71 lines
2.3 KiB
Go
71 lines
2.3 KiB
Go
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// Copyright 2016 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Contains the Whisper protocol Topic element. For formal details please see
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// the specs at https://github.com/ethereum/wiki/wiki/Whisper-PoC-1-Protocol-Spec#topics.
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package whisperv5
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import (
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"fmt"
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"strings"
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"github.com/ethereum/go-ethereum/common"
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)
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// Topic represents a cryptographically secure, probabilistic partial
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// classifications of a message, determined as the first (left) 4 bytes of the
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// SHA3 hash of some arbitrary data given by the original author of the message.
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type TopicType [TopicLength]byte
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func BytesToTopic(b []byte) (t TopicType) {
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sz := TopicLength
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if x := len(b); x < TopicLength {
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sz = x
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}
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for i := 0; i < sz; i++ {
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t[i] = b[i]
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}
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return t
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}
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// String converts a topic byte array to a string representation.
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func (topic *TopicType) String() string {
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return string(common.ToHex(topic[:]))
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}
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// UnmarshalJSON parses a hex representation to a topic.
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func (t *TopicType) UnmarshalJSON(input []byte) error {
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length := len(input)
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if length >= 2 && input[0] == '"' && input[length-1] == '"' {
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input = input[1 : length-1]
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}
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// strip "0x" for length check
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if len(input) > 1 && strings.ToLower(string(input[:2])) == "0x" {
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input = input[2:]
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}
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// validate the length of the input
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if len(input) != TopicLength*2 {
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return fmt.Errorf("unmarshalJSON failed: topic must be exactly %d bytes", TopicLength)
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}
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b := common.FromHex(string(input))
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if b == nil {
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return fmt.Errorf("unmarshalJSON failed: wrong topic format")
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}
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*t = BytesToTopic(b)
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return nil
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}
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