104 lines
2.7 KiB
Go
104 lines
2.7 KiB
Go
// written by Daniel Oaks <daniel@danieloaks.net>
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// released under the ISC license
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package ircmsg
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import (
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"strings"
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"unicode/utf8"
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)
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var (
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// valtoescape replaces real characters with message tag escapes.
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valtoescape = strings.NewReplacer("\\", "\\\\", ";", "\\:", " ", "\\s", "\r", "\\r", "\n", "\\n")
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escapedCharLookupTable [256]byte
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)
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func init() {
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// most chars escape to themselves
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for i := 0; i < 256; i += 1 {
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escapedCharLookupTable[i] = byte(i)
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}
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// these are the exceptions
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escapedCharLookupTable[':'] = ';'
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escapedCharLookupTable['s'] = ' '
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escapedCharLookupTable['r'] = '\r'
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escapedCharLookupTable['n'] = '\n'
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}
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// EscapeTagValue takes a value, and returns an escaped message tag value.
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//
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// This function is automatically used when lines are created from an
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// Message, so you don't need to call it yourself before creating a line.
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func EscapeTagValue(inString string) string {
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return valtoescape.Replace(inString)
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}
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// UnescapeTagValue takes an escaped message tag value, and returns the raw value.
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//
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// This function is automatically used when lines are interpreted by ParseLine,
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// so you don't need to call it yourself after parsing a line.
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func UnescapeTagValue(inString string) string {
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// buf.Len() == 0 is the fastpath where we have not needed to unescape any chars
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var buf strings.Builder
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remainder := inString
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for {
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backslashPos := strings.IndexByte(remainder, '\\')
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if backslashPos == -1 {
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if buf.Len() == 0 {
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return inString
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} else {
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buf.WriteString(remainder)
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break
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}
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} else if backslashPos == len(remainder)-1 {
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// trailing backslash, which we strip
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if buf.Len() == 0 {
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return inString[:len(inString)-1]
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} else {
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buf.WriteString(remainder[:len(remainder)-1])
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break
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}
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}
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// non-trailing backslash detected; we're now on the slowpath
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// where we modify the string
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if buf.Len() == 0 {
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buf.Grow(len(inString)) // just an optimization
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}
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buf.WriteString(remainder[:backslashPos])
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buf.WriteByte(escapedCharLookupTable[remainder[backslashPos+1]])
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remainder = remainder[backslashPos+2:]
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}
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return buf.String()
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}
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// https://ircv3.net/specs/extensions/message-tags.html#rules-for-naming-message-tags
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func validateTagName(name string) bool {
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if len(name) == 0 {
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return false
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}
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if name[0] == '+' {
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name = name[1:]
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}
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if len(name) == 0 {
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return false
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}
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// let's err on the side of leniency here; allow -./ (45-47) in any position
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for i := 0; i < len(name); i++ {
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c := name[i]
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if !(('-' <= c && c <= '/') || ('0' <= c && c <= '9') || ('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z')) {
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return false
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}
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}
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return true
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}
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// "Tag values MUST be encoded as UTF8."
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func validateTagValue(value string) bool {
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return utf8.ValidString(value)
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}
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