Bitfield Gap Inventory
Inventory unoccupied bit positions and positive-width field overlaps in a bounded register; half-open spans.
Description
Inventory unoccupied bit positions and positive-width field overlaps in a bounded register; half-open spans.
A bitfield layout can contain both uncovered positions and overlapping declared fields. Both conditions matter independently.
When to use this tool
Inventory unoccupied bit positions and positive-width field overlaps in a bounded register; half-open spans.
- Prepare the supplied width, fieldsJson 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 width, fieldsJson. 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.unusedBits, result.overlapPairs. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Require width 0 to 128 and ordered integer spans inside it. Build occupied positions from each half-open span, return unusedBits and all positive-overlap span-index pairs.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| width | width. | Integer from 0 to 128 inclusive |
| fieldsJson | JSON text, entered as one text field. The decoded structure is illustrated below; it is not a separate file. | Text |
For the JSON text fields, the following decoded structures show the example records before they are serialized into input strings. Keep field names, list nesting and value types as shown.
[
{
"field": "fieldsJson",
"decoded": [
[
0,
2
],
[
3,
4
]
]
}
]| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.unusedBits | The unused bits list in the ordering and representation described above. |
| result.overlapPairs | The overlap pairs list in the ordering and representation described above. |
{
"input": {
"width": 5,
"fieldsJson": "[[0,2],[3,4]]"
},
"output": {
"result": {
"unusedBits": [
2,
4
],
"overlapPairs": []
}
}
}Limitations and assumptions
- No storage endian order or semantic field names are inferred. Empty fields occupy no bits and touching endpoints do not overlap.
- Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
- Lists are limited to 128 entries. JSON text must meet bounded size and depth checks, and numeric outputs beyond the safe finite magnitude are rejected. Exact large integers use decimal strings.
- Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.
Alternative or Complementary methods
Retain the field-width, bit-index and byte-order conventions when combining operations. Slicing, escaping, permutation and alignment are separate transforms; none supplies a complete framing or cryptographic protocol.
References
Similar or alternative tools
- Bitfield Mask Integer String
Build an exact arbitrary-width bitfield mask as a decimal integer string; zero width has a zero mask.
- Bitfield Overlap Mask
Intersect exact nonnegative integer bit masks and retain the overlapping mask as decimal text.