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  <h1>Package asn1</h1>


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			<dd><code>import "encoding/asn1"</code></dd>
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				<p>
Package asn1 implements parsing of DER-encoded ASN.1 data structures,
as defined in ITU-T Rec X.690.
</p>
<p>
See also &ldquo;A Layman&#39;s Guide to a Subset of ASN.1, BER, and DER,&rdquo;
<a href="http://luca.ntop.org/Teaching/Appunti/asn1.html">http://luca.ntop.org/Teaching/Appunti/asn1.html</a>.
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			<dl>
			
				<dd><a href="index.html#pkg-constants">Constants</a></dd>
			
			
				<dd><a href="index.html#Marshal">func Marshal(val interface{}) ([]byte, error)</a></dd>
			
				
				<dd><a href="index.html#Unmarshal">func Unmarshal(b []byte, val interface{}) (rest []byte, err error)</a></dd>
			
				
				<dd><a href="index.html#UnmarshalWithParams">func UnmarshalWithParams(b []byte, val interface{}, params string) (rest []byte, err error)</a></dd>
			
			
				<dd><a href="index.html#BitString">type BitString</a></dd>
				
				
					<dd>&nbsp; &nbsp; <a href="index.html#BitString.At">func (b BitString) At(i int) int</a></dd>
				
					
					<dd>&nbsp; &nbsp; <a href="index.html#BitString.RightAlign">func (b BitString) RightAlign() []byte</a></dd>
				
			
				<dd><a href="index.html#Enumerated">type Enumerated</a></dd>
				
				
				<dd><a href="index.html#Flag">type Flag</a></dd>
				
				
				<dd><a href="index.html#ObjectIdentifier">type ObjectIdentifier</a></dd>
				
				
					<dd>&nbsp; &nbsp; <a href="index.html#ObjectIdentifier.Equal">func (oi ObjectIdentifier) Equal(other ObjectIdentifier) bool</a></dd>
				
					
					<dd>&nbsp; &nbsp; <a href="index.html#ObjectIdentifier.String">func (oi ObjectIdentifier) String() string</a></dd>
				
			
				<dd><a href="index.html#RawContent">type RawContent</a></dd>
				
				
				<dd><a href="index.html#RawValue">type RawValue</a></dd>
				
				
				<dd><a href="index.html#StructuralError">type StructuralError</a></dd>
				
				
					<dd>&nbsp; &nbsp; <a href="index.html#StructuralError.Error">func (e StructuralError) Error() string</a></dd>
				
			
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			<h4>Package files</h4>
			<p>
			<span style="font-size:90%">
			
				<a href="http://localhost:6060/src/encoding/asn1/asn1.go">asn1.go</a>
			
				<a href="http://localhost:6060/src/encoding/asn1/common.go">common.go</a>
			
				<a href="http://localhost:6060/src/encoding/asn1/marshal.go">marshal.go</a>
			
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			  In the call graph viewer below, each node
			  is a function belonging to this package
			  and its children are the functions it
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			  The root nodes are the entry points of the
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			<h2 id="pkg-constants">Constants</h2>
			
				<pre>const (
    <span id="TagBoolean">TagBoolean</span>         = 1
    <span id="TagInteger">TagInteger</span>         = 2
    <span id="TagBitString">TagBitString</span>       = 3
    <span id="TagOctetString">TagOctetString</span>     = 4
    <span id="TagOID">TagOID</span>             = 6
    <span id="TagEnum">TagEnum</span>            = 10
    <span id="TagUTF8String">TagUTF8String</span>      = 12
    <span id="TagSequence">TagSequence</span>        = 16
    <span id="TagSet">TagSet</span>             = 17
    <span id="TagPrintableString">TagPrintableString</span> = 19
    <span id="TagT61String">TagT61String</span>       = 20
    <span id="TagIA5String">TagIA5String</span>       = 22
    <span id="TagUTCTime">TagUTCTime</span>         = 23
    <span id="TagGeneralizedTime">TagGeneralizedTime</span> = 24
    <span id="TagGeneralString">TagGeneralString</span>   = 27
)</pre>
				<p>
ASN.1 tags represent the type of the following object.
</p>

			
				<pre>const (
    <span id="ClassUniversal">ClassUniversal</span>       = 0
    <span id="ClassApplication">ClassApplication</span>     = 1
    <span id="ClassContextSpecific">ClassContextSpecific</span> = 2
    <span id="ClassPrivate">ClassPrivate</span>         = 3
)</pre>
				<p>
ASN.1 class types represent the namespace of the tag.
</p>

			
			<h2 id="Marshal">func <a href="http://localhost:6060/src/encoding/asn1/marshal.go?s=13656:13701#L635">Marshal</a></h2>
			<pre>func Marshal(val interface{}) ([]<a href="../../builtin/index.html#byte">byte</a>, <a href="../../builtin/index.html#error">error</a>)</pre>
			<p>
Marshal returns the ASN.1 encoding of val.
</p>
<p>
In addition to the struct tags recognised by Unmarshal, the following can be
used:
</p>
<pre>ia5:		causes strings to be marshaled as ASN.1, IA5 strings
omitempty:	causes empty slices to be skipped
printable:	causes strings to be marshaled as ASN.1, PrintableString strings.
utf8:		causes strings to be marshaled as ASN.1, UTF8 strings
</pre>

			
			<h2 id="Unmarshal">func <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=27223:27289#L972">Unmarshal</a></h2>
			<pre>func Unmarshal(b []<a href="../../builtin/index.html#byte">byte</a>, val interface{}) (rest []<a href="../../builtin/index.html#byte">byte</a>, err <a href="../../builtin/index.html#error">error</a>)</pre>
			<p>
Unmarshal parses the DER-encoded ASN.1 data structure b
and uses the reflect package to fill in an arbitrary value pointed at by val.
Because Unmarshal uses the reflect package, the structs
being written to must use upper case field names.
</p>
<p>
An ASN.1 INTEGER can be written to an int, int32, int64,
or *big.Int (from the math/big package).
If the encoded value does not fit in the Go type,
Unmarshal returns a parse error.
</p>
<p>
An ASN.1 BIT STRING can be written to a BitString.
</p>
<p>
An ASN.1 OCTET STRING can be written to a []byte.
</p>
<p>
An ASN.1 OBJECT IDENTIFIER can be written to an
ObjectIdentifier.
</p>
<p>
An ASN.1 ENUMERATED can be written to an Enumerated.
</p>
<p>
An ASN.1 UTCTIME or GENERALIZEDTIME can be written to a time.Time.
</p>
<p>
An ASN.1 PrintableString or IA5String can be written to a string.
</p>
<p>
Any of the above ASN.1 values can be written to an interface{}.
The value stored in the interface has the corresponding Go type.
For integers, that type is int64.
</p>
<p>
An ASN.1 SEQUENCE OF x or SET OF x can be written
to a slice if an x can be written to the slice&#39;s element type.
</p>
<p>
An ASN.1 SEQUENCE or SET can be written to a struct
if each of the elements in the sequence can be
written to the corresponding element in the struct.
</p>
<p>
The following tags on struct fields have special meaning to Unmarshal:
</p>
<pre>application	specifies that a APPLICATION tag is used
default:x	sets the default value for optional integer fields
explicit	specifies that an additional, explicit tag wraps the implicit one
optional	marks the field as ASN.1 OPTIONAL
set		causes a SET, rather than a SEQUENCE type to be expected
tag:x		specifies the ASN.1 tag number; implies ASN.1 CONTEXT SPECIFIC
</pre>
<p>
If the type of the first field of a structure is RawContent then the raw
ASN1 contents of the struct will be stored in it.
</p>
<p>
If the type name of a slice element ends with &#34;SET&#34; then it&#39;s treated as if
the &#34;set&#34; tag was set on it. This can be used with nested slices where a
struct tag cannot be given.
</p>
<p>
Other ASN.1 types are not supported; if it encounters them,
Unmarshal returns a parse error.
</p>

			
			<h2 id="UnmarshalWithParams">func <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=27482:27573#L978">UnmarshalWithParams</a></h2>
			<pre>func UnmarshalWithParams(b []<a href="../../builtin/index.html#byte">byte</a>, val interface{}, params <a href="../../builtin/index.html#string">string</a>) (rest []<a href="../../builtin/index.html#byte">byte</a>, err <a href="../../builtin/index.html#error">error</a>)</pre>
			<p>
UnmarshalWithParams allows field parameters to be specified for the
top-level element. The form of the params is the same as the field tags.
</p>

			
			<h2 id="BitString">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=4186:4293#L147">BitString</a></h2>
			<pre>type BitString struct {
    Bytes     []<a href="../../builtin/index.html#byte">byte</a> <span class="comment">// bits packed into bytes.</span>
    BitLength <a href="../../builtin/index.html#int">int</a>    <span class="comment">// length in bits.</span>
}</pre>
			<p>
BitString is the structure to use when you want an ASN.1 BIT STRING type. A
bit string is padded up to the nearest byte in memory and the number of
valid bits is recorded. Padding bits will be zero.
</p>


				<h3 id="BitString.At">func (BitString) <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=4387:4419#L154">At</a></h3>
				<pre>func (b <a href="index.html#BitString">BitString</a>) At(i <a href="../../builtin/index.html#int">int</a>) <a href="../../builtin/index.html#int">int</a></pre>
				<p>
At returns the bit at the given index. If the index is out of range it
returns false.
</p>

				
				<h3 id="BitString.RightAlign">func (BitString) <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=4659:4697#L165">RightAlign</a></h3>
				<pre>func (b <a href="index.html#BitString">BitString</a>) RightAlign() []<a href="../../builtin/index.html#byte">byte</a></pre>
				<p>
RightAlign returns a slice where the padding bits are at the beginning. The
slice may share memory with the BitString.
</p>

				
			<h2 id="Enumerated">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=7186:7205#L275">Enumerated</a></h2>
			<pre>type Enumerated <a href="../../builtin/index.html#int">int</a></pre>
			<p>
An Enumerated is represented as a plain int.
</p>


			<h2 id="Flag">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=7274:7288#L280">Flag</a></h2>
			<pre>type Flag <a href="../../builtin/index.html#bool">bool</a></pre>
			<p>
A Flag accepts any data and is set to true if present.
</p>


			<h2 id="ObjectIdentifier">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=5585:5612#L202">ObjectIdentifier</a></h2>
			<pre>type ObjectIdentifier []<a href="../../builtin/index.html#int">int</a></pre>
			<p>
An ObjectIdentifier represents an ASN.1 OBJECT IDENTIFIER.
</p>


				<h3 id="ObjectIdentifier.Equal">func (ObjectIdentifier) <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=5683:5744#L205">Equal</a></h3>
				<pre>func (oi <a href="index.html#ObjectIdentifier">ObjectIdentifier</a>) Equal(other <a href="index.html#ObjectIdentifier">ObjectIdentifier</a>) <a href="../../builtin/index.html#bool">bool</a></pre>
				<p>
Equal reports whether oi and other represent the same identifier.
</p>

				
				<h3 id="ObjectIdentifier.String">func (ObjectIdentifier) <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=5890:5932#L218">String</a></h3>
				<pre>func (oi <a href="index.html#ObjectIdentifier">ObjectIdentifier</a>) String() <a href="../../builtin/index.html#string">string</a></pre>
				
				
			<h2 id="RawContent">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=11130:11152#L425">RawContent</a></h2>
			<pre>type RawContent []<a href="../../builtin/index.html#byte">byte</a></pre>
			<p>
RawContent is used to signal that the undecoded, DER data needs to be
preserved for a struct. To use it, the first field of the struct must have
this type. It&#39;s an error for any of the other fields to have this type.
</p>


			<h2 id="RawValue">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=10776:10902#L415">RawValue</a></h2>
			<pre>type RawValue struct {
    Class, Tag <a href="../../builtin/index.html#int">int</a>
    IsCompound <a href="../../builtin/index.html#bool">bool</a>
    Bytes      []<a href="../../builtin/index.html#byte">byte</a>
    FullBytes  []<a href="../../builtin/index.html#byte">byte</a> <span class="comment">// includes the tag and length</span>
}</pre>
			<p>
A RawValue represents an undecoded ASN.1 object.
</p>


			<h2 id="StructuralError">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=1169:1212#L24">StructuralError</a></h2>
			<pre>type StructuralError struct {
    Msg <a href="../../builtin/index.html#string">string</a>
}</pre>
			<p>
A StructuralError suggests that the ASN.1 data is valid, but the Go type
which is receiving it doesn&#39;t match.
</p>


				<h3 id="StructuralError.Error">func (StructuralError) <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=1214:1253#L28">Error</a></h3>
				<pre>func (e <a href="index.html#StructuralError">StructuralError</a>) Error() <a href="../../builtin/index.html#string">string</a></pre>
				
				
			<h2 id="SyntaxError">type <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=1358:1397#L31">SyntaxError</a></h2>
			<pre>type SyntaxError struct {
    Msg <a href="../../builtin/index.html#string">string</a>
}</pre>
			<p>
A SyntaxError suggests that the ASN.1 data is invalid.
</p>


				<h3 id="SyntaxError.Error">func (SyntaxError) <a href="http://localhost:6060/src/encoding/asn1/asn1.go?s=1399:1434#L35">Error</a></h3>
				<pre>func (e <a href="index.html#SyntaxError">SyntaxError</a>) Error() <a href="../../builtin/index.html#string">string</a></pre>
				
				
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