425 lines
11 KiB
Go
425 lines
11 KiB
Go
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// Copyright The OpenTelemetry Authors
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//
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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 attribute // import "go.opentelemetry.io/otel/attribute"
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import (
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"encoding/json"
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"reflect"
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"sort"
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)
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type (
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// Set is the representation for a distinct attribute set. It manages an
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// immutable set of attributes, with an internal cache for storing
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// attribute encodings.
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//
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// This type supports the Equivalent method of comparison using values of
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// type Distinct.
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Set struct {
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equivalent Distinct
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}
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// Distinct wraps a variable-size array of KeyValue, constructed with keys
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// in sorted order. This can be used as a map key or for equality checking
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// between Sets.
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Distinct struct {
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iface interface{}
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}
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// Filter supports removing certain attributes from attribute sets. When
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// the filter returns true, the attribute will be kept in the filtered
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// attribute set. When the filter returns false, the attribute is excluded
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// from the filtered attribute set, and the attribute instead appears in
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// the removed list of excluded attributes.
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Filter func(KeyValue) bool
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// Sortable implements sort.Interface, used for sorting KeyValue. This is
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// an exported type to support a memory optimization. A pointer to one of
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// these is needed for the call to sort.Stable(), which the caller may
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// provide in order to avoid an allocation. See NewSetWithSortable().
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Sortable []KeyValue
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)
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var (
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// keyValueType is used in computeDistinctReflect.
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keyValueType = reflect.TypeOf(KeyValue{})
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// emptySet is returned for empty attribute sets.
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emptySet = &Set{
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equivalent: Distinct{
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iface: [0]KeyValue{},
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},
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}
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)
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// EmptySet returns a reference to a Set with no elements.
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//
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// This is a convenience provided for optimized calling utility.
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func EmptySet() *Set {
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return emptySet
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}
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// reflectValue abbreviates reflect.ValueOf(d).
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func (d Distinct) reflectValue() reflect.Value {
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return reflect.ValueOf(d.iface)
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}
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// Valid returns true if this value refers to a valid Set.
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func (d Distinct) Valid() bool {
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return d.iface != nil
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}
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// Len returns the number of attributes in this set.
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func (l *Set) Len() int {
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if l == nil || !l.equivalent.Valid() {
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return 0
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}
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return l.equivalent.reflectValue().Len()
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}
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// Get returns the KeyValue at ordered position idx in this set.
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func (l *Set) Get(idx int) (KeyValue, bool) {
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if l == nil {
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return KeyValue{}, false
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}
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value := l.equivalent.reflectValue()
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if idx >= 0 && idx < value.Len() {
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// Note: The Go compiler successfully avoids an allocation for
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// the interface{} conversion here:
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return value.Index(idx).Interface().(KeyValue), true
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}
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return KeyValue{}, false
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}
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// Value returns the value of a specified key in this set.
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func (l *Set) Value(k Key) (Value, bool) {
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if l == nil {
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return Value{}, false
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}
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rValue := l.equivalent.reflectValue()
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vlen := rValue.Len()
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idx := sort.Search(vlen, func(idx int) bool {
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return rValue.Index(idx).Interface().(KeyValue).Key >= k
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})
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if idx >= vlen {
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return Value{}, false
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}
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keyValue := rValue.Index(idx).Interface().(KeyValue)
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if k == keyValue.Key {
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return keyValue.Value, true
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}
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return Value{}, false
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}
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// HasValue tests whether a key is defined in this set.
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func (l *Set) HasValue(k Key) bool {
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if l == nil {
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return false
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}
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_, ok := l.Value(k)
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return ok
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}
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// Iter returns an iterator for visiting the attributes in this set.
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func (l *Set) Iter() Iterator {
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return Iterator{
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storage: l,
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idx: -1,
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}
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}
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// ToSlice returns the set of attributes belonging to this set, sorted, where
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// keys appear no more than once.
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func (l *Set) ToSlice() []KeyValue {
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iter := l.Iter()
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return iter.ToSlice()
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}
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// Equivalent returns a value that may be used as a map key. The Distinct type
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// guarantees that the result will equal the equivalent. Distinct value of any
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// attribute set with the same elements as this, where sets are made unique by
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// choosing the last value in the input for any given key.
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func (l *Set) Equivalent() Distinct {
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if l == nil || !l.equivalent.Valid() {
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return emptySet.equivalent
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}
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return l.equivalent
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}
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// Equals returns true if the argument set is equivalent to this set.
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func (l *Set) Equals(o *Set) bool {
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return l.Equivalent() == o.Equivalent()
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}
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// Encoded returns the encoded form of this set, according to encoder.
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func (l *Set) Encoded(encoder Encoder) string {
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if l == nil || encoder == nil {
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return ""
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}
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return encoder.Encode(l.Iter())
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}
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func empty() Set {
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return Set{
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equivalent: emptySet.equivalent,
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}
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}
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// NewSet returns a new Set. See the documentation for
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// NewSetWithSortableFiltered for more details.
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//
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// Except for empty sets, this method adds an additional allocation compared
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// with calls that include a Sortable.
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func NewSet(kvs ...KeyValue) Set {
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// Check for empty set.
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if len(kvs) == 0 {
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return empty()
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}
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s, _ := NewSetWithSortableFiltered(kvs, new(Sortable), nil)
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return s
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}
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// NewSetWithSortable returns a new Set. See the documentation for
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// NewSetWithSortableFiltered for more details.
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//
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// This call includes a Sortable option as a memory optimization.
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func NewSetWithSortable(kvs []KeyValue, tmp *Sortable) Set {
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// Check for empty set.
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if len(kvs) == 0 {
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return empty()
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}
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s, _ := NewSetWithSortableFiltered(kvs, tmp, nil)
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return s
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}
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// NewSetWithFiltered returns a new Set. See the documentation for
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// NewSetWithSortableFiltered for more details.
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//
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// This call includes a Filter to include/exclude attribute keys from the
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// return value. Excluded keys are returned as a slice of attribute values.
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func NewSetWithFiltered(kvs []KeyValue, filter Filter) (Set, []KeyValue) {
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// Check for empty set.
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if len(kvs) == 0 {
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return empty(), nil
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}
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return NewSetWithSortableFiltered(kvs, new(Sortable), filter)
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}
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// NewSetWithSortableFiltered returns a new Set.
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//
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// Duplicate keys are eliminated by taking the last value. This
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// re-orders the input slice so that unique last-values are contiguous
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// at the end of the slice.
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//
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// This ensures the following:
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//
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// - Last-value-wins semantics
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// - Caller sees the reordering, but doesn't lose values
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// - Repeated call preserve last-value wins.
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//
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// Note that methods are defined on Set, although this returns Set. Callers
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// can avoid memory allocations by:
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//
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// - allocating a Sortable for use as a temporary in this method
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// - allocating a Set for storing the return value of this constructor.
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//
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// The result maintains a cache of encoded attributes, by attribute.EncoderID.
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// This value should not be copied after its first use.
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//
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// The second []KeyValue return value is a list of attributes that were
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// excluded by the Filter (if non-nil).
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func NewSetWithSortableFiltered(kvs []KeyValue, tmp *Sortable, filter Filter) (Set, []KeyValue) {
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// Check for empty set.
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if len(kvs) == 0 {
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return empty(), nil
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}
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*tmp = kvs
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// Stable sort so the following de-duplication can implement
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// last-value-wins semantics.
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sort.Stable(tmp)
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*tmp = nil
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position := len(kvs) - 1
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offset := position - 1
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// The requirements stated above require that the stable
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// result be placed in the end of the input slice, while
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// overwritten values are swapped to the beginning.
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//
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// De-duplicate with last-value-wins semantics. Preserve
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// duplicate values at the beginning of the input slice.
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for ; offset >= 0; offset-- {
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if kvs[offset].Key == kvs[position].Key {
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continue
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}
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position--
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kvs[offset], kvs[position] = kvs[position], kvs[offset]
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}
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if filter != nil {
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return filterSet(kvs[position:], filter)
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}
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return Set{
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equivalent: computeDistinct(kvs[position:]),
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}, nil
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}
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// filterSet reorders kvs so that included keys are contiguous at the end of
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// the slice, while excluded keys precede the included keys.
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func filterSet(kvs []KeyValue, filter Filter) (Set, []KeyValue) {
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var excluded []KeyValue
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// Move attributes that do not match the filter so they're adjacent before
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// calling computeDistinct().
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distinctPosition := len(kvs)
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// Swap indistinct keys forward and distinct keys toward the
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// end of the slice.
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offset := len(kvs) - 1
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for ; offset >= 0; offset-- {
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if filter(kvs[offset]) {
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distinctPosition--
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kvs[offset], kvs[distinctPosition] = kvs[distinctPosition], kvs[offset]
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continue
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}
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}
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excluded = kvs[:distinctPosition]
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return Set{
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equivalent: computeDistinct(kvs[distinctPosition:]),
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}, excluded
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}
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// Filter returns a filtered copy of this Set. See the documentation for
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// NewSetWithSortableFiltered for more details.
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func (l *Set) Filter(re Filter) (Set, []KeyValue) {
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if re == nil {
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return Set{
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equivalent: l.equivalent,
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}, nil
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}
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// Note: This could be refactored to avoid the temporary slice
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// allocation, if it proves to be expensive.
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return filterSet(l.ToSlice(), re)
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}
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// computeDistinct returns a Distinct using either the fixed- or
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// reflect-oriented code path, depending on the size of the input. The input
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// slice is assumed to already be sorted and de-duplicated.
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func computeDistinct(kvs []KeyValue) Distinct {
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iface := computeDistinctFixed(kvs)
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if iface == nil {
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iface = computeDistinctReflect(kvs)
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}
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return Distinct{
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iface: iface,
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}
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}
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// computeDistinctFixed computes a Distinct for small slices. It returns nil
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// if the input is too large for this code path.
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func computeDistinctFixed(kvs []KeyValue) interface{} {
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switch len(kvs) {
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case 1:
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ptr := new([1]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 2:
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ptr := new([2]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 3:
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ptr := new([3]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 4:
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ptr := new([4]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 5:
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ptr := new([5]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 6:
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ptr := new([6]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 7:
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ptr := new([7]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 8:
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ptr := new([8]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 9:
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ptr := new([9]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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case 10:
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ptr := new([10]KeyValue)
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copy((*ptr)[:], kvs)
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return *ptr
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default:
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return nil
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}
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}
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// computeDistinctReflect computes a Distinct using reflection, works for any
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// size input.
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func computeDistinctReflect(kvs []KeyValue) interface{} {
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at := reflect.New(reflect.ArrayOf(len(kvs), keyValueType)).Elem()
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for i, keyValue := range kvs {
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*(at.Index(i).Addr().Interface().(*KeyValue)) = keyValue
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}
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return at.Interface()
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}
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// MarshalJSON returns the JSON encoding of the Set.
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func (l *Set) MarshalJSON() ([]byte, error) {
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return json.Marshal(l.equivalent.iface)
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}
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// MarshalLog is the marshaling function used by the logging system to represent this exporter.
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func (l Set) MarshalLog() interface{} {
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kvs := make(map[string]string)
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for _, kv := range l.ToSlice() {
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kvs[string(kv.Key)] = kv.Value.Emit()
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}
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return kvs
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}
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// Len implements sort.Interface.
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func (l *Sortable) Len() int {
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return len(*l)
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}
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// Swap implements sort.Interface.
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func (l *Sortable) Swap(i, j int) {
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(*l)[i], (*l)[j] = (*l)[j], (*l)[i]
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}
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// Less implements sort.Interface.
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func (l *Sortable) Less(i, j int) bool {
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return (*l)[i].Key < (*l)[j].Key
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}
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