Swift RFC 2045

Swift implementation of RFC 2045: Multipurpose Internet Mail Extensions (MIME) Part One

Overview

This package provides a Swift implementation of MIME fundamentals as defined in RFC 2045. These types enable proper content type specification and transfer encoding for email messages.

Features

• ✅ Content-Type header support (type/subtype with parameters)
• ✅ Content-Transfer-Encoding support (7bit, 8bit, binary, quoted-printable, base64)
• ✅ Type-safe Content-Type construction
• ✅ RFC-compliant header rendering
• ✅ Common content type presets
• ✅ Parameter handling (charset, boundary, etc.)
• ✅ Swift 6 strict concurrency support
• ✅ Full Sendable conformance

Installation

Add swift-rfc-2045 to your package dependencies:

dependencies: [
    .package(url: "https://github.com/swift-standards/swift-rfc-2045.git", from: "0.1.0")
]

Then add it to your target:

.target(
    name: "YourTarget",
    dependencies: [
        .product(name: "RFC 2045", package: "swift-rfc-2045")
    ]
)

Quick Start

Content-Type

import RFC_2045

// Simple text type
let plain = RFC_2045.ContentType(type: "text", subtype: "plain")

// With charset parameter
let html = RFC_2045.ContentType(
    type: "text",
    subtype: "html",
    parameters: ["charset": "UTF-8"]
)

// Multipart with boundary
let multipart = RFC_2045.ContentType(
    type: "multipart",
    subtype: "alternative",
    parameters: ["boundary": "----=_Part_1234"]
)

// Use in email headers
let headers = [
    "Content-Type": html.headerValue  // "text/html; charset=UTF-8"
]

Content-Transfer-Encoding

// Common encodings
let base64 = RFC_2045.ContentTransferEncoding.base64
let quotedPrintable = RFC_2045.ContentTransferEncoding.quotedPrintable
let sevenBit = RFC_2045.ContentTransferEncoding.sevenBit

// Use in email headers
let headers = [
    "Content-Transfer-Encoding": base64.headerValue  // "base64"
]

// Check encoding properties
base64.isBinarySafe  // true
base64.isEncoded     // true

Common Content Types

// Preset content types
RFC_2045.ContentType.textPlain
RFC_2045.ContentType.textPlainUTF8
RFC_2045.ContentType.textHTML
RFC_2045.ContentType.textHTMLUTF8

// Multipart types with boundary
RFC_2045.ContentType.multipartAlternative(boundary: "----=_Part_1234")
RFC_2045.ContentType.multipartMixed(boundary: "----=_Part_5678")

Parsing Headers

// Parse Content-Type header
let contentType = try RFC_2045.ContentType(
    parsing: "text/html; charset=UTF-8"
)

print(contentType.type)      // "text"
print(contentType.subtype)   // "html"
print(contentType.charset)   // "UTF-8"

// Parse Content-Transfer-Encoding header
let encoding = try RFC_2045.ContentTransferEncoding(parsing: "base64")
print(encoding.headerValue)  // "base64"

Usage

Type Overview

RFC_2045.ContentType

Represents the Content-Type header with type, subtype, and parameters.

public struct ContentType {
    public let type: String
    public let subtype: String
    public let parameters: [String: String]

    public var headerValue: String
    public var charset: String?
    public var boundary: String?
    public var isMultipart: Bool
    public var isText: Bool
}

RFC_2045.ContentTransferEncoding

Represents the Content-Transfer-Encoding header.

public enum ContentTransferEncoding {
    case sevenBit        // "7bit"
    case eightBit        // "8bit"
    case binary          // "binary"
    case quotedPrintable // "quoted-printable"
    case base64          // "base64"

    public var headerValue: String
    public var isBinarySafe: Bool
    public var isEncoded: Bool
}

RFC 2045 Compliance

This implementation follows RFC 2045 specifications:

• ✅ Content-Type format: type/subtype; parameter=value
• ✅ Case-insensitive type/subtype matching
• ✅ Parameter quoting for special characters
• ✅ All five standard transfer encodings
• ✅ Binary-safe encoding identification

Requirements

• Swift 6.0+
• macOS 14+, iOS 17+, tvOS 17+, watchOS 10+

Related Packages

Used By

• swift-rfc-2046 - MIME Part Two: Media Types
• swift-rfc-7578 - Returning Values from Forms: multipart/form-data

Related

• swift-rfc-2388 - Returning Values from Forms: multipart/form-data encoding

License

This library is released under the Apache License 2.0. See LICENSE for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.