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https://gitlab.com/pulsechaincom/erigon-pulse.git
synced 2024-12-25 04:57:17 +00:00
64 lines
1.4 KiB
Go
64 lines
1.4 KiB
Go
package hexutility
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import (
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"encoding/hex"
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"fmt"
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)
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const (
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badNibble = ^uint64(0)
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)
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// UnmarshalFixedText decodes the input as a string with 0x prefix. The length of out
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// determines the required input length. This function is commonly used to implement the
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// UnmarshalText method for fixed-size types.
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func UnmarshalFixedText(typname string, input, out []byte) error {
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raw, err := checkText(input, true)
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if err != nil {
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return err
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}
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if len(raw)/2 != len(out) {
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return fmt.Errorf("hex string has length %d, want %d for %s", len(raw), len(out)*2, typname)
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}
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// Pre-verify syntax before modifying out.
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for _, b := range raw {
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if decodeNibble(b) == badNibble {
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return ErrSyntax
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}
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}
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_, err = hex.Decode(out, raw)
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return err
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}
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func checkText(input []byte, wantPrefix bool) ([]byte, error) {
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if len(input) == 0 {
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return nil, nil // empty strings are allowed
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}
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if bytesHave0xPrefix(input) {
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input = input[2:]
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} else if wantPrefix {
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return nil, ErrMissingPrefix
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}
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if len(input)%2 != 0 {
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return nil, ErrOddLength
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}
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return input, nil
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}
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func bytesHave0xPrefix(input []byte) bool {
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return len(input) >= 2 && input[0] == '0' && (input[1] == 'x' || input[1] == 'X')
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}
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func decodeNibble(in byte) uint64 {
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switch {
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case in >= '0' && in <= '9':
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return uint64(in - '0')
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case in >= 'A' && in <= 'F':
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return uint64(in - 'A' + 10)
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case in >= 'a' && in <= 'f':
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return uint64(in - 'a' + 10)
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default:
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return badNibble
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}
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}
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