Struct ExtendedHeader 

pub struct ExtendedHeader {
    pub extended_header_size: u16,
    pub metadata_header_size: u16,
    pub metadata_size: u32,
    pub message_id: u32,
    pub additional_fields: Vec<u8>,
}

OpenIGTLink Version 3 Extended Header structure

The Extended Header is a fixed 12-byte structure (minimum) that appears immediately after the standard 58-byte header when version >= 3.

Structure (12 bytes minimum)

• extended_header_size (2 bytes) - Total size including this field and any additional fields
• metadata_header_size (2 bytes) - Number of metadata key-value pairs
• metadata_size (4 bytes) - Total metadata size in bytes
• message_id (4 bytes) - Unique message identifier
• additional_fields (variable) - Optional implementation-specific data

C++ Compatibility

This structure matches the igtlMessageHeader.h ExtendedHeader format from the OpenIGTLink C++ reference implementation.

Fields

extended_header_size: u16

Total size of extended header in bytes (including this field) Minimum value: 12 (for standard Extended Header) Larger values indicate additional implementation-specific fields

metadata_header_size: u16

Number of metadata key-value pairs that follow the message content This is a count, not a size in bytes

metadata_size: u32

Total size of metadata section in bytes (not including this Extended Header) The metadata section appears at the end of the message body

message_id: u32

Unique message identifier for this message Can be used for:

• Request/response correlation
• Message tracking and debugging
• Transfer checkpointing and resumption

additional_fields: Vec<u8>

Additional implementation-specific fields (if extended_header_size > 12) These are optional and can contain custom protocol extensions

Implementations

impl ExtendedHeader

pub const MIN_SIZE: usize = 12usize

Minimum Extended Header size (standard fields only)

pub fn new() -> Self

Create a new Extended Header with default values

Returns

Extended Header with:

• extended_header_size = 12 (minimum)
• metadata_header_size = 0
• metadata_size = 0
• message_id = 0
• no additional fields

pub fn with_metadata(metadata_count: u16, metadata_size: u32) -> Self

Create an Extended Header with metadata information

Arguments

• metadata_count - Number of metadata key-value pairs
• metadata_size - Total metadata size in bytes

Returns

Extended Header configured for metadata

pub fn with_message_id(message_id: u32) -> Self

Create an Extended Header with a message ID

Arguments

• message_id - Unique message identifier

Returns

Extended Header with the specified message ID

pub fn set_additional_fields(&mut self, data: Vec<u8>)

Add additional implementation-specific fields

Arguments

• data - Additional field data

Notes

This automatically updates extended_header_size to include the additional data

pub fn encode(&self) -> Vec<u8>

Encode the Extended Header to bytes

Returns

Byte vector containing the encoded Extended Header

pub fn decode(data: &[u8]) -> Result<Self>

Decode an Extended Header from bytes

Arguments

• data - Byte slice containing at least 12 bytes

Returns

Decoded Extended Header or error

Errors

Returns error if data is less than 12 bytes or if extended_header_size is less than 12 or larger than available data

pub fn size(&self) -> usize

Get the total size of this Extended Header

pub fn has_metadata(&self) -> bool

Check if this Extended Header indicates metadata is present

pub fn get_metadata_size(&self) -> usize

Get the metadata size in bytes (size of metadata data)

pub fn get_metadata_header_size(&self) -> usize

Get the metadata header size in bytes (size of metadata structure definitions)

pub fn get_metadata_count(&self) -> usize

👎Deprecated: Use get_metadata_header_size() instead - metadata_header_size is size in bytes, not count

Get the number of metadata entries (deprecated - metadata_header_size is not entry count)

pub fn get_message_id(&self) -> u32

Get the message ID

Trait Implementations

impl Clone for ExtendedHeader

fn clone(&self) -> ExtendedHeader

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ExtendedHeader

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ExtendedHeader

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for ExtendedHeader

fn eq(&self, other: &ExtendedHeader) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for ExtendedHeader

impl StructuralPartialEq for ExtendedHeader