Fixed Width Record Padder

Pad caller cells into explicit UTF-16 fixed-width fields; overflow is rejected instead of silently truncated.

Description

Pad caller cells into explicit UTF-16 fixed-width fields; overflow is rejected instead of silently truncated.

Fixed-width text padding aligns fields by code-unit width and must reject content already too long.

When to use this tool

Pad caller cells into explicit UTF-16 fixed-width fields; overflow is rejected instead of silently truncated.

Prepare the supplied cells, widths, pad 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 cells, widths, pad. 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.record. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.

Require aligned cells/widths and a one-unit pad string. Each width is an integer from 0 to 8,192; right-pad each cell to its width, then concatenate parts.^[1]

Input field	Meaning and representation	Accepted input
cells	cells.	List of strings; at most 128 entries
widths	widths.	List of finite numbers; at most 128 entries
pad	pad.	Text; at most 8,192 UTF-16 code units, subject to the grammar above

Output field	Interpretation
result	Object containing the named outputs below.
result.record	The record value under the stated formula or text convention.

json

{
  "input": {
    "cells": [
      "a",
      "bc"
    ],
    "widths": [
      3,
      3
    ],
    "pad": " "
  },
  "output": {
    "result": {
      "record": "a  bc "
    }
  }
}

Limitations and assumptions

Widths are UTF-16 units, not display columns or bytes. No truncation, multicolumn glyph handling or left padding is applied.
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

Choose the exact text grammar before combining serializers and parsers. UTF-16 record lengths, raw separators and custom backslash escapes differ from byte framing, CSV, Markdown and spreadsheet semantics.

References

Tool behavior and example: Fixed Width Record Padder — tool.io

Similar or alternative tools

Fixed Width Layout Overlap Check
Audit positive overlap between half-open fixed-width text layout spans; touching and zero-width spans do not overlap.
Length Prefixed Text Record Decoder
Decode complete decimal-length-prefixed UTF-16 text records; reject malformed lengths or incomplete payloads.