source: code/trunk/vendor/github.com/prometheus/client_golang/prometheus/labels.go@ 822

// Copyright 2018 The Prometheus 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 prometheus

import (
        "errors"
        "fmt"
        "strings"
        "unicode/utf8"

        "github.com/prometheus/common/model"
)

// Labels represents a collection of label name -> value mappings. This type is
// commonly used with the With(Labels) and GetMetricWith(Labels) methods of
// metric vector Collectors, e.g.:
//
//      myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)
//
// The other use-case is the specification of constant label pairs in Opts or to
// create a Desc.
type Labels map[string]string

// reservedLabelPrefix is a prefix which is not legal in user-supplied
// label names.
const reservedLabelPrefix = "__"

var errInconsistentCardinality = errors.New("inconsistent label cardinality")

func makeInconsistentCardinalityError(fqName string, labels, labelValues []string) error {
        return fmt.Errorf(
                "%w: %q has %d variable labels named %q but %d values %q were provided",
                errInconsistentCardinality, fqName,
                len(labels), labels,
                len(labelValues), labelValues,
        )
}

func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
        if len(labels) != expectedNumberOfValues {
                return fmt.Errorf(
                        "%w: expected %d label values but got %d in %#v",
                        errInconsistentCardinality, expectedNumberOfValues,
                        len(labels), labels,
                )
        }

        for name, val := range labels {
                if !utf8.ValidString(val) {
                        return fmt.Errorf("label %s: value %q is not valid UTF-8", name, val)
                }
        }

        return nil
}

func validateLabelValues(vals []string, expectedNumberOfValues int) error {
        if len(vals) != expectedNumberOfValues {
                return fmt.Errorf(
                        "%w: expected %d label values but got %d in %#v",
                        errInconsistentCardinality, expectedNumberOfValues,
                        len(vals), vals,
                )
        }

        for _, val := range vals {
                if !utf8.ValidString(val) {
                        return fmt.Errorf("label value %q is not valid UTF-8", val)
                }
        }

        return nil
}

func checkLabelName(l string) bool {
        return model.LabelName(l).IsValid() && !strings.HasPrefix(l, reservedLabelPrefix)
}