Main author:
   Daniel-Constantin Mierla <miconda (at) gmail.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.

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

Available transformations in this class:

Return strlen of PV value

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

Return integer value of a string-represented number

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

Return md5 over PV value

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

Return sha 256 over PV value

xlog("sha 256 over From username: $(fU{s.sha256})");

Return sha 384 over PV value

xlog("sha 384 over From username: $(fU{s.sha384})");

Return sha 512 over PV value

xlog("sha 512 over From username: $(fU{s.sha512})");

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"

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 a 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"

Return encoding in hexa of PV value

Return decoding from hexa of PV value

Return base64 encoding of PV value

Decode base64 encoded PV and return value

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).

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

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

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

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.

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

Return string with lower case ASCII letters.

Return string with upper case ASCII letters.

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"

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

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

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'

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

Example:

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

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})

Remove left and right whitespaces (' ', '\t', '\r', '\n') around PV value.

$(var(x){s.trim})

Remove right whitespaces (' ', '\t', '\r', '\n') around PV value.

$(var(x){s.rtrim})

Remove left whitespaces (' ', '\t', '\r', '\n') around PV value.

$(var(x){s.ltrim})

Remove occurrences of 'match' from PV. 'match' can be static string or variable.

$(var(x){s.rm,test})

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:

Return the user part

(same as {uri.domain})

Return the domain part

Return the password

Return the port

Return the URI parameters in a string

Return the value of parameter with name 'name'

Return URI headers

Return the value of transport parameter

Return the value of ttl parameter

Return the value of user parameter

Return the value of maddr parameter

Return the value of method parameter

Return the value of lr parameter

Return the value of r2 parameter

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:

Return the value of parameter 'name'

Example:

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

'name' can be a pseudo-variable

'delimiter' allows you to specify a single character to use as the parameter delimiter. For example, when parsing HTTP URL query strings use '&'.

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

Example:

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

'index' can be a pseudo-variable

'delimiter' allows you to specify a single character to use as the parameter delimiter. For example, when parsing HTTP URL query strings use '&'.

Return the name of parameter at position 'index'.

Example:

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

'delimiter' allows you to specify a single character to use as the parameter delimiter. For example, when parsing HTTP URL query strings use '&'.

Return the number of parameters in the list.

Example:

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

'delimiter' allows you to specify a single character to use as the parameter delimiter. For example, when parsing HTTP URL query strings use '&'.

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:

Return the value of display name

Example:

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

Return the value of URI

Example:

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

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

This transformation class is exported by pv module.

Access parts of a ToBody-like structure.

* return URI from To body

* return Display name from To body

* return Tag parameter from To body

* return URI User from To body

* return URI Host from To body

* return parameters part from To body

Line-based operations on text values.

Return the number of lines.

Example:

$(var(x){line.count})

Return the line at position 'pos'. The index start from 0. Negative position can be used to count from last line (which is -1).

Example:

$(var(x){line.at,2})

Return the line starting with match.

Example:

$(var(x){line.sw,mytext})

This transformation class is exported by msrp module.

User part of a MSRP URI.

Host part of a MSRP URI.

Port part of a MSRP URI.

Session ID part of a MSRP URI.

Transport layer part of a MSRP URI.

Parameters part of a MSRP URI.

User-Info part of a MSRP URI. This is the same as user part, when there are no user parameters or password fields. Otherwise, it include the whole part after scheme and before '@' in front of host.

This transformation class is exported by textops module.

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

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

This transformation outputs valid SQL values for various PV values:

• <null> 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'

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

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

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 if 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");

This transformation class is exported by xhttp module.

Path part of an HTTP URL.

For example,

# When the first line of HTTP request is
# "GET /path/to/file/?this=is&the=querystring"

$(hu{url.path}) => "/path/to/file/"

Query string part of an HTTP URL. For example,

# When the first line of HTTP request is
# "GET /path/to/file/?this=is&the=querystring"

$(hu{url.querystring}) => "this=is&the=querystring"