doc/thrift.bnf

Thrift Protocol Structure

Mark Slee (mcslee@facebook.com)

Last Modified: 2007-Jun-29

Thrift is distributed under the Thrift open source software license.
Please see the included LICENSE file.

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This document describes the structure of the Thrift protocol
without specifying the encoding. Thus, the order of elements
could in some cases be rearranged depending upon the TProtocol
implementation, but this document specifies the minimum required
structure. There are some "dumb" terminals like STRING and INT
that take the place of an actual encoding specification.

They key point to notice is that ALL messages are just one wrapped
<struct>. Depending upon the message type, the <struct> can be
interpreted as the argument list to a function, the return value
of a function, or an exception.

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       <message> ::= <message-begin> <struct> <message-end>

 <message-begin> ::= <method-name> <message-type> <message-seqid>

   <method-name> ::= STRING

  <message-type> ::= T_CALL | T_REPLY | T_EXCEPTION

 <message-seqid> ::= I32

        <struct> ::= <struct-begin> <field>* <field-stop> <struct-end>

  <struct-begin> ::= <struct-name>

   <struct-name> ::= STRING

    <field-stop> ::= T_STOP

         <field> ::= <field-begin> <field-data> <field-end>

   <field-begin> ::= <field-name> <field-type> <field-id>

    <field-name> ::= STRING

    <field-type> ::= T_BOOL | T_BYTE | T_I8 | T_I16 | T_I32 | T_I64 | T_DOUBLE
                     | T_STRING | T_BINARY | T_STRUCT | T_MAP | T_SET | T_LIST

      <field-id> ::= I16

    <field-data> ::= I8 | I16 | I32 | I64 | DOUBLE | STRING | BINARY
                     <struct> | <map> | <list> | <set>

           <map> ::= <map-begin> <field-datum>* <map-end>

     <map-begin> ::= <map-key-type> <map-value-type> <map-size>

  <map-key-type> ::= <field-type>

<map-value-type> ::= <field-type>

      <map-size> ::= I32

          <list> ::= <list-begin> <field-data>* <list-end>

    <list-begin> ::= <list-elem-type> <list-size>

<list-elem-type> ::= <field-type>

     <list-size> ::= I32

           <set> ::= <set-begin> <field-data>* <set-end>

     <set-begin> ::= <set-elem-type> <set-size>

 <set-elem-type> ::= <field-type>

      <set-size> ::= I32