draft-ietf-httpbis-header-structure-11.txt   draft-ietf-httpbis-header-structure-12.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: January 9, 2020 The Varnish Cache Project Expires: February 20, 2020 The Varnish Cache Project
July 8, 2019 August 19, 2019
Structured Headers for HTTP Structured Headers for HTTP
draft-ietf-httpbis-header-structure-11 draft-ietf-httpbis-header-structure-12
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 January 9, 2020. This Internet-Draft will expire on February 20, 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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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 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Dictionaries . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3. Items . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Integers . . . . . . . . . . . . . . . . . . . . . . . . 8 3.4. Integers . . . . . . . . . . . . . . . . . . . . . . . . 9
3.5. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.5. Floats . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.6. Strings . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.7. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.7. Tokens . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.8. Byte Sequences . . . . . . . . . . . . . . . . . . . . . 10 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 . . . 11
4.1. Serializing Structured Headers . . . . . . . . . . . . . 11 4.1. Serializing Structured Headers . . . . . . . . . . . . . 11
4.2. Parsing Header Fields into Structured Headers . . . . . . 17 4.2. Parsing Header Fields into Structured Headers . . . . . . 18
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
6. Security Considerations . . . . . . . . . . . . . . . . . . . 26 6. Security Considerations . . . . . . . . . . . . . . . . . . . 27
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.1. Normative References . . . . . . . . . . . . . . . . . . 26 7.1. Normative References . . . . . . . . . . . . . . . . . . 27
7.2. Informative References . . . . . . . . . . . . . . . . . 27 7.2. Informative References . . . . . . . . . . . . . . . . . 28
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 28 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 29
Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 28 Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 29
B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 28 B.1. Why not JSON? . . . . . . . . . . . . . . . . . . . . . . 29
B.2. Structured Headers don't "fit" my data. . . . . . . . . . 29 B.2. Structured Headers don't "fit" my data. . . . . . . . . . 30
Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 29 Appendix C. Implementation Notes . . . . . . . . . . . . . . . . 30
Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 30 Appendix D. Changes . . . . . . . . . . . . . . . . . . . . . . 31
D.1. Since draft-ietf-httpbis-header-structure-10 . . . . . . 30 D.1. Since draft-ietf-httpbis-header-structure-11 . . . . . . 31
D.2. Since draft-ietf-httpbis-header-structure-09 . . . . . . 30 D.2. Since draft-ietf-httpbis-header-structure-10 . . . . . . 31
D.3. Since draft-ietf-httpbis-header-structure-08 . . . . . . 31 D.3. Since draft-ietf-httpbis-header-structure-09 . . . . . . 31
D.4. Since draft-ietf-httpbis-header-structure-07 . . . . . . 31 D.4. Since draft-ietf-httpbis-header-structure-08 . . . . . . 31
D.5. Since draft-ietf-httpbis-header-structure-06 . . . . . . 32 D.5. Since draft-ietf-httpbis-header-structure-07 . . . . . . 32
D.6. Since draft-ietf-httpbis-header-structure-05 . . . . . . 32 D.6. Since draft-ietf-httpbis-header-structure-06 . . . . . . 32
D.7. Since draft-ietf-httpbis-header-structure-04 . . . . . . 32 D.7. Since draft-ietf-httpbis-header-structure-05 . . . . . . 32
D.8. Since draft-ietf-httpbis-header-structure-03 . . . . . . 32 D.8. Since draft-ietf-httpbis-header-structure-04 . . . . . . 33
D.9. Since draft-ietf-httpbis-header-structure-02 . . . . . . 32 D.9. Since draft-ietf-httpbis-header-structure-03 . . . . . . 33
D.10. Since draft-ietf-httpbis-header-structure-01 . . . . . . 33 D.10. Since draft-ietf-httpbis-header-structure-02 . . . . . . 33
D.11. Since draft-ietf-httpbis-header-structure-00 . . . . . . 33 D.11. Since draft-ietf-httpbis-header-structure-01 . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 D.12. Since draft-ietf-httpbis-header-structure-00 . . . . . . 33
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 [RFC7231], Section 8.3.1, 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
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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
within that scope. within that scope.
The ABNF for lists is: The ABNF for lists 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 ) *parameter
inner-list = "(" OWS [ sh-item *( SP sh-item ) OWS ] ")" inner-list = "(" OWS [ sh-item *( SP sh-item ) OWS ] ")"
parameter = OWS ";" OWS param-name [ "=" param-value ] parameter = OWS ";" OWS param-name [ "=" param-value ]
param-name = key param-name = key
key = lcalpha *( lcalpha / DIGIT / "_" / "-" ) key = lcalpha *( lcalpha / DIGIT / "_" / "-" / "*" )
lcalpha = %x61-7A ; a-z lcalpha = %x61-7A ; a-z
param-value = sh-item param-value = sh-item
In textual HTTP headers, each member is separated by a comma and In textual HTTP headers, each member is separated by a comma and
optional whitespace. For example, a header field whose value is optional whitespace. For example, a header field whose value is
defined as a list of strings could look like: defined as a 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 textual HTTP headers, inner lists are denoted by surrounding
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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_123;a=1;b=2; cdef_456, (ghi jkl);q="9";r="w"
In textual HTTP headers, an empty list is denoted by not serialising
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
values (including that of individual inner-list members and values (including that of individual inner-list members and
parameters) if necessary. parameters) if necessary.
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. There can be zero or more members, and their names
are required to be unique within the scope of the dictionary they are required to be unique within the scope of the dictionary they
occur within. 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 textual 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 dict-member = member-name "=" member-value *parameter
member-name = key member-name = key
member-value = sh-item / inner-list member-value = sh-item / inner-list
In textual HTTP headers, members are separated by a comma with In textual HTTP headers, members are separated by a comma with
optional whitespace, while names and values are separated by "=" optional whitespace, while names and values are separated by "="
(without 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)
Typically, a header field specification will define the semantics of A dictionary with a mix of singular and list values, some with
individual member names, as well as whether their presence is parameters:
Example-MixDict: a=(1,2), b=3, c=4;aa=bb, d=(5,6);valid=?T
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
using individual member names, as well as whether their presence is
required or optional. Recipients MUST ignore names that are required or optional. Recipients MUST ignore names that are
undefined or unknown, unless the header field's specification undefined or unknown, unless the header field's specification
specifically disallows them. 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 3.4), float (Section 3.5),
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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 3.5. Floats
Floats are integers with a fractional part, that can be stored as Floats are decimal numbers with an integer and a fractional
IEEE 754 double precision numbers (binary64) ([IEEE754]). component. The fractional component has at most six digits of
precision. Additionally, like integers, it can have no more than
fifteen digits in total, which in some cases further constrains its
precision.
The ABNF for floats in textual HTTP headers is: The ABNF for floats in textual HTTP headers is:
sh-float = ["-"] ( sh-float = ["-"] (1*9DIGIT "." 1*6DIGIT /
DIGIT "." 1*14DIGIT / 10DIGIT "." 1*5DIGIT /
2DIGIT "." 1*13DIGIT / 11DIGIT "." 1*4DIGIT /
3DIGIT "." 1*12DIGIT / 12DIGIT "." 1*3DIGIT /
4DIGIT "." 1*11DIGIT / 13DIGIT "." 1*2DIGIT /
5DIGIT "." 1*10DIGIT / 14DIGIT "." 1DIGIT )
6DIGIT "." 1*9DIGIT /
7DIGIT "." 1*8DIGIT /
8DIGIT "." 1*7DIGIT /
9DIGIT "." 1*6DIGIT /
10DIGIT "." 1*5DIGIT /
11DIGIT "." 1*4DIGIT /
12DIGIT "." 1*3DIGIT /
13DIGIT "." 1*2DIGIT /
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 3.6. 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 0x20 to 0x7E). Note that this excludes tabs, newlines,
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Given a structure defined in this specification: Given a structure defined in this specification:
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).
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
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1. If member is an array, let mem_value be the result of 1. If member is an array, let mem_value be the result of
applying Serialising an Inner List (Section 4.1.1.1) to applying Serialising an Inner List (Section 4.1.1.1) to
member. member.
2. Otherwise, let mem_value be the result of applying 2. Otherwise, let mem_value be the result of applying
Serializing an Item (Section 4.1.3) to member. Serializing an Item (Section 4.1.3) to member.
3. Append mem_value to output. 3. Append mem_value to output.
4. For each parameter in parameters: 4. Append the result of Serializing Parameters Section 4.1.1.2
with parameters to output.
1. Append ";" to output.
2. Let name be the result of applying Serializing a Key
(Section 4.1.1.2) to parameter's param-name.
3. Append name to output.
4. If parameter has a param-value:
1. Let value be the result of applying Serializing an
Item (Section 4.1.3) to parameter's param-value.
2. Append "=" to output.
3. Append value to output.
5. If more members remain in input_plist: 5. If more members 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
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(Section 4.1.3) to mem. (Section 4.1.3) to mem.
2. Append value to output. 2. Append value to output.
3. If inner_list is not empty, append a single WS to output. 3. 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 a Key 4.1.1.2. Serializing Parameters
Given an ordered dictionary parameters:
1. Let output be an empty string.
2. For each parameter in 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.
6. If parameter has a param-value:
1. Let value be the result of applying Serializing an Item
(Section 4.1.3) to parameter's param-value.
2. Append "=" to output.
3. Append value to output.
7. Return output.
4.1.1.3. Serializing a Key
Given a key as input_key: Given a key as input_key:
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 allowed in the ABNF for key, 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 a dictionary as input_dictionary:
1. Let output be an empty string. 1. Let output be an empty string.
2. For each member mem of input_dictionary: 2. For each (member, parameters) of input_dictionary:
1. Let name be the result of applying Serializing a Key 1. Let name be the result of applying Serializing a Key
(Section 4.1.1.2) to mem's member-name. (Section 4.1.1.3) to member's member-name.
2. Append name to output. 2. Append name to output.
3. Append "=" to output. 3. Append "=" to output.
4. If mem is an array, let value be the result of applying 4. If member is an array, let value be the result of applying
Serialising an Inner List (Section 4.1.1.1) to mem. Serialising an Inner List (Section 4.1.1.1) to member.
5. Otherwise, let value be the result of applying Serializing an 5. Otherwise, let value be the result of applying Serializing an
Item (Section 4.1.3) to mem. Item (Section 4.1.3) to member.
6. Append value to output. 6. Append value to output.
7. If more members remain in input_dictionary: 7. Append the result of Serializing Parameters Section 4.1.1.2
with parameters to output.
8. 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:
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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:
1. If input_float is not a IEEE 754 double precision number, fail 1. If input_float's fractional component has more than six digits of
serialisation. precision, fail serialisation.
2. Let output be an empty string. 2. If the number of digits of precision in input_float's fractional
component plus those in its integer component add to more than
fifteen digits, fail serialisation.
3. If input_float is less than (but not equal to) 0, append "-" to 3. Let output be an empty string.
4. If input_float is less than (but not equal to) 0, append "-" to
output. output.
4. Append input_float's integer component represented in base 10 5. Append input_float's integer component represented in base 10
using only decimal digits to output; if it is zero, append "0". using only decimal digits to output; if it is zero, append "0".
5. Append "." to output. 6. Append "." to output.
6. Append input_float's decimal component represented in base 10 7. Append input_float's fractional component represented in base 10
using only decimal digits to output; if it is zero, append "0". using only decimal digits to output; if it is zero, append "0".
7. Return output. 8. 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:
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 allowed by VCHAR or SP, fail
serialisation. serialisation.
2. Let output be an empty string. 2. Let output be an empty string.
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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:
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 allowed in Section 3.7, 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:
skipping to change at page 21, line 8 skipping to change at page 21, line 41
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 4.2.3) 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. If the first character of input_string is "(", let 4. Let member be the result of running Parsing a Parameterized
this_value be the result of running Parsing an Inner List Member from Text (Section 4.2.1.1) with input_string.
(Section 4.2.1.2) with input_string.
5. Else, let this_value be the result of running Parsing an
Item (Section 4.2.4) with input_string.
6. Add name this_key with value this_value to dictionary. 5. Add name this_key with value member to dictionary.
7. Discard any leading OWS from input_string. 6. Discard any leading OWS from input_string.
8. If input_string is empty, return dictionary. 7. If input_string is empty, return dictionary.
9. 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.
10. Discard any leading OWS from input_string. 9. Discard any leading OWS from input_string.
11. 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 a Key from Text
Given an ASCII string input_string, return a key. input_string is Given an ASCII string input_string, return a key. 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 1. If the first character of input_string is not lcalpha, 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 removing the first character of 1. Let char be the result of removing the first character of
input_string. input_string.
2. If char is not one of lcalpha, DIGIT, "_", or "-": 2. If char is not one of lcalpha, DIGIT, "*", "_", or "-":
1. Prepend char to input_string. 1. Prepend char to input_string.
2. Return output_string. 2. Return output_string.
3. Append char to output_string. 3. Append char to output_string.
4. Return output_string. 4. Return output_string.
4.2.4. Parsing an Item from Text 4.2.4. Parsing an Item from Text
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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 4.2.7) 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 4.2.5. Parsing a Number from Text
Given an ASCII string input_string, return a number. input_string is Given an ASCII string input_string, return a number. input_string is
modified to remove the parsed value. 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.
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.
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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 3.4, 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. Parse input_number as a float and let output_number be the 2. If the number of characters after "." in input_number is
greater than six, fail parsing.
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 4.2.6. Parsing a String from Text
Given an ASCII string input_string, return an unquoted string. Given an ASCII string 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.
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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-10 D.1. Since draft-ietf-httpbis-header-structure-11
o Allow * in key (#844).
o Constrain floats to six digits of precision (#848).
o Allow dictionary members to have parameters (#842).
D.2. 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.2. Since draft-ietf-httpbis-header-structure-09 D.3. 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.3. Since draft-ietf-httpbis-header-structure-08 D.4. 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).
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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.4. Since draft-ietf-httpbis-header-structure-07 D.5. 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.5. Since draft-ietf-httpbis-header-structure-06 D.6. 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.6. Since draft-ietf-httpbis-header-structure-05 D.7. 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.7. Since draft-ietf-httpbis-header-structure-04 D.8. 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.8. Since draft-ietf-httpbis-header-structure-03 D.9. Since draft-ietf-httpbis-header-structure-03
o Strengthen language around failure handling. o Strengthen language around failure handling.
D.9. Since draft-ietf-httpbis-header-structure-02 D.10. 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.10. Since draft-ietf-httpbis-header-structure-01 D.11. Since draft-ietf-httpbis-header-structure-01
o Replaced with draft-nottingham-structured-headers. o Replaced with draft-nottingham-structured-headers.
D.11. Since draft-ietf-httpbis-header-structure-00 D.12. 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. 52 change blocks. 
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