C++ JSFlatString类代码示例

/*
 * When the jschars reside in a freshly allocated buffer the memory can be used
 * as a new JSAtom's storage without copying. The contract is that the caller no
 * longer owns the memory and this method is responsible for freeing the memory.
 */
MOZ_ALWAYS_INLINE
static JSAtom *
AtomizeAndtake(ExclusiveContext *cx, jschar *tbchars, size_t length, InternBehavior ib)
{
    JS_ASSERT(tbchars[length] == 0);

    if (JSAtom *s = cx->staticStrings().lookup(tbchars, length)) {
        js_free(tbchars);
        return s;
    }

    AtomHasher::Lookup lookup(tbchars, length);

    AtomSet::Ptr pp = cx->permanentAtoms().readonlyThreadsafeLookup(lookup);
    if (pp) {
        js_free(tbchars);
        return pp->asPtr();
    }

    AutoLockForExclusiveAccess lock(cx);

    /*
     * If a GC occurs at js_NewStringCopy then |p| will still have the correct
     * hash, allowing us to avoid rehashing it. Even though the hash is
     * unchanged, we need to re-lookup the table position because a last-ditch
     * GC will potentially free some table entries.
     */
    AtomSet& atoms = cx->atoms();
    AtomSet::AddPtr p = atoms.lookupForAdd(lookup);
    if (p) {
        JSAtom *atom = p->asPtr();
        p->setTagged(bool(ib));
        js_free(tbchars);
        return atom;
    }

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

    JSFlatString *flat = js_NewString<NoGC>(cx, tbchars, length);
    if (!flat) {
        js_free(tbchars);
        js_ReportOutOfMemory(cx);
        return nullptr;
    }

    JSAtom *atom = flat->morphAtomizedStringIntoAtom();

    if (!atoms.relookupOrAdd(p, lookup, AtomStateEntry(atom, bool(ib)))) {
        js_ReportOutOfMemory(cx); /* SystemAllocPolicy does not report OOM. */
        return nullptr;
    }

    return atom;
}

MOZ_ALWAYS_INLINE
static JSAtom *
AtomizeAndCopyChars(ExclusiveContext *cx, const CharT *tbchars, size_t length, InternBehavior ib)
{
    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->setTagged(bool(ib));
        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();

    // 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(ib)))) {
        ReportOutOfMemory(cx); /* SystemAllocPolicy does not report OOM. */
        return nullptr;
    }

    return atom;
}

JS_ALWAYS_INLINE
static JSAtom *
AtomizeAndCopyChars(ExclusiveContext *cx, const jschar *tbchars, size_t length, InternBehavior ib)
{
    if (JSAtom *s = cx->staticStrings().lookup(tbchars, length))
         return s;

    /*
     * If a GC occurs at js_NewStringCopy then |p| will still have the correct
     * hash, allowing us to avoid rehashing it. Even though the hash is
     * unchanged, we need to re-lookup the table position because a last-ditch
     * GC will potentially free some table entries.
     */

    AutoLockForExclusiveAccess lock(cx);

    AtomSet& atoms = cx->atoms();
    AtomSet::AddPtr p = atoms.lookupForAdd(AtomHasher::Lookup(tbchars, length));
    SkipRoot skipHash(cx, &p); /* Prevent the hash from being poisoned. */
    if (p) {
        JSAtom *atom = p->asPtr();
        p->setTagged(bool(ib));
        return atom;
    }

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

    JSFlatString *flat = js_NewStringCopyN<allowGC>(cx, tbchars, length);
    if (!flat)
        return NULL;

    JSAtom *atom = flat->morphAtomizedStringIntoAtom();

    if (!atoms.relookupOrAdd(p, AtomHasher::Lookup(tbchars, length),
                             AtomStateEntry(atom, bool(ib)))) {
        if (allowGC)
            js_ReportOutOfMemory(cx); /* SystemAllocPolicy does not report OOM. */
        return NULL;
    }

    return atom;
}

static JSFlatString*
FinishStringFlat(ExclusiveContext* cx, StringBuffer& sb, Buffer& cb)
{
    size_t len = sb.length();
    if (!sb.append('\0'))
        return nullptr;

    ScopedJSFreePtr<CharT> buf(ExtractWellSized<CharT>(cx, cb));
    if (!buf)
        return nullptr;

    JSFlatString* str = NewStringDontDeflate<CanGC>(cx, buf.get(), len);
    if (!str)
        return nullptr;

    /*
     * The allocation was made on a TempAllocPolicy, so account for the string
     * data on the string's zone.
     */
    str->zone()->updateMallocCounter(sizeof(CharT) * len);

    buf.forget();
    return str;
}

bool
StaticStrings::init(JSContext* cx)
{
    AutoLockForExclusiveAccess lock(cx);
    AutoCompartment ac(cx, cx->runtime()->atomsCompartment());

    static_assert(UNIT_STATIC_LIMIT - 1 <= JSString::MAX_LATIN1_CHAR,
                  "Unit strings must fit in Latin1Char.");

    for (uint32_t i = 0; i < UNIT_STATIC_LIMIT; i++) {
        Latin1Char buffer[] = { Latin1Char(i), '\0' };
        JSFlatString* s = NewStringCopyN<NoGC>(cx, buffer, 1);
        if (!s)
            return false;
        unitStaticTable[i] = s->morphAtomizedStringIntoPermanentAtom();
    }

    for (uint32_t i = 0; i < NUM_SMALL_CHARS * NUM_SMALL_CHARS; i++) {
        Latin1Char buffer[] = { FROM_SMALL_CHAR(i >> 6), FROM_SMALL_CHAR(i & 0x3F), '\0' };
        JSFlatString* s = NewStringCopyN<NoGC>(cx, buffer, 2);
        if (!s)
            return false;
        length2StaticTable[i] = s->morphAtomizedStringIntoPermanentAtom();
    }

    for (uint32_t i = 0; i < INT_STATIC_LIMIT; i++) {
        if (i < 10) {
            intStaticTable[i] = unitStaticTable[i + '0'];
        } else if (i < 100) {
            size_t index = ((size_t)TO_SMALL_CHAR((i / 10) + '0') << 6) +
                TO_SMALL_CHAR((i % 10) + '0');
            intStaticTable[i] = length2StaticTable[index];
        } else {
            Latin1Char buffer[] = { Latin1Char('0' + (i / 100)),
                                    Latin1Char('0' + ((i / 10) % 10)),
                                    Latin1Char('0' + (i % 10)),
                                    '\0' };
            JSFlatString* s = NewStringCopyN<NoGC>(cx, buffer, 3);
            if (!s)
                return false;
            intStaticTable[i] = s->morphAtomizedStringIntoPermanentAtom();
        }
    }

    return true;
}

JSObject*
Library::Create(JSContext* cx, jsval path, JSCTypesCallbacks* callbacks)
{
  JSObject* libraryObj = JS_NewObject(cx, &sLibraryClass, NULL, NULL);
  if (!libraryObj)
    return NULL;
  js::AutoObjectRooter root(cx, libraryObj);

  // initialize the library
  if (!JS_SetReservedSlot(cx, libraryObj, SLOT_LIBRARY, PRIVATE_TO_JSVAL(NULL)))
    return NULL;

  // attach API functions
  if (!JS_DefineFunctions(cx, libraryObj, sLibraryFunctions))
    return NULL;

  if (!JSVAL_IS_STRING(path)) {
    JS_ReportError(cx, "open takes a string argument");
    return NULL;
  }

  PRLibSpec libSpec;
  JSFlatString* pathStr = JS_FlattenString(cx, JSVAL_TO_STRING(path));
  if (!pathStr)
    return NULL;
#ifdef XP_WIN
  // On Windows, converting to native charset may corrupt path string.
  // So, we have to use Unicode path directly.
  const PRUnichar* pathChars = JS_GetFlatStringChars(pathStr);
  if (!pathChars)
    return NULL;

  libSpec.value.pathname_u = pathChars;
  libSpec.type = PR_LibSpec_PathnameU;
#else
  // Convert to platform native charset if the appropriate callback has been
  // provided.
  char* pathBytes;
  if (callbacks && callbacks->unicodeToNative) {
    pathBytes = 
      callbacks->unicodeToNative(cx, pathStr->chars(), pathStr->length());
    if (!pathBytes)
      return NULL;

  } else {
    // Fallback: assume the platform native charset is UTF-8. This is true
    // for Mac OS X, Android, and probably Linux.
    size_t nbytes =
      js_GetDeflatedUTF8StringLength(cx, pathStr->chars(), pathStr->length());
    if (nbytes == (size_t) -1)
      return NULL;

    pathBytes = static_cast<char*>(JS_malloc(cx, nbytes + 1));
    if (!pathBytes)
      return NULL;

    ASSERT_OK(js_DeflateStringToUTF8Buffer(cx, pathStr->chars(),
                pathStr->length(), pathBytes, &nbytes));
    pathBytes[nbytes] = 0;
  }

  libSpec.value.pathname = pathBytes;
  libSpec.type = PR_LibSpec_Pathname;
#endif

  PRLibrary* library = PR_LoadLibraryWithFlags(libSpec, 0);
#ifndef XP_WIN
  JS_free(cx, pathBytes);
#endif
  if (!library) {
    JS_ReportError(cx, "couldn't open library");
    return NULL;
  }

  // stash the library
  if (!JS_SetReservedSlot(cx, libraryObj, SLOT_LIBRARY,
         PRIVATE_TO_JSVAL(library)))
    return NULL;

  return libraryObj;
}