facet-postcard

facet-postcard

Postcard binary format for facet with Tier-0 and Tier-2 JIT deserialization support.

Wire Compatibility

For statically-typed structs, enums, and primitives, facet-postcard produces wire-compatible output with the standard postcard crate. You can serialize with facet-postcard and deserialize with serde's postcard (and vice versa), as long as both sides agree on the schema.

Dynamic Values (facet_value::Value)

Warning: Value serialization uses a facet-specific tagged encoding that is NOT compatible with standard postcard.

Since postcard is not a self-describing format, there's no standard way to serialize dynamic/any values. facet-postcard solves this by prefixing each Value with a type tag byte:

This means:

• You cannot deserialize facet-postcard Value bytes using serde's postcard
• You cannot serialize with serde's postcard and deserialize as Value with facet-postcard
• Both sides of an RPC/serialization boundary must use facet-postcard when Value is involved

Example wire format for {"name": "Alice", "age": 30}:

08                      # tag 8 = Object
02                      # 2 entries
04 6e 61 6d 65          # key: string "name" (len=4)
05                      # tag 5 = String
05 41 6c 69 63 65       # value: string "Alice" (len=5)
03 61 67 65             # key: string "age" (len=3)
03                      # tag 3 = U64
1e                      # value: varint 30

Sponsors

Thanks to all individual sponsors:

...along with corporate sponsors:

...without whom this work could not exist.

Special thanks

The facet logo was drawn by Misiasart.

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.