js/src/jsatom.cpp

/* -*- 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/. */

/*
 * JS atom table.
 */

#include "jsatominlines.h"

#include "mozilla/ArrayUtils.h"
#include "mozilla/RangedPtr.h"

#include <string.h>

#include "jscntxt.h"
#include "jsstr.h"
#include "jstypes.h"

#include "gc/Marking.h"
#include "vm/Symbol.h"
#include "vm/Xdr.h"

#include "jscntxtinlines.h"
#include "jscompartmentinlines.h"
#include "jsobjinlines.h"

#include "vm/String-inl.h"

using namespace js;
using namespace js::gc;

using mozilla::ArrayEnd;
using mozilla::ArrayLength;
using mozilla::RangedPtr;

const char*
js::AtomToPrintableString(ExclusiveContext* cx, JSAtom* atom, JSAutoByteString* bytes)
{
    JSString* str = QuoteString(cx, atom, 0);
    if (!str)
        return nullptr;
    return bytes->encodeLatin1(cx, str);
}

#define DEFINE_PROTO_STRING(name,code,init,clasp) const char js_##name##_str[] = #name;
JS_FOR_EACH_PROTOTYPE(DEFINE_PROTO_STRING)
#undef DEFINE_PROTO_STRING

#define CONST_CHAR_STR(idpart, id, text) const char js_##idpart##_str[] = text;
FOR_EACH_COMMON_PROPERTYNAME(CONST_CHAR_STR)
#undef CONST_CHAR_STR

/* Constant strings that are not atomized. */
const char js_break_str[]           = "break";
const char js_case_str[]            = "case";
const char js_catch_str[]           = "catch";
const char js_class_str[]           = "class";
const char js_const_str[]           = "const";
const char js_continue_str[]        = "continue";
const char js_debugger_str[]        = "debugger";
const char js_default_str[]         = "default";
const char js_do_str[]              = "do";
const char js_else_str[]            = "else";
const char js_enum_str[]            = "enum";
const char js_export_str[]          = "export";
const char js_extends_str[]         = "extends";
const char js_finally_str[]         = "finally";
const char js_for_str[]             = "for";
const char js_getter_str[]          = "getter";
const char js_if_str[]              = "if";
const char js_implements_str[]      = "implements";
const char js_import_str[]          = "import";
const char js_in_str[]              = "in";
const char js_instanceof_str[]      = "instanceof";
const char js_interface_str[]       = "interface";
const char js_package_str[]         = "package";
const char js_private_str[]         = "private";
const char js_protected_str[]       = "protected";
const char js_public_str[]          = "public";
const char js_send_str[]            = "send";
const char js_setter_str[]          = "setter";
const char js_switch_str[]          = "switch";
const char js_this_str[]            = "this";
const char js_try_str[]             = "try";
const char js_typeof_str[]          = "typeof";
const char js_void_str[]            = "void";
const char js_while_str[]           = "while";
const char js_with_str[]            = "with";

// Use a low initial capacity for atom hash tables to avoid penalizing runtimes
// which create a small number of atoms.
static const uint32_t JS_STRING_HASH_COUNT = 64;

AtomSet::Ptr js::FrozenAtomSet::readonlyThreadsafeLookup(const AtomSet::Lookup& l) const {
    return mSet->readonlyThreadsafeLookup(l);
}

struct CommonNameInfo
{
    const char* str;
    size_t length;
};

bool
JSRuntime::initializeAtoms(JSContext* cx)
{
    atoms_ = cx->new_<AtomSet>();
    if (!atoms_ || !atoms_->init(JS_STRING_HASH_COUNT))
        return false;

    // |permanentAtoms| hasn't been created yet.
    MOZ_ASSERT(!permanentAtoms);

    if (parentRuntime) {
        staticStrings = parentRuntime->staticStrings;
        commonNames = parentRuntime->commonNames;
        emptyString = parentRuntime->emptyString;
        permanentAtoms = parentRuntime->permanentAtoms;
        wellKnownSymbols = parentRuntime->wellKnownSymbols;
        return true;
    }

    staticStrings = cx->new_<StaticStrings>();
    if (!staticStrings || !staticStrings->init(cx))
        return false;

    static const CommonNameInfo cachedNames[] = {
#define COMMON_NAME_INFO(idpart, id, text) { js_##idpart##_str, sizeof(text) - 1 },
        FOR_EACH_COMMON_PROPERTYNAME(COMMON_NAME_INFO)
#undef COMMON_NAME_INFO
#define COMMON_NAME_INFO(name, code, init, clasp) { js_##name##_str, sizeof(#name) - 1 },
        JS_FOR_EACH_PROTOTYPE(COMMON_NAME_INFO)
#undef COMMON_NAME_INFO
    };

    commonNames = cx->new_<JSAtomState>();
    if (!commonNames)
        return false;

    ImmutablePropertyNamePtr* names = reinterpret_cast<ImmutablePropertyNamePtr*>(commonNames);
    for (size_t i = 0; i < ArrayLength(cachedNames); i++, names++) {
        JSAtom* atom = Atomize(cx, cachedNames[i].str, cachedNames[i].length, PinAtom);
        if (!atom)
            return false;
        names->init(atom->asPropertyName());
    }
    MOZ_ASSERT(uintptr_t(names) == uintptr_t(commonNames + 1));

    emptyString = commonNames->empty;

    // Create the well-known symbols.
    wellKnownSymbols = cx->new_<WellKnownSymbols>();
    if (!wellKnownSymbols)
        return false;

    ImmutablePropertyNamePtr* descriptions = commonNames->wellKnownSymbolDescriptions();
    ImmutableSymbolPtr* symbols = reinterpret_cast<ImmutableSymbolPtr*>(wellKnownSymbols);
    for (size_t i = 0; i < JS::WellKnownSymbolLimit; i++) {
        JS::Symbol* symbol = JS::Symbol::new_(cx, JS::SymbolCode(i), descriptions[i]);
        if (!symbol) {
            ReportOutOfMemory(cx);
            return false;
        }
        symbols[i].init(symbol);
    }

    return true;
}

void
JSRuntime::finishAtoms()
{
    js_delete(atoms_);

    if (!parentRuntime) {
        js_delete(staticStrings);
        js_delete(commonNames);
        js_delete(permanentAtoms);
        js_delete(wellKnownSymbols);
    }

    atoms_ = nullptr;
    staticStrings = nullptr;
    commonNames = nullptr;
    permanentAtoms = nullptr;
    wellKnownSymbols = nullptr;
    emptyString = nullptr;
}

void
js::MarkAtoms(JSTracer* trc)
{
    JSRuntime* rt = trc->runtime();
    for (AtomSet::Enum e(rt->atoms()); !e.empty(); e.popFront()) {
        const AtomStateEntry& entry = e.front();
        if (!entry.isPinned())
            continue;

        JSAtom* atom = entry.asPtrUnbarriered();
        TraceRoot(trc, &atom, "interned_atom");
        MOZ_ASSERT(entry.asPtrUnbarriered() == atom);
    }
}

void
js::MarkPermanentAtoms(JSTracer* trc)
{
    JSRuntime* rt = trc->runtime();

    // Permanent atoms only need to be marked in the runtime which owns them.
    if (rt->parentRuntime)
        return;

    // Static strings are not included in the permanent atoms table.
    if (rt->staticStrings)
        rt->staticStrings->trace(trc);

    if (rt->permanentAtoms) {
        for (FrozenAtomSet::Range r(rt->permanentAtoms->all()); !r.empty(); r.popFront()) {
            const AtomStateEntry& entry = r.front();

            JSAtom* atom = entry.asPtr();
            TraceProcessGlobalRoot(trc, atom, "permanent_table");
        }
    }
}

void
js::MarkWellKnownSymbols(JSTracer* trc)
{
    JSRuntime* rt = trc->runtime();

    if (rt->parentRuntime)
        return;

    if (WellKnownSymbols* wks = rt->wellKnownSymbols) {
        for (size_t i = 0; i < JS::WellKnownSymbolLimit; i++)
            TraceProcessGlobalRoot(trc, wks->get(i).get(), "well_known_symbol");
    }
}

void
JSRuntime::sweepAtoms()
{
    if (atoms_)
        atoms_->sweep();
}

bool
JSRuntime::transformToPermanentAtoms(JSContext* cx)
{
    MOZ_ASSERT(!parentRuntime);

    // All static strings were created as permanent atoms, now move the contents
    // of the atoms table into permanentAtoms and mark each as permanent.

    MOZ_ASSERT(!permanentAtoms);
    permanentAtoms = cx->new_<FrozenAtomSet>(atoms_);   // takes ownership of atoms_

    atoms_ = cx->new_<AtomSet>();
    if (!atoms_ || !atoms_->init(JS_STRING_HASH_COUNT))
        return false;

    for (FrozenAtomSet::Range r(permanentAtoms->all()); !r.empty(); r.popFront()) {
        AtomStateEntry entry = r.front();
        JSAtom* atom = entry.asPtr();
        atom->morphIntoPermanentAtom();
    }

    return true;
}

bool
AtomIsPinned(JSContext* cx, JSAtom* atom)
{
    /* We treat static strings as interned because they're never collected. */
    if (StaticStrings::isStatic(atom))
        return true;

    AtomHasher::Lookup lookup(atom);

    /* Likewise, permanent strings are considered to be interned. */
    MOZ_ASSERT(cx->isPermanentAtomsInitialized());
    AtomSet::Ptr p = cx->permanentAtoms().readonlyThreadsafeLookup(lookup);
    if (p)
        return true;

    AutoLockForExclusiveAccess lock(cx);

    p = cx->runtime()->atoms().lookup(lookup);
    if (!p)
        return false;

    return p->isPinned();
}

/* |tbchars| must not point into an inline or short string. */
template <typename CharT>
MOZ_ALWAYS_INLINE
static JSAtom*
AtomizeAndCopyChars(ExclusiveContext* cx, const CharT* tbchars, size_t length, PinningBehavior pin)
{
    if (JSAtom* s = cx->staticStrings().lookup(tbchars, length))
         return s;

    AtomHasher::Lookup lookup(tbchars, length);

    // Note: when this function is called while the permanent atoms table is
    // being initialized (in initializeAtoms()), |permanentAtoms| is not yet
    // initialized so this lookup is always skipped. Only once
    // transformToPermanentAtoms() is called does |permanentAtoms| get
    // initialized and then this lookup will go ahead.
    if (cx->isPermanentAtomsInitialized()) {
        AtomSet::Ptr pp = cx->permanentAtoms().readonlyThreadsafeLookup(lookup);
        if (pp)
            return pp->asPtr();
    }

    AutoLockForExclusiveAccess lock(cx);

    AtomSet& atoms = cx->atoms();
    AtomSet::AddPtr p = atoms.lookupForAdd(lookup);
    if (p) {
        JSAtom* atom = p->asPtr();
        p->setPinned(bool(pin));
        return atom;
    }

    AutoCompartment ac(cx, cx->atomsCompartment());

    JSFlatString* flat = NewStringCopyN<NoGC>(cx, tbchars, length);
    if (!flat) {
        // Grudgingly forgo last-ditch GC. The alternative would be to release
        // the lock, manually GC here, and retry from the top. If you fix this,
        // please also fix or comment the similar case in Symbol::new_.
        ReportOutOfMemory(cx);
        return nullptr;
    }

    JSAtom* atom = flat->morphAtomizedStringIntoAtom(lookup.hash);
    MOZ_ASSERT(atom->hash() == lookup.hash);

    // We have held the lock since looking up p, and the operations we've done
    // since then can't GC; therefore the atoms table has not been modified and
    // p is still valid.
    if (!atoms.add(p, AtomStateEntry(atom, bool(pin)))) {
        ReportOutOfMemory(cx); /* SystemAllocPolicy does not report OOM. */
        return nullptr;
    }

    return atom;
}

template JSAtom*
AtomizeAndCopyChars(ExclusiveContext* cx, const char16_t* tbchars, size_t length, PinningBehavior pin);

template JSAtom*
AtomizeAndCopyChars(ExclusiveContext* cx, const Latin1Char* tbchars, size_t length, PinningBehavior pin);

JSAtom*
js::AtomizeString(ExclusiveContext* cx, JSString* str,
                  js::PinningBehavior pin /* = js::DoNotPinAtom */)
{
    if (str->isAtom()) {
        JSAtom& atom = str->asAtom();
        /* N.B. static atoms are effectively always interned. */
        if (pin != PinAtom || js::StaticStrings::isStatic(&atom))
            return &atom;

        AtomHasher::Lookup lookup(&atom);

        /* Likewise, permanent atoms are always interned. */
        MOZ_ASSERT(cx->isPermanentAtomsInitialized());
        AtomSet::Ptr p = cx->permanentAtoms().readonlyThreadsafeLookup(lookup);
        if (p)
            return &atom;

        AutoLockForExclusiveAccess lock(cx);

        p = cx->atoms().lookup(lookup);
        MOZ_ASSERT(p); /* Non-static atom must exist in atom state set. */
        MOZ_ASSERT(p->asPtr() == &atom);
        MOZ_ASSERT(pin == PinAtom);
        p->setPinned(bool(pin));
        return &atom;
    }

    JSLinearString* linear = str->ensureLinear(cx);
    if (!linear)
        return nullptr;

    JS::AutoCheckCannotGC nogc;
    return linear->hasLatin1Chars()
           ? AtomizeAndCopyChars(cx, linear->latin1Chars(nogc), linear->length(), pin)
           : AtomizeAndCopyChars(cx, linear->twoByteChars(nogc), linear->length(), pin);
}

JSAtom*
js::Atomize(ExclusiveContext* cx, const char* bytes, size_t length, PinningBehavior pin)
{
    CHECK_REQUEST(cx);

    if (!JSString::validateLength(cx, length))
        return nullptr;

    const Latin1Char* chars = reinterpret_cast<const Latin1Char*>(bytes);
    return AtomizeAndCopyChars(cx, chars, length, pin);
}

template <typename CharT>
JSAtom*
js::AtomizeChars(ExclusiveContext* cx, const CharT* chars, size_t length, PinningBehavior pin)
{
    CHECK_REQUEST(cx);

    if (!JSString::validateLength(cx, length))
        return nullptr;

    return AtomizeAndCopyChars(cx, chars, length, pin);
}

template JSAtom*
js::AtomizeChars(ExclusiveContext* cx, const Latin1Char* chars, size_t length, PinningBehavior pin);

template JSAtom*
js::AtomizeChars(ExclusiveContext* cx, const char16_t* chars, size_t length, PinningBehavior pin);

bool
js::IndexToIdSlow(ExclusiveContext* cx, uint32_t index, MutableHandleId idp)
{
    MOZ_ASSERT(index > JSID_INT_MAX);

    char16_t buf[UINT32_CHAR_BUFFER_LENGTH];
    RangedPtr<char16_t> end(ArrayEnd(buf), buf, ArrayEnd(buf));
    RangedPtr<char16_t> start = BackfillIndexInCharBuffer(index, end);

    JSAtom* atom = AtomizeChars(cx, start.get(), end - start);
    if (!atom)
        return false;

    idp.set(JSID_FROM_BITS((size_t)atom));
    return true;
}

template <AllowGC allowGC>
static JSAtom*
ToAtomSlow(ExclusiveContext* cx, typename MaybeRooted<Value, allowGC>::HandleType arg)
{
    MOZ_ASSERT(!arg.isString());

    Value v = arg;
    if (!v.isPrimitive()) {
        if (!cx->shouldBeJSContext() || !allowGC)
            return nullptr;
        RootedValue v2(cx, v);
        if (!ToPrimitive(cx->asJSContext(), JSTYPE_STRING, &v2))
            return nullptr;
        v = v2;
    }

    if (v.isString())
        return AtomizeString(cx, v.toString());
    if (v.isInt32())
        return Int32ToAtom(cx, v.toInt32());
    if (v.isDouble())
        return NumberToAtom(cx, v.toDouble());
    if (v.isBoolean())
        return v.toBoolean() ? cx->names().true_ : cx->names().false_;
    if (v.isNull())
        return cx->names().null;
    return cx->names().undefined;
}

template <AllowGC allowGC>
JSAtom*
js::ToAtom(ExclusiveContext* cx, typename MaybeRooted<Value, allowGC>::HandleType v)
{
    if (!v.isString())
        return ToAtomSlow<allowGC>(cx, v);

    JSString* str = v.toString();
    if (str->isAtom())
        return &str->asAtom();

    JSAtom* atom = AtomizeString(cx, str);
    if (!atom && !allowGC) {
        MOZ_ASSERT_IF(cx->isJSContext(), cx->asJSContext()->isThrowingOutOfMemory());
        cx->recoverFromOutOfMemory();
    }
    return atom;
}

template JSAtom*
js::ToAtom<CanGC>(ExclusiveContext* cx, HandleValue v);

template JSAtom*
js::ToAtom<NoGC>(ExclusiveContext* cx, Value v);

template<XDRMode mode>
bool
js::XDRAtom(XDRState<mode>* xdr, MutableHandleAtom atomp)
{
    if (mode == XDR_ENCODE) {
        static_assert(JSString::MAX_LENGTH <= INT32_MAX, "String length must fit in 31 bits");
        uint32_t length = atomp->length();
        uint32_t lengthAndEncoding = (length << 1) | uint32_t(atomp->hasLatin1Chars());
        if (!xdr->codeUint32(&lengthAndEncoding))
            return false;

        JS::AutoCheckCannotGC nogc;
        return atomp->hasLatin1Chars()
               ? xdr->codeChars(atomp->latin1Chars(nogc), length)
               : xdr->codeChars(const_cast<char16_t*>(atomp->twoByteChars(nogc)), length);
    }

    /* Avoid JSString allocation for already existing atoms. See bug 321985. */
    uint32_t lengthAndEncoding;
    if (!xdr->codeUint32(&lengthAndEncoding))
        return false;

    uint32_t length = lengthAndEncoding >> 1;
    bool latin1 = lengthAndEncoding & 0x1;

    JSContext* cx = xdr->cx();
    JSAtom* atom;
    if (latin1) {
        const Latin1Char* chars = reinterpret_cast<const Latin1Char*>(xdr->buf.read(length));
        atom = AtomizeChars(cx, chars, length);
    } else {
#if IS_LITTLE_ENDIAN
        /* Directly access the little endian chars in the XDR buffer. */
        const char16_t* chars = reinterpret_cast<const char16_t*>(xdr->buf.read(length * sizeof(char16_t)));
        atom = AtomizeChars(cx, chars, length);
#else
        /*
         * We must copy chars to a temporary buffer to convert between little and
         * big endian data.
         */
        char16_t* chars;
        char16_t stackChars[256];
        if (length <= ArrayLength(stackChars)) {
            chars = stackChars;
        } else {
            /*
             * This is very uncommon. Don't use the tempLifoAlloc arena for this as
             * most allocations here will be bigger than tempLifoAlloc's default
             * chunk size.
             */
            chars = cx->runtime()->pod_malloc<char16_t>(length);
            if (!chars)
                return false;
        }

        JS_ALWAYS_TRUE(xdr->codeChars(chars, length));
        atom = AtomizeChars(cx, chars, length);
        if (chars != stackChars)
            js_free(chars);
#endif /* !IS_LITTLE_ENDIAN */
    }

    if (!atom)
        return false;
    atomp.set(atom);
    return true;
}

template bool
js::XDRAtom(XDRState<XDR_ENCODE>* xdr, MutableHandleAtom atomp);

template bool
js::XDRAtom(XDRState<XDR_DECODE>* xdr, MutableHandleAtom atomp);