// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef PPAPI_CPP_COMPLETION_CALLBACK_H_
#define PPAPI_CPP_COMPLETION_CALLBACK_H_
#include <stdint.h>
#include "ppapi/c/pp_completion_callback.h"
#include "ppapi/c/pp_errors.h"
#include "ppapi/cpp/logging.h"
#include "ppapi/cpp/module.h" // nogncheck http://crbug.com/1228394
#include "ppapi/cpp/output_traits.h" // nogncheck http://crbug.com/1228394
/// @file
/// This file defines the API to create and run a callback.
namespace pp {
/// This API enables you to implement and receive callbacks when
/// Pepper operations complete asynchronously.
///
/// You can create these objects yourself, but it is most common to use the
/// CompletionCallbackFactory to allow the callbacks to call class member
/// functions.
class CompletionCallback {
public:
/// The default constructor will create a blocking
/// <code>CompletionCallback</code> that can be passed to a method to
/// indicate that the calling thread should be blocked until the asynchronous
/// operation corresponding to the method completes.
///
/// <strong>Note:</strong> Blocking completion callbacks are only allowed from
/// from background threads.
CompletionCallback() {
cc_ = PP_BlockUntilComplete();
}
/// A constructor for creating a <code>CompletionCallback</code>.
///
/// @param[in] func The function to be called on completion.
/// @param[in] user_data The user data to be passed to the callback function.
/// This is optional and is typically used to help track state in case of
/// multiple pending callbacks.
CompletionCallback(PP_CompletionCallback_Func func, void* user_data) {
cc_ = PP_MakeCompletionCallback(func, user_data);
}
/// A constructor for creating a <code>CompletionCallback</code> with
/// specified flags.
///
/// @param[in] func The function to be called on completion.
/// @param[in] user_data The user data to be passed to the callback function.
/// This is optional and is typically used to help track state in case of
/// multiple pending callbacks.
/// @param[in] flags Bit field combination of
/// <code>PP_CompletionCallback_Flag</code> flags used to control how
/// non-NULL callbacks are scheduled by asynchronous methods.
CompletionCallback(PP_CompletionCallback_Func func, void* user_data,
int32_t flags) {
cc_ = PP_MakeCompletionCallback(func, user_data);
cc_.flags = flags;
}
/// The set_flags() function is used to set the flags used to control
/// how non-NULL callbacks are scheduled by asynchronous methods.
///
/// @param[in] flags Bit field combination of
/// <code>PP_CompletionCallback_Flag</code> flags used to control how
/// non-NULL callbacks are scheduled by asynchronous methods.
void set_flags(int32_t flags) { cc_.flags = flags; }
/// Run() is used to run the <code>CompletionCallback</code>.
/// Normally, the system runs a <code>CompletionCallback</code> after an
/// asynchronous operation completes, but programs may wish to run the
/// <code>CompletionCallback</code> manually in order to reuse the same code
/// paths.
///
/// @param[in] result The result of the operation to be passed to the
/// callback function. Non-positive values correspond to the error codes
/// from <code>pp_errors.h</code> (excluding
/// <code>PP_OK_COMPLETIONPENDING</code>). Positive values indicate
/// additional information such as bytes read.
void Run(int32_t result) {
PP_DCHECK(cc_.func);
PP_RunCompletionCallback(&cc_, result);
}
/// RunAndClear() is used to run the <code>CompletionCallback</code> and
/// clear out the callback so that it cannot be run a second time.
///
/// @param[in] result The result of the operation to be passed to the
/// callback function. Non-positive values correspond to the error codes
/// from <code>pp_errors.h</code> (excluding
/// <code>PP_OK_COMPLETIONPENDING</code>). Positive values indicate
/// additional information such as bytes read.
void RunAndClear(int32_t result) {
PP_DCHECK(cc_.func);
PP_RunAndClearCompletionCallback(&cc_, result);
}
/// IsOptional() is used to determine the setting of the
/// <code>PP_COMPLETIONCALLBACK_FLAG_OPTIONAL</code> flag. This flag allows
/// any method taking such callback to complete synchronously
/// and not call the callback if the operation would not block. This is useful
/// when performance is an issue, and the operation bandwidth should not be
/// limited to the processing speed of the message loop.
///
/// On synchronous method completion, the completion result will be returned
/// by the method itself. Otherwise, the method will return
/// PP_OK_COMPLETIONPENDING, and the callback will be invoked asynchronously
/// on the same thread where the PPB method was invoked.
///
/// @return true if this callback is optional, otherwise false.
bool IsOptional() const {
return (cc_.func == NULL ||
(cc_.flags & PP_COMPLETIONCALLBACK_FLAG_OPTIONAL) != 0);
}
/// The pp_completion_callback() function returns the underlying
/// <code>PP_CompletionCallback</code>
///
/// @return A <code>PP_CompletionCallback</code>.
const PP_CompletionCallback& pp_completion_callback() const { return cc_; }
/// The flags() function returns flags used to control how non-NULL callbacks
/// are scheduled by asynchronous methods.
///
/// @return An int32_t containing a bit field combination of
/// <code>PP_CompletionCallback_Flag</code> flags.
int32_t flags() const { return cc_.flags; }
/// MayForce() is used when implementing functions taking callbacks.
/// If the callback is required and <code>result</code> indicates that it has
/// not been scheduled, it will be forced on the main thread.
///
/// <strong>Example:</strong>
///
/// @code
///
/// int32_t OpenURL(pp::URLLoader* loader,
/// pp::URLRequestInfo* url_request_info,
/// const CompletionCallback& cc) {
/// if (loader == NULL || url_request_info == NULL)
/// return cc.MayForce(PP_ERROR_BADRESOURCE);
/// return loader->Open(*loader, *url_request_info, cc);
/// }
///
/// @endcode
///
/// @param[in] result PP_OK_COMPLETIONPENDING or the result of the completed
/// operation to be passed to the callback function. PP_OK_COMPLETIONPENDING
/// indicates that the callback has already been scheduled. Other
/// non-positive values correspond to error codes from
/// <code>pp_errors.h</code>. Positive values indicate additional information
/// such as bytes read.
///
/// @return <code>PP_OK_COMPLETIONPENDING</code> if the callback has been
/// forced, result parameter otherwise.
int32_t MayForce(int32_t result) const {
if (result == PP_OK_COMPLETIONPENDING || IsOptional())
return result;
// FIXME(dmichael): Use pp::MessageLoop here once it's out of Dev.
Module::Get()->core()->CallOnMainThread(0, *this, result);
return PP_OK_COMPLETIONPENDING;
}
protected:
PP_CompletionCallback cc_;
};
/// A CompletionCallbackWithOutput defines a completion callback that
/// additionally stores a pointer to some output data. Some C++ wrappers
/// take a CompletionCallbackWithOutput when the browser is returning a
/// bit of data as part of the function call. The "output" parameter
/// stored in the CompletionCallbackWithOutput will receive the data from
/// the browser.
///
/// You can create this yourself, but it is most common to use with the
/// CompletionCallbackFactory's NewCallbackWithOutput, which manages the
/// storage for the output parameter for you and passes it as an argument
/// to your callback function.
///
/// Note that this class doesn't actually do anything with the output data,
/// it just stores a pointer to it. C++ wrapper objects that accept a
/// CompletionCallbackWithOutput will retrieve this pointer and pass it to
/// the browser as the output parameter.
template<typename T>
class CompletionCallbackWithOutput : public CompletionCallback {
public:
/// The type that will actually be stored in the completion callback. In the
/// common case, this will be equal to the template parameter (for example,
/// CompletionCallbackWithOutput<int> would obviously take an int*. However,
/// resources are passed as PP_Resource, vars as PP_Var, and arrays as our
/// special ArrayOutputAdapter object. The CallbackOutputTraits defines
/// specializations for all of these cases.
typedef typename internal::CallbackOutputTraits<T>::StorageType
OutputStorageType;
typedef typename internal::CallbackOutputTraits<T>::APIArgType
APIArgType;
/// The default constructor will create a blocking
/// <code>CompletionCallback</code> that references the given output
/// data.
///
/// @param[in] output A pointer to the data associated with the callback. The
/// caller must ensure that this pointer outlives the completion callback.
///
/// <strong>Note:</strong> Blocking completion callbacks are only allowed from
/// from background threads.
CompletionCallbackWithOutput(OutputStorageType* output)
: CompletionCallback(),
output_(output) {
}
/// A constructor for creating a <code>CompletionCallback</code> that
/// references the given output data.
///
/// @param[in] func The function to be called on completion.
/// @param[in] user_data The user data to be passed to the callback function.
/// This is optional and is typically used to help track state in case of
/// multiple pending callbacks.
/// @param[in] output A pointer to the data associated with the callback. The
/// caller must ensure that this pointer outlives the completion callback.
CompletionCallbackWithOutput(PP_CompletionCallback_Func func,
void* user_data,
OutputStorageType* output)
: CompletionCallback(func, user_data),
output_(output) {
}
/// A constructor for creating a <code>CompletionCallback</code> that
/// references the given output data.
///
/// @param[in] func The function to be called on completion.
///
/// @param[in] user_data The user data to be passed to the callback function.
/// This is optional and is typically used to help track state in case of
/// multiple pending callbacks.
///
/// @param[in] flags Bit field combination of
/// <code>PP_CompletionCallback_Flag</code> flags used to control how
/// non-NULL callbacks are scheduled by asynchronous methods.
///
/// @param[in] output A pointer to the data associated with the callback. The
/// caller must ensure that this pointer outlives the completion callback.
CompletionCallbackWithOutput(PP_CompletionCallback_Func func,
void* user_data,
int32_t flags,
OutputStorageType* output)
: CompletionCallback(func, user_data, flags),
output_(output) {
}
APIArgType output() const {
return internal::CallbackOutputTraits<T>::StorageToAPIArg(*output_);
}
private:
OutputStorageType* output_;
};
/// BlockUntilComplete() is used in place of an actual completion callback
/// to request blocking behavior. If specified, the calling thread will block
/// until the function completes. Blocking completion callbacks are only
/// allowed from background threads.
///
/// @return A <code>CompletionCallback</code> corresponding to a NULL callback.
inline CompletionCallback BlockUntilComplete() {
// Note: Explicitly inlined to avoid link errors when included into
// ppapi_proxy and ppapi_cpp_objects.
return CompletionCallback();
}
} // namespace pp
#endif // PPAPI_CPP_COMPLETION_CALLBACK_H_
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