littlezipper
v0.1.4
Published
Extremely simple .zip file creation with no dependencies
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16,940
Readme
littlezipper
This project uses the CompressionStream
facility — supported by all recent browsers, Node and Deno — to create .zip
files.
This is not entirely trivial since, a little frustratingly, CompressionStream
can natively produce .gz
format data but not .zip
. Thus, we pick out both the deflated data and the CRC from the .gz
stream, and write them into a .zip
file instead.
We don't actually have to implement any compression, so the library is fast and small.
Where CompressionStream
is not available, we fall back to producing uncompressed .zip
files (and calculate the CRC in heavily-optimized JavaScript). This may be OK if you are creating a .zip
that is actually an .xlsx
, .apk
or .xpi
file, for example.
The library is currently suitable for small- and medium-sized files, since it briefly requires just over 2x the total uncompressed size of your files in memory. That's because you pass it an array of files data, and for the .zip
output it allocates a Uint8Array
backed by a worst-case ArrayBuffer
, which is the size of all the uncompressed data plus a little more for headers.
Potential future improvements could include implementing a TransformStream
instead, which could enable smaller memory use and larger file sizes. However, the .zip
format annoyingly puts the CRC and compressed data size before the compressed data, which limits opportunities for memory saving.
Installation
npm install littlezipper
Usage
The library exposes a single function, createZip
.
import { createZip } from 'littlezipper';
const zip = await createZip([
{ path: 'test.txt', data: 'This is a test', lastModified: new Date('2020-01-01T00:00:00') },
{ path: 'test.bin', data: new Uint8Array([1, 2, 3]) },
]);
The first argument to createZip
is an array of file entries. Each entry must have path
(string
) and data
(string
, Uint8Array
or ArrayBuffer
) keys, and may have a lastModified
(Date
) key, which otherwise defaults to the current date and time.
The optional second argument defines whether we attempt to deflate the data (default: true
). If false
, the resulting .zip
file will be as large as the input data plus a few bytes for headers.