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unit_parser.go
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/
unit_parser.go
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/*
* Copyright 2017 Google Inc.
*
* 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 nozzle
import (
"fmt"
"regexp"
)
const (
prefixRegex = "k|M|G|T|P|E|Z|Y|m|μ|n|p|f|a|z|y|Ki|Mi|Gi|Ti"
unitRegex = "b|B|s|M|h|d"
)
/*
Expression = Component { "." Component } { "/" Component } ;
Component = [ PREFIX ] UNIT [ Annotation ]
| Annotation
| "1"
;
Annotation = "{" NAME "}" ;
*/
type UnitParser interface {
Parse(string) string
}
func NewUnitParser() UnitParser {
componentRegex := regexp.MustCompile(fmt.Sprintf("^(%s)?(%s)$", prefixRegex, unitRegex))
annotationRegex := regexp.MustCompile("[{}]")
expressionRegex := regexp.MustCompile("^([^/]*)(/([^/]*))?$")
return &unitParser{
componentRegex: componentRegex,
annotationRegex: annotationRegex,
expressionRegex: expressionRegex,
}
}
type unitParser struct {
componentRegex *regexp.Regexp
annotationRegex *regexp.Regexp
expressionRegex *regexp.Regexp
}
func (up *unitParser) Parse(input string) string {
matches := up.expressionRegex.FindStringSubmatch(input)
if matches == nil {
return up.annotate(input)
}
numerator := up.parseComponent(matches[1])
if matches[2] == "" {
return numerator
}
denominator := up.parseComponent(matches[3])
return fmt.Sprintf("%s/%s", numerator, denominator)
}
func (up *unitParser) parseComponent(input string) string {
matches := up.componentRegex.FindStringSubmatch(input)
if matches == nil {
return up.annotate(input)
}
prefix := prefixLookup(matches[1])
unit := unitLookup(matches[2])
return fmt.Sprintf("%s%s", prefix, unit)
}
// Not sure if this is faster than a map or not - if we
// are looking for perf gains, maybe do some benchmarking
// around here.
func unitLookup(unit string) string {
switch unit {
case "b":
return "bit"
case "B":
return "By"
case "M":
return "min"
default:
return unit
}
}
func prefixLookup(prefix string) string {
if prefix == "μ" {
return "u"
}
return prefix
}
func (up *unitParser) annotate(input string) string {
return fmt.Sprintf("{%s}", up.annotationRegex.ReplaceAllString(input, ""))
}