HTTP Field Line Folding Audit

Audit obsolete field folding and bare CR/LF in a supplied header block; does not normalize potentially ambiguous HTTP framing.

Description

Audit obsolete field folding and bare CR/LF in a supplied header block; does not normalize potentially ambiguous HTTP framing.

HTTP header observations can expose folded lines and non-CRLF separators without rewriting them.

When to use this tool

Audit obsolete field folding and bare CR/LF in a supplied header block; does not normalize potentially ambiguous HTTP framing.

Prepare the supplied headerBlock 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 headerBlock. 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.foldedLineNumbers, result.bareLfLineNumbers, result.bareCrLineNumbers. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.

Split headerBlock while recognizing CRLF, LF and CR. Return one-based line numbers whose text starts with space/tab, plus lists terminated by bare LF or bare CR.^[1]

Input field	Meaning and representation	Accepted input
headerBlock	header block.	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.foldedLineNumbers	The folded line numbers list in the ordering and representation described above.
result.bareLfLineNumbers	The bare lf line numbers list in the ordering and representation described above.
result.bareCrLineNumbers	The bare cr line numbers list in the ordering and representation described above.

json

{
  "input": {
    "headerBlock": "X: a\r\n b\r\nY: c\n"
  },
  "output": {
    "result": {
      "foldedLineNumbers": [
        2
      ],
      "bareLfLineNumbers": [
        3
      ],
      "bareCrLineNumbers": []
    }
  }
}

Limitations and assumptions

No header grammar, message framing or security decision is completed. The audit neither unfolds lines nor silently normalizes line endings.
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.
String lists have at most 128 entries of at most 128 code units; matrices have at most 128 rows and columns. Larger numeric lists and parsed JSON have separate bounded budgets. Nonfinite results and excessively large serialized outputs are rejected.
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

Use a complete protocol or URL parser when interpreting a whole message or address. Preserve raw spelling when required and distinguish HTTP token grammar, URL path normalization and form-style query decoding.

References

Tool behavior and example: HTTP Field Line Folding Audit — tool.io

Similar or alternative tools

HTTP Content Length Decimal Parser
Parse Content-Length as exact unsigned ASCII decimal text without unsafe numeric conversion, signs, whitespace or exponent syntax.
HTTP Content Length List Consistency
Audit comma-combined Content-Length decimal members for exact numeric consistency after OWS trimming; does not accept empty members.