Bitmask Outside Width Count Tool

Description

Count set bits inside and outside a supplied width.

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.

Count set bits inside and outside a supplied width.

When to use this tool

Use Bitmask Outside Width Count when checking the stated mask, field, parity or bit-index convention.

How to use the tool and how it works

Enter mask, width. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read outsideBits, insideBits. Use the output convention below.

Count set bits inside and outside a supplied width. Require nonnegative safe-integer mask and width 0..53; insideBits counts low width bits, outsideBits counts the rest.^[1]

Input field	Meaning and units	Accepted input
mask	Mask	Required. Safe integer; minimum 0.
width	Nonnegative whole width; zero is allowed and makes every set bit outside.	Required. Safe integer; minimum 0; maximum 53.

Output field	Interpretation	Returned shape
outsideBits	Outside Bits	Required. Safe integer.
insideBits	Inside Bits	Required. Safe integer.

json

{
  "input": {
    "mask": 45,
    "width": 4
  },
  "output": {
    "outsideBits": 1,
    "insideBits": 3
  }
}

Limitations and assumptions

Out-of-width bits are reported rather than rejected; width zero places every set bit outside.
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

Calculation and input contract: bitwise/bitmask-outside-width-count — tool.io

Similar or alternative tools

Bitmask Run End Boundary Mask
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Bitmask Run Start Boundary Mask
Return low boundaries of one-bit runs.