In this section, a sample CSN.1 file is presented, along with the corresponding ASN.1. There is little to no commentary here, as the chapter that defines the mappings really is the commentary. The majority of the patterns that may be recognized are illustrated in this sample.
Example 18.5. CSN.1 Example
ASN1MODULE : UserGuide;
-- This is a definition where the right hand side is mapped to a component and
-- the whole is therefore mapped into a SEQUENCE
<SingleComponent> ::= 0 | 1 <fields: <field1: bit(4)> <field2: bit(3)>>;
-- This example illustrates some of the effects of naming
<Naming> ::=
<ALL CAPS 1: bit(1)> --becomes all-caps-1
<PART Caps: bit(1)> --becomes part-Caps
<CamelCase: bit(1)> --becomes camelCase
;
--Illustrate various patterns of alternation
<Alternations> ::=
<l bit or h bit?: L | H>
<particular general:
010 <Naming> |
{<pg determinant: bit(3)> exclude 010} <something else: bit(4)>
>
<stereo choice 1 :
0 <first: bit(1)> | 1 <second: bit(2)> >
<stereo choice 2 :
00 | 01 <first: bit(1)> | 11 <second: bit(2)> | <third: 10> >
<optional with presence bit: 0 | 1 <maybe : bit(4)>>
<optional with presence bit and container determined: null | 0 | 1 <possibly : bit(3)>>
<optional container determined: null | <questionable: bit(2)>>
;
<padding> ::= {<bit> send 0} **;
<Length Constrained Content> ::=
<length : bit(7)>
{
{ <willy nilly: bit(4)>
{ 0 | 1 bit(3) }
<padding>
} & octet(val(length))
}
;
<Concat> ::=
{
<e1: bit(1)>
{
--This nesting will get removed
<e2: bit(2)>
<e3: bit(3)>
}
<e4: bit(4)>
<a pad bit: <bit> send 0>
<some literal bits: 0101001>
<single bit: bit>
<single octet: octet>
<ref to a name: Naming>
{ 1 <two bit value using more/done bit: bit(2)> }** 0
<named list: { 1 <two bit value using more/done bit: bit(2)> }** 0 >
<list of 10: <value: bit(4)>(10)>
<list ending with container: bit(3)>**
};
--Truncated concatenation.
<Truncated Concat> ::=
{
<e1: bit(1)>
{
--This nesting will NOT get removed
<e2: bit(2)>
<e3: bit(3)>
}
<e4: bit(4)>
}//
;
<Things With Exponents> ::=
<a 23-bit int: bit(23)>
<a fixed length bit string: bit(45)>
<a var length bit string: bit(val(a 23-bit int))>
<a fixed length octet str: octet(4)>
<a var len octet str: octet(val(a 23-bit int))>
<repeating optional component: {0 | 1 <opt comp: bit(4)>}(5)>
<five pad bits: <bit> send 0>(5)
<count bit encoding: 0** 1>
<fixed num of type: Naming(5)>
<var num of type: Naming(val(a 23-bit int))>
;
The resulting ASN.1 follows. Our tool generates tags in the ASN.1; these have been removed to improve readability.
Example 18.6. The resulting ASN.1
UserGuide DEFINITIONS AUTOMATIC TAGS ::= BEGIN
-- Productions
LHType ::= ENUMERATED { lbit(0), hbit(1) }
Naming ::= SEQUENCE {
all-caps-1 INTEGER (0..1),
part-Caps INTEGER (0..1),
camelCase INTEGER (0..1)
}
Alternations ::= SEQUENCE {
l-bit-or-h-bit LHType,
pg-determinant INTEGER (0..7),
particular-general CHOICE {
naming Naming,
something-else INTEGER (0..15)
},
stereo-choice-1 CHOICE {
first INTEGER (0..1),
second INTEGER (0..3)
},
stereo-choice-2 CHOICE {
choice-1 NULL,
first INTEGER (0..1),
second INTEGER (0..3),
third NULL
},
maybe INTEGER (0..15) OPTIONAL,
possibly INTEGER (0..7) OPTIONAL,
questionable INTEGER (0..3) OPTIONAL
}
Concat ::= SEQUENCE {
e1 INTEGER (0..1),
e2 INTEGER (0..3),
e3 INTEGER (0..7),
e4 INTEGER (0..15),
a-pad-bit INTEGER (0..1) DEFAULT 0,
some-literal-bits INTEGER (41) DEFAULT 41,
single-bit INTEGER (0..1),
single-octet INTEGER (0..255),
ref-to-a-name Naming,
two-bit-value-using-more-done-bit-list SEQUENCE OF INTEGER (0..3),
named-list SEQUENCE OF INTEGER (0..3),
list-of-10 SEQUENCE (SIZE (10)) OF INTEGER (0..15),
list-ending-with-container SEQUENCE OF INTEGER (0..7)
}
Length-Constrained-Content ::= SEQUENCE {
length INTEGER (0..127),
willy-nilly INTEGER (0..15),
component-3 INTEGER (0..7) OPTIONAL
}
SingleComponent ::= SEQUENCE {
fields SEQUENCE {
field1 INTEGER (0..15),
field2 INTEGER (0..7)
} OPTIONAL
}
Things-With-Exponents ::= SEQUENCE {
a-23-bit-int INTEGER (0..8388607),
a-fixed-length-bit-string BIT STRING (SIZE (45)),
a-var-length-bit-string BIT STRING (SIZE (0..8388607)),
a-fixed-length-octet-str OCTET STRING (SIZE (4)),
a-var-len-octet-str OCTET STRING (SIZE (0..8388607)),
repeating-optional-component SEQUENCE (SIZE (5)) OF SEQUENCE {
opt-comp INTEGER (0..15) OPTIONAL
},
five-pad-bits INTEGER (0..31) DEFAULT 0,
count-bit-encoding INTEGER (0..255),
fixed-num-of-type SEQUENCE (SIZE (5)) OF Naming,
var-num-of-type SEQUENCE (SIZE (0..8388607)) OF Naming
}
Truncated-Concat ::= SEQUENCE {
e1 INTEGER (0..1) OPTIONAL,
component-2 SEQUENCE {
e2 INTEGER (0..3),
e3 INTEGER (0..7)
} OPTIONAL,
e4 INTEGER (0..15) OPTIONAL
}
END