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authorBjörn Gustavsson <[email protected]>2013-01-08 10:56:27 +0100
committerBjörn Gustavsson <[email protected]>2013-01-23 15:22:56 +0100
commit74cee7dc1cc5b0332cd851da4953ebbb98224b5f (patch)
treeff539fdce7055f51fb437bc906358f073d77a620 /lib/asn1/doc/src/asn1_ug.xml
parent625d2b01dcaa0b15cc9ff7f98438bcd81a5bddc8 (diff)
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By default, encode BIT STRING to bitstrings
Add the option 'legacy_bit_string' to decode to the old list format.
Diffstat (limited to 'lib/asn1/doc/src/asn1_ug.xml')
-rw-r--r--lib/asn1/doc/src/asn1_ug.xml77
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 This format may be withdrawn in a future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 = &lt;&lt;0:1,1:1,0:1,1:1,1:1&gt;&gt;,
Bits1Val2 = 16#1A,
-Bits1Val3 = {3,&lt;&lt;0:1,1:1,0:1,1:1,1:1,0:3&gt;&gt;}
+Bits1Val3 = {3,&lt;&lt;0:1,1:1,0:1,1:1,1:1,0:3&gt;&gt;},
+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 = &lt;&lt;2#1110:4&gt;&gt;,
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>