options for FileHandle.readableWebStream()

[jimmywarting]

Is your feature request related to a problem? Please describe.
I have just found out that a FileHandle got a readableWebStream function. I wish to use it on fetch-blob but i can't. I need to be able to slice a file and read from a different start/end position, much like

const file = fileFromSync('./readme.md')
const readbleWebStream = file.slice(1, 2).stream()

Describe the solution you'd like
Similar to fs.createReadableStream(fd, options) you also have options to start and stop. this is what i'm currently using. It would be useful if readableWebStream got them as well. for now i will have to resort to using stream.Readable.toWeb(streamReadable) instead...

Describe alternatives you've considered
I wish we got a #39015 and #37340 implemented into core natively. This is the only two blocker we have from ditching fetch-blob. only using Buffer.Blob dose not work for us since we need to handle large files and big FormData payloads that dose not live in memory

[jasnell]

+1 to this. It would be a good addition.

[dubiousjim]

The whatwg spec gives an example implementation. (Below snippet incorporates some fixes I proposed to the spec, and adds in start/stop options.)

    const fsp = require('node:fs/promises');
    const DEFAULT_CHUNK_SIZE = 65536; // 64K, perhaps make 4096K or 512K?
    function openReadableFileStream(path, start=0, stop=Number.MAX_SAFE_INTEGER) {
        let fileHandle;
        return new ReadableStream({
            type: 'bytes',
            autoAllocateChunkSize: DEFAULT_CHUNK_SIZE,
            async start() {
                fileHandle = await fsp.open(path, 'r');
            },
            async pull(ctrl) {
                const v = ctrl.byobRequest.view;
                const { bytesRead } = await fileHandle.read(v, 0, Math.min(v.byteLength, stop - start), start);
                if (bytesRead === 0) {
                    await fileHandle.close();
                    ctrl.close();
                    ctrl.byobRequest.respond(0);
                } else {
                    start += bytesRead;
                    ctrl.byobRequest.respond(bytesRead);
                }
            },
            cancel() {
                return fileHandle.close();
            }
        });
    };

[github-actions]

There has been no activity on this feature request for 5 months and it is unlikely to be implemented. It will be closed 6 months after the last non-automated comment.

For more information on how the project manages feature requests, please consult the feature request management document.

[github-actions]

There has been no activity on this feature request and it is being closed. If you feel closing this issue is not the right thing to do, please leave a comment.

For more information on how the project manages feature requests, please consult the feature request management document.