Byte Slicer

Category: Utility · Node Type ID: utility-slicer

Extracts bytes like the script slice b[offset, length]: empty length = to the end, negative = end position counted from the back (excluded)

Overview

Extracts a contiguous sub-array from the input byte array using the exact same two-argument semantics as the built-in Script byte slice b[offset, length].

Offset specifies the starting byte index (0-based; negative values count backward from the end of the buffer, e.g., -16 starts 16 bytes from the end). Length has three modes depending on its value: if left blank (empty), it slices all the way to the end of the buffer; if ≥ 0, it extracts at most that many bytes; if negative (< 0), it specifies the exclusive end position counted backward from the end of the buffer (for example, Offset = 0, Length = -16 extracts everything except the final 16-byte authentication tag). Both values can be overridden dynamically via the optional Offset and Length input ports.

When to Use

Splitting a combined wire payload (such as Nonce || Ciphertext || Tag) into separate fields for decryption.
Truncating a hash or KDF output to a shorter key or IV length (e.g., taking the first 16 bytes or last 12 bytes).

Parameter Configuration

Parameter (ID)	Type & Default	Visibility Condition	Description & Options
Offset (Start) `offset`	`number` Default: `0` Supports Variable Reference (`$var`: `int`)	Always visible	Starting byte index (`0`-based; negative values count from the end of the input buffer). Overridden at runtime if the `Offset` input port is connected.
Length `length`	`text` Default: `""` (empty) Supports Variable Reference (`$var`: `string`)	Always visible	When blank: slices to the end of the buffer. When `≥ 0`: number of bytes to extract. When `< 0`: exclusive end index counted from the end of the buffer (e.g., `-16` stops 16 bytes before the end). Overridden at runtime if the `Length` input port is connected.

Port I/O Specification

See Ports & Connections for general wiring rules, data type colors, and dynamic port creation.

Input Ports

Port Nature: Fixed Input Ports (1 total).

Port Name	Port ID	Data Type	Required	Visibility Condition	Description
`Data`	`data`	`Bytes`	Required	Always visible	Source byte array (`Uint8Array`) to slice.

Output Ports

Port Nature: Fixed Output Ports (1 total).

Port Name	Port ID	Data Type	Visibility Condition	Description
`Sliced Bytes`	`sliced`	`Bytes`	Always visible	Extracted sub-array (`Uint8Array`). Out-of-bounds ranges are safely clamped without throwing an error.

Error Cases

When any of the following conditions occurs at runtime, this node transitions to an ERROR state and downstream nodes connected to its outputs do not execute.

Error Code	Default Engine Message	Trigger Condition
`BYTES_OUT_OF_RANGE`	Index or range is outside the value	Raised when a byte or bit index/slice range falls outside the valid bounds of the buffer.
`BYTES_INVALID_ARGUMENT`	Invalid argument value	Raised when an argument (such as bit shift count, byte length, or negative integer) is invalid or negative.

Examples

Splitting a Combined (Ciphertext || 16B GCM Tag) Payload

Use two Byte Slicer nodes to separate the ciphertext body from the trailing 16-byte authentication tag.

On the first Byte Slicer (Ciphertext), set Offset to 0 and Length to -16 (extracts from byte 0 up to 16 bytes before the end).
On the second Byte Slicer (Tag), set Offset to -16 and leave Length blank (extracts the last 16 bytes to the end).