This library can be used stand-alone for debugging purposes, but is largely intended to be a dependency for protoc-gen-erlang.

Decoding

protocol_buffers:decode(Binary).

Will return a list such as:

[{1,{fixed32,<<123:32/unsigned-little-integer>>}}, {2,{length_encoded,<<…>>}}]

where each term in the list is {field_number, {wiretype, value}}.

The three argument function can be used as:

protocol_buffers:decode(Binary, Acc, Fun)

Binary is the binary to decode
Acc is the starting Accumulator
Callback has a signature of Callback(Key::integer(), {Wiretype(),Value}, Acc) and returns a new Acc.

Encoding

protocol_buffers:encode(Field, Type, Value)
Field is the field number.
Type is one of bool | int32 | int64 | uint32 | uint64 | sint32 | sint64 | fixed32 | fixed64 | sfixed32 | sfixed64 | bytes | string | float | double.
Value is an appropriate erlang type for Type.

Note that any type but bytes or string can be a list, which will encode the type as a packed repeated value.

Features

• All types.
• Packed formats.
• Capacity to merge records (output of one encode as the Acc of the next and binary concatenation have same effect).
• Zig-zag encoding of sint.
• Nested binaries.
• DOES NOT SUPPORT GROUPS. It is deprecated, anyway.