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Document Marshaller

This is an experiment - use at your own risk!

The purpose of this library is provide a mechanism for marshalling and unmarshalling data using a single document, allowing for the transportation and storage of related data in a single file.

Notes on implementation:

• Booleans will be converted into integers

Installation

composer require punkstar/document-marshaller

Usage

Create your document using Document and DocumentFragment, for example:

$document = new Document([
    new DocumentFragment("Fragment One", "This is the content in this fragment"),
    new DocumentFragment("Fragment Two", "This is the content in this fragment, the second")
]);

Create the marshallers and the checksum calculator:

$checksumCalculator = new Checksum();
$fragmentMarshaller = new DocumentFragment\Marshaller();

$marshaller = new DocumentMarshaller($fragmentMarshaller, $checksumCalculator);

The marshall the document:

$marshalledDocument = $marshaller->marshall($document);

Document Format

The document is encoded using JSON in the following structure:

{
    "v": "", // Document Version
    "c": ""  // Document Checksum
    "f": [   // Document Fragments
        {
            "n": "" // Document Fragment Name
            "d": "" // Document Fragment Data
        }
        ...
    ]
}

Document

• A document MUST be an object.
• A document SHOULD have a version indicated by the value of the key: v. If a version is absent then a version value of 1 MUST be assumed.
• A document SHOULD have a checksum indicated by the value of the key: c. If a checksum is absent then any verification logic should be skipped and the user SHOULD be presented with a non fatal warning if appropriate.
• A document SHOULD have a fragments array indicated by the value of the key: f. If the fragments array is absent then it MUST be assumed that the document has no fragments.

Document Version

• The document version MUST be expressed as an integer.

Document Fragments

• The document fragments MUST be an array of objects with a name key: n, and a data key: d.
• The name and the data of the document fragment MUST be encoded with base64.

Document Checksum

• The document checksum MUST be calculated by: sorting the fragments objects by name, then performing a hash of the JSON fragments array using sha256.

Some examples are provided below:

The first document consists of two fragments, one called Header; the other Body. The content of the Header fragment is the string Hello. The content of the Body fragment is World. The JSON representation of these fragments is as follows:

[
    {
        "n": "Header",
        "d": "Hello"
    },
    {
        "n": "Body",
        "d": "World"
    }
]

The checksum of this document would therefore be:

sha256([{"n":"SGVhZGVy","d":"SGVsbG8="},{"n":"Qm9keQ==","d":"V29ybGQ="}]) == "d827049039f82a8b65a9b0f52e637cf3bc5d1e0dec7d6198edf901a5e3dcae7d"

The entire document expressed would therefore be:

{

    "v": 1,
    "c": "d827049039f82a8b65a9b0f52e637cf3bc5d1e0dec7d6198edf901a5e3dcae7d",
    "f": [{
         "n": "Header",
         "d": "Hello"
     }, {
         "n": "Body",
         "d": "World"
    }]
}