Remove http Writer suspend and resume feature (API Change):

fix #154

The resume_context parameter passed to instances
of Writer during HTTP serialization is removed.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 * Add io_service completion invariants test
 
+API Changes:
+
+* Remove http Writer suspend and resume feature
+
 --------------------------------------------------------------------------------
 
 1.0.0-b31

doc/quickref.xml

@@ -42,7 +42,6 @@
             <member><link linkend="beast.ref.http__request_header">request_header</link></member>
             <member><link linkend="beast.ref.http__response">response</link></member>
             <member><link linkend="beast.ref.http__response_header">response_header</link></member>
-            <member><link linkend="beast.ref.http__resume_context">resume_context</link></member>
             <member><link linkend="beast.ref.http__streambuf_body">streambuf_body</link></member>
             <member><link linkend="beast.ref.http__string_body">string_body</link></member>
           </simplelist>
@@ -190,6 +189,7 @@
             <member><link linkend="beast.ref.buffer_cat">buffer_cat</link></member>
             <member><link linkend="beast.ref.prepare_buffer">prepare_buffer</link></member>
             <member><link linkend="beast.ref.prepare_buffers">prepare_buffers</link></member>
+            <member><link linkend="beast.ref.system_category">system_category</link></member>
             <member><link linkend="beast.ref.to_string">to_string</link></member>
             <member><link linkend="beast.ref.write">write</link></member>
           </simplelist>

doc/types/Writer.qbk

@@ -28,8 +28,6 @@ In this table:
 * `m`  denotes a value of type `message const&` where
         `std::is_same<decltype(m.body), Body::value_type>:value == true`.
 
-* `rc` is an object of type [link beast.ref.http__resume_context `resume_context`].
-
 * `ec` is a value of type [link beast.ref.error_code `error_code&`]
 
 * `wf` is a [*write function]: a function object of unspecified type provided
@@ -72,8 +70,8 @@ In this table:
     ]
 ]
 [
-    [`a.write(rc, ec, wf)`]
+    [`a.write(ec, wf)`]
-    [`boost::tribool`]
+    [`bool`]
     [
         Called repeatedly after `init` succeeds. `wf` is a function object
         which takes as its single parameter any value meeting the requirements
@@ -81,12 +79,7 @@ In this table:
         must remain valid until the next member function of `writer` is
         invoked (which may be the destructor). This function returns `true`
         to indicate all message body data has been written, or `false` if
-        there is more body data. If the return value is `boost::indeterminate`,
+        there is more body data.
-        the implementation will suspend the operation until the writer invokes
-        `rc`. It is the writers responsibility when returning
-        `boost::indeterminate`, to acquire ownership of `rc` via move
-        construction and eventually call it or else undefined behavior
-        results. This function must be `noexcept`.
     ]
 ]
 ]
@@ -139,7 +132,6 @@ public:
         Postconditions:
 
             If return value is `true`:
-                * Callee does not take ownership of resume.
                 * Callee made zero or one calls to `write`.
                 * There is no more data remaining to write.
 
@@ -147,18 +139,6 @@ public:
                 * Callee does not take ownership of resume.
                 * Callee made one call to `write`.
 
-            If return value is boost::indeterminate:
-                * Callee takes ownership of `resume`.
-                * Caller suspends the write operation
-                  until `resume` is invoked.
-
-        When the caller takes ownership of resume, the
-        asynchronous operation will not complete until the
-        caller destroys the object.
-
-        @param resume A functor to call to resume the write operation
-        after the writer has returned boost::indeterminate.
-
         @param ec Set to indicate an error. This will cause an
         asynchronous write operation to complete with the error.
 
@@ -168,16 +148,11 @@ public:
         next member function is invoked, which may be the destructor.
 
         @return `true` if there is no more data to send,
-                `false` when there may be more data,
+                `false` when there may be more data.
-                boost::indeterminate to suspend.
-
-        @note Undefined behavior if the callee takes ownership
-              of resume but does not return boost::indeterminate.
     */
     template<class WriteFunction>
-    boost::tribool
+    bool
     write(
-        resume_context&&,
         error_code&,
         WriteFunction&& wf) noexcept;
 };

examples/file_body.hpp

@@ -10,10 +10,8 @@
 
 #include <beast/core/error.hpp>
 #include <beast/http/message.hpp>
-#include <beast/http/resume_context.hpp>
 #include <boost/asio/buffer.hpp>
 #include <boost/filesystem.hpp>
-#include <boost/logic/tribool.hpp>
 #include <cstdio>
 #include <cstdint>
 
@@ -38,7 +36,8 @@ struct file_body
         writer& operator=(writer const&) = delete;
 
         template<bool isRequest, class Fields>
-        writer(message<isRequest, file_body, Fields> const& m) noexcept
+        writer(message<isRequest,
+                file_body, Fields> const& m) noexcept
             : path_(m.body)
         {
         }
@@ -54,8 +53,8 @@ struct file_body
         {
             file_ = fopen(path_.c_str(), "rb");
             if(! file_)
-                ec = boost::system::errc::make_error_code(
+                ec = error_code{errno,
-                    static_cast<boost::system::errc::errc_t>(errno));
+                    system_category()};
             else
                 size_ = boost::filesystem::file_size(path_);
         }
@@ -67,9 +66,8 @@ struct file_body
         }
 
         template<class WriteFunction>
-        boost::tribool
+        bool
-        write(resume_context&&, error_code&,
+        write(error_code& ec, WriteFunction&& wf) noexcept
-            WriteFunction&& wf) noexcept
         {
             if(size_ - offset_ < sizeof(buf_))
                 buf_len_ = static_cast<std::size_t>(
@@ -77,7 +75,12 @@ struct file_body
             else
                 buf_len_ = sizeof(buf_);
             auto const nread = fread(buf_, 1, sizeof(buf_), file_);
-            (void)nread;
+            if(ferror(file_))
+            {
+                ec = error_code(errno,
+                    system_category());
+                return true;
+            }
             offset_ += buf_len_;
             wf(boost::asio::buffer(buf_, buf_len_));
             return offset_ >= size_;

include/beast/core/error.hpp

@@ -22,6 +22,14 @@ using system_error = boost::system::system_error;
 /// The type of error category used by the library
 using error_category = boost::system::error_category;
 
+/// A function to return the system error category used by the library
+#if GENERATING_DOCS
+error_category const&
+system_category();
+#else
+using boost::system::system_category;
+#endif
+
 /// The type of error condition used by the library
 using error_condition = boost::system::error_condition;
 

include/beast/http.hpp

@@ -19,7 +19,6 @@
 #include <beast/http/parser_v1.hpp>
 #include <beast/http/read.hpp>
 #include <beast/http/reason.hpp>
-#include <beast/http/resume_context.hpp>
 #include <beast/http/rfc7230.hpp>
 #include <beast/http/streambuf_body.hpp>
 #include <beast/http/string_body.hpp>

include/beast/http/basic_dynabuf_body.hpp

@@ -10,10 +10,8 @@
 
 #include <beast/core/error.hpp>
 #include <beast/http/message.hpp>
-#include <beast/http/resume_context.hpp>
 #include <beast/core/detail/type_traits.hpp>
 #include <boost/asio/buffer.hpp>
-#include <boost/logic/tribool.hpp>
 
 namespace beast {
 namespace http {
@@ -87,9 +85,8 @@ private:
         }
 
         template<class WriteFunction>
-        boost::tribool
+        bool
-        write(resume_context&&, error_code&,
+        write(error_code&, WriteFunction&& wf) noexcept
-            WriteFunction&& wf) noexcept
         {
             wf(body_.data());
             return true;

include/beast/http/concepts.hpp

@@ -10,9 +10,7 @@
 
 #include <beast/core/error.hpp>
 #include <beast/core/detail/type_traits.hpp>
-#include <beast/http/resume_context.hpp>
 #include <boost/asio/buffer.hpp>
-#include <boost/logic/tribool.hpp>
 #include <type_traits>
 #include <utility>
 
@@ -50,38 +48,6 @@ struct has_content_length<T, beast::detail::void_t<decltype(
         "Writer::content_length requirements not met");
 };
 
-#if 0
-template<class T, class M, class = beast::detail::void_t<>>
-struct is_Writer : std::false_type {};
-
-template<class T, class M>
-struct is_Writer<T, M, beast::detail::void_t<decltype(
-    std::declval<T>().init(
-        std::declval<error_code&>())
-    // VFALCO This is unfortunate, we have to provide the template
-    //        argument type because this is not a deduced context?
-    //
-    ,std::declval<T>().template write<detail::write_function>(
-        std::declval<resume_context>(),
-        std::declval<error_code&>(),
-        std::declval<detail::write_function>())
-            )> > : std::integral_constant<bool,
-    std::is_nothrow_constructible<T, M const&>::value &&
-    std::is_convertible<decltype(
-        std::declval<T>().template write<detail::write_function>(
-            std::declval<resume_context>(),
-            std::declval<error_code&>(),
-            std::declval<detail::write_function>())),
-                boost::tribool>::value
-        >
-{
-    static_assert(std::is_same<
-        typename M::body_type::writer, T>::value,
-            "Mismatched writer and message");
-};
-
-#else
-
 template<class T, class M>
 class is_Writer
 {
@@ -99,10 +65,9 @@ class is_Writer
     template<class U, class R =
         std::is_convertible<decltype(
             std::declval<U>().template write<detail::write_function>(
-                std::declval<resume_context>(),
                 std::declval<error_code&>(),
                 std::declval<detail::write_function>()))
-            , boost::tribool>>
+            , bool>>
     static R check2(int);
     template<class>
     static std::false_type check2(...);
@@ -120,8 +85,6 @@ public:
     >;
 };
 
-#endif
-
 template<class T>
 class is_Parser
 {

include/beast/http/empty_body.hpp

@@ -10,10 +10,8 @@
 
 #include <beast/core/error.hpp>
 #include <beast/http/message.hpp>
-#include <beast/http/resume_context.hpp>
 #include <beast/core/detail/type_traits.hpp>
 #include <boost/asio/buffer.hpp>
-#include <boost/logic/tribool.hpp>
 #include <memory>
 #include <string>
 
@@ -59,9 +57,8 @@ private:
         }
 
         template<class WriteFunction>
-        boost::tribool
+        bool
-        write(resume_context&&, error_code&,
+        write(error_code&, WriteFunction&& wf) noexcept
-            WriteFunction&& wf) noexcept
         {
             wf(boost::asio::null_buffers{});
             return true;

include/beast/http/impl/write.ipp

@@ -9,7 +9,6 @@
 #define BEAST_HTTP_IMPL_WRITE_IPP
 
 #include <beast/http/concepts.hpp>
-#include <beast/http/resume_context.hpp>
 #include <beast/http/chunk_encode.hpp>
 #include <beast/core/buffer_cat.hpp>
 #include <beast/core/bind_handler.hpp>
@@ -21,7 +20,6 @@
 #include <beast/core/write_dynabuf.hpp>
 #include <beast/core/detail/sync_ostream.hpp>
 #include <boost/asio/write.hpp>
-#include <boost/logic/tribool.hpp>
 #include <condition_variable>
 #include <mutex>
 #include <ostream>
@@ -296,8 +294,6 @@ class write_op
         // VFALCO How do we use handler_alloc in write_preparation?
         write_preparation<
             isRequest, Body, Fields> wp;
-        resume_context resume;
-        resume_context copy;
         int state = 0;
 
         data(Handler& handler, Stream& s_,
@@ -375,27 +371,9 @@ public:
         : d_(std::forward<DeducedHandler>(h),
             s, std::forward<Args>(args)...)
     {
-        auto& d = *d_;
-        auto sp = d_;
-        d.resume = {
-            [sp]() mutable
-            {
-                write_op self{std::move(sp)};
-                self.d_->cont = false;
-                auto& ios = self.d_->s.get_io_service();
-                ios.dispatch(bind_handler(std::move(self),
-                    error_code{}, 0, false));
-            }};
-        d.copy = d.resume;
         (*this)(error_code{}, 0, false);
     }
 
-    explicit
-    write_op(handler_ptr<data, Handler> d)
-        : d_(std::move(d))
-    {
-    }
-
     void
     operator()(error_code ec,
         std::size_t bytes_transferred, bool again = true);
@@ -460,8 +438,9 @@ operator()(error_code ec, std::size_t, bool again)
 
         case 1:
         {
-            boost::tribool const result = d.wp.w.write(
+            auto const result =
-                std::move(d.copy), ec, writef0_lambda{*this});
+                d.wp.w.write(ec,
+                    writef0_lambda{*this});
             if(ec)
             {
                 // call handler
@@ -470,12 +449,6 @@ operator()(error_code ec, std::size_t, bool again)
                     std::move(*this), ec, false));
                 return;
             }
-            if(boost::indeterminate(result))
-            {
-                // suspend
-                d.copy = d.resume;
-                return;
-            }
             if(result)
                 d.state = d.wp.chunked ? 4 : 5;
             else
@@ -491,20 +464,15 @@ operator()(error_code ec, std::size_t, bool again)
 
         case 3:
         {
-            boost::tribool result = d.wp.w.write(
+            auto const result =
-                std::move(d.copy), ec, writef_lambda{*this});
+                d.wp.w.write(ec,
+                    writef_lambda{*this});
             if(ec)
             {
                 // call handler
                 d.state = 99;
                 break;
             }
-            if(boost::indeterminate(result))
-            {
-                // suspend
-                d.copy = d.resume;
-                return;
-            }
             if(result)
                 d.state = d.wp.chunked ? 4 : 5;
             else
@@ -533,8 +501,6 @@ operator()(error_code ec, std::size_t, bool again)
             break;
         }
     }
-    d.copy = {};
-    d.resume = {};
     d_.invoke(ec);
 }
 
@@ -640,37 +606,12 @@ write(SyncWriteStream& stream,
     wp.init(ec);
     if(ec)
         return;
-    std::mutex m;
+    auto result = wp.w.write(
-    std::condition_variable cv;
+        ec, detail::writef0_lambda<
-    bool ready = false;
+            SyncWriteStream, decltype(wp.sb)>{
-    resume_context resume{
+                stream, wp.sb, wp.chunked, ec});
-        [&]
-        {
-            std::lock_guard<std::mutex> lock(m);
-            ready = true;
-            cv.notify_one();
-        }};
-    auto copy = resume;
-    boost::tribool result =
-        wp.w.write(std::move(copy), ec,
-            detail::writef0_lambda<SyncWriteStream,
-                decltype(wp.sb)>{stream,
-                    wp.sb, wp.chunked, ec});
     if(ec)
         return;
-    if(boost::indeterminate(result))
-    {
-        copy = resume;
-        {
-            std::unique_lock<std::mutex> lock(m);
-            cv.wait(lock, [&]{ return ready; });
-            ready = false;
-        }
-        boost::asio::write(stream, wp.sb.data(), ec);
-        if(ec)
-            return;
-        result = false;
-    }
     wp.sb.consume(wp.sb.size());
     if(! result)
     {
@@ -678,17 +619,11 @@ write(SyncWriteStream& stream,
             stream, wp.chunked, ec};
         for(;;)
         {
-            result = wp.w.write(std::move(copy), ec, wf);
+            result = wp.w.write(ec, wf);
             if(ec)
                 return;
             if(result)
                 break;
-            if(! result)
-                continue;
-            copy = resume;
-            std::unique_lock<std::mutex> lock(m);
-            cv.wait(lock, [&]{ return ready; });
-            ready = false;
         }
     }
     if(wp.chunked)

include/beast/http/resume_context.hpp

@@ -1,34 +0,0 @@
-//
-// Copyright (c) 2013-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
-//
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-//
-
-#ifndef BEAST_HTTP_RESUME_CONTEXT_HPP
-#define BEAST_HTTP_RESUME_CONTEXT_HPP
-
-#include <functional>
-
-namespace beast {
-namespace http {
-
-/** A functor that resumes a write operation.
-
-    An rvalue reference to an object of this type is provided by the
-    write implementation to the `writer` associated with the body of
-    a message being sent.
-
-    If it is desired that the `writer` suspend the write operation (for
-    example, to wait until data is ready), it can take ownership of
-    the resume context using a move. Then, it returns `boost::indeterminate`
-    to indicate that the write operation should suspend. Later, the calling
-    code invokes the resume function and the write operation continues
-    from where it left off.
-*/
-using resume_context = std::function<void(void)>;
-
-} // http
-} // beast
-
-#endif

include/beast/http/string_body.hpp

@@ -10,10 +10,8 @@
 
 #include <beast/core/error.hpp>
 #include <beast/http/message.hpp>
-#include <beast/http/resume_context.hpp>
 #include <beast/core/detail/type_traits.hpp>
 #include <boost/asio/buffer.hpp>
-#include <boost/logic/tribool.hpp>
 #include <memory>
 #include <string>
 
@@ -87,9 +85,8 @@ private:
         }
 
         template<class WriteFunction>
-        boost::tribool
+        bool
-        write(resume_context&&, error_code&,
+        write(error_code&, WriteFunction&& wf) noexcept
-            WriteFunction&& wf) noexcept
         {
             wf(boost::asio::buffer(body_));
             return true;

test/Jamfile

@@ -58,7 +58,6 @@ unit-test http-tests :
     http/parser_v1.cpp
     http/read.cpp
     http/reason.cpp
-    http/resume_context.cpp
     http/rfc7230.cpp
     http/streambuf_body.cpp
     http/string_body.cpp

test/http/CMakeLists.txt

@@ -23,7 +23,6 @@ add_executable (http-tests
     parser_v1.cpp
     read.cpp
     reason.cpp
-    resume_context.cpp
     rfc7230.cpp
     streambuf_body.cpp
     string_body.cpp

test/http/resume_context.cpp

@@ -1,9 +0,0 @@
-//
-// Copyright (c) 2013-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
-//
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-//
-
-// Test that header file is self-contained.
-#include <beast/http/resume_context.hpp>

test/http/write.cpp

@@ -55,9 +55,8 @@ public:
             }
 
             template<class WriteFunction>
-            boost::tribool
+            bool
-            write(resume_context&&, error_code&,
+            write(error_code&, WriteFunction&& wf) noexcept
-                WriteFunction&& wf) noexcept
             {
                 wf(boost::asio::buffer(body_));
                 return true;
@@ -103,8 +102,6 @@ public:
         {
             std::size_t n_ = 0;
             value_type const& body_;
-            bool suspend_ = false;
-            enable_yield_to yt_;
 
         public:
             template<bool isRequest, class Allocator>
@@ -120,37 +117,12 @@ public:
                 body_.fc_.fail(ec);
             }
 
-            class do_resume
-            {
-                resume_context rc_;
-
-            public:
-                explicit
-                do_resume(resume_context&& rc)
-                    : rc_(std::move(rc))
-                {
-                }
-
-                void
-                operator()()
-                {
-                    rc_();
-                }
-            };
-
             template<class WriteFunction>
-            boost::tribool
+            bool
-            write(resume_context&& rc, error_code& ec,
+            write(error_code& ec, WriteFunction&& wf) noexcept
-                WriteFunction&& wf) noexcept
             {
                 if(body_.fc_.fail(ec))
                     return false;
-                suspend_ = ! suspend_;
-                if(suspend_)
-                {
-                    yt_.get_io_service().post(do_resume{std::move(rc)});
-                    return boost::indeterminate;
-                }
                 if(n_ >= body_.s_.size())
                     return true;
                 wf(boost::asio::buffer(body_.s_.data() + n_, 1));