gecko-dev/dom/bindings/WebIDLGlobalNameHash.cpp
Nicholas Nethercote c2306345d5 Bug 1297658 - Avoid unnecessary checking in memory reporters. r=erahm.
This patch removes checking of all the callback calls in memory reporter
CollectReport() functions, because it's not useful.

The patch also does some associated clean-up.

- Replaces some uses of nsIMemoryReporterCallback with the preferred
  nsIHandleReportCallback typedef.

- Replaces aCallback/aCb/aClosure with aHandleRepor/aData for CollectReports()
  parameter names, for consistency.

- Adds MOZ_MUST_USE/[must_use] in a few places in nsIMemoryReporter.idl.

- Uses the MOZ_COLLECT_REPORT macro in all suitable places.

Overall the patch reduces code size by ~300 lines and reduces the size of
libxul by about 37 KiB on my Linux64 builds.

--HG--
extra : rebase_source : e94323614bd10463a0c5134a7276238a7ca1cf23
2016-08-24 15:23:45 +10:00

319 lines
10 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */
#include "WebIDLGlobalNameHash.h"
#include "js/GCAPI.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/Maybe.h"
#include "mozilla/dom/DOMJSProxyHandler.h"
#include "mozilla/dom/RegisterBindings.h"
#include "nsIMemoryReporter.h"
#include "nsTHashtable.h"
namespace mozilla {
namespace dom {
struct MOZ_STACK_CLASS WebIDLNameTableKey
{
explicit WebIDLNameTableKey(JSFlatString* aJSString)
: mLength(js::GetFlatStringLength(aJSString))
{
mNogc.emplace();
JSLinearString* jsString = js::FlatStringToLinearString(aJSString);
if (js::LinearStringHasLatin1Chars(jsString)) {
mLatin1String = reinterpret_cast<const char*>(
js::GetLatin1LinearStringChars(*mNogc, jsString));
mTwoBytesString = nullptr;
mHash = mLatin1String ? HashString(mLatin1String, mLength) : 0;
} else {
mLatin1String = nullptr;
mTwoBytesString = js::GetTwoByteLinearStringChars(*mNogc, jsString);
mHash = mTwoBytesString ? HashString(mTwoBytesString, mLength) : 0;
}
}
explicit WebIDLNameTableKey(const char* aString, size_t aLength)
: mLatin1String(aString),
mTwoBytesString(nullptr),
mLength(aLength),
mHash(HashString(aString, aLength))
{
MOZ_ASSERT(aString[aLength] == '\0');
}
Maybe<JS::AutoCheckCannotGC> mNogc;
const char* mLatin1String;
const char16_t* mTwoBytesString;
size_t mLength;
uint32_t mHash;
};
struct WebIDLNameTableEntry : public PLDHashEntryHdr
{
typedef const WebIDLNameTableKey& KeyType;
typedef const WebIDLNameTableKey* KeyTypePointer;
explicit WebIDLNameTableEntry(KeyTypePointer aKey)
: mNameOffset(0),
mNameLength(0),
mDefine(nullptr),
mEnabled(nullptr)
{}
WebIDLNameTableEntry(WebIDLNameTableEntry&& aEntry)
: mNameOffset(aEntry.mNameOffset),
mNameLength(aEntry.mNameLength),
mDefine(aEntry.mDefine),
mEnabled(aEntry.mEnabled)
{}
~WebIDLNameTableEntry()
{}
bool KeyEquals(KeyTypePointer aKey) const
{
if (mNameLength != aKey->mLength) {
return false;
}
const char* name = WebIDLGlobalNameHash::sNames + mNameOffset;
if (aKey->mLatin1String) {
return PodEqual(aKey->mLatin1String, name, aKey->mLength);
}
return nsCharTraits<char16_t>::compareASCII(aKey->mTwoBytesString, name,
aKey->mLength) == 0;
}
static KeyTypePointer KeyToPointer(KeyType aKey)
{
return &aKey;
}
static PLDHashNumber HashKey(KeyTypePointer aKey)
{
return aKey->mHash;
}
enum { ALLOW_MEMMOVE = true };
uint16_t mNameOffset;
uint16_t mNameLength;
WebIDLGlobalNameHash::DefineGlobalName mDefine;
// May be null if enabled unconditionally
WebIDLGlobalNameHash::ConstructorEnabled* mEnabled;
};
static nsTHashtable<WebIDLNameTableEntry>* sWebIDLGlobalNames;
class WebIDLGlobalNamesHashReporter final : public nsIMemoryReporter
{
MOZ_DEFINE_MALLOC_SIZE_OF(MallocSizeOf)
~WebIDLGlobalNamesHashReporter() {}
public:
NS_DECL_ISUPPORTS
NS_IMETHOD CollectReports(nsIHandleReportCallback* aHandleReport,
nsISupports* aData, bool aAnonymize) override
{
int64_t amount =
sWebIDLGlobalNames ?
sWebIDLGlobalNames->ShallowSizeOfIncludingThis(MallocSizeOf) : 0;
MOZ_COLLECT_REPORT(
"explicit/dom/webidl-globalnames", KIND_HEAP, UNITS_BYTES, amount,
"Memory used by the hash table for WebIDL's global names.");
return NS_OK;
}
};
NS_IMPL_ISUPPORTS(WebIDLGlobalNamesHashReporter, nsIMemoryReporter)
/* static */
void
WebIDLGlobalNameHash::Init()
{
sWebIDLGlobalNames = new nsTHashtable<WebIDLNameTableEntry>(sCount);
RegisterWebIDLGlobalNames();
RegisterStrongMemoryReporter(new WebIDLGlobalNamesHashReporter());
}
/* static */
void
WebIDLGlobalNameHash::Shutdown()
{
delete sWebIDLGlobalNames;
}
/* static */
void
WebIDLGlobalNameHash::Register(uint16_t aNameOffset, uint16_t aNameLength,
DefineGlobalName aDefine,
ConstructorEnabled* aEnabled)
{
const char* name = sNames + aNameOffset;
WebIDLNameTableKey key(name, aNameLength);
WebIDLNameTableEntry* entry = sWebIDLGlobalNames->PutEntry(key);
entry->mNameOffset = aNameOffset;
entry->mNameLength = aNameLength;
entry->mDefine = aDefine;
entry->mEnabled = aEnabled;
}
/* static */
void
WebIDLGlobalNameHash::Remove(const char* aName, uint32_t aLength)
{
WebIDLNameTableKey key(aName, aLength);
sWebIDLGlobalNames->RemoveEntry(key);
}
/* static */
bool
WebIDLGlobalNameHash::DefineIfEnabled(JSContext* aCx,
JS::Handle<JSObject*> aObj,
JS::Handle<jsid> aId,
JS::MutableHandle<JS::PropertyDescriptor> aDesc,
bool* aFound)
{
MOZ_ASSERT(JSID_IS_STRING(aId), "Check for string id before calling this!");
const WebIDLNameTableEntry* entry;
{
WebIDLNameTableKey key(JSID_TO_FLAT_STRING(aId));
// Rooting analysis thinks nsTHashtable<...>::GetEntry may GC because it
// ends up calling through PLDHashTableOps' matchEntry function pointer, but
// we know WebIDLNameTableEntry::KeyEquals can't cause a GC.
JS::AutoSuppressGCAnalysis suppress;
entry = sWebIDLGlobalNames->GetEntry(key);
}
if (!entry) {
*aFound = false;
return true;
}
*aFound = true;
ConstructorEnabled* checkEnabledForScope = entry->mEnabled;
// We do the enabled check on the current compartment of aCx, but for the
// actual object we pass in the underlying object in the Xray case. That
// way the callee can decide whether to allow access based on the caller
// or the window being touched.
JS::Rooted<JSObject*> global(aCx,
js::CheckedUnwrap(aObj, /* stopAtWindowProxy = */ false));
if (!global) {
return Throw(aCx, NS_ERROR_DOM_SECURITY_ERR);
}
{
DebugOnly<nsGlobalWindow*> win;
MOZ_ASSERT(NS_SUCCEEDED(UNWRAP_OBJECT(Window, global, win)));
}
if (checkEnabledForScope && !checkEnabledForScope(aCx, global)) {
return true;
}
// The DOM constructor resolve machinery interacts with Xrays in tricky
// ways, and there are some asymmetries that are important to understand.
//
// In the regular (non-Xray) case, we only want to resolve constructors
// once (so that if they're deleted, they don't reappear). We do this by
// stashing the constructor in a slot on the global, such that we can see
// during resolve whether we've created it already. This is rather
// memory-intensive, so we don't try to maintain these semantics when
// manipulating a global over Xray (so the properties just re-resolve if
// they've been deleted).
//
// Unfortunately, there's a bit of an impedance-mismatch between the Xray
// and non-Xray machinery. The Xray machinery wants an API that returns a
// JS::PropertyDescriptor, so that the resolve hook doesn't have to get
// snared up with trying to define a property on the Xray holder. At the
// same time, the DefineInterface callbacks are set up to define things
// directly on the global. And re-jiggering them to return property
// descriptors is tricky, because some DefineInterface callbacks define
// multiple things (like the Image() alias for HTMLImageElement).
//
// So the setup is as-follows:
//
// * The resolve function takes a JS::PropertyDescriptor, but in the
// non-Xray case, callees may define things directly on the global, and
// set the value on the property descriptor to |undefined| to indicate
// that there's nothing more for the caller to do. We assert against
// this behavior in the Xray case.
//
// * We make sure that we do a non-Xray resolve first, so that all the
// slots are set up. In the Xray case, this means unwrapping and doing
// a non-Xray resolve before doing the Xray resolve.
//
// This all could use some grand refactoring, but for now we just limp
// along.
if (xpc::WrapperFactory::IsXrayWrapper(aObj)) {
JS::Rooted<JSObject*> interfaceObject(aCx);
{
JSAutoCompartment ac(aCx, global);
interfaceObject = entry->mDefine(aCx, global, aId, false);
}
if (NS_WARN_IF(!interfaceObject)) {
return Throw(aCx, NS_ERROR_FAILURE);
}
if (!JS_WrapObject(aCx, &interfaceObject)) {
return Throw(aCx, NS_ERROR_FAILURE);
}
FillPropertyDescriptor(aDesc, aObj, 0, JS::ObjectValue(*interfaceObject));
return true;
}
JS::Rooted<JSObject*> interfaceObject(aCx,
entry->mDefine(aCx, aObj, aId, true));
if (NS_WARN_IF(!interfaceObject)) {
return Throw(aCx, NS_ERROR_FAILURE);
}
// We've already defined the property. We indicate this to the caller
// by filling a property descriptor with JS::UndefinedValue() as the
// value. We still have to fill in a property descriptor, though, so
// that the caller knows the property is in fact on this object. It
// doesn't matter what we pass for the "readonly" argument here.
FillPropertyDescriptor(aDesc, aObj, JS::UndefinedValue(), false);
return true;
}
/* static */
bool
WebIDLGlobalNameHash::MayResolve(jsid aId)
{
WebIDLNameTableKey key(JSID_TO_FLAT_STRING(aId));
// Rooting analysis thinks nsTHashtable<...>::Contains may GC because it ends
// up calling through PLDHashTableOps' matchEntry function pointer, but we
// know WebIDLNameTableEntry::KeyEquals can't cause a GC.
JS::AutoSuppressGCAnalysis suppress;
return sWebIDLGlobalNames->Contains(key);
}
/* static */
void
WebIDLGlobalNameHash::GetNames(JSContext* aCx, JS::Handle<JSObject*> aObj,
nsTArray<nsString>& aNames)
{
for (auto iter = sWebIDLGlobalNames->Iter(); !iter.Done(); iter.Next()) {
const WebIDLNameTableEntry* entry = iter.Get();
if (!entry->mEnabled || entry->mEnabled(aCx, aObj)) {
AppendASCIItoUTF16(nsDependentCString(sNames + entry->mNameOffset,
entry->mNameLength),
*aNames.AppendElement());
}
}
}
} // namespace dom
} // namespace mozilla