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// Copyright 2013 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_V8_PLATFORM_H_
#define V8_V8_PLATFORM_H_
#include <stddef.h>
#include <stdint.h>
namespace v8 {
class Isolate;
/**
* A Task represents a unit of work.
*/
class Task {
public:
virtual ~Task() {}
virtual void Run() = 0;
};
/**
* An IdleTask represents a unit of work to be performed in idle time.
* The Run method is invoked with an argument that specifies the deadline in
* seconds returned by MonotonicallyIncreasingTime().
* The idle task is expected to complete by this deadline.
*/
class IdleTask {
public:
virtual ~IdleTask() {}
virtual void Run(double deadline_in_seconds) = 0;
};
/**
* V8 Platform abstraction layer.
*
* The embedder has to provide an implementation of this interface before
* initializing the rest of V8.
*/
class Platform {
public:
/**
* This enum is used to indicate whether a task is potentially long running,
* or causes a long wait. The embedder might want to use this hint to decide
* whether to execute the task on a dedicated thread.
*/
enum ExpectedRuntime {
kShortRunningTask,
kLongRunningTask
};
virtual ~Platform() {}
/**
* Gets the number of threads that are used to execute background tasks. Is
* used to estimate the number of tasks a work package should be split into.
* A return value of 0 means that there are no background threads available.
* Note that a value of 0 won't prohibit V8 from posting tasks using
* |CallOnBackgroundThread|.
*/
virtual size_t NumberOfAvailableBackgroundThreads() { return 0; }
/**
* Schedules a task to be invoked on a background thread. |expected_runtime|
* indicates that the task will run a long time. The Platform implementation
* takes ownership of |task|. There is no guarantee about order of execution
* of tasks wrt order of scheduling, nor is there a guarantee about the
* thread the task will be run on.
*/
virtual void CallOnBackgroundThread(Task* task,
ExpectedRuntime expected_runtime) = 0;
/**
* Schedules a task to be invoked on a foreground thread wrt a specific
* |isolate|. Tasks posted for the same isolate should be execute in order of
* scheduling. The definition of "foreground" is opaque to V8.
*/
virtual void CallOnForegroundThread(Isolate* isolate, Task* task) = 0;
/**
* Schedules a task to be invoked on a foreground thread wrt a specific
* |isolate| after the given number of seconds |delay_in_seconds|.
* Tasks posted for the same isolate should be execute in order of
* scheduling. The definition of "foreground" is opaque to V8.
*/
virtual void CallDelayedOnForegroundThread(Isolate* isolate, Task* task,
double delay_in_seconds) = 0;
/**
* Schedules a task to be invoked on a foreground thread wrt a specific
* |isolate| when the embedder is idle.
* Requires that SupportsIdleTasks(isolate) is true.
* Idle tasks may be reordered relative to other task types and may be
* starved for an arbitrarily long time if no idle time is available.
* The definition of "foreground" is opaque to V8.
*/
virtual void CallIdleOnForegroundThread(Isolate* isolate, IdleTask* task) {
// TODO(ulan): Make this function abstract after V8 roll in Chromium.
}
/**
* Returns true if idle tasks are enabled for the given |isolate|.
*/
virtual bool IdleTasksEnabled(Isolate* isolate) {
// TODO(ulan): Make this function abstract after V8 roll in Chromium.
return false;
}
/**
* Monotonically increasing time in seconds from an arbitrary fixed point in
* the past. This function is expected to return at least
* millisecond-precision values. For this reason,
* it is recommended that the fixed point be no further in the past than
* the epoch.
**/
virtual double MonotonicallyIncreasingTime() = 0;
/**
* Called by TRACE_EVENT* macros, don't call this directly.
* The name parameter is a category group for example:
* TRACE_EVENT0("v8,parse", "V8.Parse")
* The pointer returned points to a value with zero or more of the bits
* defined in CategoryGroupEnabledFlags.
**/
virtual const uint8_t* GetCategoryGroupEnabled(const char* name) {
static uint8_t no = 0;
return &no;
}
/**
* Gets the category group name of the given category_enabled_flag pointer.
* Usually used while serliazing TRACE_EVENTs.
**/
virtual const char* GetCategoryGroupName(
const uint8_t* category_enabled_flag) {
static const char dummy[] = "dummy";
return dummy;
}
/**
* Adds a trace event to the platform tracing system. This function call is
* usually the result of a TRACE_* macro from trace_event_common.h when
* tracing and the category of the particular trace are enabled. It is not
* advisable to call this function on its own; it is really only meant to be
* used by the trace macros. The returned handle can be used by
* UpdateTraceEventDuration to update the duration of COMPLETE events.
*/
virtual uint64_t AddTraceEvent(
char phase, const uint8_t* category_enabled_flag, const char* name,
uint64_t id, uint64_t bind_id, int32_t num_args, const char** arg_names,
const uint8_t* arg_types, const uint64_t* arg_values,
unsigned int flags) {
return 0;
}
/**
* Sets the duration field of a COMPLETE trace event. It must be called with
* the handle returned from AddTraceEvent().
**/
virtual void UpdateTraceEventDuration(const uint8_t* category_enabled_flag,
const char* name, uint64_t handle) {}
};
} // namespace v8
#endif // V8_V8_PLATFORM_H_
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