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// Copyright 2020-2022 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package parser
import (
"errors"
"fmt"
)
const (
AckDomainTokenPos = iota + 2
AckAccHashTokenPos
AckStreamTokenPos
AckConsumerTokenPos
AckNumDeliveredTokenPos
AckStreamSeqTokenPos
AckConsumerSeqTokenPos
AckTimestampSeqTokenPos
AckNumPendingTokenPos
)
var ErrInvalidSubjectFormat = errors.New("invalid format of ACK subject")
// Quick parser for positive numbers in ack reply encoding.
// NOTE: This parser does not detect uint64 overflow
func ParseNum(d string) (n uint64) {
if len(d) == 0 {
return 0
}
// ASCII numbers 0-9
const (
asciiZero = 48
asciiNine = 57
)
for _, dec := range d {
if dec < asciiZero || dec > asciiNine {
return 0
}
n = n*10 + uint64(dec) - asciiZero
}
return
}
func GetMetadataFields(subject string) ([]string, error) {
v1TokenCounts, v2TokenCounts := 9, 12
var start int
tokens := make([]string, 0, v2TokenCounts)
for i := 0; i < len(subject); i++ {
if subject[i] == '.' {
tokens = append(tokens, subject[start:i])
start = i + 1
}
}
tokens = append(tokens, subject[start:])
//
// Newer server will include the domain name and account hash in the subject,
// and a token at the end.
//
// Old subject was:
// $JS.ACK.<stream>.<consumer>.<delivered>.<sseq>.<cseq>.<tm>.<pending>
//
// New subject would be:
// $JS.ACK.<domain>.<account hash>.<stream>.<consumer>.<delivered>.<sseq>.<cseq>.<tm>.<pending>.<a token with a random value>
//
// v1 has 9 tokens, v2 has 12, but we must not be strict on the 12th since
// it may be removed in the future. Also, the library has no use for it.
// The point is that a v2 ACK subject is valid if it has at least 11 tokens.
//
tokensLen := len(tokens)
// If lower than 9 or more than 9 but less than 11, report an error
if tokensLen < v1TokenCounts || (tokensLen > v1TokenCounts && tokensLen < v2TokenCounts-1) {
return nil, ErrInvalidSubjectFormat
}
if tokens[0] != "$JS" || tokens[1] != "ACK" {
return nil, fmt.Errorf("%w: subject should start with $JS.ACK", ErrInvalidSubjectFormat)
}
// For v1 style, we insert 2 empty tokens (domain and hash) so that the
// rest of the library references known fields at a constant location.
if tokensLen == v1TokenCounts {
// Extend the array (we know the backend is big enough)
tokens = append(tokens[:AckDomainTokenPos+2], tokens[AckDomainTokenPos:]...)
// Clear the domain and hash tokens
tokens[AckDomainTokenPos], tokens[AckAccHashTokenPos] = "", ""
} else if tokens[AckDomainTokenPos] == "_" {
// If domain is "_", replace with empty value.
tokens[AckDomainTokenPos] = ""
}
return tokens, nil
}
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