Byte Frame Trailer Position
Locate the half-open trailer span from a complete frame byte count and explicit trailer width; does not identify a checksum format.
Description
Locate the half-open trailer span from a complete frame byte count and explicit trailer width; does not identify a checksum format.
A fixed-size trailer occupies the final portion of a declared frame. Half-open offsets make an empty trailer unambiguous.
When to use this tool
Locate the half-open trailer span from a complete frame byte count and explicit trailer width; does not identify a checksum format.
- Prepare the supplied frameBytes, trailerBytes fields for this operation.
- Compare the complete example with the representation used by your own input before carrying the result into another step.
How to use the tool and how it works
- Enter frameBytes, trailerBytes. Use the exact text syntax, units and index conventions explained below.
- Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
- Read result.start, result.end. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Require frameBytes from 0 to 128 and trailerBytes from zero through frameBytes. Return start = frameBytes minus trailerBytes and end = frameBytes.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| frameBytes | frame bytes. | Integer from 0 to 128 inclusive |
| trailerBytes | trailer bytes. | Integer from 0 to frameBytes inclusive |
| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.start | The start value under the stated formula or text convention. |
| result.end | The end value under the stated formula or text convention. |
{
"input": {
"frameBytes": 10,
"trailerBytes": 3
},
"output": {
"result": {
"start": 7,
"end": 10
}
}
}Limitations and assumptions
- No actual frame bytes or trailer contents are inspected. The lengths must already reflect the intended protocol.
- All declared input fields are required and unexpected top-level fields are rejected. Numbers must be finite; lists are limited to 128 entries and ordinary text fields to 8,192 UTF-16 code units, with tighter limits where stated.
- JSON text inputs must parse within bounded nesting and size limits. Numeric outputs outside the safe finite range are rejected; large exact integer results use decimal strings. Indexes and half-open spans are zero-based unless a rank is explicitly described as one-based.
Alternative or Complementary methods
Use a stateful protocol parser when processing partial streams or validating complete packets. Retain the declared prefix width, byte order and payload-versus-frame boundary convention when composing these operations.
References
Similar or alternative tools
- Byte Frame Chunk Carry Tool
Advance one fixed-byte streaming frame chunk with explicit incomplete carry, emitting complete frames and retaining the new tail; no sync search.
- Byte Frame Chunk Rejoin Tool
Rejoin explicit bounded byte chunks and report each chunk’s half-open source span, preserving empty-chunk provenance.