Moving from govendor to dep, updated dependencies (#48)
* Moving from govendor to dep. * Making the pull request template more friendly. * Fixing akward space in PR template. * goimports run on whole project using ` goimports -w $(find . -type f -name '*.go' -not -path "./vendor/*" -not -path "./gen-go/*")` source of command: https://gist.github.com/bgentry/fd1ffef7dbde01857f66
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Renan DelValle
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vendor/git.apache.org/thrift.git/doc/specs/thrift-binary-protocol.md
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Thrift Binary protocol encoding
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===============================
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<!--
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--------------------------------------------------------------------
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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--------------------------------------------------------------------
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-->
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This documents describes the wire encoding for RPC using the older Thrift *binary protocol*.
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The information here is _mostly_ based on the Java implementation in the Apache thrift library (version 0.9.1 and
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0.9.3). Other implementation however, should behave the same.
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For background on Thrift see the [Thrift whitepaper (pdf)](https://thrift.apache.org/static/files/thrift-20070401.pdf).
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# Contents
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* Binary protocol
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* Base types
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* Message
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* Struct
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* List and Set
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* Map
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* BNF notation used in this document
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# Binary protocol
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## Base types
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### Integer encoding
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In the _binary protocol_ integers are encoded with the most significant byte first (big endian byte order, aka network
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order). An `int8` needs 1 byte, an `int16` 2, an `int32` 4 and an `int64` needs 8 bytes.
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The CPP version has the option to use the binary protocol with little endian order. Little endian gives a small but
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noticeable performance boost because contemporary CPUs use little endian when storing integers to RAM.
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### Enum encoding
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The generated code encodes `Enum`s by taking the ordinal value and then encoding that as an int32.
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### Binary encoding
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Binary is sent as follows:
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```
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Binary protocol, binary data, 4+ bytes:
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+--------+--------+--------+--------+--------+...+--------+
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| byte length | bytes |
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+--------+--------+--------+--------+--------+...+--------+
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```
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Where:
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* `byte length` is the length of the byte array, a signed 32 bit integer encoded in network (big endian) order (must be >= 0).
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* `bytes` are the bytes of the byte array.
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### String encoding
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*String*s are first encoded to UTF-8, and then send as binary.
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### Double encoding
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Values of type `double` are first converted to an int64 according to the IEEE 754 floating-point "double format" bit
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layout. Most run-times provide a library to make this conversion. Both the binary protocol as the compact protocol then
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encode the int64 in 8 bytes in big endian order.
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### Boolean encoding
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Values of `bool` type are first converted to an int8. True is converted to `1`, false to `0`.
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## Message
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A `Message` can be encoded in two different ways:
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```
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Binary protocol Message, strict encoding, 12+ bytes:
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+--------+--------+--------+--------+--------+--------+--------+--------+--------+...+--------+--------+--------+--------+--------+
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|1vvvvvvv|vvvvvvvv|unused |00000mmm| name length | name | seq id |
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+--------+--------+--------+--------+--------+--------+--------+--------+--------+...+--------+--------+--------+--------+--------+
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```
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Where:
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* `vvvvvvvvvvvvvvv` is the version, an unsigned 15 bit number fixed to `1` (in binary: `000 0000 0000 0001`).
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The leading bit is `1`.
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* `unused` is an ignored byte.
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* `mmm` is the message type, an unsigned 3 bit integer. The 5 leading bits must be `0` as some clients (checked for
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java in 0.9.1) take the whole byte.
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* `name length` is the byte length of the name field, a signed 32 bit integer encoded in network (big endian) order (must be >= 0).
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* `name` is the method name, a UTF-8 encoded string.
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* `seq id` is the sequence id, a signed 32 bit integer encoded in network (big endian) order.
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The second, older encoding (aka non-strict) is:
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```
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Binary protocol Message, old encoding, 9+ bytes:
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+--------+--------+--------+--------+--------+...+--------+--------+--------+--------+--------+--------+
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| name length | name |00000mmm| seq id |
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+--------+--------+--------+--------+--------+...+--------+--------+--------+--------+--------+--------+
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```
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Where `name length`, `name`, `mmm`, `seq id` are as above.
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Because `name length` must be positive (therefore the first bit is always `0`), the first bit allows the receiver to see
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whether the strict format or the old format is used. Therefore a server and client using the different variants of the
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binary protocol can transparently talk with each other. However, when strict mode is enforced, the old format is
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rejected.
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Message types are encoded with the following values:
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* _Call_: 1
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* _Reply_: 2
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* _Exception_: 3
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* _Oneway_: 4
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## Struct
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A *Struct* is a sequence of zero or more fields, followed by a stop field. Each field starts with a field header and
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is followed by the encoded field value. The encoding can be summarized by the following BNF:
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```
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struct ::= ( field-header field-value )* stop-field
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field-header ::= field-type field-id
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```
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Because each field header contains the field-id (as defined by the Thrift IDL file), the fields can be encoded in any
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order. Thrift's type system is not extensible; you can only encode the primitive types and structs. Therefore is also
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possible to handle unknown fields while decoding; these are simply ignored. While decoding the field type can be used to
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determine how to decode the field value.
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Note that the field name is not encoded so field renames in the IDL do not affect forward and backward compatibility.
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The default Java implementation (Apache Thrift 0.9.1) has undefined behavior when it tries to decode a field that has
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another field-type then what is expected. Theoretically this could be detected at the cost of some additional checking.
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Other implementation may perform this check and then either ignore the field, or return a protocol exception.
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A *Union* is encoded exactly the same as a struct with the additional restriction that at most 1 field may be encoded.
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An *Exception* is encoded exactly the same as a struct.
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### Struct encoding
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In the binary protocol field headers and the stop field are encoded as follows:
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```
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Binary protocol field header and field value:
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+--------+--------+--------+--------+...+--------+
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|tttttttt| field id | field value |
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+--------+--------+--------+--------+...+--------+
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Binary protocol stop field:
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+--------+
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|00000000|
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+--------+
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```
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Where:
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* `tttttttt` the field-type, a signed 8 bit integer.
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* `field id` the field-id, a signed 16 bit integer in big endian order.
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* `field-value` the encoded field value.
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The following field-types are used:
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* `BOOL`, encoded as `2`
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* `BYTE`, encoded as `3`
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* `DOUBLE`, encoded as `4`
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* `I16`, encoded as `6`
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* `I32`, encoded as `8`
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* `I64`, encoded as `10`
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* `STRING`, used for binary and string fields, encoded as `11`
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* `STRUCT`, used for structs and union fields, encoded as `12`
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* `MAP`, encoded as `13`
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* `SET`, encoded as `14`
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* `LIST`, encoded as `15`
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## List and Set
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List and sets are encoded the same: a header indicating the size and the element-type of the elements, followed by the
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encoded elements.
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```
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Binary protocol list (5+ bytes) and elements:
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+--------+--------+--------+--------+--------+--------+...+--------+
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|tttttttt| size | elements |
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+--------+--------+--------+--------+--------+--------+...+--------+
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```
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Where:
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* `tttttttt` is the element-type, encoded as an int8
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* `size` is the size, encoded as an int32, positive values only
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* `elements` the element values
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The element-type values are the same as field-types. The full list is included in the struct section above.
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The maximum list/set size is configurable. By default there is no limit (meaning the limit is the maximum int32 value:
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2147483647).
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## Map
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Maps are encoded with a header indicating the size, the element-type of the keys and the element-type of the elements,
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followed by the encoded elements. The encoding follows this BNF:
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```
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map ::= key-element-type value-element-type size ( key value )*
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```
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```
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Binary protocol map (6+ bytes) and key value pairs:
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+--------+--------+--------+--------+--------+--------+--------+...+--------+
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|kkkkkkkk|vvvvvvvv| size | key value pairs |
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+--------+--------+--------+--------+--------+--------+--------+...+--------+
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```
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Where:
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* `kkkkkkkk` is the key element-type, encoded as an int8
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* `vvvvvvvv` is the value element-type, encoded as an int8
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* `size` is the size of the map, encoded as an int32, positive values only
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* `key value pairs` are the encoded keys and values
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The element-type values are the same as field-types. The full list is included in the struct section above.
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The maximum map size is configurable. By default there is no limit (meaning the limit is the maximum int32 value:
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2147483647).
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# BNF notation used in this document
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The following BNF notation is used:
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* a plus `+` appended to an item represents repetition; the item is repeated 1 or more times
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* a star `*` appended to an item represents optional repetition; the item is repeated 0 or more times
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* a pipe `|` between items represents choice, the first matching item is selected
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* parenthesis `(` and `)` are used for grouping multiple items
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