For unmarshalling, a simple heuristic is used on length-delimited segments: first interpret it as a message; if that fails, try to interpret as a UTF8 string; otherwise, leave it as a "blob" (if the heuristic was wrong, you can convert to a string or a blob by using protobuf_segment_convert/2). 32-bit and 64-bit numbers are left as codes because they could be either integers or floating point (use int32_codes_when/2, float32_codes_when/2, int64_codes_when/2, uint32_codes_when/2, uint64_codes_when/2, float64_codes_when/2 as appropriate); variable-length numbers ("varint" in the Protocol Buffers encoding documentation), might require "zigzag" conversion, int64_zigzag_when/2.

For marshalling, use the predicates int32_codes_when/2, float32_codes_when/2, int64_codes_when/2, uint32_codes_when/2, uint64_codes_when/2, float64_codes_when/2, int64_zigzag_when/2 to put integer and floating point values into the appropriate form.

Arguments:

Segments

- a list containing terms of the following form (Tag is the field number; Codes is a list of integers): varint(Tag,Varint) - Varint may need int64_zigzag_when/2 fixed64(Tag,Int) - Int signed, derived from the 8 codes fixed32(Tag,Codes) - Int is signed, derived from the 4 codes message(Tag,Segments) group(Tag,Segments) string(Tag,String) - String is a SWI-Prolog string packed(Tag,Type(Scalars)) - Type is one of varint, fixed64, fixed32; Scalars is a list of Varint or Codes, which should be interpreted as described under those items. Note that the protobuf specification does not allow packed repeated string. length_delimited(Tag,Codes) repeated(List) - List of segments Of these, group is deprecated in the protobuf documentation and shouldn't appear in modern code, having been superseded by nested message types. For deciding how to interpret a length-delimited item (when Segments is a variable), an attempt is made to parse the item in the following order (although code should not rely on this order): message string (it must be in the form of a UTF string) packed (which can backtrack through the various Types) length_delimited - which always is possible. The interpretation of length-delimited items can sometimes guess wrong; the interpretation can be undone by either backtracking or by using protobuf_segment_convert/2 to convert the incorrect segment to a string or a list of codes. Backtracking through all the possibilities is not recommended, because of combinatoric explosion (there is an example in the unit tests); instead, it is suggested that you take the first result and iterate through its items, calling protobuf_segment_convert/2 as needed to reinterpret incorrectly guessed segments.

WireStream

- a code list that was generated by a protobuf endoder.

See also

- https://developers.google.com/protocol-buffers/docs/encoding

bug

- This predicate is preliminary and may change as additional functionality is added.