🔣 Escaping (Internal)

The escaping module implements the character-escaping rules defined by NISTIR 7695 for binding a WFN to the FS (formatted string) and URI forms, plus the quoting rules used by the WFN string representation.

This module is entirely internal. Every identifier declared in escaping.go — including all functions and the percent-encoding maps — starts with a lowercase letter and is therefore unexported. There are no exported functions, types, variables, or constants in this module. The escaping behavior is exposed to callers only indirectly, through the binding module (BindToFS, UnbindFS, BindToURI, UnbindURI) and the wfn module (FromCPE23String, ToCPE23String, FromCPE22String, ToCPE22String, WFNString).

The following unexported helpers are documented here for reference and to clarify the escaping rules they implement. They cannot be called from outside the cpeskills package.

Internal FS escapers

func escapeForFS(value string) string
func unescapeFromFS(value string) string

escapeForFS escapes a raw WFN value for the CPE 2.3 FS form: the characters ., -, _ are escaped with a backslash, and other non-alphanumeric characters are percent-encoded per NISTIR 7695. unescapeFromFS reverses this. Logical values (*, -) and the empty string pass through unchanged.

Internal URI escapers

func escapeForURI(value string) string
func unescapeFromURI(value string) string

escapeForURI escapes a raw WFN value for the CPE 2.2 URI form: every non-alphanumeric character is percent-encoded. unescapeFromURI reverses this. Logical values and the empty string pass through unchanged.

Internal WFN-string quoters

func quoteForWFN(value string) string
func unquoteFromWFN(value string) string

quoteForWFN escapes the " and \ characters inside a value so it can be embedded in the wfn:[...] string representation produced by WFN.WFNString. unquoteFromWFN reverses it.

Internal logical-value & wildcard helpers

func isLogicalValue(value string) bool
func hasUnquotedWildcard(value string) bool
func isAlphanumeric(c byte) bool
func toHex(c byte) string

isLogicalValue reports whether a value is * (ANY) or - (NA). hasUnquotedWildcard reports whether the value contains a * or ? not preceded by a backslash; it is used by WFN.IsIdentifierName. isAlphanumeric and toHex are small primitives used by the escapers.

Internal extended-attribute packers

func packExtendedAttributes(edition, language, swEdition, targetSw, targetHw, other string) string
func unpackExtendedAttributes(packed string) (edition, language, swEdition, targetSw, targetHw, other string)

These pack and unpack the six extended attributes of a CPE 2.2 URI into and out of the ~-separated segment. Trailing empty values are trimmed on packing; missing segments are reported as ANY on unpacking.

Internal percent-encoding maps

var quotedCharToPercentEncode = map[byte]string{ /* NISTIR 7695 table 6-2 */ }
var percentEncodeToQuotedChar = /* reverse of the above */

The forward and reverse percent-encoding tables for binding to URI / FS.

How to use escaping

Callers do not invoke the escaping helpers directly. Instead, use the higher-level exported APIs:

Goal	Exported function to use
Build a CPE 2.3 FS string	BindToFS, WFN.ToCPE23String
Parse a CPE 2.3 FS string	UnbindFS, FromCPE23String
Build a CPE 2.2 URI string	BindToURI, WFN.ToCPE22String
Parse a CPE 2.2 URI string	UnbindURI, FromCPE22String
Get the WFN string form	WFN.WFNString

📐 Escaping Layer Diagram