draft-ietf-httpbis-header-structure-13.txt   draft-ietf-httpbis-header-structure-14.txt 
HTTP M. Nottingham HTTP M. Nottingham
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track P-H. Kamp Intended status: Standards Track P-H. Kamp
Expires: February 25, 2020 The Varnish Cache Project Expires: May 2, 2020 The Varnish Cache Project
August 24, 2019 October 30, 2019
Structured Headers for HTTP Structured Headers for HTTP
draft-ietf-httpbis-header-structure-13 draft-ietf-httpbis-header-structure-14
Abstract Abstract
This document describes a set of data types and associated algorithms This document describes a set of data types and associated algorithms
that are intended to make it easier and safer to define and handle that are intended to make it easier and safer to define and handle
HTTP header fields. It is intended for use by specifications of new HTTP header fields. It is intended for use by specifications of new
HTTP header fields that wish to use a common syntax that is more HTTP header fields that wish to use a common syntax that is more
restrictive than traditional HTTP field values. restrictive than traditional HTTP field values.
Note to Readers Note to Readers
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 25, 2020. This Internet-Draft will expire on May 2, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Intentionally Strict Processing . . . . . . . . . . . . . 4 1.1. Intentionally Strict Processing . . . . . . . . . . . . . 4
1.2. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.2. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Defining New Structured Headers . . . . . . . . . . . . . . . 5 2. Defining New Structured Headers . . . . . . . . . . . . . . . 5
3. Structured Header Data Types . . . . . . . . . . . . . . . . 6 3. Structured Data Types . . . . . . . . . . . . . . . . . . . . 7
3.1. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 8 3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.4. Integers . . . . . . . . . . . . . . . . . . . . . . . . 9 4. Working With Structured Headers in HTTP Headers . . . . . . . 13
3.5. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1. Serializing Structured Headers . . . . . . . . . . . . . 13
3.6. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.2. Parsing Header Fields into Structured Headers . . . . . . 20
3.7. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
3.8. Byte Sequences . . . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 30
3.9. Booleans . . . . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
4. Working With Structured Headers in Textual HTTP Headers . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . 30
4.1. Serializing Structured Headers . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . 31
4.2. Parsing Header Fields into Structured Headers . . . . . . 18 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 32
6. Security Considerations . . . . . . . . . . . . . . . . . . . 27 Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 32
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 32
7.1. Normative References . . . . . . . . . . . . . . . . . . 27 B.2. Structured Headers don't "fit" my data. . . . . . . . . . 33
7.2. Informative References . . . . . . . . . . . . . . . . . 28 Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 33
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 34
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 29 D.1. Since draft-ietf-httpbis-header-structure-13 . . . . . . 34
Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 29 D.2. Since draft-ietf-httpbis-header-structure-12 . . . . . . 34
B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 29 D.3. Since draft-ietf-httpbis-header-structure-11 . . . . . . 34
B.2. Structured Headers don't "fit" my data. . . . . . . . . . 30 D.4. Since draft-ietf-httpbis-header-structure-10 . . . . . . 34
Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 31 D.5. Since draft-ietf-httpbis-header-structure-09 . . . . . . 35
Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 31 D.6. Since draft-ietf-httpbis-header-structure-08 . . . . . . 35
D.1. Since draft-ietf-httpbis-header-structure-12 . . . . . . 31 D.7. Since draft-ietf-httpbis-header-structure-07 . . . . . . 35
D.2. Since draft-ietf-httpbis-header-structure-11 . . . . . . 31 D.8. Since draft-ietf-httpbis-header-structure-06 . . . . . . 36
D.3. Since draft-ietf-httpbis-header-structure-10 . . . . . . 31 D.9. Since draft-ietf-httpbis-header-structure-05 . . . . . . 36
D.4. Since draft-ietf-httpbis-header-structure-09 . . . . . . 32 D.10. Since draft-ietf-httpbis-header-structure-04 . . . . . . 36
D.5. Since draft-ietf-httpbis-header-structure-08 . . . . . . 32 D.11. Since draft-ietf-httpbis-header-structure-03 . . . . . . 36
D.6. Since draft-ietf-httpbis-header-structure-07 . . . . . . 33 D.12. Since draft-ietf-httpbis-header-structure-02 . . . . . . 36
D.7. Since draft-ietf-httpbis-header-structure-06 . . . . . . 33 D.13. Since draft-ietf-httpbis-header-structure-01 . . . . . . 37
D.8. Since draft-ietf-httpbis-header-structure-05 . . . . . . 33 D.14. Since draft-ietf-httpbis-header-structure-00 . . . . . . 37
D.9. Since draft-ietf-httpbis-header-structure-04 . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
D.10. Since draft-ietf-httpbis-header-structure-03 . . . . . . 34
D.11. Since draft-ietf-httpbis-header-structure-02 . . . . . . 34
D.12. Since draft-ietf-httpbis-header-structure-01 . . . . . . 34
D.13. Since draft-ietf-httpbis-header-structure-00 . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction 1. Introduction
Specifying the syntax of new HTTP header fields is an onerous task; Specifying the syntax of new HTTP header fields is an onerous task;
even with the guidance in Section 8.3.1 of [RFC7231], there are many even with the guidance in Section 8.3.1 of [RFC7231], there are many
decisions - and pitfalls - for a prospective HTTP header field decisions - and pitfalls - for a prospective HTTP header field
author. author.
Once a header field is defined, bespoke parsers and serializers often Once a header field is defined, bespoke parsers and serializers often
need to be written, because each header has slightly different need to be written, because each header has slightly different
handling of what looks like common syntax. handling of what looks like common syntax.
This document introduces a set of common data structures for use in This document introduces a set of common data structures for use in
definitions of new HTTP header field values to address these definitions of new HTTP header field values to address these
problems. In particular, it defines a generic, abstract model for problems. In particular, it defines a generic, abstract model for
header field values, along with a concrete serialisation for header field values, along with a concrete serialisation for
expressing that model in textual HTTP [RFC7230] header fields. expressing that model in HTTP [RFC7230] header fields.
HTTP headers that are defined as "Structured Headers" use the types HTTP headers that are defined as "Structured Headers" use the types
defined in this specification to define their syntax and basic defined in this specification to define their syntax and basic
handling rules, thereby simplifying both their definition by handling rules, thereby simplifying both their definition by
specification writers and handling by implementations. specification writers and handling by implementations.
Additionally, future versions of HTTP can define alternative Additionally, future versions of HTTP can define alternative
serialisations of the abstract model of these structures, allowing serialisations of the abstract model of these structures, allowing
headers that use it to be transmitted more efficiently without being headers that use it to be transmitted more efficiently without being
redefined. redefined.
Note that it is not a goal of this document to redefine the syntax of Note that it is not a goal of this document to redefine the syntax of
existing HTTP headers; the mechanisms described herein are only existing HTTP headers; the mechanisms described herein are only
intended to be used with headers that explicitly opt into them. intended to be used with headers that explicitly opt into them.
Section 2 describes how to specify a Structured Header. Section 2 describes how to specify a Structured Header.
Section 3 defines a number of abstract data types that can be used in Section 3 defines a number of abstract data types that can be used in
Structured Headers. Those abstract types can be serialized into and Structured Headers. Those abstract types can be serialized into and
parsed from textual HTTP headers using the algorithms described in parsed from HTTP headers using the algorithms described in Section 4.
Section 4.
1.1. Intentionally Strict Processing 1.1. Intentionally Strict Processing
This specification intentionally defines strict parsing and This specification intentionally defines strict parsing and
serialisation behaviours using step-by-step algorithms; the only serialisation behaviours using step-by-step algorithms; the only
error handling defined is to fail the operation altogether. error handling defined is to fail the operation altogether.
It is designed to encourage faithful implementation and therefore It is designed to encourage faithful implementation and therefore
good interoperability. Therefore, an implementation that tried to be good interoperability. Therefore, an implementation that tried to be
"helpful" by being more tolerant of input would make interoperability "helpful" by being more tolerant of input would make interoperability
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1.2. Notational Conventions 1.2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This document uses algorithms to specify parsing and serialisation This document uses algorithms to specify parsing and serialisation
behaviours, and the Augmented Backus-Naur Form (ABNF) notation of behaviours, and the Augmented Backus-Naur Form (ABNF) notation of
[RFC5234] to illustrate expected syntax in textual HTTP header [RFC5234] to illustrate expected syntax in HTTP header fields. In
fields. In doing so, uses the VCHAR, SP, DIGIT, ALPHA and DQUOTE doing so, uses the VCHAR, SP, DIGIT, ALPHA and DQUOTE rules from
rules from [RFC5234]. It also includes the OWS rule from [RFC7230]. [RFC5234]. It also includes the OWS and tchar rules from [RFC7230].
When parsing from textual HTTP header fields, implementations MUST When parsing from HTTP header fields, implementations MUST follow the
follow the algorithms, but MAY vary in implementation so as the algorithms, but MAY vary in implementation so as the behaviours are
behaviours are indistinguishable from specified behaviour. If there indistinguishable from specified behaviour. If there is disagreement
is disagreement between the parsing algorithms and ABNF, the between the parsing algorithms and ABNF, the specified algorithms
specified algorithms take precedence. In some places, the algorithms take precedence. In some places, the algorithms are "greedy" with
are "greedy" with whitespace, but this should not affect conformance. whitespace, but this should not affect conformance.
For serialisation to textual header fields, the ABNF illustrates the For serialisation to header fields, the ABNF illustrates the range of
range of acceptable wire representations with as much fidelity as acceptable wire representations with as much fidelity as possible,
possible, and the algorithms define the recommended way to produce and the algorithms define the recommended way to produce them.
them. Implementations MAY vary from the specified behaviour so long Implementations MAY vary from the specified behaviour so long as the
as the output still matches the ABNF. output still matches the ABNF.
2. Defining New Structured Headers 2. Defining New Structured Headers
To define a HTTP header as a structured header, its specification To specify a HTTP header as a structured header, its authors needs
needs to: to:
o Reference this specification. Recipients and generators of the o Reference this specification. Recipients and generators of the
header need to know that the requirements of this document are in header need to know that the requirements of this document are in
effect. effect.
o Specify the header field's allowed syntax for values, in terms of o Specify the type of the header field itself; either Dictionary
the types described in Section 3, along with their associated (Section 3.2), List (Section 3.1), or Item (Section 3.3).
semantics. Syntax definitions are encouraged to use the ABNF
rules beginning with "sh-" defined in this specification; other
rules in this specification are not intended for use outside it.
o Specify any additional constraints upon the syntax of the o Define the semantics of those structures.
structures used, as well as the consequences when those
constraints are violated. When Structured Headers parsing fails, o Specify any additional constraints upon the structures used, as
the header is ignored (see Section 4.2); in most situations, well as the consequences when those constraints are violated.
header-specific constraints should do likewise.
Typically, this means that a header definition will specify the top-
level type - Dictionary, List or Item - and then define its allowable
types, and constraints upon them. For example, a header defined as a
List might have all Integer members, or a mix of types; a header
defined as an Item might allow only Strings, and additionally only
strings beginning with the letter "Q".
When Structured Headers parsing fails, the header is ignored (see
Section 4.2); in most situations, violating header-specific
constraints should have the same effect. Thus, if a header is
defined as an Item and required to be an Integer, but a String is
received, it will by default be ignored. If the header requires
different error handling, this should be explicitly specified.
However, both Items and Inner Lists allow parameters as an
extensibility mechanism; this means that values can later be extended
to accommodate more information, if need be. As a result, header
specifications are discouraged from defining the presence of an
unrecognised parameter as an error condition.
Conversely, inner lists are only valid when a header definition
explicitly allows them.
Note that a header field definition cannot relax the requirements of Note that a header field definition cannot relax the requirements of
this specification because doing so would preclude handling by this specification because doing so would preclude handling by
generic software; they can only add additional constraints (for generic software; they can only add additional constraints (for
example, on the numeric range of integers and floats, the format of example, on the numeric range of integers and floats, the format of
strings and tokens, the types allowed in a dictionary's values, or strings and tokens, the types allowed in a dictionary's values, or
the number of items in a list). Likewise, header field definitions the number of items in a list). Likewise, header field definitions
can only use Structured Headers for the entire header field value, can only use Structured Headers for the entire header field value,
not a portion thereof. not a portion thereof.
This specification defines minimums for the length or number of This specification defines minimums for the length or number of
various structures supported by Structured Headers implementations. various structures supported by Structured Headers implementations.
It does not specify maximum sizes in most cases, but header authors It does not specify maximum sizes in most cases, but header authors
should be aware that HTTP implementations do impose various limits on should be aware that HTTP implementations do impose various limits on
the size of individual header fields, the total number of fields, the size of individual header fields, the total number of fields,
and/or the size of the entire header block. and/or the size of the entire header block.
Specifications can refer to a Structured Header's field-name as a
"structured header name" and its field-value as a "structured header
value" as necessary. Header definitions are encouraged to use the
ABNF rules beginning with "sh-" defined in this specification; other
rules in this specification are not intended for their use.
For example, a fictitious Foo-Example header field might be specified For example, a fictitious Foo-Example header field might be specified
as: as:
42. Foo-Example Header 42. Foo-Example Header
The Foo-Example HTTP header field conveys information about how The Foo-Example HTTP header field conveys information about how
much Foo the message has. much Foo the message has.
Foo-Example is a Structured Header [RFCxxxx]. Its value MUST be a Foo-Example is a Item Structured Header [RFCxxxx]. Its value MUST be
dictionary (Section Y.Y of [RFCxxxx]). Its ABNF is: an Integer (Section Y.Y of [RFCxxxx]). Its ABNF is:
Foo-Example = sh-dictionary Foo-Example = sh-integer
The dictionary MUST contain: Its value indicates the amount of Foo in the message, and MUST
be between 0 and 10, inclusive; other values MUST cause
the entire header to be ignored.
* Exactly one member whose name is "foo", and whose value is an The following parameters are defined:
integer (Section Y.Y of [RFCxxxx]), indicating the number of foos * A parameter whose name is "fooUrl", and whose value is a string
in the message. (Section Y.Y of [RFCxxxx]), conveying the Foo URLs
* Exactly one member whose name is "barUrl", and whose value is a
list of strings (Section Y.Y of [RFCxxxx]), conveying the Bar URLs
for the message. See below for processing requirements. for the message. See below for processing requirements.
If the parsed header field does not contain both, it MUST be "fooUrl" contains a URI-reference (Section 4.1 of
ignored. [RFC3986], Section 4.1). If its value is not a valid URI-reference,
that URL MUST be ignored. If its value is a relative reference
"foo" MUST be between 0 and 10, inclusive; other values MUST cause (Section 4.2 of [RFC3986]), it MUST be resolved (Section 5 of
the header to be ignored. [RFC3986]) before being used.
"barUrl" contains one or more URI-references (Section 4.1 of
[RFC3986], Section 4.1). If barURL is not a valid URI-reference,
it MUST be ignored. If barURL is a relative reference (Section 4.2
of [RFC3986]), it MUST be resolved (Section 5 of [RFC3986]) before
being used.
For example: For example:
Foo-Example: foo=2, barUrl=("https://bar.example.com/") Foo-Example: 2; fooUrl="https://foo.example.com/"
3. Structured Header Data Types 3. Structured Data Types
This section defines the abstract value types that can be composed This section defines the abstract value types that can be composed
into Structured Headers. The ABNF provided represents the on-wire into Structured Headers. The ABNF provided represents the on-wire
format in textual HTTP headers. format in HTTP headers.
In summary:
o There are three top-level types that a HTTP header can be defined
as; Lists, Dictionaries, and Items.
o Lists and Dictionaries are containers; their members can be Items
or Inner Lists (which are themselves lists of items).
o Both Items and Inner Lists can be parameterised with key/value
pairs.
3.1. Lists 3.1. Lists
Lists are arrays of zero or more members, each of which can be an Lists are arrays of zero or more members, each of which can be an
item (Section 3.3) or an inner list (an array of zero or more items). item (Section 3.3) or an inner list (Section 3.1.1), both of which
can be parameterised (Section 3.1.2).
Each member of the top-level list can also have associated parameters
- an ordered map of key-value pairs where the keys are short, textual
strings and the values are items (Section 3.3). There can be zero or
more parameters on a member, and their keys are required to be unique
within that scope.
The ABNF for lists is: The ABNF for lists in HTTP headers is:
sh-list = list-member *( OWS "," OWS list-member ) sh-list = list-member *( OWS "," OWS list-member )
list-member = ( sh-item / inner-list ) *parameter list-member = sh-item / inner-list
inner-list = "(" OWS [ sh-item *( SP sh-item ) OWS ] ")"
parameter = OWS ";" OWS param-name [ "=" param-value ]
param-name = key
key = lcalpha *( lcalpha / DIGIT / "_" / "-" / "*" )
lcalpha = %x61-7A ; a-z
param-value = sh-item
In textual HTTP headers, each member is separated by a comma and In HTTP headers, each member is separated by a comma and optional
optional whitespace. For example, a header field whose value is whitespace. For example, a header field whose value is defined as a
defined as a list of strings could look like: list of strings could look like:
Example-StrListHeader: "foo", "bar", "It was the best of times." Example-StrListHeader: "foo", "bar", "It was the best of times."
In textual HTTP headers, inner lists are denoted by surrounding In HTTP headers, an empty list is denoted by not serialising the
parenthesis, and have their values delimited by a single space. A header at all.
header field whose value is defined as a list of lists of strings
could look like: Parsers MUST support lists containing at least 1024 members. Header
specifications can constrain the types and cardinality of individual
list values as they require.
3.1.1. Inner Lists
An inner list is an array of zero or more items (Section 3.3). Both
the individual items and the inner-list itself can be parameterised
(Section 3.1.2).
The ABNF for inner-lists in HTTP headers is:
inner-list = "(" OWS [ sh-item *( SP OWS sh-item ) OWS ] ")"
*parameter
In HTTP headers, inner lists are denoted by surrounding parenthesis,
and have their values delimited by a single space. A header field
whose value is defined as a list of inner-lists of strings could look
like:
Example-StrListListHeader: ("foo" "bar"), ("baz"), ("bat" "one"), () Example-StrListListHeader: ("foo" "bar"), ("baz"), ("bat" "one"), ()
Note that the last member in this example is an empty inner list. Note that the last member in this example is an empty inner list.
In textual HTTP headers, members' parameters are separated from the A header field whose value is defined as a list of inner-lists with
member and each other by semicolons. For example: parameters at both levels could look like:
Example-ParamListHeader: abc;a=1;b=2; cde_456, (ghi jkl);q="9";r=w Example-ListListParam: ("foo"; a=1;b=2);lvl=5, ("bar", "baz");lvl=1
Parsers MUST support inner-lists containing at least 256 members.
Header specifications can constrain the types and cardinality of
individual inner-list members as they require.
In textual HTTP headers, an empty list is denoted by not serialising 3.1.2. Parameters
the header at all.
Parsers MUST support lists containing at least 1024 members, support Parameters are an ordered map of key-values pairs that are associated
members with at least 256 parameters, support inner-lists containing with an item (Section 3.3) or inner-list (Section 3.1.1). The keys
at least 256 members, and support parameter keys with at least 64 are required to be unique within the scope of a map of parameters,
characters. and the values are bare items (i.e., they themselves cannot be
parameterised; see Section 3.3).
Header specifications can constrain the types of individual list The ABNF for parameters in HTTP headers is:
values (including that of individual inner-list members and
parameters) if necessary. parameter = ";" OWS param-name [ "=" param-value ]
param-name = key
key = lcalpha *( lcalpha / DIGIT / "_" / "-" / "*" )
lcalpha = %x61-7A ; a-z
param-value = bare-item
In HTTP headers, parameters are separated from their item or inner-
list and each other by semicolons. For example:
Example-ParamListHeader: abc;a=1;b=2; cde_456, (ghi;jk=4 l);q="9";r=w
Parsers MUST support at least 256 parameters on an item or inner-
list, and support parameter keys with at least 64 characters. Header
specifications can constrain the types and cardinality of individual
parameter names and values as they require.
3.2. Dictionaries 3.2. Dictionaries
Dictionaries are ordered maps of name-value pairs, where the names Dictionaries are ordered maps of name-value pairs, where the names
are short, textual strings and the values are items (Section 3.3) or are short, textual strings and the values are items (Section 3.3) or
arrays of items. There can be zero or more members, and their names arrays of items, both of which can be parameterised (Section 3.1.2).
are required to be unique within the scope of the dictionary they There can be zero or more members, and their names are required to be
occur within. unique within the scope of the dictionary they occur within.
Each member of the dictionary can also have associated parameters -
an ordered map of key-value pairs where the keys are short, textual
strings and the values are items (Section 3.3). There can be zero or
more parameters on a member, and their keys are required to be unique
within that scope.
Implementations MUST provide access to dictionaries both by index and Implementations MUST provide access to dictionaries both by index and
by name. Specifications MAY use either means of accessing the by name. Specifications MAY use either means of accessing the
members. members.
The ABNF for dictionaries in textual HTTP headers is: The ABNF for dictionaries in HTTP headers is:
sh-dictionary = dict-member *( OWS "," OWS dict-member ) sh-dictionary = dict-member *( OWS "," OWS dict-member )
dict-member = member-name "=" member-value *parameter dict-member = member-name "=" member-value
member-name = key member-name = key
member-value = sh-item / inner-list member-value = sh-item / inner-list
In HTTP headers, members are separated by a comma with optional
In textual HTTP headers, members are separated by a comma with whitespace, while names and values are separated by "=" (without
optional whitespace, while names and values are separated by "=" whitespace). For example:
(without whitespace). For example:
Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGU=* Example-DictHeader: en="Applepie", da=*w4ZibGV0w6ZydGU=*
A dictionary with a member whose value is an inner-list of tokens: A dictionary with a member whose value is an inner-list of tokens:
Example-DictListHeader: rating=1.5, feelings=(joy sadness) Example-DictListHeader: rating=1.5, feelings=(joy sadness)
A dictionary with a mix of singular and list values, some with A dictionary with a mix of singular and list values, some with
parameters: parameters:
Example-MixDict: a=(1,2), b=3, c=4;aa=bb, d=(5,6);valid=?T Example-MixDict: a=(1 2), b=3, c=4;aa=bb, d=(5 6);valid=?1
As with lists, an empty dictionary is represented in textual HTTP
headers by omitting the entire header field.
Typically, a header field specification will define the semantics As with lists, an empty dictionary is represented in HTTP headers by
using individual member names, as well as whether their presence is omitting the entire header field.
required or optional. Recipients MUST ignore names that are
undefined or unknown, unless the header field's specification Typically, a header field specification will define the semantics of
specifically disallows them. dictionaries by specifying the allowed type(s) for individual member
names, as well as whether their presence is required or optional.
Recipients MUST ignore names that are undefined or unknown, unless
the header field's specification specifically disallows them.
Parsers MUST support dictionaries containing at least 1024 name/value Parsers MUST support dictionaries containing at least 1024 name/value
pairs, and names with at least 64 characters. pairs, and names with at least 64 characters.
3.3. Items 3.3. Items
An item is can be a integer (Section 3.4), float (Section 3.5), An item is can be a integer (Section 3.3.1), float (Section 3.3.2),
string (Section 3.6), token (Section 3.7), byte sequence string (Section 3.3.3), token (Section 3.3.4), byte sequence
(Section 3.8), or Boolean (Section 3.9). (Section 3.3.5), or Boolean (Section 3.3.6). It can have associated
parameters (Section 3.1.2).
The ABNF for items in textual HTTP headers is: The ABNF for items in HTTP headers is:
sh-item = sh-integer / sh-float / sh-string / sh-token / sh-binary sh-item = bare-item *parameter
/ sh-boolean bare-item = sh-integer / sh-float / sh-string / sh-token / sh-binary
/ sh-boolean
3.4. Integers For example, a header field that is defined to be an Item that is an
integer might look like:
Example-IntItemHeader: 5
or with parameters:
Example-IntItemHeader: 5; foo=bar
3.3.1. Integers
Integers have a range of -999,999,999,999,999 to 999,999,999,999,999 Integers have a range of -999,999,999,999,999 to 999,999,999,999,999
inclusive (i.e., up to fifteen digits, signed), for IEEE 754 inclusive (i.e., up to fifteen digits, signed), for IEEE 754
compatibility ([IEEE754]). compatibility ([IEEE754]).
The ABNF for integers in textual HTTP headers is: The ABNF for integers in HTTP headers is:
sh-integer = ["-"] 1*15DIGIT sh-integer = ["-"] 1*15DIGIT
For example: For example:
Example-IntegerHeader: 42 Example-IntegerHeader: 42
Note that commas in integers are used in this section's prose only Note that commas in integers are used in this section's prose only
for readability; they are not valid in the wire format. for readability; they are not valid in the wire format.
3.5. Floats 3.3.2. Floats
Floats are decimal numbers with an integer and a fractional Floats are decimal numbers with an integer and a fractional
component. The fractional component has at most six digits of component. The fractional component has at most six digits of
precision. Additionally, like integers, it can have no more than precision. Additionally, like integers, it can have no more than
fifteen digits in total, which in some cases further constrains its fifteen digits in total, which in some cases further constrains its
precision. precision.
The ABNF for floats in textual HTTP headers is: The ABNF for floats in HTTP headers is:
sh-float = ["-"] (1*9DIGIT "." 1*6DIGIT / sh-float = ["-"] (1*9DIGIT "." 1*6DIGIT /
10DIGIT "." 1*5DIGIT / 10DIGIT "." 1*5DIGIT /
11DIGIT "." 1*4DIGIT / 11DIGIT "." 1*4DIGIT /
12DIGIT "." 1*3DIGIT / 12DIGIT "." 1*3DIGIT /
13DIGIT "." 1*2DIGIT / 13DIGIT "." 1*2DIGIT /
14DIGIT "." 1DIGIT ) 14DIGIT "." 1DIGIT )
For example, a header whose value is defined as a float could look For example, a header whose value is defined as a float could look
like: like:
Example-FloatHeader: 4.5 Example-FloatHeader: 4.5
3.6. Strings 3.3.3. Strings
Strings are zero or more printable ASCII [RFC0020] characters (i.e., Strings are zero or more printable ASCII [RFC0020] characters (i.e.,
the range 0x20 to 0x7E). Note that this excludes tabs, newlines, the range %x20 to %x7E). Note that this excludes tabs, newlines,
carriage returns, etc. carriage returns, etc.
The ABNF for strings in textual HTTP headers is: The ABNF for strings in HTTP headers is:
sh-string = DQUOTE *(chr) DQUOTE sh-string = DQUOTE *(chr) DQUOTE
chr = unescaped / escaped chr = unescaped / escaped
unescaped = %x20-21 / %x23-5B / %x5D-7E unescaped = %x20-21 / %x23-5B / %x5D-7E
escaped = "\" ( DQUOTE / "\" ) escaped = "\" ( DQUOTE / "\" )
In textual HTTP headers, strings are delimited with double quotes, In HTTP headers, strings are delimited with double quotes, using a
using a backslash ("\") to escape double quotes and backslashes. For backslash ("\") to escape double quotes and backslashes. For
example: example:
Example-StringHeader: "hello world" Example-StringHeader: "hello world"
Note that strings only use DQUOTE as a delimiter; single quotes do Note that strings only use DQUOTE as a delimiter; single quotes do
not delimit strings. Furthermore, only DQUOTE and "\" can be not delimit strings. Furthermore, only DQUOTE and "\" can be
escaped; other sequences MUST cause parsing to fail. escaped; other characters after "\" MUST cause parsing to fail.
Unicode is not directly supported in this document, because it causes Unicode is not directly supported in strings, because it causes a
a number of interoperability issues, and - with few exceptions - number of interoperability issues, and - with few exceptions - header
header values do not require it. values do not require it.
When it is necessary for a field value to convey non-ASCII string When it is necessary for a field value to convey non-ASCII content, a
content, a byte sequence (Section 3.8) SHOULD be specified, along byte sequence (Section 3.3.5) SHOULD be specified, along with a
with a character encoding (preferably UTF-8). character encoding (preferably [UTF-8]).
Parsers MUST support strings with at least 1024 characters. Parsers MUST support strings with at least 1024 characters.
3.7. Tokens 3.3.4. Tokens
Tokens are short textual words; their abstract model is identical to Tokens are short textual words; their abstract model is identical to
their expression in the textual HTTP serialisation. their expression in the HTTP header serialisation.
The ABNF for tokens in textual HTTP headers is: The ABNF for tokens in HTTP headers is:
sh-token = ALPHA sh-token = ALPHA *( tchar / ":" / "/" )
*( ALPHA / DIGIT / "_" / "-" / "." / ":" / "%"
/ "*" / "/" )
Parsers MUST support tokens with at least 512 characters. Parsers MUST support tokens with at least 512 characters.
Note that a Structured Header token is not the same as the "token" Note that a Structured Header token allows the characters as the
ABNF rule defined in [RFC7230]. "token" ABNF rule defined in [RFC7230], with the exceptions that the
first character is required to be ALPHA, and ":" and "/" are also
allowed.
3.8. Byte Sequences 3.3.5. Byte Sequences
Byte sequences can be conveyed in Structured Headers. Byte sequences can be conveyed in Structured Headers.
The ABNF for a byte sequence in textual HTTP headers is: The ABNF for a byte sequence in HTTP headers is:
sh-binary = "*" *(base64) "*" sh-binary = "*" *(base64) "*"
base64 = ALPHA / DIGIT / "+" / "/" / "=" base64 = ALPHA / DIGIT / "+" / "/" / "="
In textual HTTP headers, a byte sequence is delimited with asterisks In HTTP headers, a byte sequence is delimited with asterisks and
and encoded using base64 ([RFC4648], Section 4). For example: encoded using base64 ([RFC4648], Section 4). For example:
Example-BinaryHdr: *cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==* Example-BinaryHdr: *cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==*
Parsers MUST support byte sequences with at least 16384 octets after Parsers MUST support byte sequences with at least 16384 octets after
decoding. decoding.
3.9. Booleans 3.3.6. Booleans
Boolean values can be conveyed in Structured Headers. Boolean values can be conveyed in Structured Headers.
The ABNF for a Boolean in textual HTTP headers is: The ABNF for a Boolean in HTTP headers is:
sh-boolean = "?" boolean sh-boolean = "?" boolean
boolean = "0" / "1" boolean = "0" / "1"
In textual HTTP headers, a boolean is indicated with a leading "?" In HTTP headers, a boolean is indicated with a leading "?" character
character. For example: followed by a "1" for a true value or "0" for false. For example:
Example-BoolHdr: ?1 Example-BoolHdr: ?1
4. Working With Structured Headers in Textual HTTP Headers 4. Working With Structured Headers in HTTP Headers
This section defines how to serialize and parse Structured Headers in This section defines how to serialize and parse Structured Headers in
textual header fields, and protocols compatible with them (e.g., in header fields, and protocols compatible with them (e.g., in HTTP/2
HTTP/2 [RFC7540] before HPACK [RFC7541] is applied). [RFC7540] before HPACK [RFC7541] is applied).
4.1. Serializing Structured Headers 4.1. Serializing Structured Headers
Given a structure defined in this specification, return an ASCII Given a structure defined in this specification, return an ASCII
string suitable for use in a textual HTTP header value. string suitable for use in a HTTP header value.
1. If the structure is a dictionary or list and its value is empty 1. If the structure is a dictionary or list and its value is empty
(i.e., it has no members), do not send the serialize field at all (i.e., it has no members), do not serialize the field at all
(i.e., omit both the field-name and field-value). (i.e., omit both the field-name and field-value).
2. If the structure is a dictionary, let output_string be the result 2. If the structure is a dictionary, let output_string be the result
of Serializing a Dictionary (Section 4.1.2). of running Serializing a Dictionary (Section 4.1.2) with the
structure.
3. Else if the structure is a list, let output_string be the result 3. Else if the structure is a list, let output_string be the result
of Serializing a List (Section 4.1.1). of running Serializing a List (Section 4.1.1) with the structure.
4. Else if the structure is an item, let output_string be the result 4. Else if the structure is an item, let output_string be the result
of Serializing an Item (Section 4.1.3). of running Serializing an Item (Section 4.1.3) with the
structure.
5. Else, fail serialisation. 5. Else, fail serialisation.
6. Return output_string converted into an array of bytes, using 6. Return output_string converted into an array of bytes, using
ASCII encoding [RFC0020]. ASCII encoding [RFC0020].
4.1.1. Serializing a List 4.1.1. Serializing a List
Given a list of (member-value, parameters) as input_list, return an Given an array of (member-value, parameters) tuples as input_list,
ASCII string suitable for use in a textual HTTP header value. return an ASCII string suitable for use in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each (member-value, parameters) of input_list: 2. For each (member-value, parameters) of input_list:
1. If member-value is an array, append the result of applying 1. If member-value is an array, append the result of running
Serialising an Inner List (Section 4.1.1.1) with member-value Serialising an Inner List (Section 4.1.1.1) with (member-
to output. value, parameters) to output.
2. Otherwise, append the result of applying Serializing an Item
(Section 4.1.3) with member-value to output.
3. Append the result of Serializing Parameters Section 4.1.1.2 2. Otherwise, append the result of running Serializing an Item
with parameters to output. (Section 4.1.3) with (member-value, parameters) to output.
4. If more member-values remain in input_plist: 3. If more member-values remain in input_list:
1. Append a COMMA to output. 1. Append a COMMA to output.
2. Append a single WS to output. 2. Append a single WS to output.
3. Return output. 3. Return output.
4.1.1.1. Serialising an Inner List 4.1.1.1. Serialising an Inner List
Given an array as inner_list, return an ASCII string suitable for use Given an array of (member-value, parameters) tuples as inner_list,
in a textual HTTP header value. and parameters as list_parameters, return an ASCII string suitable
for use in a HTTP header value.
1. Let output be the string "(". 1. Let output be the string "(".
2. For each member-value of inner_list: 2. For each (member-value, parameters) of inner_list:
1. Append the result of applying Serializing an Item 1. Append the result of running Serializing an Item
(Section 4.1.3) with member-value to output. (Section 4.1.3) with (member-value, parameters) to output.
2. If inner_list is not empty, append a single WS to output. 2. If more values remain in inner_list, append a single WS to
output.
3. Append ")" to output. 3. Append ")" to output.
4. Return output. 4. Append the result of running Serializing Parameters
Section 4.1.1.2 with list_parameters to output.
5. Return output.
4.1.1.2. Serializing Parameters 4.1.1.2. Serializing Parameters
Given an ordered dictionary as input_parameters (each member having a Given an ordered dictionary as input_parameters (each member having a
param-name and a param-value), return an ASCII string suitable for param-name and a param-value), return an ASCII string suitable for
use in a textual HTTP header value. use in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each parameter-name with a value of param-value in 2. For each parameter-name with a value of param-value in
input_parameters: input_parameters:
1. Append ";" to output. 1. Append ";" to output.
2. Append the result of applying Serializing a Key 2. Append the result of running Serializing a Key
(Section 4.1.1.3) with param-name to output. (Section 4.1.1.3) with param-name to output.
3. If param-value is not null: 3. If param-value is not null:
1. Append "=" to output. 1. Append "=" to output.
2. Append the result of applying Serializing an Item 2. Append the result of running Serializing a bare Item
(Section 4.1.3) with param-value to output. (Section 4.1.3.1) with param-value to output.
3. Return output. 3. Return output.
4.1.1.3. Serializing a Key 4.1.1.3. Serializing a Key
Given a key as input_key, return an ASCII string suitable for use in Given a key as input_key, return an ASCII string suitable for use in
a textual HTTP header value. a HTTP header value.
1. If input_key is not a sequence of characters, or contains 1. If input_key is not a sequence of characters, or contains
characters not in lcalpha, DIGIT, "*", "_", or "-", fail characters not in lcalpha, DIGIT, "*", "_", or "-", fail
serialisation. serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append input_key to output. 3. Append input_key to output.
4. Return output. 4. Return output.
4.1.2. Serializing a Dictionary 4.1.2. Serializing a Dictionary
Given an ordered dictionary as input_dictionary (each member having a Given an ordered dictionary as input_dictionary (each member having a
member-name and a tuple value of (member-value, parameters)), return member-name and a tuple value of (member-value, parameters)), return
an ASCII string suitable for use in a textual HTTP header value. an ASCII string suitable for use in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each member-name with a value of (member-value, parameters) 2. For each member-name with a value of (member-value, parameters)
in input_dictionary: in input_dictionary:
1. Append the result of applying Serializing a Key 1. Append the result of running Serializing a Key
(Section 4.1.1.3) with member's member-name to output. (Section 4.1.1.3) with member's member-name to output.
2. Append "=" to output. 2. Append "=" to output.
3. If member-value is an array, append the result of applying 3. If member-value is an array, append the result of running
Serialising an Inner List (Section 4.1.1.1) with member-value Serialising an Inner List (Section 4.1.1.1) with (member-
to output. value, parameters) to output.
4. Otherwise, append the result of applying Serializing an Item
(Section 4.1.3) with member-value to output.
5. Append the result of Serializing Parameters Section 4.1.1.2 4. Otherwise, append the result of running Serializing an Item
with parameters to output. (Section 4.1.3) with (member-value, parameters) to output.
6. If more members remain in input_dictionary: 5. If more members remain in input_dictionary:
1. Append a COMMA to output. 1. Append a COMMA to output.
2. Append a single WS to output. 2. Append a single WS to output.
3. Return output. 3. Return output.
4.1.3. Serializing an Item 4.1.3. Serializing an Item
Given an item bare_item and parameters item_parameters as input,
return an ASCII string suitable for use in a HTTP header value.
1. Let output be an empty string.
2. Append the result of running Serializing a Bare Item
Section 4.1.3.1 with bare_item to output.
3. Append the result of running Serializing Parameters
Section 4.1.1.2 with item_parameters to output.
4. Return output.
4.1.3.1. Serialising a Bare Item
Given an item as input_item, return an ASCII string suitable for use Given an item as input_item, return an ASCII string suitable for use
in a textual HTTP header value. in a HTTP header value.
1. If input_item is an integer, return the result of applying 1. If input_item is an integer, return the result of running
Serializing an Integer (Section 4.1.4) to input_item. Serializing an Integer (Section 4.1.4) with input_item.
2. If input_item is a float, return the result of applying 2. If input_item is a float, return the result of running
Serializing a Float (Section 4.1.5) to input_item. Serializing a Float (Section 4.1.5) with input_item.
3. If input_item is a string, return the result of applying 3. If input_item is a string, return the result of running
Serializing a String (Section 4.1.6) to input_item. Serializing a String (Section 4.1.6) with input_item.
4. If input_item is a token, return the result of Serializing a 4. If input_item is a token, return the result of running
Token (Section 4.1.7) to input_item. Serializing a Token (Section 4.1.7) with input_item.
5. If input_item is a Boolean, return the result of applying 5. If input_item is a Boolean, return the result of running
Serializing a Boolean (Section 4.1.9) to input_item. Serializing a Boolean (Section 4.1.9) with input_item.
6. If input_item is a byte sequence, return the result of applying 6. If input_item is a byte sequence, return the result of running
Serializing a Byte Sequence (Section 4.1.8) to input_item. Serializing a Byte Sequence (Section 4.1.8) with input_item.
7. Otherwise, fail serialisation. 7. Otherwise, fail serialisation.
4.1.4. Serializing an Integer 4.1.4. Serializing an Integer
Given an integer as input_integer, return an ASCII string suitable Given an integer as input_integer, return an ASCII string suitable
for use in a textual HTTP header value. for use in a HTTP header value.
1. If input_integer is not an integer in the range of 1. If input_integer is not an integer in the range of
-999,999,999,999,999 to 999,999,999,999,999 inclusive, fail -999,999,999,999,999 to 999,999,999,999,999 inclusive, fail
serialisation. serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. If input_integer is less than (but not equal to) 0, append "-" to 3. If input_integer is less than (but not equal to) 0, append "-" to
output. output.
4. Append input_integer's numeric value represented in base 10 using 4. Append input_integer's numeric value represented in base 10 using
only decimal digits to output. only decimal digits to output.
5. Return output. 5. Return output.
4.1.5. Serializing a Float 4.1.5. Serializing a Float
Given a float as input_float, return an ASCII string suitable for use Given a float as input_float, return an ASCII string suitable for use
in a textual HTTP header value. in a HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. If input_float is less than (but not equal to) 0, append "-" to 2. If input_float is less than (but not equal to) 0, append "-" to
output. output.
3. Append input_float's integer component represented in base 10 3. Append input_float's integer component represented in base 10
(using only decimal digits) to output; if it is zero, append (using only decimal digits) to output; if it is zero, append
"0". "0".
skipping to change at page 16, line 41 skipping to change at page 18, line 41
9. Append at most fractional_digits_avail digits of input_float's 9. Append at most fractional_digits_avail digits of input_float's
fractional component represented in base 10 to output (using fractional component represented in base 10 to output (using
only decimal digits, and truncating any remaining digits); if it only decimal digits, and truncating any remaining digits); if it
is zero, append "0". is zero, append "0".
10. Return output. 10. Return output.
4.1.6. Serializing a String 4.1.6. Serializing a String
Given a string as input_string, return an ASCII string suitable for Given a string as input_string, return an ASCII string suitable for
use in a textual HTTP header value. use in a HTTP header value.
1. If input_string is not a sequence of characters, or contains 1. If input_string is not a sequence of characters, or contains
characters outside the range %x00-1f or %x7f (i.e., is not in characters in the range %x00-1f or %x7f (i.e., is not in VCHAR or
VCHAR or SP), fail serialisation. SP), fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append DQUOTE to output. 3. Append DQUOTE to output.
4. For each character char in input_string: 4. For each character char in input_string:
1. If char is "\" or DQUOTE: 1. If char is "\" or DQUOTE:
1. Append "\" to output. 1. Append "\" to output.
2. Append char to output. 2. Append char to output.
5. Append DQUOTE to output. 5. Append DQUOTE to output.
6. Return output. 6. Return output.
4.1.7. Serializing a Token 4.1.7. Serializing a Token
Given a token as input_token, return an ASCII string suitable for use Given a token as input_token, return an ASCII string suitable for use
in a textual HTTP header value. in a HTTP header value.
1. If input_token is not a sequence of characters, or contains 1. If input_token is not a sequence of characters, or contains
characters not in ALPHA, DIGIT, "_", "-", ".", ":", "%", "*" or characters not allowed by the tchar ABNF rule, fail
"/", fail serialisation. serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append input_token to output. 3. Append input_token to output.
4. Return output. 4. Return output.
4.1.8. Serializing a Byte Sequence 4.1.8. Serializing a Byte Sequence
Given a byte sequence as input_bytes, return an ASCII string suitable Given a byte sequence as input_bytes, return an ASCII string suitable
for use in a textual HTTP header value. for use in a HTTP header value.
1. If input_bytes is not a sequence of bytes, fail serialisation. 1. If input_bytes is not a sequence of bytes, fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append "*" to output. 3. Append "*" to output.
4. Append the result of base64-encoding input_bytes as per 4. Append the result of base64-encoding input_bytes as per
[RFC4648], Section 4, taking account of the requirements below. [RFC4648], Section 4, taking account of the requirements below.
skipping to change at page 18, line 12 skipping to change at page 20, line 12
The encoded data is required to be padded with "=", as per [RFC4648], The encoded data is required to be padded with "=", as per [RFC4648],
Section 3.2. Section 3.2.
Likewise, encoded data SHOULD have pad bits set to zero, as per Likewise, encoded data SHOULD have pad bits set to zero, as per
[RFC4648], Section 3.5, unless it is not possible to do so due to [RFC4648], Section 3.5, unless it is not possible to do so due to
implementation constraints. implementation constraints.
4.1.9. Serializing a Boolean 4.1.9. Serializing a Boolean
Given a Boolean as input_boolean, return an ASCII string suitable for Given a Boolean as input_boolean, return an ASCII string suitable for
use in a textual HTTP header value. use in a HTTP header value.
1. If input_boolean is not a boolean, fail serialisation. 1. If input_boolean is not a boolean, fail serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
3. Append "?" to output. 3. Append "?" to output.
4. If input_boolean is true, append "1" to output. 4. If input_boolean is true, append "1" to output.
5. If input_boolean is false, append "0" to output. 5. If input_boolean is false, append "0" to output.
6. Return output. 6. Return output.
4.2. Parsing Header Fields into Structured Headers 4.2. Parsing Header Fields into Structured Headers
When a receiving implementation parses textual HTTP header fields When a receiving implementation parses HTTP header fields that are
that are known to be Structured Headers, it is important that care be known to be Structured Headers, it is important that care be taken,
taken, as there are a number of edge cases that can cause as there are a number of edge cases that can cause interoperability
interoperability or even security problems. This section specifies or even security problems. This section specifies the algorithm for
the algorithm for doing so. doing so.
Given an array of bytes input_bytes that represents the chosen Given an array of bytes input_bytes that represents the chosen
header's field-value (which is an empty string if that header is not header's field-value (which is empty if that header is not present),
present), and header_type (one of "dictionary", "list", or "item"), and header_type (one of "dictionary", "list", or "item"), return the
return the parsed header value. parsed header value.
1. Convert input_bytes into an ASCII string input_string; if 1. Convert input_bytes into an ASCII string input_string; if
conversion fails, fail parsing. conversion fails, fail parsing.
2. Discard any leading OWS from input_string. 2. Discard any leading OWS from input_string.
3. If header_type is "list", let output be the result of Parsing a 3. If header_type is "list", let output be the result of running
List from Text (Section 4.2.1). Parsing a List (Section 4.2.1) with input_string.
4. If header_type is "dictionary", let output be the result of 4. If header_type is "dictionary", let output be the result of
Parsing a Dictionary from Text (Section 4.2.2). running Parsing a Dictionary (Section 4.2.2) with input_string.
5. If header_type is "item", let output be the result of Parsing an 5. If header_type is "item", let output be the result of running
Item from Text (Section 4.2.3). Parsing an Item (Section 4.2.3) with input_string.
6. Discard any leading OWS from input_string. 6. Discard any leading OWS from input_string.
7. If input_string is not empty, fail parsing. 7. If input_string is not empty, fail parsing.
8. Otherwise, return output. 8. Otherwise, return output.
When generating input_bytes, parsers MUST combine all instances of When generating input_bytes, parsers MUST combine all instances of
the target header field into one comma-separated field-value, as per the target header field into one comma-separated field-value, as per
[RFC7230], Section 3.2.2; this assures that the header is processed [RFC7230], Section 3.2.2; this assures that the header is processed
skipping to change at page 19, line 42 skipping to change at page 21, line 42
entire header field's value MUST be ignored (i.e., treated as if the entire header field's value MUST be ignored (i.e., treated as if the
header field were not present in the message). This is intentionally header field were not present in the message). This is intentionally
strict, to improve interoperability and safety, and specifications strict, to improve interoperability and safety, and specifications
referencing this document are not allowed to loosen this requirement. referencing this document are not allowed to loosen this requirement.
Note that this requirement does not apply to an implementation that Note that this requirement does not apply to an implementation that
is not parsing the header field; for example, an intermediary is not is not parsing the header field; for example, an intermediary is not
required to strip a failing header field from a message before required to strip a failing header field from a message before
forwarding it. forwarding it.
4.2.1. Parsing a List from Text 4.2.1. Parsing a List
Given an ASCII string as input_string, return an array of (member, Given an ASCII string as input_string, return an array of
parameters). input_string is modified to remove the parsed value. (item_or_inner_list, parameters) tuples. input_string is modified to
remove the parsed value.
1. Let members be an empty array. 1. Let members be an empty array.
2. While input_string is not empty: 2. While input_string is not empty:
1. Let member be the result of running Parsing a Parameterized 1. Append the result of running Parsing an Item or Inner List
Member from Text (Section 4.2.1.1) with input_string. (Section 4.2.1.1) with input_string to members.
2. Append member to members.
3. Discard any leading OWS from input_string. 2. Discard any leading OWS from input_string.
4. If input_string is empty, return members. 3. If input_string is empty, return members.
5. Consume the first character of input_string; if it is not 4. Consume the first character of input_string; if it is not
COMMA, fail parsing. COMMA, fail parsing.
6. Discard any leading OWS from input_string. 5. Discard any leading OWS from input_string.
7. If input_string is empty, there is a trailing comma; fail 6. If input_string is empty, there is a trailing comma; fail
parsing. parsing.
3. No structured data has been found; return members (which is 3. No structured data has been found; return members (which is
empty). empty).
4.2.1.1. Parsing a Parameterized Member from Text 4.2.1.1. Parsing an Item or Inner List
Given an ASCII string as input_string, return a member (either a list Given an ASCII string as input_string, return the tuple
of items, or a single item) with an ordered map of parameters. (item_or_inner_list, parameters), where item_or_inner_list can be
input_string is modified to remove the parsed value. either a single bare item, or an array of (bare_item, parameters)
tuples. input_string is modified to remove the parsed value.
1. If the first character of input_string is "(", let member be the 1. If the first character of input_string is "(", return the result
result of running Parsing an Inner List (Section 4.2.1.2) with of running Parsing an Inner List (Section 4.2.1.2) with
input_string. input_string.
2. Else, let member be the result of running Parsing an Item 2. Return the result of running Parsing an Item (Section 4.2.3) with
(Section 4.2.3) with input_string. input_string.
3. Let parameters be an empty, ordered map.
4. While input_string is not empty:
1. Discard any leading OWS from input_string.
2. If the first character of input_string is not ";", exit the
loop.
3. Consume a ";" character from the beginning of input_string.
4. Discard any leading OWS from input_string.
5. let param_name be the result of Parsing a key from Text
(Section 4.2.1.3) from input_string.
6. If param_name is already present in parameters, there is a
duplicate; fail parsing.
7. Let param_value be a null value.
8. If the first character of input_string is "=":
1. Consume the "=" character at the beginning of
input_string.
2. Let param_value be the result of Parsing an Item from
Text (Section 4.2.3) from input_string.
9. Append key param_name with value param_value to parameters.
5. Return the tuple (member, parameters).
4.2.1.2. Parsing an Inner List 4.2.1.2. Parsing an Inner List
Given an ASCII string as input_string, return an array of items. Given an ASCII string as input_string, return the tuple (inner_list,
input_string is modified to remove the parsed value. parameters), where inner_list is an array of (bare_item, parameters)
tuples. input_string is modified to remove the parsed value.
1. Consume the first character of input_string; if it is not "(", 1. Consume the first character of input_string; if it is not "(",
fail parsing. fail parsing.
2. Let inner_list be an empty array. 2. Let inner_list be an empty array.
3. While input_string is not empty: 3. While input_string is not empty:
1. Discard any leading OWS from input_string. 1. Discard any leading OWS from input_string.
2. If the first character of input_string is ")": 2. If the first character of input_string is ")":
1. Consume the first character of input_string. 1. Consume the first character of input_string.
2. Return inner_list. 2. Let parameters be the result of running Parsing
Parameters (Section 4.2.3.2) with input_string.
3. Let item be the result of running Parsing an Item from Text 3. Return the tuple (inner_list, parameters).
3. Let item be the result of running Parsing an Item
(Section 4.2.3) with input_string. (Section 4.2.3) with input_string.
4. Append item to inner_list. 4. Append item to inner_list.
5. If the first character of input_string is not SP or ")", fail 5. If the first character of input_string is not SP or ")", fail
parsing. parsing.
4. The end of the inner list was not found; fail parsing. 4. The end of the inner list was not found; fail parsing.
4.2.1.3. Parsing a Key from Text 4.2.2. Parsing a Dictionary
Given an ASCII string as input_string, return a key. input_string is Given an ASCII string as input_string, return an ordered map whose
values are (item_or_inner_list, parameters) tuples. input_string is
modified to remove the parsed value. modified to remove the parsed value.
1. If the first character of input_string is not lcalpha, fail
parsing.
2. Let output_string be an empty string.
3. While input_string is not empty:
1. If the first character of input_string is not one of lcalpha,
DIGIT, "*", "_", or "-", return output_string.
2. Let char be the result of removing the first character of
input_string.
3. Append char to output_string.
4. Return output_string.
4.2.2. Parsing a Dictionary from Text
Given an ASCII string as input_string, return an ordered map of (key,
item). input_string is modified to remove the parsed value.
1. Let dictionary be an empty, ordered map. 1. Let dictionary be an empty, ordered map.
2. While input_string is not empty: 2. While input_string is not empty:
1. Let this_key be the result of running Parsing a Key from 1. Let this_key be the result of running Parsing a Key
Text (Section 4.2.1.3) with input_string. (Section 4.2.3.3) with input_string.
2. If dictionary already contains the name this_key, there is a 2. If dictionary already contains the name this_key, there is a
duplicate; fail parsing. duplicate; fail parsing.
3. Consume the first character of input_string; if it is not 3. Consume the first character of input_string; if it is not
"=", fail parsing. "=", fail parsing.
4. Let member be the result of running Parsing a Parameterized 4. Let member be the result of running Parsing an Item or Inner
Member from Text (Section 4.2.1.1) with input_string. List (Section 4.2.1.1) with input_string.
5. Add name this_key with value member to dictionary. 5. Add name this_key with value member to dictionary.
6. Discard any leading OWS from input_string. 6. Discard any leading OWS from input_string.
7. If input_string is empty, return dictionary. 7. If input_string is empty, return dictionary.
8. Consume the first character of input_string; if it is not 8. Consume the first character of input_string; if it is not
COMMA, fail parsing. COMMA, fail parsing.
9. Discard any leading OWS from input_string. 9. Discard any leading OWS from input_string.
10. If input_string is empty, there is a trailing comma; fail 10. If input_string is empty, there is a trailing comma; fail
parsing. parsing.
3. No structured data has been found; return dictionary (which is 3. No structured data has been found; return dictionary (which is
empty). empty).
4.2.3. Parsing an Item from Text 4.2.3. Parsing an Item
Given an ASCII string as input_string, return an item. input_string Given an ASCII string as input_string, return a (bare_item,
is modified to remove the parsed value. parameters) tuple. input_string is modified to remove the parsed
value.
1. Let bare_item be the result of running Parsing a Bare Item
(Section 4.2.3.1) with input_string.
2. Let parameters be the result of running Parsing Parameters
(Section 4.2.3.2) with input_string.
3. Return the tuple (bare_item, parameters).
4.2.3.1. Parsing a Bare Item
Given an ASCII string as input_string, return a bare item.
input_string is modified to remove the parsed value.
1. If the first character of input_string is a "-" or a DIGIT, 1. If the first character of input_string is a "-" or a DIGIT,
process input_string as a number (Section 4.2.4) and return the return the result of running Parsing a Number (Section 4.2.4)
result. with input_string.
2. If the first character of input_string is a DQUOTE, process 2. If the first character of input_string is a DQUOTE, return the
input_string as a string (Section 4.2.5) and return the result. result of running Parsing a String (Section 4.2.5) with
input_string.
3. If the first character of input_string is "*", process 3. If the first character of input_string is "*", return the result
input_string as a byte sequence (Section 4.2.7) and return the of running Parsing a Byte Sequence (Section 4.2.7) with
result. input_string.
4. If the first character of input_string is "?", process 4. If the first character of input_string is "?", return the result
input_string as a Boolean (Section 4.2.8) and return the result. of running Parsing a Boolean (Section 4.2.8) with input_string.
5. If the first character of input_string is an ALPHA, process 5. If the first character of input_string is an ALPHA, return the
input_string as a token (Section 4.2.6) and return the result. result of running Parsing a Token (Section 4.2.6) with
input_string.
6. Otherwise, the item type is unrecognized; fail parsing. 6. Otherwise, the item type is unrecognized; fail parsing.
4.2.3.2. Parsing Parameters
Given an ASCII string as input_string, return an ordered map whose
values are bare items. input_string is modified to remove the parsed
value.
1. Let parameters be an empty, ordered map.
2. While input_string is not empty:
1. If the first character of input_string is not ";", exit the
loop.
2. Consume a ";" character from the beginning of input_string.
3. Discard any leading OWS from input_string.
4. let param_name be the result of running Parsing a Key
(Section 4.2.3.3) with input_string.
5. If param_name is already present in parameters, there is a
duplicate; fail parsing.
6. Let param_value be a null value.
7. If the first character of input_string is "=":
1. Consume the "=" character at the beginning of
input_string.
2. Let param_value be the result of running Parsing a Bare
Item (Section 4.2.3.1) with input_string.
8. Append key param_name with value param_value to parameters.
3. Return parameters.
4.2.3.3. Parsing a Key from Text
Given an ASCII string as input_string, return a key. input_string is
modified to remove the parsed value.
1. If the first character of input_string is not lcalpha, fail
parsing.
2. Let output_string be an empty string.
3. While input_string is not empty:
1. If the first character of input_string is not one of lcalpha,
DIGIT, "*", "_", or "-", return output_string.
2. Let char be the result of removing the first character of
input_string.
3. Append char to output_string.
4. Return output_string.
4.2.4. Parsing a Number from Text 4.2.4. Parsing a Number from Text
Given an ASCII string as input_string, return a number. input_string Given an ASCII string as input_string, return a number. input_string
is modified to remove the parsed value. is modified to remove the parsed value.
NOTE: This algorithm parses both Integers (Section 3.4) and Floats NOTE: This algorithm parses both Integers (Section 3.3.1) and Floats
(Section 3.5), and returns the corresponding structure. (Section 3.3.2), and returns the corresponding structure.
1. Let type be "integer". 1. Let type be "integer".
2. Let sign be 1. 2. Let sign be 1.
3. Let input_number be an empty string. 3. Let input_number be an empty string.
4. If the first character of input_string is "-", consume it and 4. If the first character of input_string is "-", consume it and
set sign to -1. set sign to -1.
skipping to change at page 24, line 38 skipping to change at page 27, line 14
6. If type is "float" and input_number contains more than 16 6. If type is "float" and input_number contains more than 16
characters, fail parsing. characters, fail parsing.
8. If type is "integer": 8. If type is "integer":
1. Parse input_number as an integer and let output_number be 1. Parse input_number as an integer and let output_number be
the product of the result and sign. the product of the result and sign.
2. If output_number is outside the range defined in 2. If output_number is outside the range defined in
Section 3.4, fail parsing. Section 3.3.1, fail parsing.
9. Otherwise: 9. Otherwise:
1. If the final character of input_number is ".", fail parsing. 1. If the final character of input_number is ".", fail parsing.
2. If the number of characters after "." in input_number is 2. If the number of characters after "." in input_number is
greater than six, fail parsing. greater than six, fail parsing.
3. Parse input_number as a float and let output_number be the 3. Parse input_number as a float and let output_number be the
product of the result and sign. product of the result and sign.
skipping to change at page 26, line 7 skipping to change at page 28, line 29
Given an ASCII string as input_string, return a token. input_string Given an ASCII string as input_string, return a token. input_string
is modified to remove the parsed value. is modified to remove the parsed value.
1. If the first character of input_string is not ALPHA, fail 1. If the first character of input_string is not ALPHA, fail
parsing. parsing.
2. Let output_string be an empty string. 2. Let output_string be an empty string.
3. While input_string is not empty: 3. While input_string is not empty:
1. If the first character of input_string is not one of ALPHA, 1. If the first character of input_string is not allowed by the
DIGIT, "_", "-", ".", ":", "%", "*" or "/", return tchar ABNF rule, return output_string.
output_string.
2. Let char be the result of consuming the first character of 2. Let char be the result of consuming the first character of
input_string. input_string.
3. Append char to output_string. 3. Append char to output_string.
4. Return output_string. 4. Return output_string.
4.2.7. Parsing a Byte Sequence from Text 4.2.7. Parsing a Byte Sequence from Text
skipping to change at page 28, line 31 skipping to change at page 31, line 8
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References 7.2. Informative References
[IEEE754] IEEE, "IEEE Standard for Floating-Point Arithmetic", [IEEE754] IEEE, "IEEE Standard for Floating-Point Arithmetic",
IEEE 754-2008, DOI 10.1109/IEEESTD.2008.4610935, IEEE 754-2019, DOI 10.1109/IEEESTD.2019.8766229,
ISBN 978-0-7381-5752-8, August 2008, ISBN 978-1-5044-5924-2, July 2019,
<http://ieeexplore.ieee.org/document/4610935/>. <https://ieeexplore.ieee.org/document/8766229>.
See also http://grouper.ieee.org/groups/754/ [6].
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>. <https://www.rfc-editor.org/info/rfc7231>.
[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493, [RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015, DOI 10.17487/RFC7493, March 2015,
<https://www.rfc-editor.org/info/rfc7493>. <https://www.rfc-editor.org/info/rfc7493>.
skipping to change at page 29, line 14 skipping to change at page 31, line 35
[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for [RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for
HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015, HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
<https://www.rfc-editor.org/info/rfc7541>. <https://www.rfc-editor.org/info/rfc7541>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259, Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017, DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>. <https://www.rfc-editor.org/info/rfc8259>.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/std63>.
7.3. URIs 7.3. URIs
[1] https://lists.w3.org/Archives/Public/ietf-http-wg/ [1] https://lists.w3.org/Archives/Public/ietf-http-wg/
[2] https://httpwg.github.io/ [2] https://httpwg.github.io/
[3] https://github.com/httpwg/http-extensions/labels/header-structure [3] https://github.com/httpwg/http-extensions/labels/header-structure
[4] https://github.com/httpwg/structured-header-tests [4] https://github.com/httpwg/structured-header-tests
skipping to change at page 31, line 15 skipping to change at page 33, line 41
Appendix C. Implementation Notes Appendix C. Implementation Notes
A generic implementation of this specification should expose the top- A generic implementation of this specification should expose the top-
level parse (Section 4.2) and serialize (Section 4.1) functions. level parse (Section 4.2) and serialize (Section 4.1) functions.
They need not be functions; for example, it could be implemented as They need not be functions; for example, it could be implemented as
an object, with methods for each of the different top-level types. an object, with methods for each of the different top-level types.
For interoperability, it's important that generic implementations be For interoperability, it's important that generic implementations be
complete and follow the algorithms closely; see Section 1.1. To aid complete and follow the algorithms closely; see Section 1.1. To aid
this, a common test suite is being maintained by the community at this, a common test suite is being maintained by the community at
https://github.com/httpwg/structured-header-tests [7]. https://github.com/httpwg/structured-header-tests [6].
Implementers should note that dictionaries and parameters are order- Implementers should note that dictionaries and parameters are order-
preserving maps. Some headers may not convey meaning in the ordering preserving maps. Some headers may not convey meaning in the ordering
of these data types, but it should still be exposed so that of these data types, but it should still be exposed so that
applications which need to use it will have it available. applications which need to use it will have it available.
Likewise, implementations should note that it's important to preserve Likewise, implementations should note that it's important to preserve
the distinction between tokens and strings. While most programming the distinction between tokens and strings. While most programming
languages have native types that map to the other types well, it may languages have native types that map to the other types well, it may
be necessary to create a wrapper "token" object or use a parameter on be necessary to create a wrapper "token" object or use a parameter on
functions to assure that these types remain separate. functions to assure that these types remain separate.
Appendix D. Changes Appendix D. Changes
_RFC Editor: Please remove this section before publication._ _RFC Editor: Please remove this section before publication._
D.1. Since draft-ietf-httpbis-header-structure-12 D.1. Since draft-ietf-httpbis-header-structure-13
o Editorial improvements.
o Define "structured header name" and "structured header value"
terms (#908).
o Corrected text about valid characters in strings (#931).
o Removed most instances of the word "textual", as it was redundant
(#915).
o Allowed parameters on Items and Inner Lists (#907).
o Expand the range of characters in token (#961).
D.2. Since draft-ietf-httpbis-header-structure-12
o Editorial improvements. o Editorial improvements.
o Reworked float serialisation (#896). o Reworked float serialisation (#896).
D.2. Since draft-ietf-httpbis-header-structure-11 o Don't add a trailing space in inner-list (#904).
D.3. Since draft-ietf-httpbis-header-structure-11
o Allow * in key (#844). o Allow * in key (#844).
o Constrain floats to six digits of precision (#848). o Constrain floats to six digits of precision (#848).
o Allow dictionary members to have parameters (#842). o Allow dictionary members to have parameters (#842).
D.3. Since draft-ietf-httpbis-header-structure-10 D.4. Since draft-ietf-httpbis-header-structure-10
o Update abstract (#799). o Update abstract (#799).
o Input and output are now arrays of bytes (#662). o Input and output are now arrays of bytes (#662).
o Implementations need to preserve difference between token and o Implementations need to preserve difference between token and
string (#790). string (#790).
o Allow empty dictionaries and lists (#781). o Allow empty dictionaries and lists (#781).
o Change parameterized lists to have primary items (#797). o Change parameterized lists to have primary items (#797).
o Allow inner lists in both dictionaries and lists; removes lists of o Allow inner lists in both dictionaries and lists; removes lists of
lists (#816). lists (#816).
o Subsume Parameterised Lists into Lists (#839). o Subsume Parameterised Lists into Lists (#839).
D.4. Since draft-ietf-httpbis-header-structure-09 D.5. Since draft-ietf-httpbis-header-structure-09
o Changed Boolean from T/F to 1/0 (#784). o Changed Boolean from T/F to 1/0 (#784).
o Parameters are now ordered maps (#765). o Parameters are now ordered maps (#765).
o Clamp integers to 15 digits (#737). o Clamp integers to 15 digits (#737).
D.5. Since draft-ietf-httpbis-header-structure-08 D.6. Since draft-ietf-httpbis-header-structure-08
o Disallow whitespace before items properly (#703). o Disallow whitespace before items properly (#703).
o Created "key" for use in dictionaries and parameters, rather than o Created "key" for use in dictionaries and parameters, rather than
relying on identifier (#702). Identifiers have a separate minimum relying on identifier (#702). Identifiers have a separate minimum
supported size. supported size.
o Expanded the range of special characters allowed in identifier to o Expanded the range of special characters allowed in identifier to
include all of ALPHA, ".", ":", and "%" (#702). include all of ALPHA, ".", ":", and "%" (#702).
skipping to change at page 33, line 5 skipping to change at page 35, line 42
o Gave better names for referring specs to use in Parameterised o Gave better names for referring specs to use in Parameterised
Lists (#720). Lists (#720).
o Added Lists of Lists (#721). o Added Lists of Lists (#721).
o Rename Identifier to Token (#725). o Rename Identifier to Token (#725).
o Add implementation guidance (#727). o Add implementation guidance (#727).
D.6. Since draft-ietf-httpbis-header-structure-07 D.7. Since draft-ietf-httpbis-header-structure-07
o Make Dictionaries ordered mappings (#659). o Make Dictionaries ordered mappings (#659).
o Changed "binary content" to "byte sequence" to align with Infra o Changed "binary content" to "byte sequence" to align with Infra
specification (#671). specification (#671).
o Changed "mapping" to "map" for #671. o Changed "mapping" to "map" for #671.
o Don't fail if byte sequences aren't "=" padded (#658). o Don't fail if byte sequences aren't "=" padded (#658).
o Add Booleans (#683). o Add Booleans (#683).
o Allow identifiers in items again (#629). o Allow identifiers in items again (#629).
o Disallowed whitespace before items (#703). o Disallowed whitespace before items (#703).
o Explain the consequences of splitting a string across multiple o Explain the consequences of splitting a string across multiple
headers (#686). headers (#686).
D.7. Since draft-ietf-httpbis-header-structure-06 D.8. Since draft-ietf-httpbis-header-structure-06
o Add a FAQ. o Add a FAQ.
o Allow non-zero pad bits. o Allow non-zero pad bits.
o Explicitly check for integers that violate constraints. o Explicitly check for integers that violate constraints.
D.8. Since draft-ietf-httpbis-header-structure-05 D.9. Since draft-ietf-httpbis-header-structure-05
o Reorganise specification to separate parsing out. o Reorganise specification to separate parsing out.
o Allow referencing specs to use ABNF. o Allow referencing specs to use ABNF.
o Define serialisation algorithms. o Define serialisation algorithms.
o Refine relationship between ABNF, parsing and serialisation o Refine relationship between ABNF, parsing and serialisation
algorithms. algorithms.
D.9. Since draft-ietf-httpbis-header-structure-04 D.10. Since draft-ietf-httpbis-header-structure-04
o Remove identifiers from item. o Remove identifiers from item.
o Remove most limits on sizes. o Remove most limits on sizes.
o Refine number parsing. o Refine number parsing.
D.10. Since draft-ietf-httpbis-header-structure-03 D.11. Since draft-ietf-httpbis-header-structure-03
o Strengthen language around failure handling. o Strengthen language around failure handling.
D.11. Since draft-ietf-httpbis-header-structure-02 D.12. Since draft-ietf-httpbis-header-structure-02
o Split Numbers into Integers and Floats. o Split Numbers into Integers and Floats.
o Define number parsing. o Define number parsing.
o Tighten up binary parsing and give it an explicit end delimiter. o Tighten up binary parsing and give it an explicit end delimiter.
o Clarify that mappings are unordered. o Clarify that mappings are unordered.
o Allow zero-length strings. o Allow zero-length strings.
o Improve string parsing algorithm. o Improve string parsing algorithm.
o Improve limits in algorithms. o Improve limits in algorithms.
o Require parsers to combine header fields before processing. o Require parsers to combine header fields before processing.
o Throw an error on trailing garbage. o Throw an error on trailing garbage.
D.12. Since draft-ietf-httpbis-header-structure-01 D.13. Since draft-ietf-httpbis-header-structure-01
o Replaced with draft-nottingham-structured-headers. o Replaced with draft-nottingham-structured-headers.
D.13. Since draft-ietf-httpbis-header-structure-00 D.14. Since draft-ietf-httpbis-header-structure-00
o Added signed 64bit integer type. o Added signed 64bit integer type.
o Drop UTF8, and settle on BCP137 ::EmbeddedUnicodeChar for h1- o Drop UTF8, and settle on BCP137 ::EmbeddedUnicodeChar for h1-
unicode-string. unicode-string.
o Change h1_blob delimiter to ":" since "'" is valid t_char o Change h1_blob delimiter to ":" since "'" is valid t_char
Authors' Addresses Authors' Addresses
 End of changes. 155 change blocks. 
392 lines changed or deleted 505 lines changed or added

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