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A FieldsWriter provides a algorithm to obtain a sequence of buffers representing the complete serialized HTTP/1 header for a set of fields. The implementation constructs an instance of this type when needed, and calls into it once to retrieve the buffers.
| ![[Warning]](../../../../../../doc/src/images/warning.png) | Warning | 
|---|---|
| These requirements may undergo non-backward compatible changes in subsequent versions. | 
In this table:
W denotes a type that
            meets the requirements of FieldsWriter.
          F denotes a Fields
            where std::is_same<W, F::writer>::value ==
            true.
          a is a value of type
            W.
          f is a value of type
            F.
          v is an unsigned value representing the HTTP version.
          c is an unsigned representing the HTTP status-code.
          m is a value of type
            verb.
          Table 1.41. Valid expressions
| expression | type | semantics, pre/post-conditions | 
|---|---|---|
| 
                   | 
                  A type which meets the requirements of ConstBufferSequence.
                  This is the type of buffer returned by  | |
| 
                   | 
                  The implementation calls this constructor to indicate that the
                  fields being serialized form part of an HTTP request. The lifetime
                  of  | |
| 
                   | 
                  The implementation calls this constructor to indicate that the
                  fields being serialized form part of an HTTP response. The lifetime
                  of  | |
| 
                   | 
                  The implementation calls this constructor to indicate that the
                  fields being serialized form part of a chunked encoding final-chunk
                  trailer. The lifetime of  | |
| 
                   | 
                   | 
                  Called once after construction, this function returns a constant
                  buffer sequence containing the serialized representation of the
                  HTTP request or response including the final carriage return linefeed
                  sequence ( 
                  Copies may be made of the returned sequence, but the underlying
                  memory is still owned by the writer. The implementation will destroy
                  all copies of the buffer sequence before destroying  | 
struct FieldsWriter { // The type of buffers returned by `get` struct const_buffers_type; // Constructor for requests FieldsWriter(Fields const& f, unsigned version, verb method); // Constructor for responses FieldsWriter(Fields const& f, unsigned version, unsigned status); // Returns the serialized header buffers const_buffers_type get(); };