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utils.go
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/
utils.go
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package gopark
import (
"bufio"
"bytes"
"encoding/binary"
"encoding/gob"
"fmt"
"hash/fnv"
"log"
"os"
"strconv"
"sync/atomic"
)
func Range(start, end int) []interface{} {
if start > end {
log.Panicf("Range start cannot be larger than end, [%d, %d)", start, end)
}
r := make([]interface{}, end-start)
for i := start; i < end; i++ {
r[i-start] = i
}
return r
}
type AtomicInt int64
func (i *AtomicInt) Add(n int64) {
atomic.AddInt64((*int64)(i), n)
}
func (i *AtomicInt) Get() int64 {
return atomic.LoadInt64((*int64)(i))
}
func (i *AtomicInt) String() string {
return strconv.FormatInt(i.Get(), 10)
}
func MaxInt64(a, b int64) int64 {
if a > b {
return a
}
return b
}
func MinInt64(a, b int64) int64 {
if a > b {
return b
}
return a
}
func readLine(r *bufio.Reader) (string, error) {
var (
isPrefix bool = true
err error = nil
line, ln []byte
)
for isPrefix && err == nil {
line, isPrefix, err = r.ReadLine()
ln = append(ln, line...)
}
return string(ln), err
}
var _ = fmt.Println
func seekToNewLine(f *os.File, start int64) (int64, error) {
_, err := f.Seek(start, 0)
if err != nil {
return start, err
}
b := make([]byte, 1)
_, err = f.Read(b)
start++
if err != nil {
return start, err
}
for b[0] != '\n' {
_, err := f.Read(b)
if err != nil {
return start, err
}
start++
}
return start, nil
}
func hashCode(value interface{}) (hashCode int64) {
if value == nil {
hashCode = 0
return
}
hash := fnv.New32()
buffer := new(bytes.Buffer)
encoder := gob.NewEncoder(buffer)
encoder.Encode(value)
hash.Write(buffer.Bytes())
hashCode = 0
hashBytes := hash.Sum(nil)
for _, hashByte := range hashBytes {
hashCode = hashCode*256 + int64(hashByte)
}
return
}
func HashCode(value interface{}) int64 {
return hashCode(value)
}
// Encode related funcs
const ENCODE_BUFFER_SIZE = 10000
type EncodeBox struct {
Object interface{}
}
func init() {
gob.Register(new(EncodeBox))
gob.Register(make([]interface{}, 0))
}
type BufferEncoder struct {
size int
buffer []interface{}
watermark int
}
func NewBufferEncoder(size int) *BufferEncoder {
encoder := &BufferEncoder{}
encoder.size = size
encoder.buffer = make([]interface{}, size)
return encoder
}
func (e *BufferEncoder) Encode(f *os.File, value interface{}) error {
if len(e.buffer) == e.watermark {
err := encodeObjectIntoFile(f, e.buffer)
if err != nil {
return err
}
e.watermark = 0
}
e.buffer[e.watermark] = value
e.watermark++
return nil
}
func (e *BufferEncoder) Flush(f *os.File) error {
if e.watermark > 0 {
err := encodeObjectIntoFile(f, e.buffer[:e.watermark])
if err != nil {
return err
}
e.watermark = 0
}
return nil
}
func (e *BufferEncoder) Decode(f *os.File) ([]interface{}, error) {
buffer, err := decodeObjectFromFile(f)
if err != nil {
return nil, err
}
return buffer.([]interface{}), nil
}
func encodeObjectIntoFile(f *os.File, value interface{}) error {
box := EncodeBox{value}
objBuffer := new(bytes.Buffer)
err := gob.NewEncoder(objBuffer).Encode(box)
if err != nil {
return err
}
size := int32(len(objBuffer.Bytes()))
sizeBuffer := new(bytes.Buffer)
err = binary.Write(sizeBuffer, binary.LittleEndian, size)
if err != nil {
return err
}
f.Write(sizeBuffer.Bytes())
f.Write(objBuffer.Bytes())
return err
}
func decodeObjectFromFile(f *os.File) (interface{}, error) {
var (
size int32
box EncodeBox
)
err := binary.Read(f, binary.LittleEndian, &size)
if err != nil {
return nil, err
}
boxBytes := make([]byte, size)
_, err = f.Read(boxBytes)
if err != nil {
return nil, err
}
buffer := bytes.NewBuffer(boxBytes)
decoder := gob.NewDecoder(buffer)
if err = decoder.Decode(&box); err == nil {
return box.Object, nil
}
return nil, err
}