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Diffstat (limited to 'lib/asn1/doc/src/asn1_getting_started.xml')
| -rw-r--r-- | lib/asn1/doc/src/asn1_getting_started.xml | 83 |
1 files changed, 73 insertions, 10 deletions
diff --git a/lib/asn1/doc/src/asn1_getting_started.xml b/lib/asn1/doc/src/asn1_getting_started.xml index d40b294c39..907bf051d5 100644 --- a/lib/asn1/doc/src/asn1_getting_started.xml +++ b/lib/asn1/doc/src/asn1_getting_started.xml @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>1997</year><year>2016</year> + <year>1997</year><year>2017</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -187,6 +187,14 @@ erlc -o ../asnfiles -I ../asnfiles -I /usr/local/standards/asn1 Person.asn</pre> <item> <p>DER encoding rule. Only when using option <c>-ber</c>.</p> </item> + <tag><c>+maps</c></tag> + <item> + <p>Use maps instead of records to represent the <c>SEQUENCE</c> and + <c>SET</c> types. No <c>.hrl</c> files will be generated. + See the Section <seealso marker="asn1_getting_started#MAP_SEQ_SET"> + Map representation for SEQUENCE and SET</seealso> + for more information.</p> + </item> <tag><c>+asn1config</c></tag> <item> <p>This functionality works together with option @@ -258,6 +266,10 @@ asn1ct:compile("H323-MESSAGES.asn1",[per]). </pre> <c>{error, {asn1, Description}}</c> where <c>Description</c> is an Erlang term describing the error.</p> + <p>Currently, <c>Description</c> looks like this: + <c>{ErrorDescription, StackTrace}</c>. Applications should + not depend on the exact contents of <c>Description</c> as it + could change in the future.</p> </section> </section> @@ -766,8 +778,11 @@ Pdu ::= SEQUENCE { b REAL, c OBJECT IDENTIFIER, d NULL } </pre> - <p>This is a 4-component structure called <c>Pdu</c>. The record format - is the major format for representation of <c>SEQUENCE</c> in Erlang. + <p>This is a 4-component structure called <c>Pdu</c>. By default, + a <c>SEQUENCE</c> is represented by a record in Erlang. + It can also be represented as a map; see + <seealso marker="asn1_getting_started#MAP_SEQ_SET"> + Map representation for SEQUENCE and SET</seealso>. For each <c>SEQUENCE</c> and <c>SET</c> in an ASN.1 module an Erlang record declaration is generated. For <c>Pdu</c>, a record like the following is defined:</p> @@ -878,6 +893,48 @@ SExt ::= SEQUENCE { </section> <section> + <marker id="MAP_SEQ_SET"></marker> + <title>Map representation for SEQUENCE and SET</title> + <p>If the ASN.1 module has been compiled with option <c>maps</c>, + the types <c>SEQUENCE</c> and <c>SET</c> are represented as maps.</p> + <p>In the following example, this ASN.1 specification is used:</p> + <pre> +File DEFINITIONS AUTOMATIC TAGS ::= +BEGIN +Seq1 ::= SEQUENCE { + a INTEGER DEFAULT 42, + b BOOLEAN OPTIONAL, + c IA5String +} +END </pre> + + <p>Optional fields are to be omitted from the map if they have + no value:</p> + + <pre> +1> <input>asn1ct:compile('File', [per,maps]).</input> +ok +2> <input>{ok,E} = 'File':encode('Seq1', #{a=>0,c=>"string"}).</input> +{ok,<<128,1,0,6,115,116,114,105,110,103>>} </pre> + + <p>When decoding, optional fields will be omitted from the map:</p> + + <pre> +3> <input>'File':decode('Seq1', E).</input> +{ok,#{a => 0,c => "string"}} </pre> + + <p>Default values can be omitted from the map:</p> + <pre> +4> <input>{ok,E2} = 'File':encode('Seq1', #{c=>"string"}).</input> +{ok,<<0,6,115,116,114,105,110,103>>} +5> <input>'File':decode('Seq1', E2).</input> +{ok,#{a => 42,c => "string"}} </pre> + + <note><p>It is not allowed to use the atoms <c>asn1_VALUE</c> and + <c>asn1_DEFAULT</c> with maps.</p></note> + </section> + + <section> <marker id="CHOICE"></marker> <title>CHOICE</title> <p>The type <c>CHOICE</c> is a space saver and is similar to the @@ -1004,11 +1061,16 @@ T ::= CHOICE { <section> <title>Naming of Records in .hrl Files</title> + <p>When the option <c>maps</c> is given, no <c>.hrl</c> files + will be generated. The rest of this section describes the behavior + of the compiler when <c>maps</c> is not used.</p> + <p>When an ASN.1 specification is compiled, all defined types of type - <c>SET</c> or <c>SEQUENCE</c> result in a corresponding record in the - generated <c>.hrl</c> file. This is because the values for - <c>SET</c> and <c>SEQUENCE</c> are represented as records as - mentioned earlier.</p> + <c>SET</c> or <c>SEQUENCE</c> result in a corresponding record in the + generated <c>.hrl</c> file. This is because the values for + <c>SET</c> and <c>SEQUENCE</c> are represented as records + by default.</p> + <p>Some special cases of this functionality are presented in the next section.</p> @@ -1144,9 +1206,10 @@ SS ::= SET { <p>This example shows that a function is generated by the compiler that returns a valid Erlang representation of the value, although the value is of a complex type.</p> - <p>Furthermore, a macro is generated for each value in the <c>.hrl</c> - file. So, the defined value <c>tt</c> can also be extracted by - <c>?tt</c> in application code.</p> + <p>Furthermore, if the option <c>maps</c> is not used, + a macro is generated for each value in the <c>.hrl</c> + file. So, the defined value <c>tt</c> can also be extracted by + <c>?tt</c> in application code.</p> </section> <section> |