87 lines
2.5 KiB
Go
87 lines
2.5 KiB
Go
// Copyright © 2019 Weald Technology Trading
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package multicodec provides the ability to add and remove codec prefixes from data.
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package multicodec
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import (
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"encoding/binary"
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"fmt"
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)
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// AddCodec adds a codec prefix to a byte array.
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// It returns a new byte array with the relevant codec prefixed.
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func AddCodec(name string, data []byte) ([]byte, error) {
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id, err := ID(name)
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if err != nil {
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return nil, err
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}
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buf := make([]byte, binary.MaxVarintLen64)
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size := binary.PutUvarint(buf, id)
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res := make([]byte, size+len(data))
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copy(res, buf[0:size])
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copy(res[size:], data)
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return res, nil
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}
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// RemoveCodec removes a codec prefix from a byte array.
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// It returns a slice of the input byte array without the codec prefix, along with the ID of the codec that has been removed.
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func RemoveCodec(data []byte) ([]byte, uint64, error) {
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id, size := binary.Uvarint(data)
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if id == 0 {
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return nil, 0, fmt.Errorf("failed to find codec prefix to remove")
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}
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return data[size:], id, nil
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}
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// GetCodec returns the ID of the codec prefix from a byte array
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func GetCodec(data []byte) (uint64, error) {
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id, _ := binary.Uvarint(data)
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if id == 0 {
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return 0, fmt.Errorf("failed to find codec prefix to remove")
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}
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return id, nil
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}
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// IsCodec returns true if the data is of the supplied codec prefix, otherwise false
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func IsCodec(name string, data []byte) bool {
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id, err := GetCodec(data)
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if err != nil {
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return false
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}
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codecName, err := Name(id)
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if err != nil {
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// Failed to obtain name for ID
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return false
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}
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return codecName == name
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}
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// ID obtains the ID of a codec from its name
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func ID(name string) (uint64, error) {
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codec, exists := codecs[name]
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if !exists {
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return 0, fmt.Errorf("unknown name %s", name)
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}
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return codec.id, nil
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}
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// Name obtains the name of a codec from its ID
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func Name(id uint64) (string, error) {
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codec, exists := reverseCodecs[id]
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if !exists {
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return "", fmt.Errorf("unknown ID 0x%x", id)
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}
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return codec.name, nil
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}
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