35 lines
832 B
Go
35 lines
832 B
Go
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package trie
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// HexToCompact converts a hex path to the compact encoded format
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func HexToCompact(hex []byte) []byte {
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return hexToCompact(hex)
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}
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func hexToCompact(hex []byte) []byte {
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terminator := byte(0)
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if hasTerm(hex) {
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terminator = 1
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hex = hex[:len(hex)-1]
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}
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buf := make([]byte, len(hex)/2+1)
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buf[0] = terminator << 5 // the flag byte
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if len(hex)&1 == 1 {
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buf[0] |= 1 << 4 // odd flag
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buf[0] |= hex[0] // first nibble is contained in the first byte
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hex = hex[1:]
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}
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decodeNibbles(hex, buf[1:])
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return buf
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}
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func decodeNibbles(nibbles []byte, bytes []byte) {
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for bi, ni := 0, 0; ni < len(nibbles); bi, ni = bi+1, ni+2 {
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bytes[bi] = nibbles[ni]<<4 | nibbles[ni+1]
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}
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}
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// hasTerm returns whether a hex key has the terminator flag.
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func hasTerm(s []byte) bool {
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return len(s) > 0 && s[len(s)-1] == 16
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}
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