draft-ietf-httpbis-header-structure-12.txt   draft-ietf-httpbis-header-structure-13.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 20, 2020 The Varnish Cache Project Expires: February 25, 2020 The Varnish Cache Project
August 19, 2019 August 24, 2019
Structured Headers for HTTP Structured Headers for HTTP
draft-ietf-httpbis-header-structure-12 draft-ietf-httpbis-header-structure-13
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 20, 2020. This Internet-Draft will expire on February 25, 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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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 Header Data Types . . . . . . . . . . . . . . . . 6
3.1. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 8 3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Integers . . . . . . . . . . . . . . . . . . . . . . . . 9 3.4. Integers . . . . . . . . . . . . . . . . . . . . . . . . 9
3.5. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.5. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.6. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.7. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.7. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.8. Byte Sequences . . . . . . . . . . . . . . . . . . . . . 11 3.8. Byte Sequences . . . . . . . . . . . . . . . . . . . . . 11
3.9. Booleans . . . . . . . . . . . . . . . . . . . . . . . . 11 3.9. Booleans . . . . . . . . . . . . . . . . . . . . . . . . 11
4. Working With Structured Headers in Textual HTTP Headers . . . 11 4. Working With Structured Headers in Textual HTTP Headers . . . 12
4.1. Serializing Structured Headers . . . . . . . . . . . . . 11 4.1. Serializing Structured Headers . . . . . . . . . . . . . 12
4.2. Parsing Header Fields into Structured Headers . . . . . . 18 4.2. Parsing Header Fields into Structured Headers . . . . . . 18
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
6. Security Considerations . . . . . . . . . . . . . . . . . . . 27 6. Security Considerations . . . . . . . . . . . . . . . . . . . 27
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.1. Normative References . . . . . . . . . . . . . . . . . . 27 7.1. Normative References . . . . . . . . . . . . . . . . . . 27
7.2. Informative References . . . . . . . . . . . . . . . . . 28 7.2. Informative References . . . . . . . . . . . . . . . . . 28
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 29 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 29
Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 29 Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 29
B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 29 B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 29
B.2. Structured Headers don't "fit" my data. . . . . . . . . . 30 B.2. Structured Headers don't "fit" my data. . . . . . . . . . 30
Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 30 Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 31
Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 31 Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 31
D.1. Since draft-ietf-httpbis-header-structure-11 . . . . . . 31 D.1. Since draft-ietf-httpbis-header-structure-12 . . . . . . 31
D.2. Since draft-ietf-httpbis-header-structure-10 . . . . . . 31 D.2. Since draft-ietf-httpbis-header-structure-11 . . . . . . 31
D.3. Since draft-ietf-httpbis-header-structure-09 . . . . . . 31 D.3. Since draft-ietf-httpbis-header-structure-10 . . . . . . 31
D.4. Since draft-ietf-httpbis-header-structure-08 . . . . . . 31 D.4. Since draft-ietf-httpbis-header-structure-09 . . . . . . 32
D.5. Since draft-ietf-httpbis-header-structure-07 . . . . . . 32 D.5. Since draft-ietf-httpbis-header-structure-08 . . . . . . 32
D.6. Since draft-ietf-httpbis-header-structure-06 . . . . . . 32 D.6. Since draft-ietf-httpbis-header-structure-07 . . . . . . 33
D.7. Since draft-ietf-httpbis-header-structure-05 . . . . . . 32 D.7. Since draft-ietf-httpbis-header-structure-06 . . . . . . 33
D.8. Since draft-ietf-httpbis-header-structure-04 . . . . . . 33 D.8. Since draft-ietf-httpbis-header-structure-05 . . . . . . 33
D.9. Since draft-ietf-httpbis-header-structure-03 . . . . . . 33 D.9. Since draft-ietf-httpbis-header-structure-04 . . . . . . 33
D.10. Since draft-ietf-httpbis-header-structure-02 . . . . . . 33 D.10. Since draft-ietf-httpbis-header-structure-03 . . . . . . 34
D.11. Since draft-ietf-httpbis-header-structure-01 . . . . . . 33 D.11. Since draft-ietf-httpbis-header-structure-02 . . . . . . 34
D.12. Since draft-ietf-httpbis-header-structure-00 . . . . . . 33 D.12. Since draft-ietf-httpbis-header-structure-01 . . . . . . 34
D.13. Since draft-ietf-httpbis-header-structure-00 . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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 [RFC7231], Section 8.3.1, 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
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To define a HTTP header as a structured header, its specification To define a HTTP header as a structured header, its specification
needs to: needs 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 header field's allowed syntax for values, in terms of
the types described in Section 3, along with their associated the types described in Section 3, along with their associated
semantics. Syntax definitions are encouraged to use the ABNF semantics. Syntax definitions are encouraged to use the ABNF
rules beginning with "sh-" defined in this specification. 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 Specify any additional constraints upon the syntax of the
structured used, as well as the consequences when those structures used, as well as the consequences when those
constraints are violated. When Structured Headers parsing fails, constraints are violated. When Structured Headers parsing fails,
the header is discarded (see Section 4.2); in most situations, the header is ignored (see Section 4.2); in most situations,
header-specific constraints should do likewise. header-specific constraints should do likewise.
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, or the number of items in a list). Likewise, strings and tokens, the types allowed in a dictionary's values, or
header field definitions should use Structured Headers for the entire the number of items in a list). Likewise, header field definitions
header field value, not a portion thereof. can only use Structured Headers for the entire header field value,
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.
For example, For example, a fictitious Foo-Example header field might be specified
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 Structured Header [RFCxxxx]. Its value MUST be a
dictionary ([RFCxxxx], Section Y.Y). Its ABNF is: dictionary (Section Y.Y of [RFCxxxx]). Its ABNF is:
Foo-Example = sh-dictionary Foo-Example = sh-dictionary
The dictionary MUST contain: The dictionary MUST contain:
* Exactly one member whose name is "foo", and whose value is an * Exactly one member whose name is "foo", and whose value is an
integer ([RFCxxxx], Section Y.Y), indicating the number of foos integer (Section Y.Y of [RFCxxxx]), indicating the number of foos
in the message. in the message.
* Exactly one member whose name is "barUrl", and whose value is a * Exactly one member whose name is "barUrl", and whose value is a
string ([RFCxxxx], Section Y.Y), conveying the Bar URL for the list of strings (Section Y.Y of [RFCxxxx]), conveying the Bar URLs
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 If the parsed header field does not contain both, it MUST be
ignored. ignored.
"foo" MUST be between 0 and 10, inclusive; other values MUST cause "foo" MUST be between 0 and 10, inclusive; other values MUST cause
the header to be ignored. the header to be ignored.
"barUrl" contains a URI-reference ([RFC3986], Section 4.1). "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.
If barURL is not a valid URI-reference, it MUST be ignored. For example:
If barURL is a relative reference ([RFC3986], Section 4.2),
it MUST be resolved ([RFC3986], Section 5) before being used. Foo-Example: foo=2, barUrl=("https://bar.example.com/")
3. Structured Header Data Types 3. Structured Header 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 HTTP. format in textual HTTP headers.
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 (an array of zero or more items).
Each member of the top-level list can also have associated parameters 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 - 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 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 more parameters on a member, and their keys are required to be unique
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header field whose value is defined as a list of lists of strings header field whose value is defined as a list of lists of strings
could look like: 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 In textual HTTP headers, members' parameters are separated from the
member and each other by semicolons. For example: member and each other by semicolons. For example:
Example-ParamListHeader: abc_123;a=1;b=2; cdef_456, (ghi jkl);q="9";r="w" Example-ParamListHeader: abc;a=1;b=2; cde_456, (ghi jkl);q="9";r=w
In textual HTTP headers, an empty list is denoted by not serialising In textual HTTP headers, an empty list is denoted by not serialising
the header at all. the header at all.
Parsers MUST support lists containing at least 1024 members, support Parsers MUST support lists containing at least 1024 members, support
members with at least 256 parameters, support inner-lists containing members with at least 256 parameters, support inner-lists containing
at least 256 members, and support parameter keys with at least 64 at least 256 members, and support parameter keys with at least 64
characters. characters.
Header specifications can constrain the types of individual list Header specifications can constrain the types of individual list
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Example-BoolHdr: ?1 Example-BoolHdr: ?1
4. Working With Structured Headers in Textual HTTP Headers 4. Working With Structured Headers in Textual 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 textual header fields, and protocols compatible with them (e.g., in
HTTP/2 [RFC7540] before HPACK [RFC7541] is applied). HTTP/2 [RFC7540] before HPACK [RFC7541] is applied).
4.1. Serializing Structured Headers 4.1. Serializing Structured Headers
Given a structure defined in this specification: Given a structure defined in this specification, return an ASCII
string suitable for use in a textual 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 send the serialize 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 Serializing a Dictionary (Section 4.1.2).
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 Serializing a List (Section 4.1.1).
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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 Serializing an Item (Section 4.1.3).
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, parameters) as input_list: Given a list of (member-value, parameters) as input_list, return an
ASCII string suitable for use in a textual HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each (member, parameters) of input_list: 2. For each (member-value, parameters) of input_list:
1. If member is an array, let mem_value be the result of
applying Serialising an Inner List (Section 4.1.1.1) to
member.
2. Otherwise, let mem_value be the result of applying 1. If member-value is an array, append the result of applying
Serializing an Item (Section 4.1.3) to member. Serialising an Inner List (Section 4.1.1.1) with member-value
to output.
3. Append mem_value to output. 2. Otherwise, append the result of applying Serializing an Item
(Section 4.1.3) with member-value to output.
4. Append the result of Serializing Parameters Section 4.1.1.2 3. Append the result of Serializing Parameters Section 4.1.1.2
with parameters to output. with parameters to output.
5. If more members remain in input_plist: 4. If more member-values remain in input_plist:
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 inner_list: Given an array as inner_list, return an ASCII string suitable for use
in a textual HTTP header value.
1. Let output be the string "(". 1. Let output be the string "(".
2. For each member mem of inner_list: 2. For each member-value of inner_list:
1. Let value be the result of applying Serializing an Item
(Section 4.1.3) to mem.
2. Append value to output. 1. Append the result of applying Serializing an Item
(Section 4.1.3) with member-value to output.
3. If inner_list is not empty, append a single WS to output. 2. If inner_list is not empty, append a single WS to output.
3. Append ")" to output. 3. Append ")" to output.
4. Return output. 4. Return output.
4.1.1.2. Serializing Parameters 4.1.1.2. Serializing Parameters
Given an ordered dictionary parameters: Given an ordered dictionary as input_parameters (each member having a
param-name and a param-value), return an ASCII string suitable for
use in a textual HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each parameter in parameters: 2. For each parameter-name with a value of param-value in
input_parameters:
3. Append ";" to output.
4. Let name be the result of applying Serializing a Key
(Section 4.1.1.3) to parameter's param-name.
5. Append name to output. 1. Append ";" to output.
6. If parameter has a param-value: 2. Append the result of applying Serializing a Key
(Section 4.1.1.3) with param-name to output.
1. Let value be the result of applying Serializing an Item 3. If param-value is not null:
(Section 4.1.3) to parameter's param-value.
2. Append "=" to output. 1. Append "=" to output.
3. Append value to output. 2. Append the result of applying Serializing an Item
(Section 4.1.3) with param-value to output.
7. 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: Given a key as input_key, return an ASCII string suitable for use in
a textual 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 allowed in the ABNF for key, fail serialisation. characters not in lcalpha, DIGIT, "*", "_", or "-", fail
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 a dictionary as input_dictionary: Given an ordered dictionary as input_dictionary (each member having a
member-name and a tuple value of (member-value, parameters)), return
an ASCII string suitable for use in a textual HTTP header value.
1. Let output be an empty string. 1. Let output be an empty string.
2. For each (member, parameters) of input_dictionary: 2. For each member-name with a value of (member-value, parameters)
in input_dictionary:
1. Let name be the result of applying Serializing a Key
(Section 4.1.1.3) to member's member-name.
2. Append name to output.
3. Append "=" to output. 1. Append the result of applying Serializing a Key
(Section 4.1.1.3) with member's member-name to output.
4. If member is an array, let value be the result of applying 2. Append "=" to output.
Serialising an Inner List (Section 4.1.1.1) to member.
5. Otherwise, let value be the result of applying Serializing an 3. If member-value is an array, append the result of applying
Item (Section 4.1.3) to member. Serialising an Inner List (Section 4.1.1.1) with member-value
to output.
6. Append value to output. 4. Otherwise, append the result of applying Serializing an Item
(Section 4.1.3) with member-value to output.
7. Append the result of Serializing Parameters Section 4.1.1.2 5. Append the result of Serializing Parameters Section 4.1.1.2
with parameters to output. with parameters to output.
8. If more members remain in input_dictionary: 6. 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 as input_item: Given an item as input_item, return an ASCII string suitable for use
in a textual 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 applying
Serializing an Integer (Section 4.1.4) to input_item. Serializing an Integer (Section 4.1.4) to 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 applying
Serializing a Float (Section 4.1.5) to input_item. Serializing a Float (Section 4.1.5) to 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 applying
Serializing a String (Section 4.1.6) to input_item. Serializing a String (Section 4.1.6) to input_item.
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5. If input_item is a Boolean, return the result of applying 5. If input_item is a Boolean, return the result of applying
Serializing a Boolean (Section 4.1.9) to input_item. Serializing a Boolean (Section 4.1.9) to 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 applying
Serializing a Byte Sequence (Section 4.1.8) to input_item. Serializing a Byte Sequence (Section 4.1.8) to 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: Given an integer as input_integer, return an ASCII string suitable
for use in a textual 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: Given a float as input_float, return an ASCII string suitable for use
in a textual HTTP header value.
1. If input_float's fractional component has more than six digits of 1. Let output be an empty string.
precision, fail serialisation.
2. If the number of digits of precision in input_float's fractional 2. If input_float is less than (but not equal to) 0, append "-" to
component plus those in its integer component add to more than output.
fifteen digits, fail serialisation.
3. Let output be an empty string. 3. Append input_float's integer component represented in base 10
(using only decimal digits) to output; if it is zero, append
"0".
4. If input_float is less than (but not equal to) 0, append "-" to 4. Let integer_digits be the number of characters appended in the
output. previous step.
5. Append input_float's integer component represented in base 10 5. If integer_digits is greater than 14, fail serialisation.
using only decimal digits to output; if it is zero, append "0".
6. Append "." to output. 6. Let digits_avail be 15 minus integer_digits.
7. Append input_float's fractional component represented in base 10 7. Let fractional_digits_avail be the minimum of digits_avail and
using only decimal digits to output; if it is zero, append "0". 6.
8. Return output. 8. Append "." to output.
9. Append at most fractional_digits_avail digits of input_float's
fractional component represented in base 10 to output (using
only decimal digits, and truncating any remaining digits); if it
is zero, append "0".
10. Return output.
4.1.6. Serializing a String 4.1.6. Serializing a String
Given a string as input_string: Given a string as input_string, return an ASCII string suitable for
use in a textual 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 allowed by VCHAR or SP, fail characters outside the range %x00-1f or %x7f (i.e., is not in
serialisation. VCHAR or 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: Given a token as input_token, return an ASCII string suitable for use
in a textual 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 allowed in Section 3.7, fail serialisation. characters not in ALPHA, DIGIT, "_", "-", ".", ":", "%", "*" or
"/", fail 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: Given a byte sequence as input_bytes, return an ASCII string suitable
for use in a textual 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 17, line 40 skipping to change at page 18, line 11
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: Given a Boolean as input_boolean, return an ASCII string suitable for
use in a textual 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.
skipping to change at page 18, line 30 skipping to change at page 18, line 51
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 Parsing a
List from Text (Section 4.2.1). List from Text (Section 4.2.1).
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). Parsing a Dictionary from Text (Section 4.2.2).
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 Parsing an
Item from Text (Section 4.2.4). Item from Text (Section 4.2.3).
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 10 skipping to change at page 19, line 32
unpredictable results, because comma(s) and whitespace inserted upon unpredictable results, because comma(s) and whitespace inserted upon
combination will become part of the string output by the parser. combination will become part of the string output by the parser.
Since concatenation might be done by an upstream intermediary, the Since concatenation might be done by an upstream intermediary, the
results are not under the control of the serializer or the parser. results are not under the control of the serializer or the parser.
Tokens, Integers, Floats and Byte Sequences cannot be split across Tokens, Integers, Floats and Byte Sequences cannot be split across
multiple headers because the inserted commas will cause parsing to multiple headers because the inserted commas will cause parsing to
fail. fail.
If parsing fails - including when calling another algorithm - the If parsing fails - including when calling another algorithm - the
entire header field's value MUST be discarded. This is intentionally 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
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
is not parsing the header field; for example, an intermediary is not
required to strip a failing header field from a message before
forwarding it.
4.2.1. Parsing a List from Text 4.2.1. Parsing a List from Text
Given an ASCII string input_string, return an array of (member, Given an ASCII string as input_string, return an array of (member,
parameters). input_string is modified to remove the parsed value. parameters). 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. Let member be the result of running Parsing a Parameterized
Member from Text (Section 4.2.1.1) with input_string. Member from Text (Section 4.2.1.1) with input_string.
2. Append member to members. 2. Append member to members.
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6. Discard any leading OWS from input_string. 6. Discard any leading OWS from input_string.
7. If input_string is empty, there is a trailing comma; fail 7. 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 a Parameterized Member from Text
Given an ASCII string input_string, return an token with an ordered Given an ASCII string as input_string, return a member (either a list
map of parameters. input_string is modified to remove the parsed of items, or a single item) with an ordered map of parameters.
value. 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 "(", let member be the
result of running Parsing an Inner List (Section 4.2.1.2) with result 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. Else, let member be the result of running Parsing an Item
(Section 4.2.4) with input_string. (Section 4.2.3) with input_string.
3. Let parameters be an empty, ordered map. 3. Let parameters be an empty, ordered map.
4. In a loop: 4. 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 not ";", exit the 2. If the first character of input_string is not ";", exit the
loop. loop.
3. Consume a ";" character from the beginning of input_string. 3. Consume a ";" character from the beginning of input_string.
4. Discard any leading OWS from input_string. 4. Discard any leading OWS from input_string.
5. let param_name be the result of Parsing a key from Text 5. let param_name be the result of Parsing a key from Text
(Section 4.2.3) from input_string. (Section 4.2.1.3) from input_string.
6. If param_name is already present in parameters, there is a 6. If param_name is already present in parameters, there is a
duplicate; fail parsing. duplicate; fail parsing.
7. Let param_value be a null value. 7. Let param_value be a null value.
8. If the first character of input_string is "=": 8. If the first character of input_string is "=":
1. Consume the "=" character at the beginning of 1. Consume the "=" character at the beginning of
input_string. input_string.
2. Let param_value be the result of Parsing an Item from 2. Let param_value be the result of Parsing an Item from
Text (Section 4.2.4) from input_string. Text (Section 4.2.3) from input_string.
9. Append key param_name with value param_value to parameters. 9. Append key param_name with value param_value to parameters.
5. Return the tuple (member, 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 input_string, return an array of items. Given an ASCII string as input_string, return an array of items.
input_string is modified to remove the parsed value. 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. Return inner_list.
3. Let item be the result of running Parsing an Item from Text 3. Let item be the result of running Parsing an Item from Text
(Section 4.2.4) 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
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.
4.2.2. Parsing a Dictionary from Text 4.2.2. Parsing a Dictionary from Text
Given an ASCII string input_string, return an ordered map of (key, Given an ASCII string as input_string, return an ordered map of (key,
item). input_string is modified to remove the parsed value. 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 from
Text (Section 4.2.3) with input_string. Text (Section 4.2.1.3) 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 a Parameterized
Member from Text (Section 4.2.1.1) with input_string. Member from Text (Section 4.2.1.1) with input_string.
skipping to change at page 22, line 13 skipping to change at page 23, line 16
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 a Key from Text 4.2.3. Parsing an Item from Text
Given an ASCII string 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. Let char be the result of removing the first character of
input_string.
2. If char is not one of lcalpha, DIGIT, "*", "_", or "-":
1. Prepend char to input_string.
2. Return output_string.
3. Append char to output_string.
4. Return output_string.
4.2.4. Parsing an Item from Text
Given an ASCII string input_string, return an item. input_string is Given an ASCII string as input_string, return an item. input_string
modified to remove the parsed value. 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 4.2.5) and return the process input_string as a number (Section 4.2.4) and return the
result. result.
2. If the first character of input_string is a DQUOTE, process 2. If the first character of input_string is a DQUOTE, process
input_string as a string (Section 4.2.6) and return the result. input_string as a string (Section 4.2.5) and return the result.
3. If the first character of input_string is "*", process 3. If the first character of input_string is "*", process
input_string as a byte sequence (Section 4.2.8) and return the input_string as a byte sequence (Section 4.2.7) and return the
result. result.
4. If the first character of input_string is "?", process 4. If the first character of input_string is "?", process
input_string as a Boolean (Section 4.2.9) and return the result. input_string as a Boolean (Section 4.2.8) and return the result.
5. If the first character of input_string is an ALPHA, process 5. If the first character of input_string is an ALPHA, process
input_string as a token (Section 4.2.7) and return the result. input_string as a token (Section 4.2.6) and return the result.
6. Otherwise, the item type is unrecognized; fail parsing. 6. Otherwise, the item type is unrecognized; fail parsing.
4.2.5. Parsing a Number from Text 4.2.4. Parsing a Number from Text
Given an ASCII string input_string, return a number. input_string is Given an ASCII string as input_string, return a number. input_string
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 3.4) and Floats
(Section 3.5), and returns the corresponding structure. (Section 3.5), 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.
skipping to change at page 24, line 25 skipping to change at page 25, line 5
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.
10. Return output_number. 10. Return output_number.
4.2.6. Parsing a String from Text 4.2.5. Parsing a String from Text
Given an ASCII string input_string, return an unquoted string. Given an ASCII string as input_string, return an unquoted string.
input_string is modified to remove the parsed value. input_string is modified to remove the parsed value.
1. Let output_string be an empty string. 1. Let output_string be an empty string.
2. If the first character of input_string is not DQUOTE, fail 2. If the first character of input_string is not DQUOTE, fail
parsing. parsing.
3. Discard the first character of input_string. 3. Discard the first character of input_string.
4. While input_string is not empty: 4. While input_string is not empty:
1. Let char be the result of consuming the first character of 1. Let char be the result of consuming the first character of
input_string. input_string.
2. If char is a backslash ("\"): 2. If char is a backslash ("\"):
1. If input_string is now empty, fail parsing. 1. If input_string is now empty, fail parsing.
2. Else: 2. Let next_char be the result of consuming the first
character of input_string.
1. Let next_char be the result of consuming the first
character of input_string.
2. If next_char is not DQUOTE or "\", fail parsing. 3. If next_char is not DQUOTE or "\", fail parsing.
3. Append next_char to output_string. 4. Append next_char to output_string.
3. Else, if char is DQUOTE, return output_string. 3. Else, if char is DQUOTE, return output_string.
4. Else, if char is in the range %x00-1f or %x7f (i.e., is not 4. Else, if char is in the range %x00-1f or %x7f (i.e., is not
in VCHAR or SP), fail parsing. in VCHAR or SP), fail parsing.
5. Else, append char to output_string. 5. Else, append char to output_string.
5. Reached the end of input_string without finding a closing DQUOTE; 5. Reached the end of input_string without finding a closing DQUOTE;
fail parsing. fail parsing.
4.2.7. Parsing a Token from Text 4.2.6. Parsing a Token from Text
Given an ASCII string input_string, return a token. input_string is Given an ASCII string as input_string, return a token. input_string
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. Let char be the result of consuming the first character of 1. If the first character of input_string is not one of ALPHA,
input_string. DIGIT, "_", "-", ".", ":", "%", "*" or "/", return
output_string.
2. If char is not one of ALPHA, DIGIT, "_", "-", ".", ":", "%",
"*" or "/":
1. Prepend char to input_string.
2. Return output_string. 2. Let char be the result of consuming the first character of
input_string.
3. Append char to output_string. 3. Append char to output_string.
4. Return output_string. 4. Return output_string.
4.2.8. Parsing a Byte Sequence from Text 4.2.7. Parsing a Byte Sequence from Text
Given an ASCII string input_string, return a byte sequence. Given an ASCII string as input_string, return a byte sequence.
input_string is modified to remove the parsed value. input_string is modified to remove the parsed value.
1. If the first character of input_string is not "*", fail parsing. 1. If the first character of input_string is not "*", fail parsing.
2. Discard the first character of input_string. 2. Discard the first character of input_string.
3. If there is not a "*" character before the end of input_string, 3. If there is not a "*" character before the end of input_string,
fail parsing. fail parsing.
4. Let b64_content be the result of consuming content of 4. Let b64_content be the result of consuming content of
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Because some implementations of base64 do not allow rejection of Because some implementations of base64 do not allow rejection of
encoded data that has non-zero pad bits (see [RFC4648], Section 3.5), encoded data that has non-zero pad bits (see [RFC4648], Section 3.5),
parsers SHOULD NOT fail when it is present, unless they cannot be parsers SHOULD NOT fail when it is present, unless they cannot be
configured to do so. configured to do so.
This specification does not relax the requirements in [RFC4648], This specification does not relax the requirements in [RFC4648],
Section 3.1 and 3.3; therefore, parsers MUST fail on characters Section 3.1 and 3.3; therefore, parsers MUST fail on characters
outside the base64 alphabet, and on line feeds in encoded data. outside the base64 alphabet, and on line feeds in encoded data.
4.2.9. Parsing a Boolean from Text 4.2.8. Parsing a Boolean from Text
Given an ASCII string input_string, return a Boolean. input_string is Given an ASCII string as input_string, return a Boolean. input_string
modified to remove the parsed value. is modified to remove the parsed value.
1. If the first character of input_string is not "?", fail parsing. 1. If the first character of input_string is not "?", fail parsing.
2. Discard the first character of input_string. 2. Discard the first character of input_string.
3. If the first character of input_string matches "1", discard the 3. If the first character of input_string matches "1", discard the
first character, and return true. first character, and return true.
4. If the first character of input_string matches "0", discard the 4. If the first character of input_string matches "0", discard the
first character, and return false. first character, and return false.
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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; see 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 [7].
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-11 D.1. Since draft-ietf-httpbis-header-structure-12
o Editorial improvements.
o Reworked float serialisation (#896).
D.2. 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.2. Since draft-ietf-httpbis-header-structure-10 D.3. 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.3. Since draft-ietf-httpbis-header-structure-09 D.4. 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.4. Since draft-ietf-httpbis-header-structure-08 D.5. 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 32, line 18 skipping to change at page 33, line 5
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.5. Since draft-ietf-httpbis-header-structure-07 D.6. 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.6. Since draft-ietf-httpbis-header-structure-06 D.7. 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.7. Since draft-ietf-httpbis-header-structure-05 D.8. 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.8. Since draft-ietf-httpbis-header-structure-04 D.9. 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.9. Since draft-ietf-httpbis-header-structure-03 D.10. Since draft-ietf-httpbis-header-structure-03
o Strengthen language around failure handling. o Strengthen language around failure handling.
D.10. Since draft-ietf-httpbis-header-structure-02 D.11. 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.11. Since draft-ietf-httpbis-header-structure-01 D.12. Since draft-ietf-httpbis-header-structure-01
o Replaced with draft-nottingham-structured-headers. o Replaced with draft-nottingham-structured-headers.
D.12. Since draft-ietf-httpbis-header-structure-00 D.13. 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. 117 change blocks. 
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