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Multipart Delimiter Line Classifier

Classify a multipart delimiter line without its CRLF, recognizing optional closing double dash and trailing SP/HTAB only; no prefix false positives.

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Description

Classify a multipart delimiter line without its CRLF, recognizing optional closing double dash and trailing SP/HTAB only; no prefix false positives.

A media type has a type/subtype token and may carry named parameters. Multipart content uses explicit boundary delimiter lines around its parts. Token case rules, parameter quoting, repeated records and exact line endings affect how a representation is interpreted; a lexical check is narrower than parsing a complete message.1

Classify a multipart delimiter line without its CRLF, recognizing optional closing double dash and trailing SP/HTAB only; no prefix false positives.

When to use this tool

Use this tool to classify a multipart delimiter line without its CRLF, recognizing optional closing double dash and trailing SP/HTAB only; no prefix false positives.

How to use the tool and how it works

  1. Enter line, boundary using the field definitions below.
  2. Run the operation. Correct input errors before interpreting an output.
  3. Read result.kind. Use the ordering, boundary rules and absence conditions described below.

Validate the boundary and classify a newline-free line as open, close or none, allowing trailing spaces or tabs after a delimiter.2

Input fieldMeaning and unitsAccepted input
lineOne line without its CRLF ending.Text, at most 8,192 UTF-16 code units; the operation’s grammar also applies.
boundaryBoundary text without the two delimiter-prefix hyphens; 1–70 supported characters.Text, at most 8,192 UTF-16 code units; the operation’s grammar also applies.
Output fieldInterpretation
resultObject containing the named fields below.
result.kindDelimiter-line classification: open, close or none.
json
{
  "input": {
    "line": "--abc--\t",
    "boundary": "abc"
  },
  "output": {
    "result": {
      "kind": "close"
    }
  }
}

Limitations and assumptions

  • This classifies one line, not a complete multipart body or its nesting.
  • Supported boundary strings contain 1–70 characters from the declared MIME boundary subset and cannot end in a space. Single-byte envelope budgets are distinct from UTF-8 text byte counts and from a complete MIME transport.
  • Every declared top-level input field is required and unexpected fields are rejected. Ordinary strings are limited to 8,192 UTF-16 code units and lists to 128 entries, with tighter operation-specific bounds where stated. JSON text has bounded nesting and node counts.
  • Numeric outputs must be finite and no larger in absolute magnitude than the safe-integer limit; operations returning exact large integers use decimal text. Positions are zero-based and spans end exclusively unless the operation explicitly states a different convention.

Alternative or Complementary methods

Choose the target media-type and multipart conventions explicitly. Use a complete MIME parser for nested messages and encodings; these record and delimiter tools handle only their stated representations.

References

  1. RFC 2046: MIME Media Types — RFC Editor

  2. Tool behavior and example: Multipart Delimiter Line Classifier — tool.io

Similar or alternative tools

  • Multipart Boundary Delimiter Formatter

    Format one RFC 2046 multipart delimiter line with explicit closing policy and CRLF; validates the supplied boundary, does not generate a collision-safe boundary.

  • Multipart Boundary Payload Collision Audit

    Audit complete multipart delimiter-looking lines at the start or after CRLF in an explicit payload; prefix-only non-delimiter matches do not count, no byte encoding inference.

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