Skip to main content
Version: v0.0.3

Interface: FrameReaderOptions

Options for FrameReader.

All tolerance opts default to false, every framing deviation throws unless explicitly enabled. Server-level defaults (allowFsOnly, allowLfAfterFs, allowLeadingWhitespace) are applied by the server when constructing readers.

Example​

const opts: FrameReaderOptions = {
  onFrame: (payload, byteOffset, warnings) => process(payload, byteOffset, warnings),
  onWarning: (w) => logger.warn(w),
  maxFrameSizeBytes: 4 * 1024 * 1024, // 4 MiB limit
  allowFsOnly: true,
  allowLfAfterFs: true,
};

Properties​

allowFsOnly?​

optional allowFsOnly?: boolean

Tolerate FS without trailing CR; emits MLLP_FS_WITHOUT_CR.

allowLeadingWhitespace?​

optional allowLeadingWhitespace?: boolean

Tolerate SP/TAB/LF/CR before VT; emits MLLP_LEADING_WHITESPACE.

allowLfAfterFs?​

optional allowLfAfterFs?: boolean

Tolerate FS+LF instead of FS+CR; emits MLLP_LF_AFTER_FS.

allowMissingLeadingVt?​

optional allowMissingLeadingVt?: boolean

Tolerate missing leading VT; emits MLLP_MISSING_LEADING_VT.

maxFrameSizeBytes?​

optional maxFrameSizeBytes?: number

Maximum accumulated payload bytes before MllpFramingError('MLLP_FRAME_TOO_LARGE'). Default: 16 MiB (DoS prevention).

onFrame​

onFrame: (payload, byteOffset, warnings) => void

Called synchronously during push() for each complete MLLP payload.

Parameters​

payload​

Buffer

Raw MLLP payload bytes (framing stripped).

byteOffset​

number

Stream byte offset of the VT byte that opened this frame. Monotonic across the connection lifetime; reset to 0 by reset().

warnings​

readonly MllpWarning[]

Framing warnings emitted during decoding of this specific frame. Empty array when no tolerance deviations were detected.

Returns​

void

onWarning?​

optional onWarning?: (w) => void

Called for each tolerated framing deviation. Wrapped in try/catch. A throwing handler will not corrupt FSM state.

Parameters​

w​

MllpWarning

Returns​

void

strict?​

optional strict?: boolean

When true, escalates the following tolerances to thrown MllpFramingError even if individual opt-ins (allowFsOnly, allowLfAfterFs, allowMissingLeadingVt, allowLeadingWhitespace) are enabled:

  • MLLP_MISSING_LEADING_VT
  • MLLP_FS_WITHOUT_CR
  • MLLP_LF_AFTER_FS
  • MLLP_LEADING_WHITESPACE (leading whitespace escalates as MLLP_MISSING_LEADING_VT)

MLLP_EMPTY_PAYLOAD and MLLP_TRAILING_BYTES remain warnings even in strict mode.

Example​

// Hardened enforcement, no tolerance, all violations throw
const reader = new FrameReader({ onFrame: fn, strict: true });