diff options
Diffstat (limited to 'lib/asn1/doc/src/asn1_ug.xml')
| -rw-r--r-- | lib/asn1/doc/src/asn1_ug.xml | 77 |
1 files changed, 40 insertions, 37 deletions
diff --git a/lib/asn1/doc/src/asn1_ug.xml b/lib/asn1/doc/src/asn1_ug.xml index ecca287670..a0ab98cf7a 100644 --- a/lib/asn1/doc/src/asn1_ug.xml +++ b/lib/asn1/doc/src/asn1_ug.xml @@ -324,13 +324,6 @@ erlc -o ../asnfiles -I ../asnfiles -I /usr/local/standards/asn1 Person.asn are several places to search in. The compiler will always search the current directory first.</p> </item> - <tag><c>+compact_bit_string</c></tag> - <item> - <p>Gives the user the option to use a compact format of the BIT - STRING type to save memory space, typing space and - increase encode/decode performance, for details see - <seealso marker="#BIT STRING">BIT STRING </seealso>type section.</p> - </item> <tag><c>+der</c></tag> <item> <p>DER encoding rule. Only when using <c>-ber</c> option.</p> @@ -649,7 +642,7 @@ Day1 = saturday, <section> <marker id="BIT STRING"></marker> - <title>BIT STRING </title> + <title>BIT STRING</title> <p>The BIT STRING type can be used to model information which is made up of arbitrary length series of bits. It is intended to be used for a selection of flags, not for binary files. <br></br> @@ -660,56 +653,66 @@ Day1 = saturday, Bits1 ::= BIT STRING Bits2 ::= BIT STRING {foo(0),bar(1),gnu(2),gnome(3),punk(14)} </pre> - <p>There are four different notations available for representation of + <p>There are five different notations available for representation of BIT STRING values in Erlang and as input to the encode functions.</p> <list type="ordered"> - <item>A list of binary digits (0 or 1).</item> - <item>A hexadecimal number (or an integer). This format should be - avoided, since it is easy to misinterpret a <c>BIT STRING</c> - value in this format. This format may be withdrawn in a future - release.</item> + <item>A bitstring. By default, a BIT STRING with no + symbolic names will be decoded to an Erlang bitstring.</item> <item>A list of atoms corresponding to atoms in the <c>NamedBitList</c> - in the BIT STRING definition.</item> + in the BIT STRING definition. A BIT STRING with symbolic + names will always be decoded to this format.</item> + <item>A list of binary digits (0 or 1). This format is always + accepted as input to the encode functions. A BIT STRING will + be decoded to this format if <em>legacy_bit_string</em> option + has been given. <em>This format may be withdrawn in a future + release.</em> + </item> <item>As <c>{Unused,Binary}</c> where <c>Unused</c> denotes how - many trailing zero-bits 0 to 7 that are unused in the least - significant byte in <c>Binary</c>. This notation is only - available when the ASN.1 files have been compiled with the - <em>+compact_bit_string</em> flag in the option list. In - this case it is possible to use all kinds of notation when - encoding. But the result when decoding is always in the - compact form. The benefit from this notation is a more - compact notation when one has large BIT STRINGs. The - encode/decode performance is also much better in the case of - large BIT STRINGs. </item> + many trailing zero-bits 0 to 7 that are unused in the least + significant byte in <c>Binary</c>. This format is always + accepted as input to the encode functions. A BIT STRING will + be decoded to this format if <em>compact_bit_string</em> has + been given. <em>This format may be withdrawn in a future + release.</em> + </item> + <item>A hexadecimal number (or an integer). This format should be + avoided, since it is easy to misinterpret a <c>BIT STRING</c> + value in this format. <em>This format may be withdrawn in a future + release.</em> + </item> </list> <note> - <p>Note that it is advised not to use the integer format of a - BIT STRING, see the second point above.</p> + <p>It is recommended to either use the bitstring format (for + BIT STRINGs with no symbolic names) or a list of symbolic + names (for BIT STRINGs with symbolic names). The other formats + should be avoided since they may be withdrawn in a future + release. + </p> </note> <pre> -Bits1Val1 = [0,1,0,1,1], +Bits1Val1 = <<0:1,1:1,0:1,1:1,1:1>>, Bits1Val2 = 16#1A, -Bits1Val3 = {3,<<0:1,1:1,0:1,1:1,1:1,0:3>>} +Bits1Val3 = {3,<<0:1,1:1,0:1,1:1,1:1,0:3>>}, +Bits1Val4 = [0,1,0,1,1] </pre> - <p>Note that <c>Bits1Val1</c>, <c>Bits1Val2</c> and <c>Bits1Val3</c> - denote the same value.</p> + <p>Note that <c>Bits1Val1</c>, <c>Bits1Val2</c>, <c>Bits1Val3</c>, + and <c>Bits1Val1</c> denote the same value.</p> <pre> Bits2Val1 = [gnu,punk], -Bits2Val2 = 2#1110, +Bits2Val2 = <<2#1110:4>>, Bits2Val3 = [bar,gnu,gnome], -Bits2Val4 = [0,1,1,1] </pre> - <p>The above <c>Bits2Val2</c>, <c>Bits2Val3</c> and <c>Bits2Val4</c> - also all denote the same value.</p> + <p><c>Bits2Val2</c> and <c>Bits2Val3</c> above denote the same value.</p> <p><c>Bits2Val1</c> is assigned symbolic values. The assignment means that the bits corresponding to <c>gnu</c> and <c>punk</c> i.e. bits 2 and 14 are set to 1 and the rest set to 0. The symbolic values appear as a list of values. If a named value appears, which is not specified in the type definition, a run-time error will occur.</p> <p>The compact notation equivalent to the empty BIT STRING is - <c><![CDATA[{0,<<>>}]]></c>, which in the other notations is <c>[]</c> or + <c><![CDATA[{0,<<>>}]]></c>, which in the other notations is + <c><![CDATA[<<>>]]></c>, <c>[]</c>, or <c>0</c>.</p> - <p>BIT STRINGS may also be sub-typed with for example a SIZE + <p>BIT STRINGS may also be sub-typed with, for example, a SIZE specification:</p> <pre> Bits3 ::= BIT STRING (SIZE(0..31)) </pre> |