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59 lines
2.2 KiB
59 lines
2.2 KiB
// Copyright 2016 The Chromium 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 MOJO_PUBLIC_CPP_BINDINGS_STRING_TRAITS_H_
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#define MOJO_PUBLIC_CPP_BINDINGS_STRING_TRAITS_H_
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#include "mojo/public/cpp/bindings/lib/template_util.h"
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namespace mojo {
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// This must be specialized for any type |T| to be serialized/deserialized as
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// a mojom string.
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//
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// Imagine you want to specialize it for CustomString, usually you need to
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// implement:
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//
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// template <T>
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// struct StringTraits<CustomString> {
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// // These two methods are optional. Please see comments in struct_traits.h
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// static bool IsNull(const CustomString& input);
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// static void SetToNull(CustomString* output);
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//
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// static size_t GetSize(const CustomString& input);
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// static const char* GetData(const CustomString& input);
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//
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// // The caller guarantees that |!input.is_null()|.
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// static bool Read(StringDataView input, CustomString* output);
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// };
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//
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// In some cases, you may need to do conversion before you can return the size
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// and data as 8-bit characters for serialization. (For example, CustomString is
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// UTF-16 string). In that case, you can add two optional methods:
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//
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// static void* SetUpContext(const CustomString& input);
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// static void TearDownContext(const CustomString& input, void* context);
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//
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// And then you append a second parameter, void* context, to GetSize() and
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// GetData():
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//
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// static size_t GetSize(const CustomString& input, void* context);
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// static const char* GetData(const CustomString& input, void* context);
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//
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// If a CustomString instance is not null, the serialization code will call
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// SetUpContext() at the beginning, and pass the resulting context pointer to
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// GetSize()/GetData(). After serialization is done, it calls TearDownContext()
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// so that you can do any necessary cleanup.
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//
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template <typename T>
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struct StringTraits {
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static_assert(internal::AlwaysFalse<T>::value,
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"Cannot find the mojo::StringTraits specialization. Did you "
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"forget to include the corresponding header file?");
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};
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} // namespace mojo
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#endif // MOJO_PUBLIC_CPP_BINDINGS_STRING_TRAITS_H_
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