path: root/lib/stdlib/doc/src/uri_string.xml

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  <header>
    <copyright>
      <year>2017</year><year>2017</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
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      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
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    <title>uri_string</title>
    <prepared>Péter Dimitrov</prepared>
    <docno>1</docno>
    <date>2017-10-24</date>
    <rev>A</rev>
  </header>
  <module>uri_string</module>
  <modulesummary>URI processing functions.</modulesummary>
  <description>
    <p>This module contains functions for parsing and handling URIs
    (<url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>).
    </p>
    <p>A URI is an identifier consisting of a sequence of characters   matching the syntax
    rule named <em>URI</em> in <url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>.
    </p>
    <p>  The generic URI syntax consists of a hierarchical sequence of components referred
    to as the scheme, authority, path, query, and fragment:</p>
    <pre>
    URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
    hier-part   = "//" authority path-abempty
                   / path-absolute
                   / path-rootless
                   / path-empty
    scheme      = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
    authority   = [ userinfo "@" ] host [ ":" port ]
    userinfo    = *( unreserved / pct-encoded / sub-delims / ":" )

    reserved    = gen-delims / sub-delims
    gen-delims  = ":" / "/" / "?" / "#" / "[" / "]" / "@"
    sub-delims  = "!" / "$" / "&amp;" / "'" / "(" / ")"
                / "*" / "+" / "," / ";" / "="

    unreserved  = ALPHA / DIGIT / "-" / "." / "_" / "~"
    </pre><br></br>
    <p>The interpretation of a URI depends only on the characters used and not on how those
    characters are represented in a network protocol.</p>
    <p>The functions implemented by this module cover the following use cases:</p>
    <list type="bulleted">
      <item>Parsing URIs into its components and returing a map<br></br>
      <seealso marker="#parse/1"><c>parse/1</c></seealso>
      </item>
      <item>Recomposing a map of URI components into a URI string<br></br>
      <seealso marker="#recompose/1"><c>recompose/1</c></seealso>
      </item>
      <item>Changing inbound binary and percent-encoding of URIs<br></br>
      <seealso marker="#transcode/2"><c>transcode/2</c></seealso>
      </item>
      <item>Transforming URIs into a normalized form<br></br>
      <seealso marker="#normalize/1"><c>normalize/1</c></seealso>
      </item>
    </list>
    <p>There are four different encodings present during the handling of URIs:</p>
    <list type="bulleted">
      <item>Inbound binary encoding in binaries</item>
      <item>Inbound percent-encoding in lists and binaries</item>
      <item>Outbound binary encoding in binaries</item>
      <item>Outbound percent-encoding in lists and binaries</item>
    </list>
    <p>Functions with <c>uri_string()</c> argument accept lists, binaries and
    mixed lists (lists with binary elements) as input type. All of the functions but
    <c>transcode/2</c> expects input as lists of unicode codepoints, UTF-8 encoded binaries
    and UTF-8 percent-encoded URI parts ("%C3%B6" corresponds to the unicode character "ö").</p>
    <p>Unless otherwise specified the return value type and encoding are the same as the input
    type and encoding. That is, binary input returns binary output, list input returns a list
    output but mixed input returns list output.</p>
    <p>In case of lists there is only percent-encoding. In binaries, however, both binary encoding
    and percent-encoding shall be considered. <c>transcode/2</c> provides the means to convert
    between the supported encodings, it takes a <c>uri_string()</c> and a list of options
    specifying inbound and outbound encodings.</p>
    <p><url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url> does not mandate any specific
    character encoding and it is usually defined by the protocol or surrounding text. This library
    takes the same assumption, binary and percent-encoding are handled as one configuration unit,
    they cannot be set to different values.</p>
  </description>

  <datatypes>
    <datatype>
      <name name="error"/>
      <desc>
        <p>Error tuple indicating the type of error. Possible values of the second component:</p>
	<list type="bulleted">
	  <item><c>invalid_input</c></item>
	  <item><c>invalid_map</c></item>
	  <item><c>invalid_percent_encoding</c></item>
	  <item><c>invalid_scheme</c></item>
	  <item><c>invalid_uri</c></item>
	  <item><c>invalid_utf8</c></item>
	</list>
	<p>The third component is a term providing additional information about the
	cause of the error.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="uri_map"/>
      <desc>
        <p>Map holding the main components of a URI.</p>
      </desc>
    </datatype>
    <datatype>
      <name name="uri_string"/>
      <desc>
        <p>List of unicode codepoints, a UTF-8 encoded binary, or a mix of the two,
        representing an <url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>
	compliant URI (<em>percent-encoded form</em>).
        A URI is a sequence of characters from a very limited set: the letters of
        the basic Latin alphabet, digits, and a few special characters.</p>
      </desc>
    </datatype>
  </datatypes>

  <funcs>

    <func>
      <name name="normalize" arity="1"/>
      <fsummary>Syntax-based normalization.</fsummary>
      <desc>
        <p>Transforms <c><anno>URIString</anno></c> into a normalized form
	using Syntax-Based Normalization as defined by
	<url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>.</p>
	<p>This function implements case normalization, percent-encoding
	normalization, path segment normalization and scheme based normalization
	for HTTP(S) with basic support for FTP, SSH, SFTP and TFTP.</p>
        <p><em>Example:</em></p>
        <pre>
1> <input>uri_string:normalize("/a/b/c/./../../g").</input>
"/a/g"
2> <![CDATA[uri_string:normalize(<<"mid/content=5/../6">>).]]>
<![CDATA[<<"mid/6">>]]>
3> uri_string:normalize("http://localhost:80").
"https://localhost/"
	</pre>
      </desc>
    </func>

    <func>
      <name name="parse" arity="1"/>
      <fsummary>Parse URI into a map.</fsummary>
      <desc>
        <p>Parses an <url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>
	compliant <c>uri_string()</c> into a <c>uri_map()</c>, that holds the parsed
	components of the <c>URI</c>.
	If parsing fails, an error tuple is returned.</p>
	<p>See also the opposite operation <seealso marker="#recompose/1">
	<c>recompose/1</c></seealso>.</p>
        <p><em>Example:</em></p>
        <pre>
1> <input>uri_string:parse("foo://[email protected]:8042/over/there?name=ferret#nose").</input>
#{fragment => "nose",host => "example.com",
  path => "/over/there",port => 8042,query => "name=ferret",
  scheme => foo,userinfo => "user"}
2> <![CDATA[uri_string:parse(<<"foo://[email protected]:8042/over/there?name=ferret">>).]]>
<![CDATA[#{host => <<"example.com">>,path => <<"/over/there">>,
  port => 8042,query => <<"name=ferret">>,scheme => <<"foo">>,
  userinfo => <<"user">>}]]>
	</pre>
      </desc>
    </func>

    <func>
      <name name="recompose" arity="1"/>
      <fsummary>Recompose URI.</fsummary>
      <desc>
        <p>Creates an <url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url> compliant
	<c><anno>URIString</anno></c> (percent-encoded), based on the components of
	<c><anno>URIMap</anno></c>.
	If the <c><anno>URIMap</anno></c> is invalid, an error tuple is returned.</p>
	<p>See also the opposite operation <seealso marker="#parse/1">
	<c>parse/1</c></seealso>.</p>
        <p><em>Example:</em></p>
        <pre>
1> <input>URIMap = #{fragment => "nose", host => "example.com", path => "/over/there",</input>
1> port => 8042, query => "name=ferret", scheme => "foo", userinfo => "user"}.
#{fragment => "top",host => "example.com",
  path => "/over/there",port => 8042,query => "?name=ferret",
  scheme => foo,userinfo => "user"}

2> <input>uri_string:recompose(URIMap).</input>
"foo://example.com:8042/over/there?name=ferret#nose"</pre>
      </desc>
    </func>

    <func>
      <name name="transcode" arity="2"/>
      <fsummary>Transcode URI.</fsummary>
      <desc>
        <p>Transcodes an <url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>
	compliant <c><anno>URIString</anno></c>,
	where <c><anno>Options</anno></c> is a list of tagged tuples, specifying the inbound
	(<c>in_encoding</c>) and outbound (<c>out_encoding</c>) encodings. <c>in_encoding</c>
	and <c>out_encoding</c> specifies both binary encoding and percent-encoding for the
	input and output data. Mixed encoding, where binary encoding is not the same as
	percent-encoding, is not supported.
	If an argument is invalid, an error tuple is returned.</p>
        <p><em>Example:</em></p>
        <pre>
1> <input><![CDATA[uri_string:transcode(<<"foo%00%00%00%F6bar"/utf32>>,]]></input>
1> [{in_encoding, utf32},{out_encoding, utf8}]).
<![CDATA[<<"foo%C3%B6bar"/utf8>>]]>
2> uri_string:transcode("foo%F6bar", [{in_encoding, latin1},
2> {out_encoding, utf8}]).
"foo%C3%B6bar"
	</pre>
      </desc>
    </func>

  </funcs>
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