// Copyright 2015 PingCAP, 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 hack

import (
	"unsafe"
)

// MutableString can be used as string via string(MutableString) without performance loss.
type MutableString string

// String converts slice to MutableString without copy.
// The MutableString can be converts to string without copy.
// Use it at your own risk.
func String(b []byte) MutableString {
	if len(b) == 0 {
		return ""
	}
	return MutableString(unsafe.String(unsafe.SliceData(b), len(b)))
}

// Slice converts string to slice without copy.
// Use at your own risk.
func Slice(s string) []byte {
	return unsafe.Slice(unsafe.StringData(s), len(s))
}

func init() {
	checkMapABI()
}

// GetBytesFromPtr return a bytes array from the given ptr and length
func GetBytesFromPtr(ptr unsafe.Pointer, length int) []byte {
	return unsafe.Slice((*byte)(ptr), length)
}

// Memory usage constants for swiss map
const (
	DefBucketMemoryUsageForMapStringToAny = 312
	DefBucketMemoryUsageForSetString      = 248
	DefBucketMemoryUsageForSetFloat64     = 184
	DefBucketMemoryUsageForSetInt64       = 184
)