Description
Return a shifted contiguous field mask.
Bit positions are usually counted from the least-significant bit, while a displayed binary string has its own left-to-right indexing convention. Masks, fields and parity predicates describe a selected region or pattern; local agreement does not validate a complete encoded record.
Return a shifted contiguous field mask.
When to use this tool
Use Bitwise: Field Mask From Low Bit Width when checking the stated mask, field, parity or bit-index convention.
How to use the tool and how it works
- Enter lowBit, fieldWidth, wordWidth. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read result. Expand result to inspect the returned fields.
Return a shifted contiguous field mask. Require wordWidth 1..128, lowBit in [0,width] and fieldWidth in [0,width-lowBit]; mask = (2^fieldWidth-1)*2^lowBit as decimal text.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| lowBit | Bit offset can equal wordWidth only for an empty field. | Required. Safe integer. Calculation range: 0 through wordWidth, inclusive. |
| fieldWidth | Field length can be zero. | Required. Safe integer. Calculation range: 0 through wordWidth - lowBit, inclusive. |
| wordWidth | Word Width | Required. Safe integer. Calculation range: 1 through 128, inclusive. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| result | Returned calculated value or nested object under the stated output convention. | Required. Object. |
| result.mask | Mask | Calculated result member: string. |
{
"input": {
"lowBit": 2,
"fieldWidth": 3,
"wordWidth": 8
},
"output": {
"result": {
"mask": "28"
}
}
}Limitations and assumptions
- Zero-width fields are allowed, including lowBit equal to wordWidth; no word extraction or insertion is performed.
- Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Choose an explicit bit order, word width and missing-position policy; use the complete record format and appropriate parsing or checksum methods for full validation.
References
Similar or alternative tools
- Bitwise: Bitfield Width From Endpoints
Return field width from inclusive bit endpoints.
- Bitword Partial Byte Validbit Mask
Return full bytes and a final partial-byte mask from a bit count.