105 lines
3.1 KiB
Go
105 lines
3.1 KiB
Go
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// Copyright 2020-2022 The NATS Authors
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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 parser
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import (
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"errors"
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"fmt"
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)
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const (
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AckDomainTokenPos = iota + 2
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AckAccHashTokenPos
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AckStreamTokenPos
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AckConsumerTokenPos
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AckNumDeliveredTokenPos
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AckStreamSeqTokenPos
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AckConsumerSeqTokenPos
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AckTimestampSeqTokenPos
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AckNumPendingTokenPos
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)
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var ErrInvalidSubjectFormat = errors.New("invalid format of ACK subject")
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// Quick parser for positive numbers in ack reply encoding.
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// NOTE: This parser does not detect uint64 overflow
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func ParseNum(d string) (n uint64) {
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if len(d) == 0 {
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return 0
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}
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// ASCII numbers 0-9
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const (
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asciiZero = 48
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asciiNine = 57
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)
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for _, dec := range d {
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if dec < asciiZero || dec > asciiNine {
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return 0
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}
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n = n*10 + uint64(dec) - asciiZero
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}
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return
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}
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func GetMetadataFields(subject string) ([]string, error) {
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v1TokenCounts, v2TokenCounts := 9, 12
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var start int
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tokens := make([]string, 0, v2TokenCounts)
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for i := 0; i < len(subject); i++ {
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if subject[i] == '.' {
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tokens = append(tokens, subject[start:i])
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start = i + 1
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}
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}
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tokens = append(tokens, subject[start:])
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//
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// Newer server will include the domain name and account hash in the subject,
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// and a token at the end.
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//
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// Old subject was:
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// $JS.ACK.<stream>.<consumer>.<delivered>.<sseq>.<cseq>.<tm>.<pending>
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//
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// New subject would be:
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// $JS.ACK.<domain>.<account hash>.<stream>.<consumer>.<delivered>.<sseq>.<cseq>.<tm>.<pending>.<a token with a random value>
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//
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// v1 has 9 tokens, v2 has 12, but we must not be strict on the 12th since
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// it may be removed in the future. Also, the library has no use for it.
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// The point is that a v2 ACK subject is valid if it has at least 11 tokens.
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//
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tokensLen := len(tokens)
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// If lower than 9 or more than 9 but less than 11, report an error
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if tokensLen < v1TokenCounts || (tokensLen > v1TokenCounts && tokensLen < v2TokenCounts-1) {
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return nil, ErrInvalidSubjectFormat
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}
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if tokens[0] != "$JS" || tokens[1] != "ACK" {
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return nil, fmt.Errorf("%w: subject should start with $JS.ACK", ErrInvalidSubjectFormat)
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}
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// For v1 style, we insert 2 empty tokens (domain and hash) so that the
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// rest of the library references known fields at a constant location.
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if tokensLen == v1TokenCounts {
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// Extend the array (we know the backend is big enough)
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tokens = append(tokens[:AckDomainTokenPos+2], tokens[AckDomainTokenPos:]...)
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// Clear the domain and hash tokens
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tokens[AckDomainTokenPos], tokens[AckAccHashTokenPos] = "", ""
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} else if tokens[AckDomainTokenPos] == "_" {
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// If domain is "_", replace with empty value.
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tokens[AckDomainTokenPos] = ""
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}
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return tokens, nil
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}
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