peridot/vendor/go.opentelemetry.io/otel/attribute/set.go

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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package attribute // import "go.opentelemetry.io/otel/attribute"
import (
"cmp"
"encoding/json"
"reflect"
"slices"
"sort"
)
type (
// Set is the representation for a distinct attribute set. It manages an
// immutable set of attributes, with an internal cache for storing
// attribute encodings.
//
// This type will remain comparable for backwards compatibility. The
// equivalence of Sets across versions is not guaranteed to be stable.
// Prior versions may find two Sets to be equal or not when compared
// directly (i.e. ==), but subsequent versions may not. Users should use
// the Equals method to ensure stable equivalence checking.
//
// Users should also use the Distinct returned from Equivalent as a map key
// instead of a Set directly. In addition to that type providing guarantees
// on stable equivalence, it may also provide performance improvements.
Set struct {
equivalent Distinct
}
// Distinct is a unique identifier of a Set.
//
// Distinct is designed to be ensures equivalence stability: comparisons
// will return the save value across versions. For this reason, Distinct
// should always be used as a map key instead of a Set.
Distinct struct {
iface interface{}
}
// Sortable implements sort.Interface, used for sorting KeyValue.
//
// Deprecated: This type is no longer used. It was added as a performance
// optimization for Go < 1.21 that is no longer needed (Go < 1.21 is no
// longer supported by the module).
Sortable []KeyValue
)
var (
// keyValueType is used in computeDistinctReflect.
keyValueType = reflect.TypeOf(KeyValue{})
// emptySet is returned for empty attribute sets.
emptySet = &Set{
equivalent: Distinct{
iface: [0]KeyValue{},
},
}
)
// EmptySet returns a reference to a Set with no elements.
//
// This is a convenience provided for optimized calling utility.
func EmptySet() *Set {
return emptySet
}
// reflectValue abbreviates reflect.ValueOf(d).
func (d Distinct) reflectValue() reflect.Value {
return reflect.ValueOf(d.iface)
}
// Valid returns true if this value refers to a valid Set.
func (d Distinct) Valid() bool {
return d.iface != nil
}
// Len returns the number of attributes in this set.
func (l *Set) Len() int {
if l == nil || !l.equivalent.Valid() {
return 0
}
return l.equivalent.reflectValue().Len()
}
// Get returns the KeyValue at ordered position idx in this set.
func (l *Set) Get(idx int) (KeyValue, bool) {
if l == nil || !l.equivalent.Valid() {
return KeyValue{}, false
}
value := l.equivalent.reflectValue()
if idx >= 0 && idx < value.Len() {
// Note: The Go compiler successfully avoids an allocation for
// the interface{} conversion here:
return value.Index(idx).Interface().(KeyValue), true
}
return KeyValue{}, false
}
// Value returns the value of a specified key in this set.
func (l *Set) Value(k Key) (Value, bool) {
if l == nil || !l.equivalent.Valid() {
return Value{}, false
}
rValue := l.equivalent.reflectValue()
vlen := rValue.Len()
idx := sort.Search(vlen, func(idx int) bool {
return rValue.Index(idx).Interface().(KeyValue).Key >= k
})
if idx >= vlen {
return Value{}, false
}
keyValue := rValue.Index(idx).Interface().(KeyValue)
if k == keyValue.Key {
return keyValue.Value, true
}
return Value{}, false
}
// HasValue tests whether a key is defined in this set.
func (l *Set) HasValue(k Key) bool {
if l == nil {
return false
}
_, ok := l.Value(k)
return ok
}
// Iter returns an iterator for visiting the attributes in this set.
func (l *Set) Iter() Iterator {
return Iterator{
storage: l,
idx: -1,
}
}
// ToSlice returns the set of attributes belonging to this set, sorted, where
// keys appear no more than once.
func (l *Set) ToSlice() []KeyValue {
iter := l.Iter()
return iter.ToSlice()
}
// Equivalent returns a value that may be used as a map key. The Distinct type
// guarantees that the result will equal the equivalent. Distinct value of any
// attribute set with the same elements as this, where sets are made unique by
// choosing the last value in the input for any given key.
func (l *Set) Equivalent() Distinct {
if l == nil || !l.equivalent.Valid() {
return emptySet.equivalent
}
return l.equivalent
}
// Equals returns true if the argument set is equivalent to this set.
func (l *Set) Equals(o *Set) bool {
return l.Equivalent() == o.Equivalent()
}
// Encoded returns the encoded form of this set, according to encoder.
func (l *Set) Encoded(encoder Encoder) string {
if l == nil || encoder == nil {
return ""
}
return encoder.Encode(l.Iter())
}
func empty() Set {
return Set{
equivalent: emptySet.equivalent,
}
}
// NewSet returns a new Set. See the documentation for
// NewSetWithSortableFiltered for more details.
//
// Except for empty sets, this method adds an additional allocation compared
// with calls that include a Sortable.
func NewSet(kvs ...KeyValue) Set {
s, _ := NewSetWithFiltered(kvs, nil)
return s
}
// NewSetWithSortable returns a new Set. See the documentation for
// NewSetWithSortableFiltered for more details.
//
// This call includes a Sortable option as a memory optimization.
//
// Deprecated: Use [NewSet] instead.
func NewSetWithSortable(kvs []KeyValue, _ *Sortable) Set {
s, _ := NewSetWithFiltered(kvs, nil)
return s
}
// NewSetWithFiltered returns a new Set. See the documentation for
// NewSetWithSortableFiltered for more details.
//
// This call includes a Filter to include/exclude attribute keys from the
// return value. Excluded keys are returned as a slice of attribute values.
func NewSetWithFiltered(kvs []KeyValue, filter Filter) (Set, []KeyValue) {
// Check for empty set.
if len(kvs) == 0 {
return empty(), nil
}
// Stable sort so the following de-duplication can implement
// last-value-wins semantics.
slices.SortStableFunc(kvs, func(a, b KeyValue) int {
return cmp.Compare(a.Key, b.Key)
})
position := len(kvs) - 1
offset := position - 1
// The requirements stated above require that the stable
// result be placed in the end of the input slice, while
// overwritten values are swapped to the beginning.
//
// De-duplicate with last-value-wins semantics. Preserve
// duplicate values at the beginning of the input slice.
for ; offset >= 0; offset-- {
if kvs[offset].Key == kvs[position].Key {
continue
}
position--
kvs[offset], kvs[position] = kvs[position], kvs[offset]
}
kvs = kvs[position:]
if filter != nil {
if div := filteredToFront(kvs, filter); div != 0 {
return Set{equivalent: computeDistinct(kvs[div:])}, kvs[:div]
}
}
return Set{equivalent: computeDistinct(kvs)}, nil
}
// NewSetWithSortableFiltered returns a new Set.
//
// Duplicate keys are eliminated by taking the last value. This
// re-orders the input slice so that unique last-values are contiguous
// at the end of the slice.
//
// This ensures the following:
//
// - Last-value-wins semantics
// - Caller sees the reordering, but doesn't lose values
// - Repeated call preserve last-value wins.
//
// Note that methods are defined on Set, although this returns Set. Callers
// can avoid memory allocations by:
//
// - allocating a Sortable for use as a temporary in this method
// - allocating a Set for storing the return value of this constructor.
//
// The result maintains a cache of encoded attributes, by attribute.EncoderID.
// This value should not be copied after its first use.
//
// The second []KeyValue return value is a list of attributes that were
// excluded by the Filter (if non-nil).
//
// Deprecated: Use [NewSetWithFiltered] instead.
func NewSetWithSortableFiltered(kvs []KeyValue, _ *Sortable, filter Filter) (Set, []KeyValue) {
return NewSetWithFiltered(kvs, filter)
}
// filteredToFront filters slice in-place using keep function. All KeyValues that need to
// be removed are moved to the front. All KeyValues that need to be kept are
// moved (in-order) to the back. The index for the first KeyValue to be kept is
// returned.
func filteredToFront(slice []KeyValue, keep Filter) int {
n := len(slice)
j := n
for i := n - 1; i >= 0; i-- {
if keep(slice[i]) {
j--
slice[i], slice[j] = slice[j], slice[i]
}
}
return j
}
// Filter returns a filtered copy of this Set. See the documentation for
// NewSetWithSortableFiltered for more details.
func (l *Set) Filter(re Filter) (Set, []KeyValue) {
if re == nil {
return *l, nil
}
// Iterate in reverse to the first attribute that will be filtered out.
n := l.Len()
first := n - 1
for ; first >= 0; first-- {
kv, _ := l.Get(first)
if !re(kv) {
break
}
}
// No attributes will be dropped, return the immutable Set l and nil.
if first < 0 {
return *l, nil
}
// Copy now that we know we need to return a modified set.
//
// Do not do this in-place on the underlying storage of *Set l. Sets are
// immutable and filtering should not change this.
slice := l.ToSlice()
// Don't re-iterate the slice if only slice[0] is filtered.
if first == 0 {
// It is safe to assume len(slice) >= 1 given we found at least one
// attribute above that needs to be filtered out.
return Set{equivalent: computeDistinct(slice[1:])}, slice[:1]
}
// Move the filtered slice[first] to the front (preserving order).
kv := slice[first]
copy(slice[1:first+1], slice[:first])
slice[0] = kv
// Do not re-evaluate re(slice[first+1:]).
div := filteredToFront(slice[1:first+1], re) + 1
return Set{equivalent: computeDistinct(slice[div:])}, slice[:div]
}
// computeDistinct returns a Distinct using either the fixed- or
// reflect-oriented code path, depending on the size of the input. The input
// slice is assumed to already be sorted and de-duplicated.
func computeDistinct(kvs []KeyValue) Distinct {
iface := computeDistinctFixed(kvs)
if iface == nil {
iface = computeDistinctReflect(kvs)
}
return Distinct{
iface: iface,
}
}
// computeDistinctFixed computes a Distinct for small slices. It returns nil
// if the input is too large for this code path.
func computeDistinctFixed(kvs []KeyValue) interface{} {
switch len(kvs) {
case 1:
ptr := new([1]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 2:
ptr := new([2]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 3:
ptr := new([3]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 4:
ptr := new([4]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 5:
ptr := new([5]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 6:
ptr := new([6]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 7:
ptr := new([7]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 8:
ptr := new([8]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 9:
ptr := new([9]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
case 10:
ptr := new([10]KeyValue)
copy((*ptr)[:], kvs)
return *ptr
default:
return nil
}
}
// computeDistinctReflect computes a Distinct using reflection, works for any
// size input.
func computeDistinctReflect(kvs []KeyValue) interface{} {
at := reflect.New(reflect.ArrayOf(len(kvs), keyValueType)).Elem()
for i, keyValue := range kvs {
*(at.Index(i).Addr().Interface().(*KeyValue)) = keyValue
}
return at.Interface()
}
// MarshalJSON returns the JSON encoding of the Set.
func (l *Set) MarshalJSON() ([]byte, error) {
return json.Marshal(l.equivalent.iface)
}
// MarshalLog is the marshaling function used by the logging system to represent this Set.
func (l Set) MarshalLog() interface{} {
kvs := make(map[string]string)
for _, kv := range l.ToSlice() {
kvs[string(kv.Key)] = kv.Value.Emit()
}
return kvs
}
// Len implements sort.Interface.
func (l *Sortable) Len() int {
return len(*l)
}
// Swap implements sort.Interface.
func (l *Sortable) Swap(i, j int) {
(*l)[i], (*l)[j] = (*l)[j], (*l)[i]
}
// Less implements sort.Interface.
func (l *Sortable) Less(i, j int) bool {
return (*l)[i].Key < (*l)[j].Key
}