Otel.Baggage.Percent (otel v0.4.1)

W3C Baggage percent-encoding codec (W3C Baggage spec §value L64-L69, §property L82-L100).

Percent-encodes / decodes UTF-8 strings for use in the W3C Baggage wire format. Values outside the baggage-octet character range (defined in §Definition) must be percent-encoded:

baggage-octet = %x21 / %x23-2B / %x2D-3A /
                %x3C-5B / %x5D-7E

On decode, percent-encoded octet sequences that do not form valid UTF-8 are replaced with the Unicode replacement character U+FFFD, per §L69 MUST:

"When decoding the value, percent-encoded octet sequences that do not match the UTF-8 encoding scheme MUST be replaced with the replacement code point (U+FFFD)."

Replacement is performed one invalid byte at a time — offending bytes are replaced without dropping the rest of the string, so a single malformed value does not discard the whole baggage list.

Callers

Otel.Propagator.TextMap.Baggage — HTTP baggage: header value/property encoding

Public API

Function	Role
`encode/1`	Application (W3C header serialization) — percent-encode a UTF-8 value
`decode/1`	Application (W3C header parsing) — percent-decode with `U+FFFD` replacement

References

W3C Baggage §value: w3c-baggage/baggage/HTTP_HEADER_FORMAT.md L61-L80
W3C Baggage §property: w3c-baggage/baggage/HTTP_HEADER_FORMAT.md L82-L100
RFC 3986 §2.1 Percent-Encoding: https://datatracker.ietf.org/doc/html/rfc3986#section-2.1

Summary

Functions

decode(encoded)

Application (W3C header parsing) — percent-decodes a string per W3C Baggage §value L69.

encode(value)

Application (W3C header serialization) — percent-encodes a UTF-8 string per W3C Baggage §value L64-L68.

Functions

decode(encoded)

@spec decode(encoded :: String.t()) :: String.t()

Application (W3C header parsing) — percent-decodes a string per W3C Baggage §value L69.

Decodes RFC 3986 Section 2.1 percent sequences. Any decoded octet sequence that is not valid UTF-8 is replaced with U+FFFD per §L69 MUST — offending bytes only, preserving the rest of the string.

encode(value)

@spec encode(value :: String.t()) :: String.t()

Application (W3C header serialization) — percent-encodes a UTF-8 string per W3C Baggage §value L64-L68.

Emits RFC 3986 Section 2.1 percent-encoding over the URI.char_unreserved?/1 predicate. The unreserved set (A-Z / a-z / 0-9 / - . _ ~) is a strict subset of baggage-octet, so we percent-encode more conservatively than the spec MUSTs. W3C §L66 explicitly permits this:

"Code points which are not required to be percent-encoded MAY be percent-encoded."

Space (0x20) encodes as %20, matching the baggage- octet encoding of whitespace. The percent character 0x25 itself is also encoded per §L65 MUST.