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// Copyright (c) 2021 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package tally
const (
prefixSplitter = '+'
keyPairSplitter = ','
keyNameSplitter = '='
nilString = ""
)
// KeyForStringMap generates a unique key for a map string set combination.
func KeyForStringMap(
stringMap map[string]string,
) string {
return KeyForPrefixedStringMap(nilString, stringMap)
}
// KeyForPrefixedStringMap generates a unique key for a
// a prefix and a map string set combination.
func KeyForPrefixedStringMap(
prefix string,
stringMap map[string]string,
) string {
return keyForPrefixedStringMaps(prefix, stringMap)
}
// keyForPrefixedStringMapsAsKey writes a key using the prefix and the tags in a canonical form to
// the given input byte slice and returns a reference to the byte slice. Callers of this method can
// use a stack allocated byte slice to remove heap allocation.
func keyForPrefixedStringMapsAsKey(buf []byte, prefix string, maps ...map[string]string) []byte {
// stack allocated
keys := make([]string, 0, 32)
for _, m := range maps {
for k := range m {
keys = append(keys, k)
}
}
insertionSort(keys)
if prefix != nilString {
buf = append(buf, prefix...)
buf = append(buf, prefixSplitter)
}
var lastKey string // last key written to the buffer
for _, k := range keys {
if len(lastKey) > 0 {
if k == lastKey {
// Already wrote this key.
continue
}
buf = append(buf, keyPairSplitter)
}
lastKey = k
buf = append(buf, k...)
buf = append(buf, keyNameSplitter)
// Find and write the value for this key. Rightmost map takes
// precedence.
for j := len(maps) - 1; j >= 0; j-- {
if v, ok := maps[j][k]; ok {
buf = append(buf, v...)
break
}
}
}
return buf
}
// keyForPrefixedStringMaps generates a unique key for a prefix and a series
// of maps containing tags.
//
// If a key occurs in multiple maps, keys on the right take precedence.
func keyForPrefixedStringMaps(prefix string, maps ...map[string]string) string {
return string(keyForPrefixedStringMapsAsKey(make([]byte, 0, 256), prefix, maps...))
}
func insertionSort(keys []string) {
n := len(keys)
for i := 1; i < n; i++ {
for j := i; j > 0 && keys[j] < keys[j-1]; j-- {
keys[j], keys[j-1] = keys[j-1], keys[j]
}
}
}
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