1503d0e78c
R=mvstanton@chromium.org, svenpanne@chromium.org Review URL: https://codereview.chromium.org/670953003 Cr-Commit-Position: refs/heads/master@{#25348}
372 lines
13 KiB
C++
372 lines
13 KiB
C++
// Copyright 2012 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_LIVEEDIT_H_
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#define V8_LIVEEDIT_H_
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// Live Edit feature implementation.
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// User should be able to change script on already running VM. This feature
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// matches hot swap features in other frameworks.
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//
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// The basic use-case is when user spots some mistake in function body
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// from debugger and wishes to change the algorithm without restart.
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//
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// A single change always has a form of a simple replacement (in pseudo-code):
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// script.source[positions, positions+length] = new_string;
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// Implementation first determines, which function's body includes this
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// change area. Then both old and new versions of script are fully compiled
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// in order to analyze, whether the function changed its outer scope
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// expectations (or number of parameters). If it didn't, function's code is
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// patched with a newly compiled code. If it did change, enclosing function
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// gets patched. All inner functions are left untouched, whatever happened
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// to them in a new script version. However, new version of code will
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// instantiate newly compiled functions.
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#include "src/allocation.h"
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#include "src/compiler.h"
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namespace v8 {
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namespace internal {
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// This class collects some specific information on structure of functions
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// in a particular script. It gets called from compiler all the time, but
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// actually records any data only when liveedit operation is in process;
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// in any other time this class is very cheap.
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//
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// The primary interest of the Tracker is to record function scope structures
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// in order to analyze whether function code maybe safely patched (with new
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// code successfully reading existing data from function scopes). The Tracker
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// also collects compiled function codes.
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class LiveEditFunctionTracker {
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public:
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explicit LiveEditFunctionTracker(Isolate* isolate, FunctionLiteral* fun);
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~LiveEditFunctionTracker();
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void RecordFunctionInfo(Handle<SharedFunctionInfo> info,
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FunctionLiteral* lit, Zone* zone);
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void RecordRootFunctionInfo(Handle<Code> code);
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static bool IsActive(Isolate* isolate);
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private:
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Isolate* isolate_;
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};
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class LiveEdit : AllStatic {
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public:
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// Describes how exactly a frame has been dropped from stack.
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enum FrameDropMode {
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// No frame has been dropped.
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FRAMES_UNTOUCHED,
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// The top JS frame had been calling IC stub. IC stub mustn't be called now.
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FRAME_DROPPED_IN_IC_CALL,
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// The top JS frame had been calling debug break slot stub. Patch the
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// address this stub jumps to in the end.
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FRAME_DROPPED_IN_DEBUG_SLOT_CALL,
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// The top JS frame had been calling some C++ function. The return address
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// gets patched automatically.
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FRAME_DROPPED_IN_DIRECT_CALL,
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FRAME_DROPPED_IN_RETURN_CALL,
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CURRENTLY_SET_MODE
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};
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static void InitializeThreadLocal(Debug* debug);
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static bool SetAfterBreakTarget(Debug* debug);
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MUST_USE_RESULT static MaybeHandle<JSArray> GatherCompileInfo(
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Handle<Script> script,
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Handle<String> source);
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static void WrapSharedFunctionInfos(Handle<JSArray> array);
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static void ReplaceFunctionCode(Handle<JSArray> new_compile_info_array,
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Handle<JSArray> shared_info_array);
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static void FunctionSourceUpdated(Handle<JSArray> shared_info_array);
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// Updates script field in FunctionSharedInfo.
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static void SetFunctionScript(Handle<JSValue> function_wrapper,
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Handle<Object> script_handle);
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static void PatchFunctionPositions(Handle<JSArray> shared_info_array,
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Handle<JSArray> position_change_array);
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// For a script updates its source field. If old_script_name is provided
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// (i.e. is a String), also creates a copy of the script with its original
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// source and sends notification to debugger.
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static Handle<Object> ChangeScriptSource(Handle<Script> original_script,
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Handle<String> new_source,
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Handle<Object> old_script_name);
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// In a code of a parent function replaces original function as embedded
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// object with a substitution one.
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static void ReplaceRefToNestedFunction(Handle<JSValue> parent_function_shared,
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Handle<JSValue> orig_function_shared,
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Handle<JSValue> subst_function_shared);
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// Find open generator activations, and set corresponding "result" elements to
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// FUNCTION_BLOCKED_ACTIVE_GENERATOR.
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static bool FindActiveGenerators(Handle<FixedArray> shared_info_array,
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Handle<FixedArray> result, int len);
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// Checks listed functions on stack and return array with corresponding
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// FunctionPatchabilityStatus statuses; extra array element may
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// contain general error message. Modifies the current stack and
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// has restart the lowest found frames and drops all other frames above
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// if possible and if do_drop is true.
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static Handle<JSArray> CheckAndDropActivations(
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Handle<JSArray> shared_info_array, bool do_drop);
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// Restarts the call frame and completely drops all frames above it.
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// Return error message or NULL.
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static const char* RestartFrame(JavaScriptFrame* frame);
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// A copy of this is in liveedit-debugger.js.
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enum FunctionPatchabilityStatus {
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FUNCTION_AVAILABLE_FOR_PATCH = 1,
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FUNCTION_BLOCKED_ON_ACTIVE_STACK = 2,
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FUNCTION_BLOCKED_ON_OTHER_STACK = 3,
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FUNCTION_BLOCKED_UNDER_NATIVE_CODE = 4,
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FUNCTION_REPLACED_ON_ACTIVE_STACK = 5,
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FUNCTION_BLOCKED_UNDER_GENERATOR = 6,
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FUNCTION_BLOCKED_ACTIVE_GENERATOR = 7
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};
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// Compares 2 strings line-by-line, then token-wise and returns diff in form
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// of array of triplets (pos1, pos1_end, pos2_end) describing list
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// of diff chunks.
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static Handle<JSArray> CompareStrings(Handle<String> s1,
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Handle<String> s2);
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// Architecture-specific constant.
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static const bool kFrameDropperSupported;
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/**
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* Defines layout of a stack frame that supports padding. This is a regular
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* internal frame that has a flexible stack structure. LiveEdit can shift
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* its lower part up the stack, taking up the 'padding' space when additional
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* stack memory is required.
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* Such frame is expected immediately above the topmost JavaScript frame.
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*
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* Stack Layout:
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* --- Top
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* LiveEdit routine frames
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* ---
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* C frames of debug handler
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* ---
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* ...
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* ---
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* An internal frame that has n padding words:
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* - any number of words as needed by code -- upper part of frame
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* - padding size: a Smi storing n -- current size of padding
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* - padding: n words filled with kPaddingValue in form of Smi
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* - 3 context/type words of a regular InternalFrame
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* - fp
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* ---
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* Topmost JavaScript frame
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* ---
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* ...
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* --- Bottom
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*/
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// A size of frame base including fp. Padding words starts right above
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// the base.
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static const int kFrameDropperFrameSize = 4;
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// A number of words that should be reserved on stack for the LiveEdit use.
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// Stored on stack in form of Smi.
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static const int kFramePaddingInitialSize = 1;
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// A value that padding words are filled with (in form of Smi). Going
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// bottom-top, the first word not having this value is a counter word.
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static const int kFramePaddingValue = kFramePaddingInitialSize + 1;
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};
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// A general-purpose comparator between 2 arrays.
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class Comparator {
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public:
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// Holds 2 arrays of some elements allowing to compare any pair of
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// element from the first array and element from the second array.
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class Input {
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public:
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virtual int GetLength1() = 0;
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virtual int GetLength2() = 0;
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virtual bool Equals(int index1, int index2) = 0;
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protected:
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virtual ~Input() {}
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};
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// Receives compare result as a series of chunks.
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class Output {
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public:
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// Puts another chunk in result list. Note that technically speaking
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// only 3 arguments actually needed with 4th being derivable.
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virtual void AddChunk(int pos1, int pos2, int len1, int len2) = 0;
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protected:
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virtual ~Output() {}
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};
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// Finds the difference between 2 arrays of elements.
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static void CalculateDifference(Input* input,
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Output* result_writer);
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};
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// Simple helper class that creates more or less typed structures over
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// JSArray object. This is an adhoc method of passing structures from C++
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// to JavaScript.
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template<typename S>
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class JSArrayBasedStruct {
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public:
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static S Create(Isolate* isolate) {
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Factory* factory = isolate->factory();
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Handle<JSArray> array = factory->NewJSArray(S::kSize_);
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return S(array);
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}
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static S cast(Object* object) {
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JSArray* array = JSArray::cast(object);
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Handle<JSArray> array_handle(array);
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return S(array_handle);
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}
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explicit JSArrayBasedStruct(Handle<JSArray> array) : array_(array) {
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}
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Handle<JSArray> GetJSArray() {
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return array_;
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}
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Isolate* isolate() const {
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return array_->GetIsolate();
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}
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protected:
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void SetField(int field_position, Handle<Object> value) {
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JSObject::SetElement(array_, field_position, value, NONE, SLOPPY).Assert();
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}
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void SetSmiValueField(int field_position, int value) {
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SetField(field_position, Handle<Smi>(Smi::FromInt(value), isolate()));
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}
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Handle<Object> GetField(int field_position) {
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return Object::GetElement(
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isolate(), array_, field_position).ToHandleChecked();
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}
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int GetSmiValueField(int field_position) {
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Handle<Object> res = GetField(field_position);
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return Handle<Smi>::cast(res)->value();
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}
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private:
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Handle<JSArray> array_;
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};
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// Represents some function compilation details. This structure will be used
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// from JavaScript. It contains Code object, which is kept wrapped
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// into a BlindReference for sanitizing reasons.
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class FunctionInfoWrapper : public JSArrayBasedStruct<FunctionInfoWrapper> {
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public:
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explicit FunctionInfoWrapper(Handle<JSArray> array)
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: JSArrayBasedStruct<FunctionInfoWrapper>(array) {
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}
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void SetInitialProperties(Handle<String> name, int start_position,
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int end_position, int param_num, int literal_count,
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int parent_index);
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void SetFunctionCode(Handle<Code> function_code,
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Handle<HeapObject> code_scope_info);
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void SetFunctionScopeInfo(Handle<Object> scope_info_array) {
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this->SetField(kFunctionScopeInfoOffset_, scope_info_array);
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}
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void SetSharedFunctionInfo(Handle<SharedFunctionInfo> info);
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int GetLiteralCount() {
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return this->GetSmiValueField(kLiteralNumOffset_);
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}
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int GetParentIndex() {
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return this->GetSmiValueField(kParentIndexOffset_);
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}
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Handle<Code> GetFunctionCode();
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MaybeHandle<TypeFeedbackVector> GetFeedbackVector();
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Handle<Object> GetCodeScopeInfo();
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int GetStartPosition() {
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return this->GetSmiValueField(kStartPositionOffset_);
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}
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int GetEndPosition() { return this->GetSmiValueField(kEndPositionOffset_); }
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private:
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static const int kFunctionNameOffset_ = 0;
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static const int kStartPositionOffset_ = 1;
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static const int kEndPositionOffset_ = 2;
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static const int kParamNumOffset_ = 3;
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static const int kCodeOffset_ = 4;
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static const int kCodeScopeInfoOffset_ = 5;
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static const int kFunctionScopeInfoOffset_ = 6;
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static const int kParentIndexOffset_ = 7;
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static const int kSharedFunctionInfoOffset_ = 8;
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static const int kLiteralNumOffset_ = 9;
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static const int kSize_ = 10;
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friend class JSArrayBasedStruct<FunctionInfoWrapper>;
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};
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// Wraps SharedFunctionInfo along with some of its fields for passing it
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// back to JavaScript. SharedFunctionInfo object itself is additionally
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// wrapped into BlindReference for sanitizing reasons.
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class SharedInfoWrapper : public JSArrayBasedStruct<SharedInfoWrapper> {
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public:
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static bool IsInstance(Handle<JSArray> array) {
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if (array->length() != Smi::FromInt(kSize_)) return false;
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Handle<Object> element(
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Object::GetElement(array->GetIsolate(),
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array,
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kSharedInfoOffset_).ToHandleChecked());
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if (!element->IsJSValue()) return false;
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return Handle<JSValue>::cast(element)->value()->IsSharedFunctionInfo();
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}
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explicit SharedInfoWrapper(Handle<JSArray> array)
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: JSArrayBasedStruct<SharedInfoWrapper>(array) {
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}
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void SetProperties(Handle<String> name,
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int start_position,
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int end_position,
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Handle<SharedFunctionInfo> info);
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Handle<SharedFunctionInfo> GetInfo();
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private:
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static const int kFunctionNameOffset_ = 0;
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static const int kStartPositionOffset_ = 1;
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static const int kEndPositionOffset_ = 2;
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static const int kSharedInfoOffset_ = 3;
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static const int kSize_ = 4;
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friend class JSArrayBasedStruct<SharedInfoWrapper>;
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};
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} } // namespace v8::internal
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#endif /* V*_LIVEEDIT_H_ */
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