80 lines
1.5 KiB
Go
80 lines
1.5 KiB
Go
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// Complexity performs some rudimentary entropy calculations based on ASCII bi-grams, which can be
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// used to censor potential secret keys or passwords in text, and to estimate password strength.
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//
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// The matrix it uses only covers printable ASCII text, other runes are all interpreted as being \x127.
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//
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// The package isn't well tested, and the source data the matrix tabe
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package complexity
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import (
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"bufio"
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"io"
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"unicode/utf8"
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)
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type state struct {
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prev rune
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count int64
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entropy float64
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}
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func runeIdx(r rune) int {
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if r < firstRune || r > lastRune {
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return sz - 1
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}
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return int(r - firstRune)
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}
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func (s *state) put(next rune) {
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s.entropy += float64(matrix[runeIdx(s.prev)*sz+runeIdx(next)])
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s.count++
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s.prev = next
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}
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func runeReader(r io.RuneReader) (float32, int64, error) {
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s := state{prev: lastRune}
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for {
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r, _, err := r.ReadRune()
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if err != nil {
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if err == io.EOF {
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err = nil
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}
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return float32(s.entropy), s.count, err
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}
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s.put(r)
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}
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}
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func Reader(r io.Reader) (float32, int64, error) {
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if r, ok := r.(io.RuneReader); ok {
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return runeReader(r)
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}
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return runeReader(bufio.NewReader(r))
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}
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func Bytes(text []byte) (float32, int) {
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s := state{prev: lastRune}
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for i := 0; i != len(text); {
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r, sz := utf8.DecodeRune(text[i:])
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i += sz
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s.put(r)
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}
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return float32(s.entropy), int(s.count)
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}
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func String(text string) (float32, int) {
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s := state{prev: lastRune}
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for _, r := range text {
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s.put(r)
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}
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return float32(s.entropy), int(s.count)
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}
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