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|
package framestream
import (
"bufio"
"bytes"
"encoding/binary"
"io"
)
const CONTROL_ACCEPT = 0x01
const CONTROL_START = 0x02
const CONTROL_STOP = 0x03
const CONTROL_READY = 0x04
const CONTROL_FINISH = 0x05
const CONTROL_FIELD_CONTENT_TYPE = 0x01
const CONTROL_FRAME_LENGTH_MAX = 512
type ControlFrame struct {
ControlType uint32
ContentTypes [][]byte
}
var ControlStart = ControlFrame{ControlType: CONTROL_START}
var ControlStop = ControlFrame{ControlType: CONTROL_STOP}
var ControlReady = ControlFrame{ControlType: CONTROL_READY}
var ControlAccept = ControlFrame{ControlType: CONTROL_ACCEPT}
var ControlFinish = ControlFrame{ControlType: CONTROL_FINISH}
func (c *ControlFrame) Encode(w io.Writer) (err error) {
var buf bytes.Buffer
err = binary.Write(&buf, binary.BigEndian, c.ControlType)
if err != nil {
return
}
for _, ctype := range c.ContentTypes {
err = binary.Write(&buf, binary.BigEndian, uint32(CONTROL_FIELD_CONTENT_TYPE))
if err != nil {
return
}
err = binary.Write(&buf, binary.BigEndian, uint32(len(ctype)))
if err != nil {
return
}
_, err = buf.Write(ctype)
if err != nil {
return
}
}
err = binary.Write(w, binary.BigEndian, uint32(0))
if err != nil {
return
}
err = binary.Write(w, binary.BigEndian, uint32(buf.Len()))
if err != nil {
return
}
_, err = buf.WriteTo(w)
return
}
func (c *ControlFrame) EncodeFlush(w *bufio.Writer) error {
if err := c.Encode(w); err != nil {
return err
}
return w.Flush()
}
func (c *ControlFrame) Decode(r io.Reader) (err error) {
var cflen uint32
err = binary.Read(r, binary.BigEndian, &cflen)
if err != nil {
return
}
if cflen > CONTROL_FRAME_LENGTH_MAX {
return ErrDecode
}
if cflen < 4 {
return ErrDecode
}
err = binary.Read(r, binary.BigEndian, &c.ControlType)
if err != nil {
return
}
cflen -= 4
if cflen > 0 {
cfields := make([]byte, int(cflen))
_, err = io.ReadFull(r, cfields)
if err != nil {
return
}
for len(cfields) > 8 {
cftype := binary.BigEndian.Uint32(cfields[:4])
cfields = cfields[4:]
if cftype != CONTROL_FIELD_CONTENT_TYPE {
return ErrDecode
}
cflen := int(binary.BigEndian.Uint32(cfields[:4]))
cfields = cfields[4:]
if cflen > len(cfields) {
return ErrDecode
}
c.ContentTypes = append(c.ContentTypes, cfields[:cflen])
cfields = cfields[cflen:]
}
if len(cfields) > 0 {
return ErrDecode
}
}
return
}
func (c *ControlFrame) DecodeEscape(r io.Reader) error {
var zero uint32
err := binary.Read(r, binary.BigEndian, &zero)
if err != nil {
return err
}
if zero != 0 {
return ErrDecode
}
return c.Decode(r)
}
func (c *ControlFrame) DecodeTypeEscape(r io.Reader, ctype uint32) error {
err := c.DecodeEscape(r)
if err != nil {
return err
}
if ctype != c.ControlType {
return ErrDecode
}
return nil
}
// ChooseContentType selects a content type from the ControlFrame which
// also exists in the supplied ctypes. Preference is given to values occurring
// earliest in ctypes.
//
// ChooseContentType returns the chosen content type, which may be nil, and
// a bool value indicating whether a matching type was found.
//
// If either the ControlFrame types or ctypes is empty, ChooseContentType
// returns nil as a matching content type.
func (c *ControlFrame) ChooseContentType(ctypes [][]byte) (typ []byte, found bool) {
if c.ContentTypes == nil || ctypes == nil {
return nil, true
}
tm := make(map[string]bool)
for _, cfctype := range c.ContentTypes {
tm[string(cfctype)] = true
}
for _, ctype := range ctypes {
if tm[string(ctype)] {
return ctype, true
}
}
return nil, false
}
func (c *ControlFrame) MatchContentType(ctype []byte) bool {
for _, cfctype := range c.ContentTypes {
if bytes.Compare(ctype, cfctype) == 0 {
return true
}
}
return len(c.ContentTypes) == 0
}
func (c *ControlFrame) SetContentTypes(ctypes [][]byte) {
c.ContentTypes = ctypes
}
func (c *ControlFrame) SetContentType(ctype []byte) {
if ctype != nil {
c.SetContentTypes([][]byte{ctype})
} else {
c.ContentTypes = nil
}
}
|
