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Diffstat (limited to 'lib/asn1/doc/src/asn1_ug.xml')
| -rw-r--r-- | lib/asn1/doc/src/asn1_ug.xml | 113 |
1 files changed, 62 insertions, 51 deletions
diff --git a/lib/asn1/doc/src/asn1_ug.xml b/lib/asn1/doc/src/asn1_ug.xml index f2cd073ec8..12d986308f 100644 --- a/lib/asn1/doc/src/asn1_ug.xml +++ b/lib/asn1/doc/src/asn1_ug.xml @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>1997</year><year>2009</year> + <year>1997</year><year>2010</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -22,7 +22,7 @@ </legalnotice> <title>Asn1</title> - <prepared>ETX/DN/SP Kenneth. Lundin</prepared> + <prepared>Kenneth Lundin</prepared> <docno></docno> <date>1999-03-25</date> <rev>D</rev> @@ -41,17 +41,28 @@ decode functions to be used by Erlang programs sending and receiving ASN.1 specified data.</item> <item>Run-time functions used by the generated code.</item> - <item>Encoding rules supported are <em>BER</em>, the - specialized BER version <em>DER</em> and the basic form of - aligned and unaligned variants of <em>PER</em>.</item> + <item>The supported encoding rules are: + <list> + <item> + Basic Encoding Rules (<em>BER</em>) + </item> + <item> + Distinguished Encoding Rules (<em>DER</em>), a specialized form of BER that is used in security-conscious applications. + </item> + <item> + Packed Encoding Rules (<em>PER</em>) both the aligned and unaligned variant. + </item> + </list> + </item> </list> </section> <section> <title>Overview</title> - <p>ASN.1 (Abstract Syntax Notation 1) defines the abstract - syntax of information. The purpose of ASN.1 is to have - a platform independent language to express types using a + <p>ASN.1 (Abstract Syntax Notation 1) is a formal language for describing data structures to be exchanged between distributed computer systems. + The purpose of ASN.1 is to have + a platform and programming language independent notation to express + types using a standardized set of rules for the transformation of values of a defined type, into a stream of bytes. This stream of bytes can then be sent on a communication channel set up by the @@ -102,20 +113,16 @@ [<cite id="DUBUISSON"></cite>], free to download at <url href="http://www.oss.com/asn1/dubuisson.html">http://www.oss.com/asn1/dubuisson.html </url>. </p> - <p>Knowledge of Erlang programming is also essential and reading the book - <em>Concurrent Programming in ERLANG</em>, - [<cite id="erlbook2"></cite>], is recommended. Part 1 of this is available on the web in - <url href="http://www.erlang.org/download/erlang-book-part1.pdf">PDF</url> format. - </p> </section> <section> <title>Capability</title> <p>This application covers all features of ASN.1 up to the 1997 - edition of the specification. In the 2002 edition some new - extensions came up of which there are support only for some of - them. ECN (Cncoding Control Notation) and XML notation are still - unsupported. Though, the other features of 2002 edition are + edition of the specification. In the 2002 edition of ASN.1 a number of + new features where introduced of which some are supported while + others are not. For example the + ECN (Encoding Control Notation) and XML notation are still + unsupported. Though, the other features of the 2002 edition are fully or partly supported as shown below:</p> <list type="bulleted"> <item> @@ -308,7 +315,7 @@ erlc -o ../asnfiles -I ../asnfiles -I /usr/local/standards/asn1 Person.asn <p>Choice of encoding rules, if omitted <c>ber</c> is the default. The <c>ber_bin</c> and <c>per_bin</c> options allows for optimizations and are therefore recommended - instaed of the <c>ber</c> and <c>per</c> options.</p> + instead of the <c>ber</c> and <c>per</c> options.</p> </item> <tag><c>-o OutDirectory</c></tag> <item> @@ -629,7 +636,7 @@ asn1ct:decode('H323-MESSAGES','SomeChoiceType',Bytes). </pre> <c>driver</c> options does not affect the encode or decode result, just the time spent in run-time. When <c>ber_bin</c> and <c>driver</c> or <c>per_bin, optimize</c> and <c>driver</c> is - combined the C-code driver is used in choosen parts of encode / + combined the C-code driver is used in chosen parts of encode / decode procedure. </p> <table> @@ -749,11 +756,11 @@ asn1rt:decode('H323-MESSAGES','SomeChoiceType',Bytes). </pre> you may want to continue running the old asn1 run-time functionality.</item> <item>Performance issues: If you have an asn1 system with a lot - of cross references you may gain in performance. Meassurements + of cross references you may gain in performance. Measurements must be done for each case.</item> </list> <p>You may choose either the plain multi file compilation that just - merges the choosen asn1 specs or the <c>{inline,OutputModule}</c> + merges the chosen asn1 specs or the <c>{inline,OutputModule}</c> that also includes the used asn1 run-time functionality.</p> <p>For both cases you need to specify which asn1 specs you will compile in a module that must have the extension @@ -919,7 +926,7 @@ T5 ::= INTEGER (MIN<..-99) T6 ::= INTEGER {red(0),blue(1),white(2)} </pre> <p>The Erlang representation of an ASN.1 INTEGER is an integer or - an atom if a so called \011<c>Named NumberList</c> (see T6 above) + an atom if a so called <c>Named Number List</c> (see T6 above) is specified.</p> <p>Below is an example of Erlang code which assigns values for the above types: </p> @@ -934,7 +941,7 @@ T6value3 = white ASN.1 defined types. This style of value can be passed directly to the encoder for transformation into a series of bytes.</p> <p>The decoder will return an atom if the value corresponds to a - symbol in the Named NumberList.</p> + symbol in the Named Number List.</p> </section> <section> @@ -978,8 +985,9 @@ N1 = 'NULL', <p>The enumerated type can be used, when the value we wish to describe, may only take one of a set of predefined values.</p> <pre> -DaysOfTheWeek ::= ENUMERATED { sunday(1),monday(2),tuesday(3), -\011wednesday(4),thursday(5),friday(6),saturday(7) } +DaysOfTheWeek ::= ENUMERATED { + sunday(1),monday(2),tuesday(3), + wednesday(4),thursday(5),friday(6),saturday(7) } </pre> <p>For example to assign a weekday value in Erlang use the same atom as in the <c>Enumerations</c> of the type definition:</p> @@ -1273,11 +1281,14 @@ Pdu ::= SEQUENCE { <p>Values can be assigned in Erlang as shown below:</p> <pre> MyPdu = #'Pdu'{a=22,b=77.99,c={0,1,2,3,4},d='NULL'}. </pre> - <p>It is also possible to specify the value for each component in - a SEQUENCE or a SET as <c>{ComponentName,Value}</c>. It is not - recommended and is not supported if the flags <c>per_bin</c> or - <c>ber_bin</c> and <c>optimize</c> were used when the module was - compiled.</p> +<note> + <p> + In very early versions of the asn1 compiler it was also possible to + specify the values of the components in + a SEQUENCE or a SET as a list of tuples <c>{ComponentName,Value}</c>. + This is no longer supported. + </p> +</note> <p>The decode functions will return a record as result when decoding a <c>SEQUENCE</c> or a <c>SET</c>. <marker id="DEFAULT"></marker> @@ -1293,13 +1304,13 @@ MyPdu = #'Pdu'{a=22,b=77.99,c={0,1,2,3,4},d='NULL'}. </pre> <p>For instance, if the following types exists in a file "File.asn":</p> <pre> Seq1 ::= SEQUENCE { -\011a INTEGER DEFAULT 1, -\011b Seq2 DEFAULT {aa TRUE, bb 15} + a INTEGER DEFAULT 1, + b Seq2 DEFAULT {aa TRUE, bb 15} } Seq2 ::= SEQUENCE { -\011aa BOOLEAN, -\011bb INTEGER + aa BOOLEAN, + bb INTEGER } </pre> <p>Some values and the corresponding encoding in an Erlang terminal @@ -1331,7 +1342,7 @@ ok <marker id="DEFAULT DER"></marker> </p> <p>But, the DER encoding format has stronger requirements regarding - default\011values both for SET and SEQUENCE. A more elaborate and time + default values both for SET and SEQUENCE. A more elaborate and time expensive check of default values will take place. The following is an example with the same types and values as above but with der encoding format.</p> @@ -1409,7 +1420,7 @@ Bad ::= SET {i INTEGER, values is the same for SET as for SEQUENCE, and is supported by the compiler, <seealso marker="#DEFAULT DER">see above</seealso>.</p> <p>Moreover, in DER the elements of a SET will be sorted. If a - component is an untagged choice the sorting have to take place + component is an un-tagged choice the sorting have to take place in run-time. This fact emphasizes the following recommendation if DER encoding format is used.</p> <p>The concept of SET is an unusual @@ -1425,7 +1436,7 @@ Bad ::= SET {i INTEGER, </section> <section> - <title>Notes about Extendability for SEQUENCE and SET</title> + <title>Notes about Extend-ability for SEQUENCE and SET</title> <p>When a SEQUENCE or SET contains an extension marker and extension components like this:</p> <pre> @@ -1498,9 +1509,9 @@ C2 ::= CHOICE { <section> <title>Extendable CHOICE</title> <p>When a CHOICE contains an extension marker and the decoder detects - an unknown alternative of the CHIOCE the value is represented as:</p> + an unknown alternative of the CHOICE the value is represented as:</p> <pre> -\011 {asn1_ExtAlt, BytesForOpenType} +{asn1_ExtAlt, BytesForOpenType} </pre> <p>Where <c>BytesForOpenType</c> is a list of bytes constituting the encoding of the "unknown" CHOICE alternative. </p> @@ -1630,15 +1641,15 @@ V = #'Emb'{a=["qqqq",[1,2,255]], the record name is extended with an underscore and the component name. If the embedded structure is deeper with SEQUENCE, SET or CHOICE types in the line, each component-/alternative-name will - be added to the recordname.</p> + be added to the record-name.</p> <p>For example:</p> <pre> Seq ::= SEQUENCE{ - a\011CHOICE{ -\011b SEQUENCE { -\011 c INTEGER -\011 } -\011} + a CHOICE{ + b SEQUENCE { + c INTEGER + } + } } </pre> <p>will result in the following record:</p> <pre> @@ -1650,10 +1661,10 @@ Seq ::= SEQUENCE{ <pre> Seq ::= SEQUENCE { a SEQUENCE OF SEQUENCE { -\011 b + b } c SET OF SEQUENCE { -\011 d + d } } </pre> <p>This results in the records:</p> @@ -1802,16 +1813,16 @@ GENERAL-PROCEDURES GENERAL-PROCEDURE ::= { <pre> StartMessage ::= SEQUENCE { msgId GENERAL-PROCEDURE.&id ({GENERAL-PROCEDURES}), - content GENERAL-PROCEDURE.&Message\011({GENERAL-PROCEDURES}{@msgId}), + content GENERAL-PROCEDURE.&Message ({GENERAL-PROCEDURES}{@msgId}), } </pre> <p>In the type <c>StartMessage</c> the constraint following the <c>content</c> field tells that in a value of type <c>StartMessage</c> the value in the <c>content</c> field must - come from the same object that is choosen by the <c>msgId</c> + come from the same object that is chosen by the <c>msgId</c> field.</p> <p>So, the value <c>#'StartMessage'{msgId="home",content="Any Printable String"}</c> is legal to encode as a StartMessage value, while the value <c>#'StartMessage'{msgId="remote", content="Some String"}</c> is illegal since the constraint - in StartMessage tells that when you have choosen a value from a + in StartMessage tells that when you have chosen a value from a specific object in the object set GENERAL-PROCEDURES in the msgId field you have to choose a value from that same object in the content field too. In this second case it should have been @@ -1831,7 +1842,7 @@ StartMessage ::= SEQUENCE { information object sets. A part of a definition can be supplied as a parameter. For instance, if a Type is used in a definition with certain - purpose, one want the typename to express the intention. This + purpose, one want the type-name to express the intention. This can be done with parameterization.</p> <p>When many types (or an other ASN.1 entity) only differs in some minor cases, but the structure of the types are similar, only |