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178 lines
3.0 KiB
Go
178 lines
3.0 KiB
Go
8 years ago
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package iohelper
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import (
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"bytes"
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"encoding/binary"
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"io"
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"github.com/juju/errors"
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)
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var (
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cachedItob [][]byte
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)
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func init() {
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cachedItob = make([][]byte, 1024)
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for i := 0; i < len(cachedItob); i++ {
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var b bytes.Buffer
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writeVLong(&b, int64(i))
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cachedItob[i] = b.Bytes()
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}
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}
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func itob(i int) ([]byte, error) {
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if i >= 0 && i < len(cachedItob) {
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return cachedItob[i], nil
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}
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var b bytes.Buffer
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err := binary.Write(&b, binary.BigEndian, i)
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if err != nil {
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return nil, errors.Trace(err)
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}
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return b.Bytes(), nil
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}
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func decodeVIntSize(value byte) int32 {
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if int32(value) >= -112 {
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return int32(1)
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}
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if int32(value) < -120 {
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return -119 - int32(value)
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}
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return -111 - int32(value)
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}
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func isNegativeVInt(value byte) bool {
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return int32(value) < -120 || int32(value) >= -112 && int32(value) < 0
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}
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func readVLong(r io.Reader) (int64, error) {
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var firstByte byte
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err := binary.Read(r, binary.BigEndian, &firstByte)
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if err != nil {
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return 0, errors.Trace(err)
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}
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l := decodeVIntSize(firstByte)
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if l == 1 {
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return int64(firstByte), nil
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}
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var (
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i int64
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idx int32
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)
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for idx = 0; idx < l-1; idx++ {
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var b byte
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err = binary.Read(r, binary.BigEndian, &b)
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if err != nil {
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return 0, errors.Trace(err)
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}
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i <<= 8
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i |= int64(b & 255)
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}
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if isNegativeVInt(firstByte) {
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return ^i, nil
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}
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return i, nil
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}
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func writeVLong(w io.Writer, i int64) error {
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var err error
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if i >= -112 && i <= 127 {
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err = binary.Write(w, binary.BigEndian, byte(i))
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if err != nil {
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return errors.Trace(err)
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}
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} else {
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var l int32 = -112
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if i < 0 {
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i = ^i
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l = -120
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}
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var tmp int64
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for tmp = i; tmp != 0; l-- {
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tmp >>= 8
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}
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err = binary.Write(w, binary.BigEndian, byte(l))
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if err != nil {
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return errors.Trace(err)
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}
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if l < -120 {
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l = -(l + 120)
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} else {
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l = -(l + 112)
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}
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for idx := l; idx != 0; idx-- {
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var mask int64
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shiftbits := uint((idx - 1) * 8)
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mask = int64(255) << shiftbits
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err = binary.Write(w, binary.BigEndian, byte((i&mask)>>shiftbits))
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if err != nil {
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return errors.Trace(err)
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}
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}
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}
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return nil
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}
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func ReadVarBytes(r ByteMultiReader) ([]byte, error) {
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sz, err := readVLong(r)
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if err != nil {
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return nil, errors.Trace(err)
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}
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b := make([]byte, sz)
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_, err = r.Read(b)
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if err != nil {
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return nil, errors.Trace(err)
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}
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return b, nil
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}
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func WriteVarBytes(w io.Writer, b []byte) error {
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lenb, err := itob(len(b))
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if err != nil {
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return errors.Trace(err)
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}
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_, err = w.Write(lenb)
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if err != nil {
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return errors.Trace(err)
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}
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_, err = w.Write(b)
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return errors.Trace(err)
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}
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func ReadInt32(r io.Reader) (int32, error) {
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var n int32
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err := binary.Read(r, binary.BigEndian, &n)
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return n, errors.Trace(err)
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}
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func ReadN(r io.Reader, n int32) ([]byte, error) {
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b := make([]byte, n)
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_, err := io.ReadFull(r, b)
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return b, errors.Trace(err)
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}
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func ReadUint64(r io.Reader) (uint64, error) {
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var n uint64
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err := binary.Read(r, binary.BigEndian, &n)
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return n, errors.Trace(err)
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}
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