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Multipart Part Envelope Byte Budget

Budget one MIME part as opening delimiter, supplied Latin-1 header lines plus blank line, explicit payload byte count and trailing CRLF; excludes final closing delimiter.

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Description

Budget one MIME part as opening delimiter, supplied Latin-1 header lines plus blank line, explicit payload byte count and trailing CRLF; excludes final closing delimiter.

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

Budget one MIME part as opening delimiter, supplied Latin-1 header lines plus blank line, explicit payload byte count and trailing CRLF; excludes final closing delimiter.

When to use this tool

Use this tool to budget one MIME part as opening delimiter, supplied Latin-1 header lines plus blank line, explicit payload byte count and trailing CRLF; excludes final closing delimiter.

How to use the tool and how it works

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

Count an opening boundary line, single-byte header characters plus CRLF endings and the separating blank line, supplied payload bytes, and a trailing CRLF.2

Input fieldMeaning and unitsAccepted input
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.
headerLinesHeader-line texts without CRLF, each using single-byte-compatible characters.Dense list of at most 128 strings, each at most 8,192 UTF-16 code units.
payloadBytesSupplied nonnegative payload byte count.A finite safe integer within the operation’s stated bounds.
Output fieldInterpretation
resultObject containing the named fields below.
result.openingBytesByte count of opening delimiter including its CRLF.
result.headerBytesByte count of supplied header lines, their CRLF endings and the separating blank line.
result.payloadBytesSupplied payload byte count, echoed unchanged.
result.totalTotal bytes under the envelope convention stated above.
json
{
  "input": {
    "boundary": "abc",
    "headerLines": [
      "X: y"
    ],
    "payloadBytes": 10
  },
  "output": {
    "result": {
      "openingBytes": 7,
      "headerBytes": 8,
      "payloadBytes": 10,
      "total": 27
    }
  }
}

Limitations and assumptions

  • This estimates one part envelope, excluding a closing boundary and other parts; header syntax is not fully validated.
  • 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 Part Envelope Byte Budget — tool.io

Similar or alternative tools

  • Multipart Part Length Consistency Audit

    Compare explicit declared and observed part byte counts with signed discrepancies; does not parse Content-Length headers, bodies or transfer encodings.

  • MIME Parameter Byte Order Profile

    Profile byte-order source spans in canonical Latin-1 MIME parameter serialization, retaining occurrence order; not machine endianness or Unicode encoding detection.

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