mirror of https://github.com/ergochat/ergo.git
83 lines
2.0 KiB
Go
83 lines
2.0 KiB
Go
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//go:generate go run maketables.go > tables.go
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package confusables
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import (
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"bytes"
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"golang.org/x/text/unicode/norm"
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)
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// TODO: document casefolding approaches
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// (suggest to force casefold strings; explain how to catch paypal - pAypal)
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// TODO: DOC you might want to store the Skeleton and check against it later
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// TODO: implement xidmodifications.txt restricted characters
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type lookupFunc func(rune) (string)
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func lookupReplacement(r rune) string {
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return confusablesMap[r]
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}
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func lookupReplacementTweaked(r rune) string {
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if replacement, ok := tweaksMap[r]; ok {
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return replacement
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}
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return confusablesMap[r]
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}
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func skeletonBase(s string, lookup lookupFunc) string {
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// 1. Converting X to NFD format
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s = norm.NFD.String(s)
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// 2. Successively mapping each source character in X to the target string
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// according to the specified data table
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var buf bytes.Buffer
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changed := false // fast path: if this remains false, keep s intact
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prevPos := 0
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var replacement string
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for i, r := range s {
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if changed && replacement == "" {
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buf.WriteString(s[prevPos:i])
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}
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prevPos = i
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replacement = lookup(r)
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if replacement != "" {
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if !changed {
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changed = true
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// first replacement: copy over the previously unmodified text
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buf.WriteString(s[:i])
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}
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buf.WriteString(replacement)
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}
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}
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if changed && replacement == "" {
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buf.WriteString(s[prevPos:]) // loop-and-a-half
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}
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if changed {
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s = buf.String()
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}
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// 3. Reapplying NFD
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s = norm.NFD.String(s)
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return s
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}
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// Skeleton converts a string to its "skeleton" form
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// as described in http://www.unicode.org/reports/tr39/#Confusable_Detection
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func Skeleton(s string) string {
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return skeletonBase(s, lookupReplacement)
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}
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// SkeletonTweaked is like Skeleton, but it implements some custom overrides
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// to the confusables table (currently it removes the m -> rn mapping):
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func SkeletonTweaked(s string) string {
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return skeletonBase(s, lookupReplacementTweaked)
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}
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func Confusable(x, y string) bool {
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return Skeleton(x) == Skeleton(y)
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}
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