common.go

// https://github.com/dghubble/trie
//The MIT License (MIT)
//
//Copyright (c) 2014 Dalton Hubble
//
//Permission is hereby granted, free of charge, to any person obtaining a copy
//of this software and associated documentation files (the "Software"), to deal
//in the Software without restriction, including without limitation the rights
//to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//copies of the Software, and to permit persons to whom the Software is
//furnished to do so, subject to the following conditions:
//
//The above copyright notice and this permission notice shall be included in
//all copies or substantial portions of the Software.
//
//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//THE SOFTWARE.

package trie

import (
	"strings"
)

// WalkFunc defines some action to take on the given key and Value during
// a Trie Walk. Returning a non-nil error will terminate the Walk.
type WalkFunc func(key string, value interface{}) error

// StringSegmenter takes a string key with a starting index and returns
// the first segment after the start and the ending index. When the end is
// reached, the returned nextIndex should be -1.
// Implementations should NOT allocate heap memory as Trie Segmenters are
// called upon Gets. See PathSegmenter.
type StringSegmenter func(key string, start int) (segment string, nextIndex int)

// PathSegmenter segments string key paths by slash separators. For example,
// "/a/b/c" -> ("/a", 2), ("/b", 4), ("/c", -1) in successive calls. It does
// not allocate any heap memory.
func PathSegmenter(path string, start int) (segment string, next int) {
	if len(path) == 0 || start < 0 || start > len(path)-1 {
		return "", -1
	}
	end := strings.IndexRune(path[start+1:], '/') // next '/' after 0th rune
	if end == -1 {
		return path[start:], -1
	}
	return path[start : start+end+1], start + end + 1
}