HTTP Reader (API Change):

fix #114, fix #117, fix #136

* Added init() to Reader requirements
* Reader must be nothrow constructible
* Reader is now constructed right before reading the body
  - The message passed on construction is filled in

CHANGELOG.md

@@ -5,6 +5,14 @@
 * Fix basic_streambuf::capacity
 * Add basic_streambuf::alloc_size
 * Parser callbacks may not throw
+* Fix Reader concept doc typo
+
+API Changes:
+
+* Added init() to Reader requirements
+* Reader must be nothrow constructible
+* Reader is now constructed right before reading the body
+   - The message passed on construction is filled in
 
 --------------------------------------------------------------------------------
 

doc/types/Reader.qbk

@@ -8,23 +8,23 @@
 [section:Reader Reader requirements]
 
 Parsers provided by the implementation will construct the corresponding
-`reader` object during the parse. This customization point allows the
+`reader` object during parsing. This customization point allows the
 Body to determine the strategy for storing incoming message body data.
 
 In this table:
 
-* `X` denotes a type meeting the requirements of [*`Reader`]
+* `X` denotes a type meeting the requirements of [*`Reader`].
 
-* `a` denotes a value of type `X`
+* `a` denotes a value of type `X`.
 
-* `p` is any pointer
+* `n` is a value convertible to `std::size_t`.
 
-* `n` is a value convertible to `std::size_t`
+* `p` is a `void const*` to valid memory of at least `n` bytes.
 
-* `ec` is a value of type [link beast.ref.error_code `error_code&`]
+* `ec` is a value of type [link beast.ref.error_code `error_code&`].
 
-* `m` denotes a value of type `message const&` where
-    `std::is_same<decltype(m.body), Body::value_type>::value == true`
+* `m` denotes a value of type `message&` where
+    `std::is_same<decltype(m.body), Body::value_type>::value == true`.
 
 [table Reader requirements
 [[operation] [type] [semantics, pre/post-conditions]]
@@ -32,22 +32,38 @@ In this table:
     [`X a(m);`]
     []
     [
-        `a` is constructible from `m`. The lifetime of `m` is
-        guaranteed to end no earlier than after `a` is destroyed.
+        `a` is constructible from `m`. The lifetime of `m` is guaranteed
+        to end no earlier than after `a` is destroyed. The constructor
+        will be called after all headers have been stored in `m`, and
+        before any body data is deserialized. This function must be
+        `noexcept`.
+    ]
+]
+[
+    [`a.init(ec)`]
+    [`void`]
+    [
+        Called immediately after construction. If the function sets
+        an error code in `ec`, the parse is aborted and the error is
+        propagated to the caller. This function must be `noexcept`.
     ]
 ]
 [
     [`a.write(p, n, ec)`]
     [`void`]
     [
-        Deserializes the input sequence into the body.
-        If `ec` is set, the deserialization is aborted and the error
-        is returned to the caller.
+        Deserializes the input sequence into the body. If `ec` is set,
+        the deserialization is aborted and the error is propagated to
+        the caller. If the message headers specify a chunked transfer
+        encoding, the reader will receive the decoded version of the
+        body. This function must be `noexcept`.
     ]
 ]
 ]
 
-[note Definitions for required `Reader` member functions should be declared
-inline so the generated code becomes part of the implementation. ]
+[note
+    Definitions for required `Reader` member functions should be declared
+    inline so the generated code can become part of the implementation.
+]
 
 [endsect]

doc/types/Writer.qbk

@@ -28,13 +28,13 @@ 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].
+* `rc` is an object of type [link beast.ref.http__resume_context `resume_context`].
 
-* `ec` is a value of type `error_code&`.
+* `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
        by the implementation which accepts any value meeting the requirements
-       of `ConstBufferSequence` as its single parameter.
+       of __ConstBufferSequence__ as its single parameter.
 
 [table Writer requirements
 [[operation] [type] [semantics, pre/post-conditions]]
@@ -42,17 +42,18 @@ In this table:
     [`X a(m);`]
     []
     [
-        `a` is constructible from `m`. The lifetime of `m` is
-        guaranteed to end no earlier than after `a` is destroyed.
+        `a` is constructible from `m`. The lifetime of `m` is guaranteed
+        to end no earlier than after `a` is destroyed. This function must
+        be `noexcept`.
     ]
 ]
 [
     [`a.init(ec)`]
     [`void`]
     [
-        Called immediately after construction.
-        If `ec` is set, the serialization is aborted and the error
-        is propagated to the caller.
+        Called immediately after construction. If the function sets an
+        error code in `ec`, the serialization is aborted and the error
+        is propagated to the caller. This function must be `noexcept`.
     ]
 ]
 [
@@ -67,31 +68,33 @@ In this table:
         the serialized message body will be sent unmodified, with the
         error `boost::asio::error::eof` returned to the caller, to notify
         they should close the connection to indicate the end of the message.
+        This function must be `noexcept`.
     ]
 ]
 [
     [`a(rc, ec, wf)`]
     [`boost::tribool`]
     [
-        Called repeatedly after `init` succeeds.
-        `wf` is a function object which takes as its single parameter,
-        any value meeting the requirements of `ConstBufferSequence`.
-        Buffers provided by the `writer` to this [*write function] must
-        remain valid until the next member function of `writer` is
+        Called repeatedly after `init` succeeds. `wf` is a function object
+        which takes as its single parameter any value meeting the requirements
+        of __ConstBufferSequence__. Buffers provided to this write function
+        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`, the implementation will suspend the operation
-        until the writer invokes `rc`. It is the writers responsibility when
-        returning `boost::indeterminate`, to acquire ownership of the
-        `resume_context` via move construction and eventually call it or else
-        undefined behavior results.
+        to indicate all message body data has been written, or `false` if
+        there is more body data. If the return value is `boost::indeterminate`,
+        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`.
     ]
 ]
 ]
 
-[note Definitions for required `Writer` member functions should be declared
-inline so the generated code becomes part of the implementation. ]
+[note
+    Definitions for required `Writer` member functions should be declared
+    inline so the generated code can become part of the implementation.
+]
 
 Exemplar:
 ```
@@ -109,7 +112,7 @@ public:
     */
     template<bool isRequest, class Body, class Headers>
     explicit
-    writer(message<isRequest, Body, Headers> const& msg);
+    writer(message<isRequest, Body, Headers> const& msg) noexcept;
 
     /** Initialize the writer.
 
@@ -119,7 +122,7 @@ public:
         @param ec Contains the error code if any errors occur.
     */
     void
-    init(error_code& ec);
+    init(error_code& ec) noexcept;
 
     /** Returns the content length.
 
@@ -129,7 +132,7 @@ public:
         of the message.
     */
     std::uint64_t
-    content_length();
+    content_length() noexcept;
 
     /** Write zero or one buffer representing the message body.
 
@@ -172,7 +175,10 @@ public:
     */
     template<class WriteFunction>
     boost::tribool
-    operator()(resume_context&&, error_code&, WriteFunction&& write);
+    operator()(
+        resume_context&&,
+        error_code&,
+        WriteFunction&& write) noexcept;
 };
 ```
 

include/beast/http/basic_dynabuf_body.hpp

@@ -41,6 +41,11 @@ private:
         {
         }
 
+        void
+        init(error_code&) noexcept
+        {
+        }
+
         void
         write(void const* data,
             std::size_t size, error_code&) noexcept

include/beast/http/basic_parser_v1.hpp

@@ -190,9 +190,9 @@ static std::uint64_t constexpr no_content_length =
     @li `void on_complete(error_code&)`
 
         Called when the entire message has been parsed successfully.
-        At this point, @ref basic_parser_v1::complete returns `true`, and
-        the parser is ready to parse another message if keep_alive
-        would return `true`.
+        At this point, @ref complete returns `true`, and the parser
+        is ready to parse another message if @ref keep_alive would
+        return `true`.
 
     The return value of `on_headers` is special, it controls whether
     or not the parser should expect a body. See @ref body_what for

include/beast/http/parser_v1.hpp

@@ -13,6 +13,7 @@
 #include <beast/http/message_v1.hpp>
 #include <beast/core/error.hpp>
 #include <boost/assert.hpp>
+#include <boost/optional.hpp>
 #include <functional>
 #include <string>
 #include <type_traits>
@@ -87,17 +88,28 @@ public:
         message_v1<isRequest, Body, Headers>;
 
 private:
+    using reader =
+        typename message_type::body_type::reader;
+
     static_assert(is_ReadableBody<Body>::value,
         "ReadableBody requirements not met");
 
+    // Reader must be nothrow constructible
+    static_assert(std::is_nothrow_constructible<
+        reader, message_type&>::value,
+            "Reader requirements not met");
+
     std::string field_;
     std::string value_;
     message_type m_;
-    typename message_type::body_type::reader r_;
+    boost::optional<reader> r_;
     std::uint8_t skip_body_ = 0;
     bool flush_ = false;
 
 public:
+    /// Default constructor
+    parser_v1() = default;
+
     /// Move constructor
     parser_v1(parser_v1&&) = default;
 
@@ -110,12 +122,6 @@ public:
     /// Copy assignment (disallowed)
     parser_v1& operator=(parser_v1 const&) = delete;
 
-    /// Default constructor
-    parser_v1()
-        : r_(m_)
-    {
-    }
-
     /** Construct the parser.
 
         @param args A list of arguments forwarded to the message constructor.
@@ -127,7 +133,6 @@ public:
     parser_v1(Arg1&& arg1, ArgN&&... argn)
         : m_(std::forward<Arg1>(arg1),
             std::forward<ArgN>(argn)...)
-        , r_(m_)
     {
     }
 
@@ -232,12 +237,14 @@ private:
     }
 
     body_what
-    on_headers(std::uint64_t, error_code&)
+    on_headers(std::uint64_t, error_code& ec)
     {
         flush();
         m_.version = 10 * this->http_major() + this->http_minor();
         if(skip_body_)
             return body_what::skip;
+        r_.emplace(m_);
+        r_->init(ec);
         return body_what::normal;
     }
 
@@ -255,7 +262,7 @@ private:
 
     void on_body(boost::string_ref const& s, error_code& ec)
     {
-        r_.write(s.data(), s.size(), ec);
+        r_->write(s.data(), s.size(), ec);
     }
 
     void on_complete(error_code&)

include/beast/http/string_body.hpp

@@ -42,6 +42,11 @@ private:
         {
         }
 
+        void
+        init(error_code&) noexcept
+        {
+        }
+
         void
         write(void const* data,
             std::size_t size, error_code&) noexcept

test/http/read.cpp

@@ -26,8 +26,63 @@ class read_test
     , public test::enable_yield_to
 {
 public:
+    struct fail_body
+    {
+        class reader;
+
+        class value_type
+        {
+            friend class reader;
+
+            std::string s_;
+            test::fail_counter& fc_;
+
+        public:
+            explicit
+            value_type(test::fail_counter& fc)
+                : fc_(fc)
+            {
+            }
+
+            value_type&
+            operator=(std::string s)
+            {
+                s_ = std::move(s);
+                return *this;
+            }
+        };
+
+        class reader
+        {
+            std::size_t n_ = 0;
+            value_type& body_;
+
+        public:
+            template<bool isRequest, class Allocator>
+            explicit
+            reader(message<isRequest, fail_body, Allocator>& msg) noexcept
+                : body_(msg.body)
+            {
+            }
+
+            void
+            init(error_code& ec) noexcept
+            {
+                body_.fc_.fail(ec);
+            }
+
+            void
+            write(void const* data,
+                std::size_t size, error_code& ec) noexcept
+            {
+                if(body_.fc_.fail(ec))
+                    return;
+            }
+        };
+    };
+
     template<bool isRequest>
-    void failMatrix(const char* s, yield_context do_yield)
+    void failMatrix(char const* s, yield_context do_yield)
     {
         using boost::asio::buffer;
         using boost::asio::buffer_copy;
@@ -96,6 +151,20 @@ public:
                 break;
         }
         BEAST_EXPECT(n < limit);
+        for(n = 0; n < limit; ++n)
+        {
+            streambuf sb;
+            sb.commit(buffer_copy(
+                sb.prepare(len), buffer(s, len)));
+            test::fail_counter fc{n};
+            test::string_stream ss{ios_, s};
+            parser_v1<isRequest, fail_body, headers> p{fc};
+            error_code ec;
+            parse(ss, sb, p, ec);
+            if(! ec)
+                break;
+        }
+        BEAST_EXPECT(n < limit);
     }
 
     void testThrow()