88 lines
2.7 KiB
C++
Executable File
88 lines
2.7 KiB
C++
Executable File
////////////////////////////////////////////////////////////////////////////////
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//// Copyright 2017 Google LLC
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////
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//// This software is licensed under the terms defined in the Widevine Master
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//// License Agreement. For a copy of this agreement, please contact
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//// widevine-licensing@google.com.
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////////////////////////////////////////////////////////////////////////////////
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#ifndef VIDEO_WIDEVINE_EXPORT_EXPORTED_ROOT_UTIL_ERROR_SPACE_H_
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#define VIDEO_WIDEVINE_EXPORT_EXPORTED_ROOT_UTIL_ERROR_SPACE_H_
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#include <string>
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#include "absl/strings/string_view.h"
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namespace video_widevine {
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namespace util {
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class ErrorSpace {
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public:
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absl::string_view SpaceName() const { return space_name_func_(this); }
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std::string String(int code) const {
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return code_to_string_func_(this, code);
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}
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protected:
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// typedef instead of using statements for SWIG compatibility.
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typedef absl::string_view (*SpaceNameFunc)(const ErrorSpace* space);
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typedef std::string (*CodeToStringFunc)(const ErrorSpace* space, int code);
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constexpr ErrorSpace(SpaceNameFunc space_name_func,
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CodeToStringFunc code_to_string_func)
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: space_name_func_(space_name_func),
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code_to_string_func_(code_to_string_func) {}
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private:
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const SpaceNameFunc space_name_func_;
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const CodeToStringFunc code_to_string_func_;
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};
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// Manages creation of error space subclasses.
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template <typename T>
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class ErrorSpaceImpl : public ErrorSpace {
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public:
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constexpr ErrorSpaceImpl()
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: ErrorSpace(&ErrorSpaceImpl::SpaceNameImpl,
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&ErrorSpaceImpl::CodeToStringImpl) {}
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// Returns the canonical instance of the `T` error space.
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static constexpr const T* Get();
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private:
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// These functions adapt the stateful implementation that takes a space
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// pointer to stateless static methods, so that clients of ErrorSpaceImpl are
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// safe to have constexpr global instances.
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static absl::string_view SpaceNameImpl(const ErrorSpace* /*space*/) {
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return T::space_name();
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}
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static std::string CodeToStringImpl(const ErrorSpace* /*space*/, int code) {
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return T::code_to_string(code);
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}
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};
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namespace internal {
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// Provides a global constexpr instance of the error space `T`.
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// We need the indirection because ErrorSpaceImpl can't declare constexpr
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// instances of T since it is not yet fully declared.
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template <typename T>
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struct ErrorSpaceInstance {
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static constexpr T value = {};
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};
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template <typename T>
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constexpr T ErrorSpaceInstance<T>::value;
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} // namespace internal
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template <typename T>
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constexpr const T* ErrorSpaceImpl<T>::Get() {
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return &internal::ErrorSpaceInstance<T>::value;
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}
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} // namespace util
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} // namespace video_widevine
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#endif // VIDEO_WIDEVINE_EXPORT_EXPORTED_ROOT_UTIL_ERROR_SPACE_H_
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