InlineTypedObject.
//
// An ArrayBufferObject may point to any of these sources of data, except (3).
// All array buffer views may point to any of these sources of data, except
// that (3) may only be pointed to by the typed array the data is inline with.
//
// During a minor GC, (3) and (4) may move. During a compacting GC, (2), (3),
// and (4) may move.

class ArrayBufferObjectMaybeShared;

uint32_t AnyArrayBufferByteLength(const ArrayBufferObjectMaybeShared* buf);
uint8_t* AnyArrayBufferDataPointer(const ArrayBufferObjectMaybeShared* buf);
ArrayBufferObjectMaybeShared& AsAnyArrayBuffer(HandleValue val);

class ArrayBufferObjectMaybeShared : public NativeObject
{
  public:
    uint32_t byteLength() {
        return AnyArrayBufferByteLength(this);
    }

    uint8_t* dataPointer() {
        return AnyArrayBufferDataPointer(this);
    }
};

/*
 * ArrayBufferObject
 *
 * This class holds the underlying raw buffer that the various
 * ArrayBufferViewObject subclasses (DataViewObject and the TypedArrays)
 * access. It can be created explicitly and passed to an ArrayBufferViewObject
 * subclass, or can be created lazily when it is first accessed for a
 * TypedArrayObject or TypedObject that doesn't have an explicit buffer.
 *
 * ArrayBufferObject (or really the underlying memory) /is not racy/: the
 * memory is private to a single worker.
 */
class ArrayBufferObject : public ArrayBufferObjectMaybeShared
{
    static bool byteLengthGetterImpl(JSContext* cx, CallArgs args);
    static bool fun_slice_impl(JSContext* cx, CallArgs args);

  public:
    static const uint8_t DATA_SLOT = 0;
    static const uint8_t BYTE_LENGTH_SLOT = 1;
    static const uint8_t FIRST_VIEW_SLOT = 2;
    static const uint8_t FLAGS_SLOT = 3;

    static const uint8_t RESERVED_SLOTS = 4;

    static const size_t ARRAY_BUFFER_ALIGNMENT = 8;

  public:

    enum OwnsState {
        DoesntOwnData = 0,
        OwnsData = 1,
    };

    enum BufferKind {
        PLAIN               = 0, // malloced or inline data
        ASMJS_MALLOCED      = 1,
        ASMJS_MAPPED        = 2,
        MAPPED              = 3,

        KIND_MASK           = 0x3
    };

  protected:

    enum ArrayBufferFlags {
        // The flags also store the BufferKind
        BUFFER_KIND_MASK    = BufferKind::KIND_MASK,

        NEUTERED            = 0x4,

        // The dataPointer() is owned by this buffer and should be released
        // when no longer in use. Releasing the pointer may be done by either
        // freeing or unmapping it, and how to do this is determined by the
        // buffer's other flags.
        //
        // Array buffers which do not own their data include buffers that
        // allocate their data inline, and buffers that are created lazily for
        // typed objects with inline storage, in which case the buffer points
        // directly to the typed object's storage.
        OWNS_DATA           = 0x8,

        // This array buffer was created lazily for a typed object with inline
        // data. This implies both that the typed object owns the buffer's data
        // and that the list of views sharing this buffer's data might be
        // incomplete. Any missing views will be typed objects.
        FOR_INLINE_TYPED_OBJECT = 0x10,

        // Views of this buffer might include typed objects.
        TYPED_OBJECT_VIEWS  = 0x20
    };

  public:

    class BufferContents {
        uint8_t* data_;
        BufferKind kind_;

        friend class ArrayBufferObject;

        BufferContents(uint8_t* data, BufferKind kind) : data_(data), kind_(kind) {
            MOZ_ASSERT((kind_ & ~KIND_MASK) == 0);
        }

      public:

        template<BufferKind Kind>
        static BufferContents create(void* data)
        {
            return BufferContents(static_cast<uint8_t*>(data), Kind);
        }

        static BufferContents createPlain(void* data)
        {
            return BufferContents(static_cast<uint8_t*>(data), PLAIN);
        }

        uint8_t* data() const { return data_; }
        BufferKind kind() const { return kind_; }

        explicit operator bool() const { return data_ != nullptr; }
    };

    static const Class class_;

    static const Class protoClass;
    static const JSFunctionSpec jsfuncs[];
    static const JSFunctionSpec jsstaticfuncs[];

    static bool byteLengthGetter(JSContext* cx, unsigned argc, Value* vp);

    static bool fun_slice(JSContext* cx, unsigned argc, Value* vp);

    static bool fun_isView(JSContext* cx, unsigned argc, Value* vp);
#ifdef NIGHTLY_BUILD
    static bool fun_transfer(JSContext* cx, unsigned argc, Value* vp);
#endif

    static bool class_constructor(JSContext* cx, unsigned argc, Value* vp);

    static ArrayBufferObject* create(JSContext* cx, uint32_t nbytes,
                                     BufferContents contents,
                                     OwnsState ownsState = OwnsData,
                                     NewObjectKind newKind = GenericObject);
    static ArrayBufferObject* create(JSContext* cx, uint32_t nbytes,
                                     NewObjectKind newKind = GenericObject);

    static JSObject* createSlice(JSContext* cx, Handle<ArrayBufferObject*> arrayBuffer,
                                 uint32_t begin, uint32_t end);

    static bool createDataViewForThisImpl(JSContext* cx, CallArgs args);
    static bool createDataViewForThis(JSContext* cx, unsigned argc, Value* vp);

    template<typename T>
    static bool createTypedArrayFromBufferImpl(JSContext* cx, CallArgs args);

    template<typename T>
    static bool createTypedArrayFromBuffer(JSContext* cx, unsigned argc, Value* vp);

    static void trace(JSTracer* trc, JSObject* obj);
    static void objectMoved(JSObject* obj, const JSObject* old);

    static BufferContents stealContents(JSContext* cx,
                                        Handle<ArrayBufferObject*> buffer,
                                        bool hasStealableContents);

    bool hasStealableContents() const {
        // Inline elements strictly adhere to the corresponding buffer.
        if (!ownsData())
            return false;

        // Neutered contents aren't transferrable because we want a neutered
        // array's contents to be backed by zeroed memory equal in length to
        // the original buffer contents.  Transferring these contents would
        // allocate new ones based on the current byteLength, which is 0 for a
        // neutered array -- not the original byteLength.
        return !isNeutered();
    }

    // Return whether the buffer is allocated by js_malloc and should be freed
    // with js_free.
    bool hasMallocedContents() const {
        return (ownsData() && isPlain()) || isAsmJSMalloced();
    }

    static void addSizeOfExcludingThis(JSObject* obj, mozilla::MallocSizeOf mallocSizeOf,
                                       JS::ClassInfo* info);

    // ArrayBufferObjects (strongly) store the first view added to them, while
    // later views are (weakly) stored in the compartment's InnerViewTable
    // below. Buffers usually only have one view, so this slot optimizes for
    // the common case. Avoiding entries in the InnerViewTable saves memory and
    // non-incrementalized sweep time.
    ArrayBufferViewObject* firstView();

    bool addView(JSContext* cx, JSObject* view);

    void setNewOwnedData(FreeOp* fop, BufferContents newContents);
    void changeContents(JSContext* cx, BufferContents newContents);

    /*
     * Ensure data is not stored inline in the object. Used when handing back a
     * GC-safe pointer.
     */
    static bool ensureNonInline(JSContext* cx, Handle<ArrayBufferObject*> buffer);

    /* Neuter this buffer and all its views. */
    static MOZ_WARN_UNUSED_RESULT bool
    neuter(JSContext* cx, Handle<ArrayBufferObject*> buffer, BufferContents newContents);

  private:
    void neuterView(JSContext* cx, ArrayBufferViewObject* view,
                    BufferContents newContents);
    void changeViewContents(JSContext* cx, ArrayBufferViewObject* view,
                            uint8_t* oldDataPointer, BufferContents newContents);
    void setFirstView(ArrayBufferViewObject* view);

    uint8_t* inlineDataPointer() const;

  public:
    uint8_t* dataPointer() const;
    size_t byteLength() const;
    BufferContents contents() const {
        return BufferContents(dataPointer(), bufferKind());
    }
    bool hasInlineData() const {
        return dataPointer() == inlineDataPointer();
    }

    void releaseData(FreeOp* fop);

    /*
     * Check if the arrayBuffer contains any data. This will return false for
     * ArrayBuffer.prototype and neutered ArrayBuffers.
     */
    bool hasData() const {
        return getClass() == &class_;
    }

    BufferKind bufferKind() const { return BufferKind(flags() & BUFFER_KIND_MASK); }
    bool isPlain() const { return bufferKind() == PLAIN; }
    bool isAsmJSMapped() const { return bufferKind() == ASMJS_MAPPED; }
    bool isAsmJSMalloced() const { return bufferKind() == ASMJS_MALLOCED; }
    bool isAsmJS() const { return isAsmJSMapped() || isAsmJSMalloced(); }
    bool isMapped() const { return bufferKind() == MAPPED; }
    bool isNeutered() const { return flags() & NEUTERED; }

    static bool prepareForAsmJS(JSContext* cx, Handle<ArrayBufferObject*> buffer,
                                bool usesSignalHandlers);
    static bool prepareForAsmJSNoSignals(JSContext* cx, Handle<ArrayBufferObject*> buffer);

    static void finalize(FreeOp* fop, JSObject* obj);

    static BufferContents createMappedContents(int fd, size_t offset, size_t length);

    static size_t offsetOfFlagsSlot() {
        return getFixedSlotOffset(FLAGS_SLOT);
    }
    static size_t offsetOfDataSlot() {
        return getFixedSlotOffset(DATA_SLOT);
    }

    static uint32_t neuteredFlag() { return NEUTERED; }

    void setForInlineTypedObject() {
        setFlags(flags() | FOR_INLINE_TYPED_OBJECT);
    }
    void setHasTypedObjectViews() {
        setFlags(flags() | TYPED_OBJECT_VIEWS);
    }

    bool forInlineTypedObject() const { return flags() & FOR_INLINE_TYPED_OBJECT; }

  protected:
    void setDataPointer(BufferContents contents, OwnsState ownsState);
    void setByteLength(size_t length);

    uint32_t flags() const;
    void setFlags(uint32_t flags);

    bool ownsData() const { return flags() & OWNS_DATA; }
    void setOwnsData(OwnsState owns) {
        setFlags(owns ? (flags() | OWNS_DATA) : (flags() & ~OWNS_DATA));
    }

    bool hasTypedObjectViews() const { return flags() & TYPED_OBJECT_VIEWS; }

    void setIsAsmJSMalloced() { setFlags((flags() & ~KIND_MASK) | ASMJS_MALLOCED); }
    void setIsNeutered() { setFlags(flags() | NEUTERED); }

    void initialize(size_t byteLength, BufferContents contents, OwnsState ownsState) {
        setByteLength(byteLength);
        setFlags(0);
        setFirstView(nullptr);
        setDataPointer(contents, ownsState);
    }
};

/*
 * ArrayBufferViewObject
 *
 * Common definitions shared by all array buffer views.
 */

class ArrayBufferViewObject : public JSObject
{
  public:
    static ArrayBufferObject* bufferObject(JSContext* cx, Handle<ArrayBufferViewObject*> obj);

    void neuter(void* newData);

    uint8_t* dataPointer();
    void setDataPointer(uint8_t* data);

    static void trace(JSTracer* trc, JSObject* obj);
};

bool
ToClampedIndex(JSContext* cx, HandleValue v, uint32_t length, uint32_t* out);

/*
 * Tests for ArrayBufferObject, like obj->is<ArrayBufferObject>().
 */
bool IsArrayBuffer(HandleValue v);
bool IsArrayBuffer(HandleObject obj);
bool IsArrayBuffer(JSObject* obj);
ArrayBufferObject& AsArrayBuffer(HandleObject obj);
ArrayBufferObject& AsArrayBuffer(JSObject* obj);

extern uint32_t JS_FASTCALL
ClampDoubleToUint8(const double x);

struct uint8_clamped {
    uint8_t val;

    uint8_clamped() { }
    uint8_clamped(const uint8_clamped& other) : val(other.val) { }

    // invoke our assignment helpers for constructor conversion
    explicit uint8_clamped(uint8_t x)    { *this = x; }
    explicit uint8_clamped(uint16_t x)   { *this = x; }
    explicit uint8_clamped(uint32_t x)   { *this = x; }
    explicit uint8_clamped(int8_t x)     { *this = x; }
    explicit uint8_clamped(int16_t x)    { *this = x; }
    explicit uint8_clamped(int32_t x)    { *this = x; }
    explicit uint8_clamped(double x)     { *this = x; }

    uint8_clamped& operator=(const uint8_clamped& x) {
        val = x.val;
        return *this;
    }

    uint8_clamped& operator=(uint8_t x) {
        val = x;
        return *this;
    }

    uint8_clamped& operator=(uint16_t x) {
        val = (x > 255) ? 255 : uint8_t(x);
        return *this;
    }

    uint8_clamped& operator=(uint32_t x) {
        val = (x > 255) ? 255 : uint8_t(x);
        return *this;
    }

    uint8_clamped& operator=(int8_t x) {
        val = (x >= 0) ? uint8_t(x) : 0;
        return *this;
    }

    uint8_clamped& operator=(int16_t x) {
        val = (x >= 0)
              ? ((x < 255)
                 ? uint8_t(x)
                 : 255)
              : 0;
        return *this;
    }

    uint8_clamped& operator=(int32_t x) {
        val = (x >= 0)
              ? ((x < 255)
                 ? uint8_t(x)
                 : 255)
              : 0;
        return *this;
    }

    uint8_clamped& operator=(const double x) {
        val = uint8_t(ClampDoubleToUint8(x));
        return *this;
    }

    operator uint8_t() const {
        return val;
    }

    void staticAsserts() {
        static_assert(sizeof(uint8_clamped) == 1,
                      "uint8_clamped must be layout-compatible with uint8_t");
    }
};

/* Note that we can't use std::numeric_limits here due to uint8_clamped. */
template<typename T> inline bool TypeIsFloatingPoint() { return false; }
template<> inline bool TypeIsFloatingPoint<float>() { return true; }
template<> inline bool TypeIsFloatingPoint<double>() { return true; }

template<typename T> inline bool TypeIsUnsigned() { return false; }
template<> inline bool TypeIsUnsigned<uint8_t>() { return true; }
template<> inline bool TypeIsUnsigned<uint16_t>() { return true; }
template<> inline bool TypeIsUnsigned<uint32_t>() { return true; }

// Per-compartment table that manages the relationship between array buffers
// and the views that use their storage.
class InnerViewTable
{
  public:
    typedef Vector<ArrayBufferViewObject*, 1, SystemAllocPolicy> ViewVector;

    friend class ArrayBufferObject;

  private:
    typedef HashMap<JSObject*,
                    ViewVector,
                    DefaultHasher<JSObject*>,
                    SystemAllocPolicy> Map;

    // For all objects sharing their storage with some other view, this maps
    // the object to the list of such views. All entries in this map are weak.
    Map map;

    // List of keys from innerViews where either the source or at least one
    // target is in the nursery.
    Vector<JSObject*, 0, SystemAllocPolicy> nurseryKeys;

    // Whether nurseryKeys is a complete list.
    bool nurseryKeysValid;

    // Sweep an entry during GC, returning whether the entry should be removed.
    bool sweepEntry(JSObject** pkey, ViewVector& views);

    bool addView(JSContext* cx, ArrayBufferObject* obj, ArrayBufferViewObject* view);
    ViewVector* maybeViewsUnbarriered(ArrayBufferObject* obj);
    void removeViews(ArrayBufferObject* obj);

  public:
    InnerViewTable()
      : nurseryKeysValid(true)
    {}

    // Remove references to dead objects in the table and update table entries
    // to reflect moved objects.
    void sweep(JSRuntime* rt);
    void sweepAfterMinorGC(JSRuntime* rt);

    bool needsSweepAfterMinorGC() {
        return !nurseryKeys.empty() || !nurseryKeysValid;
    }

    size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf);
};

} // namespace js

template <>
bool
JSObject::is<js::ArrayBufferViewObject>() const;

#endif // vm_ArrayBufferObject_h