94 lines
2.3 KiB
Go
94 lines
2.3 KiB
Go
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// Copyright 2020 The Prometheus Authors
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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 labels
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import (
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"regexp"
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"regexp/syntax"
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"strings"
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)
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type FastRegexMatcher struct {
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re *regexp.Regexp
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prefix string
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suffix string
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}
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func NewFastRegexMatcher(v string) (*FastRegexMatcher, error) {
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re, err := regexp.Compile("^(?:" + v + ")$")
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if err != nil {
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return nil, err
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}
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parsed, err := syntax.Parse(v, syntax.Perl)
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if err != nil {
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return nil, err
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}
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m := &FastRegexMatcher{
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re: re,
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}
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if parsed.Op == syntax.OpConcat {
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m.prefix, m.suffix = optimizeConcatRegex(parsed)
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}
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return m, nil
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}
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func (m *FastRegexMatcher) MatchString(s string) bool {
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if m.prefix != "" && !strings.HasPrefix(s, m.prefix) {
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return false
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}
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if m.suffix != "" && !strings.HasSuffix(s, m.suffix) {
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return false
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}
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return m.re.MatchString(s)
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}
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func (m *FastRegexMatcher) GetRegexString() string {
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return m.re.String()
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}
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// optimizeConcatRegex returns literal prefix/suffix text that can be safely
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// checked against the label value before running the regexp matcher.
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func optimizeConcatRegex(r *syntax.Regexp) (prefix, suffix string) {
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sub := r.Sub
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// We can safely remove begin and end text matchers respectively
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// at the beginning and end of the regexp.
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if len(sub) > 0 && sub[0].Op == syntax.OpBeginText {
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sub = sub[1:]
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}
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if len(sub) > 0 && sub[len(sub)-1].Op == syntax.OpEndText {
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sub = sub[:len(sub)-1]
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}
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if len(sub) == 0 {
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return
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}
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// Given Prometheus regex matchers are always anchored to the begin/end
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// of the text, if the first/last operations are literals, we can safely
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// treat them as prefix/suffix.
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if sub[0].Op == syntax.OpLiteral {
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prefix = string(sub[0].Rune)
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}
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if last := len(sub) - 1; sub[last].Op == syntax.OpLiteral {
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suffix = string(sub[last].Rune)
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}
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return
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}
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