comparator.go

// Copyright 2015 mint.zhao.chiu@gmail.com
//
// 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 container

import (
	"reflect"
)

// compareFunc的结果值：
//   小于0: 第一个参数小于第二个参数
//   等于0: 第一个参数等于第二个参数
//   大于1: 第一个参数大于第二个参数
type CompareFunction func(interface{}, interface{}) int8

func ValidElements(elements ...interface{}) bool {
	for _, e := range elements {
		if !reflect.ValueOf(e).IsValid() {
			return false
		}
	}
	return true
}

func Float64CompareFunctionASC(e1, e2 interface{}) int8 {
	if !ValidElements(e1, e2) {
		return 0
	}

	k1 := e1.(float64)
	k2 := e2.(float64)

	if k1 < k2 {
		return -1
	} else if k1 > k2 {
		return 1
	} else {
		return 0
	}
}

func Float64CompareFunctionDESC(e1, e2 interface{}) int8 {
	return -Float64CompareFunctionASC(e1, e2)
}

func Uint64CompareFunctionASC(e1, e2 interface{}) int8 {
	if !ValidElements(e1, e2) {
		return 0
	}

	k1 := e1.(uint64)
	k2 := e2.(uint64)

	return Float64CompareFunctionASC(float64(k1), float64(k2))
}

func Uint64CompareFunctionDESC(e1, e2 interface{}) int8 {
	return -Uint64CompareFunctionASC(e1, e2)
}

func Int64CompareFunctionASC(e1, e2 interface{}) int8 {
	if !ValidElements(e1, e2) {
		return 0
	}

	k1 := e1.(int64)
	k2 := e2.(int64)

	return Float64CompareFunctionASC(float64(k1), float64(k2))
}

func Int64CompareFunctionDESC(e1, e2 interface{}) int8 {
	return -Int64CompareFunctionASC(e1, e2)
}

func IntCompareFunctionASC(e1, e2 interface{}) int8 {
	if !ValidElements(e1, e2) {
		return 0
	}

	k1 := e1.(int)
	k2 := e2.(int)

	return Float64CompareFunctionASC(float64(k1), float64(k2))
}

func IntCompareFunctionDESC(e1, e2 interface{}) int8 {
	return -IntCompareFunctionASC(e1, e2)
}

func StringCompareFunction(e1, e2 interface{}) int8 {
	if !ValidElements(e1, e2) {
		return 0
	}

	s1 := e1.(string)
	s2 := e2.(string)
	min := len(s2)
	if len(s1) < len(s2) {
		min = len(s1)
	}
	diff := 0
	for i := 0; i < min && diff == 0; i++ {
		diff = int(s1[i]) - int(s2[i])
	}
	if diff == 0 {
		diff = len(s1) - len(s2)
	}
	if diff < 0 {
		return -1
	}
	if diff > 0 {
		return 1
	}
	return 0
}