xn/doc/01_syntax.md

XN Syntax

Comments

Comments are single line only prefixed with the pound sign ('#').

Rules

Rules consists of two parts, a selector, and a block containing statements.
A selector is an XPath string surrounded with braces prefixed with a dollar sign.
The XPath selects zero or more document nodes which will serve as the context for the statement block.

Bangs

Bangs are function calls combined with a statement block.
They are prefixed with an exclaimation mark.
A bang function always produces context nodes for the statement block.

Statement Block

A statement block are multiple statements terminated with a semicolon,
surrounded by curly braces.

Statements

A statement can be an expression, a function call, a rule or a bang.
To note is that a nested rule will use its parents context to refine the selection further.

Expressions

An expression can consist of function calls, operators, strings or numbers.

Operators supported:

Operator	Function
+	addition
-	subtraction
*	multiplication
/	division
**	power
&	bitwise and
^	bitwise exclusive or
..	string concatenate

Example

# Select the RxPdo with Index 0x1600
$("RxPdo/Index[.="#x1600"]/..")
{
    # Function call
    swap("Entry[3]", "Entry[4]");

    # Of that RxPdo, select the 3rd Entry via a nested rule
    $("Entry[3]")
    {
        # This bang has "RxPdo/Index[.="#x1600"]/../Entry[3]" as its context
        !before("Entry")
        {
             # Function call contains an expression, which evaluates here to "!#xFFFF"
            !add("Index") { text("!"..hexlit(2**16-1)); };
            !add("SubIndex") { text("3"); }
            !add("BitLen") { text("256"); }
            !add("Name") { text("Test"); }
            !add("DataType") { text("UINT"); }
        }
    }
}

# One .xn can contain multiple rules
$("//Module[@Crc32]")
{
    attr("Crc32", hexlit(crc32()));
};