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// Copyright 2014 The Chromium 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 MEDIA_BASE_CDM_PROMISE_H_
#define MEDIA_BASE_CDM_PROMISE_H_
#include <string>
#include "base/basictypes.h"
#include "base/logging.h"
#include "media/base/media_export.h"
#include "media/base/media_keys.h"
namespace media {
// Interface for promises being resolved/rejected in response to various
// session actions. These may be called synchronously or asynchronously.
// The promise must be resolved or rejected exactly once. It is expected that
// the caller free the promise once it is resolved/rejected.
// These classes are almost generic, except for the parameters to reject(). If
// a generic class for promises is available, this could be changed to use the
// generic class as long as the parameters to reject() can be set appropriately.
// The base class only has a reject() method and GetResolveParameterType() that
// indicates the type of CdmPromiseTemplate. CdmPromiseTemplate<T> adds the
// resolve(T) method that is dependent on the type of promise. This base class
// is specified so that the promises can be easily saved before passing across
// the pepper interface.
class MEDIA_EXPORT CdmPromise {
public:
enum ResolveParameterType {
VOID_TYPE,
STRING_TYPE,
KEY_IDS_VECTOR_TYPE
};
CdmPromise();
virtual ~CdmPromise();
// Used to indicate that the operation failed. |exception_code| must be
// specified. |system_code| is a Key System-specific value for the error
// that occurred, or 0 if there is no associated status code or such status
// codes are not supported by the Key System. |error_message| is optional.
virtual void reject(MediaKeys::Exception exception_code,
uint32 system_code,
const std::string& error_message) = 0;
// Used to determine the template type of CdmPromiseTemplate<T> so that
// saved CdmPromise objects can be cast to the correct templated version.
virtual ResolveParameterType GetResolveParameterType() const = 0;
private:
DISALLOW_COPY_AND_ASSIGN(CdmPromise);
};
// For some reason the Windows compiler is not happy with the implementation
// of CdmPromiseTemplate being in the .cc file, so moving it here.
namespace {
template <typename... T>
struct CdmPromiseTraits {};
template <>
struct CdmPromiseTraits<> {
static const CdmPromise::ResolveParameterType kType = CdmPromise::VOID_TYPE;
};
template <>
struct CdmPromiseTraits<std::string> {
static const CdmPromise::ResolveParameterType kType = CdmPromise::STRING_TYPE;
};
template <>
struct CdmPromiseTraits<KeyIdsVector> {
static const CdmPromise::ResolveParameterType kType =
CdmPromise::KEY_IDS_VECTOR_TYPE;
};
} // namespace
// This class adds the resolve(T) method. This class is still an interface, and
// is used as the type of promise that gets passed around.
template <typename... T>
class MEDIA_EXPORT CdmPromiseTemplate : public CdmPromise {
public:
CdmPromiseTemplate() : is_settled_(false) {}
virtual ~CdmPromiseTemplate() { DCHECK(is_settled_); }
virtual void resolve(const T&... result) = 0;
// CdmPromise implementation.
virtual void reject(MediaKeys::Exception exception_code,
uint32 system_code,
const std::string& error_message) = 0;
virtual ResolveParameterType GetResolveParameterType() const override {
return CdmPromiseTraits<T...>::kType;
}
protected:
// All implementations must call this method in resolve() and reject() methods
// to indicate that the promise has been settled.
void MarkPromiseSettled() {
// Promise can only be settled once.
DCHECK(!is_settled_);
is_settled_ = true;
}
private:
// Keep track of whether the promise has been resolved or rejected yet.
bool is_settled_;
DISALLOW_COPY_AND_ASSIGN(CdmPromiseTemplate);
};
} // namespace media
#endif // MEDIA_BASE_CDM_PROMISE_H_
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