59 strings / 1277 words

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Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
HTTP Comparison to Other Libraries
HTTP Comparison to Other Libraries
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
There are a few C++ published libraries which implement some of the HTTP protocol. We analyze the message model chosen by those libraries and discuss the advantages and disadvantages relative to Beast.
There are a few C++ published libraries which implement some of the HTTP protocol. We analyze the message model chosen by those libraries and discuss the advantages and disadvantages relative to Beast.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
The general strategy used by the author to evaluate external libraries is as follows:
The general strategy used by the author to evaluate external libraries is as follows:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* Review the message model. Can it represent a complete request or
* Review the message model. Can it represent a complete request or
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* Review the stream abstraction. This is the type of object, such as
* Review the stream abstraction. This is the type of object, such as
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* Check treatment of buffers. Does the library manage the buffers
* Check treatment of buffers. Does the library manage the buffers
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* How does the library handle corner cases such as trailers,
* How does the library handle corner cases such as trailers,
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
Declarations examples from external libraries have been edited:
Declarations examples from external libraries have been edited:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
cpp-netlib
cpp-netlib
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
is a network programming library previously intended for Boost but not having gone through formal review. As of this writing it still uses the Boost name, namespace, and directory structure although the project states that Boost acceptance is no longer a goal. The library is based on Boost.Asio and bills itself as ['"a collection of network related routines/implementations geared towards providing a robust cross-platform networking library"]. It cites ['"Common Message Type"] as a feature. As of the branch previous linked, it uses these declarations: ``` template <class Tag> struct basic_message {
is a network programming library previously intended for Boost but not having gone through formal review. As of this writing it still uses the Boost name, namespace, and directory structure although the project states that Boost acceptance is no longer a goal. The library is based on Boost.Asio and bills itself as ['"a collection of network related routines/implementations geared towards providing a robust cross-platform networking library"]. It cites ['"Common Message Type"] as a feature. As of the branch previous linked, it uses these declarations: ``` template <class Tag> struct basic_message {
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
This container is the base class template used to represent HTTP messages. It uses a "tag" type style specializations for a variety of trait classes, allowing for customization of the various parts of the message. For example, a user specializes `headers_container<T>` to determine what container type holds the header fields. We note some problems with the container declaration:
This container is the base class template used to represent HTTP messages. It uses a "tag" type style specializations for a variety of trait classes, allowing for customization of the various parts of the message. For example, a user specializes `headers_container<T>` to determine what container type holds the header fields. We note some problems with the container declaration:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The header and body containers may only be default-constructed.
* The header and body containers may only be default-constructed.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* No stateful allocator support.
* No stateful allocator support.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* There is no way to defer the commitment of the type for `body_` to
* There is no way to defer the commitment of the type for `body_` to
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The message model includes a "source" and "destination." This is
* The message model includes a "source" and "destination." This is
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The use of `string_type` (a customization point) for source,
* The use of `string_type` (a customization point) for source,
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The library uses specializations of `string<Tag>` to change the type
* The library uses specializations of `string<Tag>` to change the type
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The specialized trait classes generate a proliferation of small
* The specialized trait classes generate a proliferation of small
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The `string<Tag> customization point constrains user defined body types
* The `string<Tag> customization point constrains user defined body types
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
The design of the message container in this library is cumbersome with its system of customization using trait specializations. The use of these customizations is extremely limited due to the way they are used in the container declaration, making the design overly complex without corresponding benefit.
The design of the message container in this library is cumbersome with its system of customization using trait specializations. The use of these customizations is extremely limited due to the way they are used in the container declaration, making the design overly complex without corresponding benefit.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
is a library resulting from the 2014 Google Summer of Code. It was submitted for a Boost formal review and rejected in 2015. It is based on Boost.Asio, and development on the library has continued to the present. As of the branch previously linked, it uses these message declarations: ``` template<class Headers, class Body> struct basic_message {
is a library resulting from the 2014 Google Summer of Code. It was submitted for a Boost formal review and rejected in 2015. It is based on Boost.Asio, and development on the library has continued to the present. As of the branch previously linked, it uses these message declarations: ``` template<class Headers, class Body> struct basic_message {
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
typedef basic_message<boost::http::headers, std::vector<std::uint8_t>> message;
typedef basic_message<boost::http::headers, std::vector<std::uint8_t>> message;
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
template<class Headers, class Body> struct is_message<basic_message<Headers, Body>>: public std::true_type {}; ```
template<class Headers, class Body> struct is_message<basic_message<Headers, Body>>: public std::true_type {}; ```
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* This container cannot model a complete message. The ['start-line] items
* This container cannot model a complete message. The ['start-line] items
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* `headers_`, `body_`, and `trailers_` may only be default-constructed,
* `headers_`, `body_`, and `trailers_` may only be default-constructed,
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* There is no way to defer the commitment of the [*Body] type to after
* There is no way to defer the commitment of the [*Body] type to after
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* No stateful allocator support. This follows from the previous limitation
* No stateful allocator support. This follows from the previous limitation
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The trailers are stored in a separate object. Aside from the combinatorial
* The trailers are stored in a separate object. Aside from the combinatorial
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The declarations imply that `std::vector` is a model of [*Body].
* The declarations imply that `std::vector` is a model of [*Body].
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The [*Body] customization point constrains user defined types to
* The [*Body] customization point constrains user defined types to
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
This representation addresses a narrow range of use cases. It has limited potential for customization and performance. It is more difficult to use because it excludes the start line fields from the model.
This representation addresses a narrow range of use cases. It has limited potential for customization and performance. It is more difficult to use because it excludes the start line fields from the model.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
C++ REST SDK (cpprestsdk)
C++ REST SDK (cpprestsdk)
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — English
is a Microsoft project which ['"...aims to help C++ developers connect to and interact with services"]. It offers the most functionality of the libraries reviewed here, including support for Websocket services using its websocket++ dependency. It can use native APIs such as HTTP.SYS when building Windows based applications, and it can use Boost.Asio. The WebSocket module uses Boost.Asio exclusively.
is a Microsoft project which ['"...aims to help C++ developers connect to and interact with services"]. It offers the most functionality of the libraries reviewed here, including support for Websocket services using its websocket++ dependency. It can use native APIs such as HTTP.SYS when building Windows based applications, and it can use Boost.Asio. The WebSocket module uses Boost.Asio exclusively.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
is a Microsoft project which ['"...aims to help C++ developers connect to and interact with services"]. It offers the most functionality of the libraries reviewed here, including support for Websocket services using its websocket++ dependency. It can use native APIs such as HTTP.SYS when building Windows based applications, and it can use Boost.Asio. The WebSocket module uses Boost.Asio exclusively.
is a Microsoft project which ['"...aims to help C++ developers connect to and interact with services"]. It offers the most functionality of the libraries reviewed here, including support for Websocket services using its websocket++ dependency. It can use native APIs such as HTTP.SYS when building Windows based applications, and it can use Boost.Asio. The WebSocket module uses Boost.Asio exclusively.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
As cpprestsdk is developed by a large corporation, it contains quite a bit of functionality and necessarily has more interfaces. We will break down the interfaces used to model messages into more manageable pieces. This is the container used to store the HTTP header fields: ``` class http_headers { public:
As cpprestsdk is developed by a large corporation, it contains quite a bit of functionality and necessarily has more interfaces. We will break down the interfaces used to model messages into more manageable pieces. This is the container used to store the HTTP header fields: ``` class http_headers { public:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
This declaration is quite bare-bones. We note the typical problems of most field containers:
This declaration is quite bare-bones. We note the typical problems of most field containers:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The container may only be default-constructed.
* The container may only be default-constructed.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* No support for allocators, stateful or otherwise.
* No support for allocators, stateful or otherwise.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* There are no customization points at all.
* There are no customization points at all.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
Now we analyze the structure of the larger message container. The library uses a handle/body idiom. There are two public message container interfaces, one for requests (`http_request`) and one for responses (`http_response`). Each interface maintains a private shared pointer to an implementation class. Public member function calls are routed to the internal implementation. This is the first implementation class, which forms the base class for both the request and response implementations: ``` namespace details {
Now we analyze the structure of the larger message container. The library uses a handle/body idiom. There are two public message container interfaces, one for requests (`http_request`) and one for responses (`http_response`). Each interface maintains a private shared pointer to an implementation class. Public member function calls are routed to the internal implementation. This is the first implementation class, which forms the base class for both the request and response implementations: ``` namespace details {
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
class http_msg_base { public:
class http_msg_base { public:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
protected:
protected:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
To understand these declarations we need to first understand that cpprestsdk uses the asynchronous model defined by Microsoft's [@https://msdn.microsoft.com/en-us/library/dd504870.aspx [*Concurrency Runtime]]. Identifiers from the [@https://msdn.microsoft.com/en-us/library/jj987780.aspx [*`pplx` namespace]] define common asynchronous patterns such as tasks and events. The `concurrency::streams::istream` parameter and `m_data_available` data member indicates a lack of separation of concerns. The representation of HTTP messages should not be conflated with the asynchronous model used to serialize or parse those messages in the message declarations.
To understand these declarations we need to first understand that cpprestsdk uses the asynchronous model defined by Microsoft's [@https://msdn.microsoft.com/en-us/library/dd504870.aspx [*Concurrency Runtime]]. Identifiers from the [@https://msdn.microsoft.com/en-us/library/jj987780.aspx [*`pplx` namespace]] define common asynchronous patterns such as tasks and events. The `concurrency::streams::istream` parameter and `m_data_available` data member indicates a lack of separation of concerns. The representation of HTTP messages should not be conflated with the asynchronous model used to serialize or parse those messages in the message declarations.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
The next declaration forms the complete implementation class referenced by the handle in the public interface (which follows after): ``` /// Internal representation of an HTTP request message. class _http_request final : public http::details::http_msg_base, public std::enable_shared_from_this<_http_request> { public:
The next declaration forms the complete implementation class referenced by the handle in the public interface (which follows after): ``` /// Internal representation of an HTTP request message. class _http_request final : public http::details::http_msg_base, public std::enable_shared_from_this<_http_request> { public:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
} // namespace details ```
} // namespace details ```
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
As before, we note that the implementation class for HTTP requests concerns itself more with the mechanics of sending the message asynchronously than it does with actually modeling the HTTP message as described in __rfc7230__:
As before, we note that the implementation class for HTTP requests concerns itself more with the mechanics of sending the message asynchronously than it does with actually modeling the HTTP message as described in __rfc7230__:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The constructor accepting `std::unique_ptr<http::details::_http_server_context`
* The constructor accepting `std::unique_ptr<http::details::_http_server_context`
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The "cancellation token" is stored inside the message. This breaks the
* The "cancellation token" is stored inside the message. This breaks the
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The `_reply_impl` function implies that the message implementation also
* The `_reply_impl` function implies that the message implementation also
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
Finally, here is the public class which represents an HTTP request: ``` class http_request { public:
Finally, here is the public class which represents an HTTP request: ``` class http_request { public:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
It is clear from this declaration that the goal of the message model in this library is driven by its use-case (interacting with REST servers) and not to model HTTP messages generally. We note problems similar to the other declarations:
It is clear from this declaration that the goal of the message model in this library is driven by its use-case (interacting with REST servers) and not to model HTTP messages generally. We note problems similar to the other declarations:
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* There are no compile-time customization points at all. The only
* There are no compile-time customization points at all. The only
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The extraction of the body is conflated with the asynchronous model.
* The extraction of the body is conflated with the asynchronous model.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* No way to define an allocator for the container used when extracting
* No way to define an allocator for the container used when extracting
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* A body can only be extracted once, limiting the use of this container
* A body can only be extracted once, limiting the use of this container
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* Setting the body requires either a vector or a `concurrency::streams::istream`.
* Setting the body requires either a vector or a `concurrency::streams::istream`.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
* The HTTP request container conflates HTTP response behavior (see the
* The HTTP request container conflates HTTP response behavior (see the
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
The general theme of the HTTP message model in cpprestsdk is "no user definable customizations". There is no allocator support, and no separation of concerns. It is designed to perform a specific set of behaviors. In other words, it does not follow the open/closed principle.
The general theme of the HTTP message model in cpprestsdk is "no user definable customizations". There is no allocator support, and no separation of concerns. It is designed to perform a specific set of behaviors. In other words, it does not follow the open/closed principle.
Boost Beast Translation (zh_Hans)/Doc / Qbk / 08 Design / 2 Http Comparison (qbk) — Chinese (Simplified Han script)
Tasks in the Concurrency Runtime operate in a fashion similar to `std::future`, but with some improvements such as continuations which are not yet in the C++ standard. The costs of using a task based asynchronous interface instead of completion handlers is well documented: synchronization points along the call chain of composed task operations which cannot be optimized away. See: [@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3747.pdf [*A Universal Model for Asynchronous Operations]] (Kohlhoff).
Tasks in the Concurrency Runtime operate in a fashion similar to `std::future`, but with some improvements such as continuations which are not yet in the C++ standard. The costs of using a task based asynchronous interface instead of completion handlers is well documented: synchronization points along the call chain of composed task operations which cannot be optimized away. See: [@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3747.pdf [*A Universal Model for Asynchronous Operations]] (Kohlhoff).