FormStream is a Golang streaming parser for multipart data, primarily used in web form submissions and file uploads.

• Provides a streaming parser, eliminating the need to store entire files in memory or on disk in most cases.
• Boasts extremely low memory usage.
• Delivers high performance, significantly faster than traditional methods.

Across all file sizes, FormStream outperforms the mime/multipart in both speed and memory efficiency.

go get github.com/mazrean/formstream@latest

--boundary
Content-Disposition: form-data; name="name"

mazrean
--boundary
Content-Disposition: form-data; name="password"

password
--boundary
Content-Disposition: form-data; name="icon"; filename="icon.png"
Content-Type: image/png

icon contents
--boundary--

parser, err := formstream.NewParser(r)
if err != nil {
    return err
}

err = parser.Register("icon", func(r io.Reader, header formstream.Header) error {
    name, _, _ := parser.Value("name")
    password, _, _ := parser.Value("password")

    return saveUser(r.Context(), name, password, r)
}, formstream.WithRequiredPart("name"), formstream.WithRequiredPart("password"))
if err != nil {
    return err
}

err = parser.Parse()
if err != nil {
    return err
}

FormStream offers wrappers for popular web frameworks:

FormStream introduces a more efficient method for processing multipart data.

Multipart data is organized with defined boundaries separating each segment. Here's an example:

--boundary
Content-Disposition: form-data; name="description"

file description
--boundary
Content-Disposition: form-data; name="file"; filename="large.png"
Content-Type: image/png

large png data...
--boundary--

For large files, streaming the data is vital for efficient memory usage. In the example above, streaming is made possible by sequentially processing each part from the beginning, which can be achieved using the (*Reader).NextPart method in the mime/multipart package.

The mime/multipart package also includes the (*Reader).ReadForm method. Unlike streaming, this method stores data temporarily in memory or on a file, leading to slower processing. It's widely used in frameworks like net/http, Echo, and Gin due to its ability to handle parts in any order. For instance:

--boundary
Content-Disposition: form-data; name="file"; filename="large.png"
Content-Type: image/png

large png data...
--boundary
Content-Disposition: form-data; name="description"

file description
--boundary--

With (*Reader).NextPart, processing strictly follows sequential order, making it challenging to handle such data where later parts contain information necessary for processing earlier ones.

Optimal multipart handling strategies include:

• Stream processing with (*Reader).NextPart when all necessary data is immediately available.
• Temporarily storing data on disk or memory, then processing it with (*Reader).ReadForm when needed.

FormStream enhances this process. It outpaces the (*Reader).ReadForm method and, unlike (*Reader).NextPart, can handle multipart data in any order. This adaptability makes FormStream suitable for a range of multipart data scenarios.