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// Copyright 2020 New Relic Corporation. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
package cat
import (
"crypto/md5"
"encoding/binary"
"fmt"
"regexp"
)
var pathHashValidator = regexp.MustCompile("^[0-9a-f]{8}$")
// GeneratePathHash generates a path hash given a referring path hash,
// transaction name, and application name. referringPathHash can be an empty
// string if there was no referring path hash.
func GeneratePathHash(referringPathHash, txnName, appName string) (string, error) {
var rph uint32
if referringPathHash != "" {
if !pathHashValidator.MatchString(referringPathHash) {
// Per the spec, invalid referring path hashes should be treated as "0".
referringPathHash = "0"
}
if _, err := fmt.Sscanf(referringPathHash, "%x", &rph); err != nil {
fmt.Println(rph)
return "", err
}
rph = (rph << 1) | (rph >> 31)
}
hashInput := fmt.Sprintf("%s;%s", appName, txnName)
hash := md5.Sum([]byte(hashInput))
low32 := binary.BigEndian.Uint32(hash[12:])
return fmt.Sprintf("%08x", rph^low32), nil
}
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