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contexts.cc
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// Copyright 2006-2008 Google Inc. All Rights Reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "v8.h"
#include "debug.h"
#include "scopeinfo.h"
namespace v8 { namespace internal {
#ifdef DEBUG
DEFINE_bool(trace_contexts, false, "trace contexts operations");
#else
#define FLAG_trace_contexts false
#endif
JSBuiltinsObject* Context::builtins() {
GlobalObject* object = global();
if (object->IsJSGlobalObject()) {
return JSGlobalObject::cast(object)->builtins();
} else {
ASSERT(object->IsJSBuiltinsObject());
return JSBuiltinsObject::cast(object);
}
}
Context* Context::global_context() {
// Fast case: the global object for this context has been set. In
// that case, the global object has a direct pointer to the global
// context.
if (global()->IsGlobalObject()) {
return global()->global_context();
}
// During bootstrapping, the global object might not be set and we
// have to search the context chain to find the global context.
Context* current = this;
while (!current->IsGlobalContext()) {
current = Context::cast(JSFunction::cast(current->closure())->context());
}
return current;
}
Handle<Object> Context::Lookup(Handle<String> name, ContextLookupFlags flags,
int* index_, PropertyAttributes* attributes) {
Handle<Context> context(this);
// The context must be in frame slot 0 (if not debugging).
if (kDebug && !Debug::InDebugger()) {
StackFrameLocator locator;
ASSERT(context->fcontext() ==
Context::cast(
locator.FindJavaScriptFrame(0)->context())->fcontext());
}
bool follow_context_chain = (flags & FOLLOW_CONTEXT_CHAIN) != 0;
*index_ = -1;
*attributes = ABSENT;
if (FLAG_trace_contexts) {
PrintF("Context::Lookup(");
name->ShortPrint();
PrintF(")\n");
}
do {
if (FLAG_trace_contexts) {
PrintF(" - looking in context %p", *context);
if (context->IsGlobalContext()) PrintF(" (global context)");
PrintF("\n");
}
// check extension/with object
Handle<JSObject> context_ext(context->extension());
if (*context_ext != NULL) {
if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0) {
*attributes = context_ext->GetLocalPropertyAttribute(*name);
} else {
*attributes = context_ext->GetPropertyAttribute(*name);
}
if (*attributes != ABSENT) {
// property found
if (FLAG_trace_contexts) {
PrintF("=> found property in context object %p\n", *context_ext);
}
return context_ext;
}
}
if (context->is_function_context()) {
// we have context-local slots
// check non-parameter locals in context
Handle<Code> code(context->closure()->code());
Variable::Mode mode;
int index = ScopeInfo<>::ContextSlotIndex(*code, *name, &mode);
ASSERT(index < 0 || index >= MIN_CONTEXT_SLOTS);
if (index >= 0) {
// slot found
if (FLAG_trace_contexts) {
PrintF("=> found local in context slot %d (mode = %d)\n",
index, mode);
}
*index_ = index;
// Note: Fixed context slots are statically allocated by the compiler.
// Statically allocated variables always have a statically known mode,
// which is the mode with which they were declared when added to the
// scope. Thus, the DYNAMIC mode (which corresponds to dynamically
// declared variables that were introduced through declaration nodes)
// must not appear here.
switch (mode) {
case Variable::INTERNAL : // fall through
case Variable::VAR : *attributes = NONE; break;
case Variable::CONST : *attributes = READ_ONLY; break;
case Variable::DYNAMIC : UNREACHABLE(); break;
case Variable::TEMPORARY: UNREACHABLE(); break;
}
return context;
}
// check parameter locals in context
int param_index = ScopeInfo<>::ParameterIndex(*code, *name);
if (param_index >= 0) {
// slot found
int index =
ScopeInfo<>::ContextSlotIndex(*code,
Heap::arguments_shadow_symbol(),
NULL);
ASSERT(index >= 0); // arguments must exist and be in the heap context
Handle<JSObject> arguments(JSObject::cast(context->get(index)));
ASSERT(arguments->HasLocalProperty(Heap::length_symbol()));
if (FLAG_trace_contexts) {
PrintF("=> found parameter %d in arguments object\n", param_index);
}
*index_ = param_index;
*attributes = NONE;
return arguments;
}
// check intermediate context (holding only the function name variable)
if (follow_context_chain) {
int index = ScopeInfo<>::FunctionContextSlotIndex(*code, *name);
if (index >= 0) {
// slot found
if (FLAG_trace_contexts) {
PrintF("=> found intermediate function in context slot %d\n",
index);
}
*index_ = index;
*attributes = READ_ONLY;
return context;
}
}
}
// proceed with enclosing context
if (context->IsGlobalContext()) {
follow_context_chain = false;
} else if (context->previous() != NULL) {
context = Handle<Context>(context->previous());
} else {
ASSERT(context->is_function_context());
context = Handle<Context>(Context::cast(context->closure()->context()));
}
} while (follow_context_chain);
// slot not found
if (FLAG_trace_contexts) {
PrintF("=> no property/slot found\n");
}
return Handle<Object>(reinterpret_cast<JSObject*>(NULL));
}
} } // namespace v8::internal