update xbee

internal/xbee/api_frame.go

@@ -8,8 +8,10 @@ package xbee
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
+	"sync"
 )
 
 // the frames have an outer shell - we will make a function that takes
@@ -25,6 +27,10 @@ type Frameable interface {
 	Bytes() ([]byte, error)
 }
 
+// we also need a way of tracking frame IDs - this is a uint8
+// it uses a sync.Map
+
+
 // now we can describe our function that takes a framable and contains it + calculates checksums.
 func calculateChecksum(data []byte) byte {
 	var sum byte
@@ -84,104 +90,6 @@ const (
 
 // AT commands are hard, so let's write out all the major ones here
 
-type ATCmdFrame struct {
-	Id     byte
-	Cmd    string
-	Param  []byte
-	Queued bool
-}
-
-// implement the frame stuff for us.
-func (atFrame *ATCmdFrame) Bytes() ([]byte, error) {
-	buf := new(bytes.Buffer)
-
-	if atFrame.Queued {
-		// queued (batched) at comamnds have different Frame type
-		buf.WriteByte(byte(ATCmdQueue))
-
-	} else {
-		// normal frame type
-		buf.WriteByte(byte(ATCmd))
-
-	}
-
-	buf.WriteByte(atFrame.Id)
-
-	// write cmd, if it's the right length.
-	if cmdLen := len(atFrame.Cmd); cmdLen != 2 {
-		return nil, fmt.Errorf("AT command incorrect length: %d", cmdLen)
-	}
-	buf.Write([]byte(atFrame.Cmd))
-
-	// write param.
-	buf.Write(atFrame.Param)
-	return buf.Bytes(), nil
-}
-
-// transmissions to this address are instead broadcast
-const BroadcastAddr = 0xFFFF
-
-type TxFrame struct {
-	Id          byte
-	Destination uint64
-	BCastRadius uint8
-	Options     uint8
-	Payload     []byte
-}
-
-func (txFrame *TxFrame) Bytes() ([]byte, error) {
-	buf := new(bytes.Buffer)
-
-	buf.WriteByte(byte(TxReq))
-
-	buf.WriteByte(txFrame.Id)
-
-	a := make([]byte, 8)
-	binary.LittleEndian.PutUint64(a, txFrame.Destination)
-	buf.Write(a)
-
-	// write the reserved part.
-	buf.Write([]byte{0xFF, 0xFE})
-
-	// write the radius
-	buf.WriteByte(txFrame.BCastRadius)
-
-	buf.WriteByte(txFrame.Options)
-
-	buf.Write(txFrame.Payload)
-
-	return buf.Bytes(), nil
-}
-
-type RemoteATCmdReq struct {
-	ATCmdFrame
-	Destination uint64
-	Options     uint8
-}
-
-func (remoteAT *RemoteATCmdReq) Bytes() ([]byte, error) {
-	buf := new(bytes.Buffer)
-	buf.WriteByte(byte(RemoteCmdReq))
-
-	buf.WriteByte(remoteAT.Id)
-
-	a := make([]byte, 8)
-	binary.LittleEndian.PutUint64(a, remoteAT.Destination)
-	buf.Write(a)
-
-	// write the reserved part.
-	buf.Write([]byte{0xFF, 0xFE})
-	// write options
-	buf.WriteByte(remoteAT.Options)
-
-	// now, write the AT command and the data.
-	buf.Write([]byte(remoteAT.Cmd))
-
-	buf.Write(remoteAT.Param)
-
-	return buf.Bytes(), nil
-
-}
 
 // Now we will implement receiving packets from a character stream.
 // we first need to make a thing that produces frames from a stream using a scanner.

internal/xbee/at.go

@@ -1,3 +1,73 @@
 package xbee
 
+import (
+	"bytes"
+	"fmt"
+	"encoding/binary"
+)
+
 // this file contains some AT command constants and
+type ATCmdFrame struct {
+	Id     byte
+	Cmd    string
+	Param  []byte
+	Queued bool
+}
+
+// implement the frame stuff for us.
+func (atFrame *ATCmdFrame) Bytes() ([]byte, error) {
+	buf := new(bytes.Buffer)
+
+	if atFrame.Queued {
+		// queued (batched) at comamnds have different Frame type
+		buf.WriteByte(byte(ATCmdQueue))
+
+	} else {
+		// normal frame type
+		buf.WriteByte(byte(ATCmd))
+
+	}
+
+	buf.WriteByte(atFrame.Id)
+
+	// write cmd, if it's the right length.
+	if cmdLen := len(atFrame.Cmd); cmdLen != 2 {
+		return nil, fmt.Errorf("AT command incorrect length: %d", cmdLen)
+	}
+	buf.Write([]byte(atFrame.Cmd))
+
+	// write param.
+	buf.Write(atFrame.Param)
+	return buf.Bytes(), nil
+}
+
+
+type RemoteATCmdReq struct {
+	ATCmdFrame
+	Destination uint64
+	Options     uint8
+}
+
+func (remoteAT *RemoteATCmdReq) Bytes() ([]byte, error) {
+	buf := new(bytes.Buffer)
+	buf.WriteByte(byte(RemoteCmdReq))
+
+	buf.WriteByte(remoteAT.Id)
+
+	a := make([]byte, 8)
+	binary.LittleEndian.PutUint64(a, remoteAT.Destination)
+	buf.Write(a)
+
+	// write the reserved part.
+	buf.Write([]byte{0xFF, 0xFE})
+	// write options
+	buf.WriteByte(remoteAT.Options)
+
+	// now, write the AT command and the data.
+	buf.Write([]byte(remoteAT.Cmd))
+
+	buf.Write(remoteAT.Param)
+
+	return buf.Bytes(), nil
+
+}

internal/xbee/conntrack.go

@@ -0,0 +1,54 @@
+package xbee
+import (
+	"sync"
+	"errors"
+)
+
+// A connTrack is a simple frame mark utility for xbee packets. The xbee api frame
+// takes a mark that is used when sending the response - this allows to coordinate
+// the sent packet and the response, since there may be other packets emitted
+// between them.
+type connTrack struct {
+	mu sync.RWMutex // use RW mutex to allow for multiple readers
+	internal map[uint8]bool // map frame tag to if it's been used.
+	// the map is set when writing a frame, and deleted when recieving a matching frame.
+}
+
+// GetMark finds the next available marker and takes it, returning the value of
+// the mark. If no mark can be acquired, it returns an error.
+func (ct *connTrack) GetMark() (uint8, error) {
+	// get a read lock.
+	ct.mu.RLock()
+
+	// NOTE: we start at one. This is because 0 will not return a frame ever - it's 
+	// the "silent mode" mark
+	for i := 1; i < 256; i++ {
+		if !ct.internal[uint8(i)] {
+			// it's free.
+			// discard our read lock and lock for write.
+			ct.mu.RUnlock()
+
+			ct.mu.Lock()
+			// update the value to true.
+			ct.internal[uint8(i)] = true
+			ct.mu.Unlock()
+			return uint8(i), nil
+		}
+	}
+	ct.mu.RUnlock()
+	return 0, errors.New("no available marks")
+}
+// ClearMark removes a given mark from the set if it exists, or returns an error.
+func (ct *connTrack) ClearMark(mark uint8) error {
+	ct.mu.RLock()
+	// FIXME: should this be the other way around (swap if and normal execution
+	if ct.internal[mark] {
+		ct.mu.RUnlock()
+		ct.mu.Lock()
+		delete(ct.internal, mark)
+		ct.mu.Unlock()
+		return nil
+	}
+	ct.mu.RUnlock()
+	return errors.New("mark was not set")
+}

internal/xbee/txframe.go

@@ -0,0 +1,40 @@
+package xbee
+
+import (
+	"bytes"
+	"encoding/binary"
+)
+// transmissions to this address are instead broadcast
+const BroadcastAddr = 0xFFFF
+
+type TxFrame struct {
+	Id          byte
+	Destination uint64
+	BCastRadius uint8
+	Options     uint8
+	Payload     []byte
+}
+
+func (txFrame *TxFrame) Bytes() ([]byte, error) {
+	buf := new(bytes.Buffer)
+
+	buf.WriteByte(byte(TxReq))
+
+	buf.WriteByte(txFrame.Id)
+
+	a := make([]byte, 8)
+	binary.LittleEndian.PutUint64(a, txFrame.Destination)
+	buf.Write(a)
+
+	// write the reserved part.
+	buf.Write([]byte{0xFF, 0xFE})
+
+	// write the radius
+	buf.WriteByte(txFrame.BCastRadius)
+
+	buf.WriteByte(txFrame.Options)
+
+	buf.Write(txFrame.Payload)
+
+	return buf.Bytes(), nil
+}