Kamailio SIP Server v3.2.x: Transformations

Main author:
   Daniel-Constantin Mierla <miconda (at) asipto.com>

Transformation is basically a function that is applied to a pseudo-variable (PV) to get a special value from it. The value of PV is not affected at all.

Transformations are implemented by various modules, most of them being in pv module.

The transformations are intended to facilitate access to different attributes of PV (like strlen of value, parts of value, substrings) or complete different value of PV (encoded in hexa, md5 value, escape/unescape PV value for DB operations...).

A transformation is represented in between '{' and '}' and follows the name of a PV. When using transformations, the PV name and transformations must be enclosed in between '(' and ')', following the $ sign.

# the length of From URI ($fu is PV for From URI)

$(fu{s.len})

Many transformations can be applied in the same time to a PV.

# the length of escaped 'Test' header body

$(hdr(Test){s.escape.common}{s.len})

The transformations can be used anywhere, being considered parts of PV -- in xlog, avpops or other modules' functions and parameters, in right side assignment expressions or in comparisons.

String Transformations

The name of these transformation starts with 's.'. They are intended to apply string operations to PV.

Available transformations in this class:

{s.len}

Return strlen of PV value

$var(x) = "abc";
if($(var(x){s.len}) == 3)
{
   ...
}

{s.int}

Return integer value of a string-represented number

$var(x) = "1234";
if($(var(x){s.int})==1234) {
  ...
}

{s.md5}

Return md5 over PV value

xlog("md5 over From username: $(fU{s.md5})");

{s.substr,offset,length}

Return substring starting at offset having size of 'length'. If offset is negative, then it is counted from the end of PV value, -1 being the last char. In case of positive value, 0 is first char. Length must be positive, in case of 0, substring to the end of PV value is returned. offset and length can be PV as well.

Example:

$var(x) = "abcd";
$(var(x){s.substr,1,0}); => "bcd"

{s.select,index,separator}

Return a field from PV value. The field is selected based on separator and index. The separator must be a character used to identify the fields. Index must be an integer value or a PV. If index is negative, the count of fields starts from end of PV value, -1 being last field. If index is positive, 0 is the first field.

Example:

$var(x) = "12,34,56";
$(var(x){s.select,1,,}) => "34" ;

$var(x) = "12,34,56";
$(var(x){s.select,-2,,}) => "34"

{s.encode.hexa}

Return encoding in hexa of PV value

{s.decode.hexa}

Return decoding from hexa of PV value

{s.escape.common}

Return escaped string of PV value. Characters escaped are ', ", \ and 0. Useful when doing DB queries (care should be taken for non Latin character set).

{s.unescape.common}

Return unescaped string of PV value. Reverse of above transformation.

{s.escape.user}

Return escaped string of PV value, changing to '%hexa' the characters that are not allowed in user part of SIP URI following RFC requirements.

{s.unescape.user}

Return unescaped string of PV value, changing '%hexa' to character code. Reverse of above transformation.

{s.escape.param}

Return escaped string of PV value, changing to '%hexa' the characters that are not allowed in the param part of SIP URI following RFC requirements.

{s.unescape.param}

Return unescaped string of PV value, changing '%hexa' to character code. Reverse of above transformation.

{s.tolower}

Return string with lower case ASCII letters.

{s.toupper}

Return string with upper case ASCII letters.

{s.strip,len}

Return string after removing starting 'len' characters. Parameter 'len' can be positive integer or pseudo-variable holding a positive integer.

Example:

$var(x) = "1234";
$var(y) = $(var(x){s.strip,2}); # resulted value is "34"

{s.striptail,len}

Return string after removing ending 'len' characters. Parameter 'len' can be positive integer or pseudo-variable holding a positive integer.

{s.prefixes[,len]}

Return series of comma separated prefixes of the pv. Parameter 'len' is optional and will limit the maximum prefix length.

Example:

$var(x) = "123456";
$(var(x){s.prefixes}) => 1,12,123,1234,12345,123456
$(var(x){s.prefixes,4} => 1,12,123,1234

{s.prefixes.quoted[,len]}

Return series of comma separated quoted prefixes of the pv. Parameter 'len' is optional and will limit the maximum prefix length.

Example:

$var(x) = "123456";
$(var(x){s.prefixes.quoted} => '1','12','123','1234','12345','123456'
$(var(x){s.prefixes.quoted,4} => '1','12','123','1234'

{s.replace,match,repl}

Replace all occurrences of match with repl. The parameters can be pseudo-variables.

Example:

$var(x) = "abababa";
$(var(x){s.replace,a,c} => "cbcbcbc"

{s.ftime,format}

Format the epoch in the pv according to the parameter. The parameter has to be strftime formatting string.

$(TS{s.ftime,%Y-%m-%d %H:%M:%S})

URI Transformations

The name of transformation starts with 'uri.'. The PV value is considered to be a SIP URI. This transformation returns parts of SIP URI (see struct sip_uri). If that part is missing, the returned value is an empty string.

Available transformations in this class:

{uri.user}

Return the user part

{uri.host}

(same as {uri.domain})

Return the domain part

{uri.passwd}

Return the password

{uri.port}

Return the port

{uri.params}

Return the URI parameters in a string

{uri.param,name}

Return the value of parameter with name 'name'

{uri.headers}

Return URI headers

{uri.transport}

Return the value of transport parameter

{uri.ttl}

Return the value of ttl parameter

{uri.uparam}

Return the value of user parameter

{uri.maddr}

Return the value of maddr parameter

{uri.method}

Return the value of method parameter

{uri.lr}

Return the value of lr parameter

{uri.r2}

Return the value of r2 parameter

Parameters List Transformations

The name of the transformation starts with 'param.'. The PV value is considered to be a string like name1=value1;name2=value2;...". The transformations returns the value for a specific parameter, or the name of a parameter at a specific index.

Available transformations in this class:

{param.value,name}

Return the value of parameter 'name'

Example:

"a=1;b=2;c=3"{param.value,c} = "3"

'name' can be a pseudo-variable

{param.valueat,index}

Return the value of parameter at position given by 'index' (0-based index)

Example:

"a=1;b=2;c=3"{param.valueat,1} = "2"

'index' can be a pseudo-variable

{param.name,index}

Return the name of parameter at position 'index'.

Example:

"a=1;b=2;c=3"{param.name,1} = "b"

{param.count}

Return the number of parameters in the list.

Example:

"a=1;b=2;c=3"{param.count} = 3

Name-address Transformations

The name of the transformation starts with 'nameaddr.'. The PV value is considered to be a string like '[display_name] uri'. The transformations returns the value for a specific field.

Available transformations in this class:

{nameaddr.name}

Return the value of display name

Example:

'"test" <sip:test@kamailio.net>' {nameaddr.name} = "test"

{nameaddr.uri}

Return the value of URI

Example:

'"test" <sip:test@kamailio.net>' {nameaddr.uri} = sip:test@kamailio.net

{nameaddr.len}

Return the length of the entire name-addr part from the value.

To-Body Transformations

\This transformation class is exported by pv module.\

Access parts of a ToBody-like structure.

{tobody.uri}

* return URI from To body

{tobody.display}

* return Display name from To body

{tobody.tag}

* return Tag parameter from To body

{tobody.user}

* return URI User from To body

{tobody.host}

* return URI Host from To body

{tobody.params}

* return parameters part from To body

Regular Expression Transformations

\This transformation class is exported by textops module.\

{re.subst,expression}

Perform POSIX regex substitutions on string value pseudo-variables.

# Assign Request-URI user to PV
$var(user) = $(ru{re.subst,/^sip:(.*)@(.*)/\1/});

# Assign Request-URI user to PV, where every 'A' has been replaced by 'a'
$var(user) = $(rU{re.subst,/A/a/g});

The prototype is:

{re.subst,/match_expression/replacement_expression/flags}

match_expression - Posix regular expression
replacement_expression - substitution expression with back references to matched tokes: \1, \2, ..., \9
flags:
i - match ignore case
s - match within multi-lines strings
g - replace all matches

SQL Transformations

\The transformations in this class are exported by the sqlops module.\

{sql.val}

This transformation outputs valid SQL values for various PV values:

\ values are output as NULL
integers are output as integers
everything else is output as quoted and escaped string

    $var(null) = $null;
    $avp(null) = $null;
    $avp(str) = "String with \ illegal \\characters";
    $avp(nr) = 12345;
    $avp(strnr) = "12345";

    xlog("$$rm = $rm = $(rm{s.sql})");
    xlog("$$var(null) = $var(null) = $(var(null){s.sql})");
    xlog("$$avp(null) = $avp(null) = $(avp(null){s.sql})");
    xlog("$$avp(str) = $avp(str) = $(avp(str){s.sql})");
    xlog("$$avp(nr) = $avp(nr) = $(avp(nr){s.sql})");
    xlog("$$avp(strnr) = $avp(strnr) = $(avp(strnr){s.sql})");

  Output:
    $rm = ACK = 'ACK'
    $var(null) = 0 = 0
    $avp(null) = <null> = NULL
    $avp(str) = String with \ illegal \characters = 'String with \\ illegal \\characters'
    $avp(nr) = 12345 = 12345
    $avp(strnr) = 12345 = '12345'

{sql.val.int}

Like sql.val, but output number 0 for null values.

{sql.val.str}

Like sql.val, but output string '' for null values.

Examples

Within a PV, many transformation can be applied, being executed from left to right.

* The length of the value of parameter at postion 1 (remember 0 is first position, 1 is second position)

$var(x) = "a=1;b=22;c=333";
$(var(x){param.value,$(var(x){param.name,1})}{s.len}) = 2

* Test whether is un-registration or not

if(is_method("REGISTER") && is_present_hf("Expires") && $(hdr(Expires){s.int})==0)
    xlog("This is an un-registration\n");

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