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package meshtastic
import (
"crypto/rand"
"encoding/binary"
"fmt"
"math"
"math/big"
)
// NodeID holds the node identifier. This is a uint32 value which uniquely identifies a node within a mesh.
type NodeID uint32
const (
// BroadcastNodeID is the special NodeID used when broadcasting a packet to a channel.
BroadcastNodeID NodeID = math.MaxUint32
// ReservedNodeIDThreshold is the threshold at which NodeIDs are considered reserved. Random NodeIDs should not
// be generated below this threshold.
// Source: https://github.com/meshtastic/firmware/blob/d1ea58975755e146457a8345065e4ca357555275/src/mesh/NodeDB.cpp#L461
reservedNodeIDThreshold NodeID = 4
)
// Uint32 returns the underlying uint32 value of the NodeID.
func (n NodeID) Uint32() uint32 {
return uint32(n)
}
// String converts the NodeID to a hex formatted string.
// This is typically how NodeIDs are displayed in Meshtastic UIs.
func (n NodeID) String() string {
return fmt.Sprintf("!%08x", uint32(n))
}
// Bytes converts the NodeID to a byte slice
func (n NodeID) Bytes() []byte {
bytes := make([]byte, 4) // uint32 is 4 bytes
binary.BigEndian.PutUint32(bytes, n.Uint32())
return bytes
}
// DefaultLongName returns the default long node name based on the NodeID.
// Source: https://github.com/meshtastic/firmware/blob/d1ea58975755e146457a8345065e4ca357555275/src/mesh/NodeDB.cpp#L382
func (n NodeID) DefaultLongName() string {
bytes := make([]byte, 4) // uint32 is 4 bytes
binary.BigEndian.PutUint32(bytes, n.Uint32())
return fmt.Sprintf("Meshtastic %04x", bytes[2:])
}
// DefaultShortName returns the default short node name based on the NodeID.
// Last two bytes of the NodeID represented in hex.
// Source: https://github.com/meshtastic/firmware/blob/d1ea58975755e146457a8345065e4ca357555275/src/mesh/NodeDB.cpp#L382
func (n NodeID) DefaultShortName() string {
bytes := make([]byte, 4) // uint32 is 4 bytes
binary.BigEndian.PutUint32(bytes, n.Uint32())
return fmt.Sprintf("%04x", bytes[2:])
}
// RandomNodeID returns a randomised NodeID.
// It's recommended to call this the first time a node is started and persist the result.
//
// Hardware meshtastic nodes first try a NodeID of the last four bytes of the BLE MAC address. If that ID is already in
// use or invalid, a random NodeID is generated.
// Source: https://github.com/meshtastic/firmware/blob/d1ea58975755e146457a8345065e4ca357555275/src/mesh/NodeDB.cpp#L466
func RandomNodeID() (NodeID, error) {
// Generates a random uint32 between reservedNodeIDThreshold and math.MaxUint32
randomInt, err := rand.Int(
rand.Reader,
big.NewInt(
int64(math.MaxUint32-reservedNodeIDThreshold.Uint32()),
),
)
if err != nil {
return NodeID(0), fmt.Errorf("reading entropy: %w", err)
}
r := uint32(randomInt.Uint64()) + reservedNodeIDThreshold.Uint32()
return NodeID(r), nil
}
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