Armarius

About

Armarius is a JavaScript library to read, write, and merge ZIP archives in web browsers.

This library mainly focuses on a low memory footprint, especially when reading archives with tens of thousands of
entries, and the ability to merge archives without decompressing and recompressing all entries.

For deflate/inflate support, this library uses the
Compression Streams API (if available) or
fflate. In Node.js environments, the built-in zlib module is used.

Installation

Armarius can be installed using npm:

``shell
npm install armarius
`

It can then be loaded as an ES Module:

`javascript
import * as armarius from 'armarius';
`

IO operations and compression are not part of the library itself, and are packaged separately as armarius-io:

`javascript
import * as io from 'armarius-io';
`

For use in web browsers, this library can be bundled using esbuild.
Other bundlers like webpack should work as well,
but are not officially supported.

Usage

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To read an archive, an IO context is required.
The armarius-io library provides IO implementations for Blob, ArrayBuffer, and Node.js FileHandle
objects. Other IO contexts can be implemented by extending the IO class.

`javascript
let fileInput = document.getElementById('file-input');
let reader = new io.BlobIO(fileInput.files[0]);
`

A ReadArchive can then be created from an IO context.

`javascript
let archive = new armarius.ReadArchive(reader, options);
await archive.init();
`

The ReadArchive constructor optionally accepts an ReadArchiveOptions object with
the following properties:

| Name | Type | Description |
|------------------------------------------|---------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| centralDirectoryBufferSize | number | Buffer size used when reading central directory contents.
Larger buffer sizes may improve performance, but also increase RAM usage. |
| createEntryIndex | boolean | Whether an index of all central directory entries should be created the first time they are read.
Massively increases performance when using findEntry multiple times. |
| entryOptions | EntryOptions | Options passed to each created Entry object. |
| ignoreMultiDiskErrors | boolean | Simply ignore information about multiple disks instead of throwing an error when encountering a multi disk archive |
| allowTruncatedCentralDirectory | boolean | Do not throw an error if the central directory does not contain the expected number of entries |
| allowAdditionalCentralDirectoryEntries | boolean | Continue reading central directory entries even after the expected number of entries was reached |

EntryOptions can have the following properties:

| Name | Type | Description |
|--------------------------------|-----------------------------------|---------------------------------------------------------------------------------------------------|
| dataProcessors | Map | Map of compressionMethod => DataProcessor
Can be used to implement custom compression methods |
| allowTrailingSlashInFileName | boolean | Interpret entries with non-empty data as files, even if the file name ends on /. |

#### Reading all archive entries

`javascript
let entries = await archive.getAllEntries();
`

Since this method will load all entries (not including their compressed data)
into memory, it is not recommended when working with large archives.

#### Iterating over archive entries

`javascript
let iterator = await archive.getEntryIterator();

let entry;
while (entry = await iterator.next()) {
console.log(await entry.getFileNameString());
}
`

#### Finding specific entries

`javascript
let entry = await archive.findEntry('some/file.txt');
console.log(await entry.getFileNameString());
`

In most cases, this method is faster than iterating through all archive entries multiple times, since an internal index is used to find
files quickly.

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#### Reading a full entry

`javascript
let entry = await archive.findEntry('example.txt');
let data = await entry.getData();

// Decode UTF-8
let decoder = new TextDecoder();
let text = decoder.decode(data);

console.log(text);
`

#### Reading entry data in chunks

`javascript
let entry = await archive.findEntry('example.txt');
let entryReader = await entry.getDataReader();

let chunk;
while (chunk = await reader.read(1024 * 64)) {
console.log(chunk);
}
`

Note that the length parameter passed to EntryDataReader.read is the length of the compressed data read from the
file. Since this data is decompressed, the size of the returned chunk might differ.

Also note that an empty chunk returned from EntryDataReader.read does not necessarily indicate that all data has been read.
After all data was read, null will be returned instead.

Both getDataReader and getData optionally accept an EntryDataReaderOptions object with
the following properties:

| Name | Type | Description |
|---------------------------------|---------|---------------------------------------------------------------------------------|
| ignoreInvalidChecksums | boolean | Do not throw an error if the uncompressed data does not match the checksum |
| ignoreInvalidUncompressedSize | boolean | Do not throw an error if the uncompressed data does not match the expected size |

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New archives can be created using a WriteArchive object.
The WriteArchive constructor needs to be passed a function, Iterator, or AsyncIterator that generates
new EntrySource objects when needed.

Additionally, a WriteArchiveOptions object can be passed:

| Name | Type | Description |
|----------------|---------|-------------------------------------------------------------------------------------------------|
| forceZIP64 | boolean | Whether ZIP64 structures should always be created, even if not required by the archive content. |

`javascript
async function *generateNextEntrySource() {
yield new armarius.DataStreamEntrySource(new io.ArrayBufferIO(new ArrayBuffer(0)), {fileName: 'file.txt'});
yield new armarius.DataStreamEntrySource(new io.ArrayBufferIO(new ArrayBuffer(0)), {fileName: 'file2.txt'});
return null;
}

let writeArchive = new armarius.WriteArchive(generateNextEntrySource(), options);
`

#### Generating entries

If nextEntryFunction is an Iterator or AsyncIterator, the WriteArchive will iterate over it to generate new entries.

If it is a function, it will be called whenever a new entry needs to be written to the archive and should return a new
Instance of EntrySource, or null if no more entries should be added to the archive.

This simple example will generate an archive that contains 10 text files:

`javascript
let encoder = new TextEncoder();

function *generateEntrySources() {
for (let i = 0; i < 10; i++) {
let fileName = file-${i};
let fileContent = encoder.encode(Content of file ${i});

let reader = new io.ArrayBufferIO(fileContent.buffer, fileContent.byteOffset, fileContent.byteLength);
let entry = new armarius.DataStreamEntrySource(reader, {fileName: fileName});
yield entry;
}
}

let writeArchive = new armarius.WriteArchive(generateEntrySources());
`

Any EntrySource accepts an EntrySourceOptions object with the following
properties:

| Name | Type | Description |
|--------------------------|-----------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| fileComment | string | Entry file comment |
| fileName | string | Entry file name |
| forceUTF8FileName | boolean | Always encode the filename and file comment in UTF-8, even if it could be encoded in CP437 |
| compressionMethod | number | Compression method that should be used for this entry. By default, this library only supports 0 (Store) and 8 (Deflate). More compression methods can be added using the dataProcessors option.

When using an ArchiveEntryEntrySource, this option will be ignored and the compression method of the original entry is used. |
| forceZIP64 | boolean | Whether ZIP64 structures should always be created, even if not required by the content. |
| minMadeByVersion | number | The minimum madeByVersion value to be used for this entry. If a higher version is required (e.g. because of ZIP64) is used, it will be set automatically and this option will be ignored. |
| minExtractionVersion | number | The minimum extractionVersion value to be used for this entry. If a higher version is required (e.g. because of ZIP64) is used, it will be set automatically and this option will be ignored. |
| modTime | Date | Last modified time of the entry |
| acTime | Date | Last access time of the entry. This option is ignored if extendedTimeStampField is false. |
| crTime | Date | File creation time of the entry. This option is ignored if extendedTimeStampField is false. |
| unicodeFileNameField | boolean | Whether a Unicode Path Extra Field should be added |
| unicodeCommentField | boolean | Whether a Unicode Comment Extra Field should be added |
| extendedTimeStampField | boolean | Whether an Extended Timestamp Extra Field should be added |
| internalFileAttributes | number | See https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT |
| externalFileAttributes | number | See https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT |
| dataProcessors | Map | Map of compressionMethod => DataProcessor
Can be used to implement custom compression methods |

#### Reading output chunks

The generated archive can be read using the getNextChunk function.

`javascript
let chunk;
while (chunk = await writeArchive.getNextChunk()) {
console.log('New archive chunk:', chunk);
}
`

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Armarius supports merging ZIP archives without decompressing and recompressing individual entries.

`javascript
let archies = [myReadArchive1, myReadArchive2];

let merger = new armarius.ArchiveMerger(archives, options);
let outputWriteArchive = merger.getOutputArchive();

let chunk;
while (chunk = await outputWriteArchive.getNextChunk()) {
console.log('New archive chunk:', chunk);
}
`

The ArchiveMerger constructor accepts a list
of ReadArchive or MergeSource objects and
a MergeOptions object with the following properties:

| Name | Type | Description |
|-------------------------------|-----------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| entrySourceOptions | EntrySourceOptions | Options passed to each created EntrySource object |
| writeArchiveOptions | WriteArchiveOptions | Options passed to the output WriteArchive |
| nextPrependingEntryFunction | Function | Function generating EntrySource objects that are added to the output archive before the contents of the input archives |

#### MergeSource objects

A MergeSource object allows greater control over how a source archive is merged into the
destination archive.

`javascript
let mergeSource = new armarius.MergeSource(readArchive);
mergeSource
.setBasePath('base/path/within/the/source/archive')
.setDestinationPath('path/within/the/destination/archive')
.setFilter((entry) => {
if (entry.getFileNameString().endsWith('.rar')) {
return false; //Filter entry
} else {
return true; //Allow entry
}
});
`

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While mainly intended for use in web browsers, this library can also be used in Node.js.

To read data from files, a NodeFileIO object can be used:
`javascript
import * as fs from 'node:fs';

let file = await fs.promises.open('path/to/file.zip', 'r');
let stat = await file.stat();
let reader = new io.NodeFileIO(file, 0, stat.size);
`

Armarius will automatically recognize that it is running in a Node.js environment and use the appropriate
compression implementation based on the Node.js built-in zlib` module.

License

Armarius is open source software released under the MIT license, see license.

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You can contribute to this project by forking
the repository, adding your changes to your fork, and creating
a pull request.